How to test an electric fuel pump - using a test light

[@danielarney9729]

Thanks. Thought you where gonna temporarily swap relays. Can't believe last person that wrote was 7 years ago, don't know how many of us screwed out here appreciate you sharing your knowledge, you'll be helping people 50 years from now.

[@ScannerDanner]

Thanks Daniel! This is one of the first videos I've ever done I I think

[@ScannerDanner]

exactly confirming the problem is NOT a bad ground. you can call it faulty logic if you want to, it's not. Unless you want to tell me that the pump motor circuit is open and you have a bad ground at the same time...not going to happen. test light doesn't light on the ground = it is NOT a bad ground that is causing the pump to not run! I agree the ground circuit isn't loaded but so what in this case. you have correctly identified a bad pump!

[@mikecooper4712]

Thanks I replaced the fuel pump relay, but because of how you showed the testing at the fuse block, I discovered I simply put the relay in backwards, with the numbers corresponding to the ground and GM using the positive, Works now! Thanks

[@garymarcel6372]

Man this is a quality video and very universal. Great fundamentals, i will keep this as a reference of my own. Many people young and old will enjoy your lesson

[@ScannerDanner]

One of my first videos!

[@aggiespilot]

As a young parts guy I love your videos. From watching I've grown to love the electrical and computer side of automotive repair which a LOT of people shy away from and treat it like witchcraft. I'm saving my pennies for your Ebook so that I can better help my customers with their issues (With the disclaimer that I am in no way a pro technician and could be wrong) Anyways keep them coming! great stuff Mr. Danner :)

[@mike-yp1uk]

God is blessing you with a great gift and you are sharing and that is what i call true success. thanks for your hard work may he bless you greatly.

[@ScannerDanner]

He certainly has been my friend. And all glory goes to Him. "I can do all things through Christ who strengthens me"

[@bammaez6745]

@@ScannerDanner ⁰

[@MrBurt54]

This was my 1st video...I did not have to look for another source of info. Man you ARE awesome. thanks ....and yes you are blessed with a gift of knowledge and teaching

[@patrickliverpool6487]

I have been following programs for the last two years and I have been able to solve problems true good trouble shooting skills from your classes

[@ScannerDanner]

Thank you Patrick!

[@simbas61]

Mr. Danner, Loved your video on how to test an electric fuel pump! As a Systems Engineer working on High end computers and such, you make alot of sense in your trouble shooting skills, and the way you explain them. You just saved me a trip to the parts store to buy a Chiltons for my ride! Keep up the good work!

[@orlanmedina3693]

You're awesome Paul!. Black and white. Even with no knowledge is very easy to do with what you explained in this video

[@MrBurt54]

After I got the bed tilted and had access to the wiring....I found you were absoultely right about the color coding. 95 c2500 had different plug...same color code. thanks so much

[@ScannerDanner]

@FreeThoughtCrime If the pump ground circuit is good there will only be a few hundred millivolts on that wire. If you connect your test light to the pump ground and battery ground, a few hundred millivolts will not light the light. I know this isn't the best test for a ground, but I wanted to show how to use the test light if that was all you had. Also I realize the only way the test light would light on the ground is if the ground was completely open ......

[@niterbum]

thanks Scanner Danner for thinking of us less fortunate backyard mechanics Go Flyers

[@PANOS9916]

Amazing. On every video I am getting my knowledge better and better and even though I am a DIY guy I have started talking to myself and proposing steps before being told on the videos

[@ScannerDanner]

That is awesome!

[@iamhomerj4711]

Nice video. Having trouble with my 2002 2500 Silverado. Now i know how to test before moving on to pump removal. Hoping just a bad ground. Very informative. Thank you.

[@gregscheyd4131]

very much appreciate the comment about ADAPTERS which allow the relay to remain plugged in , for testing purposes !!!! PRICELESS TO KNOW !!!!!

[@ScannerDanner]

@ScannerDanner circuit loaded of course. A high resistance ground may have tested good (no light), however I would have had some fuel pressure and pump operation. In this case it was completely dead. Never rely on a test light to check the ground circuit of a working component. It isn't accurate enough.

[@nigelstringfellow5187]

Thank you for yet another really educational video Paul I am learning so much from your site

[@ScannerDanner]

Thank you Nigel!

[@christesta7553]

Great video Paul. You make diagnostic testing look easy which it's not. Going to purchase your book. I agree with your viewer you truly are gifted and blessed!!!!

[@ScannerDanner]

Thank you so much!

[@csgorton]

i'm so used to the old school style of doing things, learning this stuff is just great!! thanks ScannerDanner

[@MrJgonzalez2]

Paul, what I've done in this situation when working by myself is hook the T-pin to the relay control (dark green & white)hook the alligator clip to T-pin and find a good ground to stuff the test light and place somewhere visible from the drivers seat to crank teh engine.

[@PlasmaHH]

2:18 you can use a little bit of rather thin wire, wrap it around the relay leads, and then attach any meter you like to it. Its quite a hack, but it works well, unless you short the wire, which isn't a big problem anyways as thin wire will melt right away ;)

[@jacobsacres6038]

Can this all be tested with just a multi meter? Sorry I’m very ignorant about all of this.

[@ScannerDanner]

Yes it can

[@mikewithers7685]

Paul you both are correct in your approach except howler using the Ohm meter for circuit testing. I think Howler is using the Load Pro test leads to check circuts. It is a easy way to check for corrosion or bad connections on a circuit since the leads allow you to apply a voltage on the circut and measure voltage drop. "see the videos on you tube under load pro". Love your videos Paul hope to see some new ones soon ! ! Would like to hear your opinion on the load pro test leads. Thank you.

[@mckoylach1622]

Paul,you are the best,with these tests diagnostic procedures,without having a high tech tool,it’s great to possess these old methodical skills...thanks...

[@syedimranshah4721]

In the service manual of an early fuel injected car, I saw that manufacturer recommended to check the resistance of the fuel pump in case of no fuel pressure. Newer cars usually do not mention checking the resistance of a fuel pump, don't know why.

[@banno6938]

I live in the sticks & don't have a scanner so I'd like to offer some shade tree advise for those in my situation if you don't mind. If I'm wrong please explain why. @11:53 IMO your loaded test is inaccurate because of an open circuit in the pump. @12:44 even with a bad ground the test light would not light up if there's no continuity through the pump. IMO easiest way to check a GM like this is to jump #30 & #87 with a "fused" wire and see if you have power @ the pump. Just a simple 10/15 amp fuse with wires attached works. Key in off position is usually OK for this test. Be careful the jump wire can get hot if the pump runs or is shorted ! This way it is easy to check the ground & power @ the plug without the trouble of finding a clean ground. & like you said DO NOT spread the plug connectors ! An old headlight with jumper wires can be used for load test but I have yet to find that necessary. Many times you can jump 30/87 & then "jar" the tank with something like a 2x4 or hammer & the pump may then run for a short time. Its a sure sigh of a bad pump when it runs & quits or sounds rough. These trucks are known for bad fuel senders & gauge cluster so be sure you have fuel. & Pressure on these Vortec's is as important as power to the plug is. I've seen some that will run on 40 lbs of pressure & I've seen some that wont even start below 52 lbs of pressure

[@ScannerDanner]

+B Ann inaccurate would be the wrong choice of words. The tests I showed were 100% accurate in identifying an open in the fuel pump itself (bad pump). There is no arguing that we need a pump. BUT you could argue that I never loaded the ground circuit of the pump and therefor there is still the possibility of an open ground wire. And I would agree with this statement, However, if this is the case, this means that my fuel pump went bad at the same time the ground opened up on the fuel pump circuit. It just doesn't happen. Great points my friend. Thanks!

[@bp22702]

ScannerDanner

[@thaddeauscaldwell7101]

B Anno Hello , great information taht you have shared . I have a 2001 Firebird 3.8 that I need to do this test on . Are the fuse boxes similar. Do you have any recommendations to to do 'jump test' that you are referring to ?

[@mikehigby7897]

That fuse box picture is about the only thing GM is good for these days.

[@Justicejamesb]

I just found your channel, awesome man, totally awesome! About time that someone made videos for people that are a little bit more mechanical, have the tools to do stuff. Thank you, thank you, thank you!!!

[@ScannerDanner]

Thanks so much and welcome! My content has always been good but not my camera and editing skills. You will see a difference in my 2017+ videos. As time goes by, I've definitely improved. Look forward to hearing more from you.

[@billwells8054]

Nice educational video. When I was unsure if the fuel pump was the cause of my car not starting, I ran a hot wire from the car battery to the terminal on the pump, easy to get to inside the trunk of my Acura (Honda, others similar). I could hear the pump running, and the car would then start. With the fuel pump fuse OK, that pretty much meant a defective main fuel pump relay. Although I could not see any bad solder connections on the relay, I replaced it and the car starts/runs fine.

[@ScannerDanner]

Thank you my friend! I also have paper versions available now too.

[@ScannerDanner]

@PDSVIDEO1966 no problem, thank you for the info. I am shooting these with an HD camera but I am not sure what the best viewing is on youtube. It seems to me that 480p looks just fine. ?? In fact I don't see any difference other than it loads slower and there are issues like you describe.

[@scottketchum2224]

This is what I call a great video, thank you for sharing your knowledge 😁

[@cheesemons]

Wish you could have seen my reaction when i finally understood this video. Thanks ScannerDanner! Your video is very informative!

[@ScannerDanner]

Thank you! I wish I did too :-)

[@michaelpearce8661]

@@ScannerDanner on the relay for the fuel pump. I don't have a good ground. Not sure why. Pulled up this video but the grounding wasn't explained other than getting to the fuel pump to check if it was bad at the pump or someplace else.

[@michaelpearce8661]

I have a big problem to drop my fuel tank on a used U-Haul truck with Grandma attic. She's a 94 GMC Sierra C3500 with a 7.4 liter engine. Have 12.3 at pin 30. No other voltage shown.

[@ScannerDanner]

@@michaelpearce8661 no other pin shows voltage during the initial key on or cranking? (very important distinction)

[@michaelpearce8661]

@@ScannerDanner being stuck in this parking lot is no fun. I've got power to 85 if what I was told is place to the left side of the female plug. Also with test light shows power on the center of the plug. The third is 86 the ground. If this is the ground it has an open circuit. I'm wondering if I set up a secondary ground to the relay plug gound to activate the fuel relay to see if I need a new fuel pump?

[@ScannerDanner]

@FreeThoughtCrime Forget the light for a second. A good ground on a running electric fuel pump is typically less than 300mv. If it was higher than this then a bad ground could be the cause or the pump motor is frozen and the circuit is carrying 5 times more current than designed. This would drive your ground voltage higher due to heat from too much current. I don't think I am answering your question, can you ask it another way?

[@JamesSmith-xs7sr]

Thanx! I volt dropped negative batt cable on a older Ford truck, (yesterday) (starter sounded awefull, barely cranked) the neg drop was .9 volts cranking. I thought the cable was bad. (It was hot, & corroded) I put a new starter in & it cranked perfectly! So the excess volt drop was from the worn/damaged starter. How would one isolate/test for the drop at the starter motor in itself? (Run an extra heavy gauge temp ground, battery neg to starter housing?, then re test?)

[@ScannerDanner]

Actually there was John. The fuel pump wiring was underneath the dump truck bed, so access was not easy until the bed was lifted. On a typical truck or car, you would have to get underneath to do these checks. So not necessarily easy, especially when you are doing road calls. Also I wanted to show the relay tests because it seems that people have a need to know how to do that.

[@HowlerWelding]

Re-read what I typed Paul - I said VOLTMETER... I have a set of test leads that allows me to introduce a load into the circuit while measuring Voltage. This DOES stress the circuit - If the voltage drops off when the circuit is loaded then I have a wiring issue. It is one simple test after that to prove if the wiring fault is on the positive or the negative side.

[@ScannerDanner]

yes a parallel circuit upstream of the pump. with the pump circuit plugged in and energized. I promise you if there was a wiring problem on the feed circuit to the pump, the test light would have gone out as soon as I plugged the pump back in. You could argue that the voltage could still be low, but my response to that would be there was NO FUEL PSI! A pump will still run and produce psi with low voltage. Also another thing, the test light brightness was exactly the same unplugged and plugged in

[@mikewithers7685]

you are both correct in your ways of diagnosis. Im sure you are probably using the load pro test leads on your DVOM. Paul is just using some fundamental approaches to his diagnosis using a test lite. Paul loading the circuit with the fuel pump plugged in during testing is the way to do it by only using a test lite. I agree Paul should have used a DVOM at least during his testing.

[@SteveRobReviews]

Fantastic !! Had to think a while about the ground to ground test.

[@nickayivor8432]

Proficient Sir ScannerDanner Tutorial great video loved it thank you very much for sharing it .take care and have a great day Proficient Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧

[@ScannerDanner]

one of my first videos my friend, thank you

[@snurb48]

Good trouble shoot process and methodical point A to B skill set. Damn hard to find because not all pick this form of diagnostics up weather is be Automotive, HVAC like myself(39 years) to even a Doctor or Eye specialist. It is a rare trait to have and I hardly see it anymore these days. Keep after it, I always found the process a absolute challenge and loved it when I won(which was everytime) Lol.

[@fordneuscheval]

my man! thank u for the video! its hard to get this fuel pump power figured out-but now its easy! 2001 gmc 3500 boxtruck fuel pump issues-39f-KS ♥scannerdanner

[@MrLoboreview]

Thank you so clear and thanks for keeping the tools simple .........snapon scanners are way too expensive......i've learned a lot from you ...ill buy your book THANKS SO MUCH!!!!!!!! Please more vids on how to use dvmm

[@HowlerWelding]

... After testing to this point, I can turn my attention to the load connected to the 87 terminal. If it is a pain in the butt to get to (like a tank mounted fuel pump) I can use the DVOM on the Ohmmeter and test between terminals 87 and 86 which tests all the wiring and connectors between the relay base and the pump, the pump itself, and the ground wiring and connections to the battery AND back up to the relay base at terminal 86. Pretty simple, and darn fast... No T-Pins, No Stabbing wires...

[@pr17bt]

Thank you for explanation and sharing your knowledge 👍🤝

[@RJC3po]

I have a general question. Why is it that some systems switch the supply side of a circuit (Fuel pumps for example) and other systems switch the grounded side? (Injectors, ignition coils for example) What is the advantage? It would seem to make more sense and save some wiring costs, by switching the supply side and have a central distribution for the signal common return path (body ground). Thanks for making these videos, I really enjoy watching them and they help me to become a better Tech.

[@jono0309]

Great video!! It is people like you that help the hobby!!!!!

[@ScannerDanner]

sorry man you are wrong here. the ohmmeter does NOT stress the circuit and you can have resistance problems that will be un-seen until the circuit is loaded. Watch my video on "Toyota Echo No Communication Case Study" to see how accurate the ohmmeter is. This car had bad computer grounds that showed 0 ohms of resistance on the meter! You cannot ohm test the load side of a fuel pump circuit and claim the circuit is good by your readings on the ohmmeter. This is basic electricity 101

[@cagonesss]

ok thanks alot yes i used crimp connectors but i didnt trust them so i dropped the tank again to make sure they were good and tight and they were ,it takes me less than one hour to drop and install back the tank not hard on this truck.guess i had a glitch in my mind nawing on me lol maybe im mental lol had a weird filling .hey but thanks now i know next time i wont blow up ill be more confident learned something new.thanks alot for sharing have a good day guy.

[@ScannerDanner]

correct, and with that comment, you yourself have just condemned the pump! Because a good pump would load the circuit and cause voltage drops in the wires that we would have seen as soon as we plugged in the connector.

[@LifeSavingDefense]

The cap on those relays comes off really easy and you can access the terminals and watch it click or even tape it to on but relays have a purpose so do at own risk

[@ScannerDanner]

first, substituting a know good component is not troubleshooting, not to mention when you work on 20 different car lines like I do you don't have vehicle specific relays laying around. Also there is NOT one way to do things. I'm sure your method works great for you. You come in here and want to critique my methods and tell me I am wrong? You have yet to do that. Show me where I am wrong. Give me a scenario where the methods I show in this video will lead to an inaccurate diagnosis.

[@ScannerDanner]

The pump current will heat this high resistance wire up even more causing a large voltage drop. Something the test light cannot do alone. And something that the ohmmeter may never see.

[@ScannerDanner]

Yes, as long as you have the adapters to "T" into the psi line or connect to a shadder valve. Most good fuel pressure kits that have all of the adapters will run you about $500, but if you are only doing GM or Chrysler you could get away with a $30 pressure gauge from your local parts store.

[@autumnrowe1297]

On. Pt cruiser. Just had the ad key remade due to j broke the one w/ fob Need key no fob, first. Ivhf rear lights stayed on without key in ignition. Still no start at this time. Few hours later car started but still tail lights stayed on. Got a new battery. And now no start . Question is how do I get this fumed started

[@ScannerDanner]

@MrLoboreview No problem, keep watching for them and thank you

[@ScannerDanner]

What did you use to hold the wires together? Hopefully at least a good crimp connector. Anyway, if the hot-wire touches ground it will blow the pump fuse. There will not be an explosion as long as there are no external fuel or vapor leaks. If the wiring splices were done inside of the tank unit, there is no danger as there is no oxygen in the tank. Even if the power wire touched ground it wouldn't explode.

[@MacroMicro99]

Wouldn't it be easier to use a power prob? That way you know you have a good ground straight from the battery?

[@ScannerDanner]

Love that tool for the ground extention too. Easier? I'd say no. Another way to test the circuit? Absolutely

[@HowlerWelding]

Big difference between Test Lights and Circuit Testers... Test Lights are usually the low impedance Incandesant Bulbs that can flow sufficient amperage to complete a circuit and overload electronics. Modern day Circuit Testers are High Impedance and as such do not load the circuit and do not pose a risk to electronics. I use both. A Test Light for down and dirty testing on things like auxilliary lighting, and a proper circuit tester for anything involving fuses, relay bases and electronics.

[@HowlerWelding]

Electricity takes the easiest path to ground - Using your method, whether the pump was working or not, the test light would illuminate... About the only condition that would affect the test light the way you have it connected would be a short to ground in the pump causing the fuse to blow... High resistance or an open in the pump would cause the test light to act exactly the same as it is connected before the pump and in parallel.

[@chrisruth2040]

Where can get tee pins. I'm looking at 2001 F-150 4.2 fuel pump not coming on. I checked fuse and relay are good. I guess next step would be is to check my ground/ positive side of fuel pump connection. Correct

[@ScannerDanner]

Walmart is the craft/sewing needle section

[@ScannerDanner]

These are NOT assumptions. I properly identified an open in the pump as the primary cause! Not guess work. I already described what an open or high resistance problem would do on both sides of the circuit! If you want to argue that I could have a wiring problem IN ADDITION to having an open in the pump, that I can give you. This vehicle is still getting a fuel pump as it is proven defective. And as the truck sits now, the fuel psi problem IS NOT because of wiring!

[@leroyking3058]

Hi Mr.Danner. you was telling me that I need to change the transfer side on my '12 dodge charger 133k miles that the fuel pump keeps. dieing. When I did change the fuel pump both times the car fire right up..is there anything else I should be looking into.. Thanks alot for your time.

[@ScannerDanner]

If we were talking before, reply to that original thread. I have ZERO context otherwise

[@Mikeoscope]

Very good video.You will make a good teacher.Good job.Keep it up!

[@ScannerDanner]

@chamosvin Great point! First we don't know if there was current flow, I never checked it. Second, lets say there was no current, you are correct, the test in itself would be inaccurate, however combined with no fuel pressure and a good power feed, if the ground was bad (causing the no current flow problem) the test light would have light when I turned the pump on. I agree the test light is not the best tool for this however I wanted to show using it just in case it is all you had.

[@gilligan1127]

I have a fuel gauge that is not working? Same thing as what u got in the video is the duel tanks 3500 GMC 2003. The gauge did work but only from 1/2 to empty. Now it don’t work at all. Question is how do the tanks work? Front tank has the sender in it or do both. How do u test the sender to c if it is working. Also dump truck.

[@ScannerDanner]

Both sending units feed an input into a module that then signals the gauge. Both float resistors have to be working or you'll have exactly what you describe. These inputs are super important as one tank only has a low psi/volume type pump that feeds the front tank (I think). And only one tank (front tank) has the high psi pump.

[@gilligan1127]

ScannerDanner so both tanks have a sending unit? The back tank is unplugged, not sure why. The plug is corroded and won’t plug in. Can u post a video on this about a fuel gauge problem with duel tanks please!

[@1188clean]

cool didnt know that the transfer pump can still work without the high pressure. going to do this on my car because only the transfer pump turns on when i jump the fuel pump relay but i dont hear the high pressure pump. going to do this test of back probing it. thanks

[@marcvario]

hey there you spoke about the pump relay pins 85&86 when i crank the engine i get nothing but do have power at the other pin long story short were should go from there

[@ScannerDanner]

Need more info! Year, make, model, engine, what relay you're testing, what other pin that you mentioned, what are you missing?, spark, injector pulse, fuel pressure?

[@HowlerWelding]

If the resistance is of a large enough value that the wire is only able to conduct milliamps?... It would be enough to light up your test light, but not enough to power up the pump to do anything. That is why I test the way that I do with my Voltmeter and the test leads I have - It gives me measurable PROOF of what the circuit can conduct in a loaded situation and removes the interpretation and guess work. I have Static Voltage and Loaded Voltage.

[@euonymus1980]

Great video! I thought i have a bad fuel pump but im getting 11 volts at the fuel pump connector with the car off and key out of the ignition. Is thst normal?? Fuse and relay are both new as well. Thank you!

[@ScannerDanner]

What year, make, model, engine? And what exact wire are you testing? I'm assuming you don't have fuel psi?

[@euonymus1980]

@@ScannerDanner Wow. thanks for the reply! 2007 kia sedona 3.8 v6. 211,000 miles. No fuel pressure and no hum from tank. Its very easy to access from the back seat floor. It kicked on once but sounded awful. Cant get it to do it again. pulled the 3 pin connector at the pump and just check dc volts there.

[@mezgebuabebe2503]

thank you very very very very very much. appreciate for taking your time to share your know how,,,,,,,,,,thank you again

[@ScannerDanner]

Thank you very, very much for watching and for your comment. I have a lot of other fuel pump related videos if you needed more help in this area. Thanks again

[@ScannerDanner]

I proved that the no fuel psi, non running fuel pump was NOT because of a bad ground. A ground that was bad enough to cause a no psi problem would have lit my test light like a power wire. It is not guessing at all. Again your last question is the same as on the power side. If the ground wire was able to support my light current and NOT the pump, as soon as you plug the pump in and load the circuit the test light would light brightly.

[@Joseph-iw7su]

My 89 Silverado manual said I had a pump test port coming off the relay. I had no port, but using the schematics, I isolated the lead to the pump coming off the relay....still NO pump action. Changed the pump....energized the lead, still no pump action. Had a brain storm and reset the computer......VIOLA! pump works. Hooked up old pump to 12v.....IT WORKED! I may have changed my pump for nothing....but it was 29 years old anyway. But.....BEFORE any troubleshooting or repairs....RESET THE COMPUTER. It may just be that.

[@iggy9907]

Joseph Hugh where is that relay at? I also have an 89 Silverado and cannot hear the fuel pump, I believe it's a relay also because the pump isn't more that 5 yrs old. Thanks

[@iggy9907]

Joseph Hugh and how did you reset the computer?

[@cheeseburgers82]

I can totally understand the pins inside of the plug being pushed apart but on your test light you don't have to shove it in there either if you just put the end of the test light touching the metal inside plug without shoving it in you can still get a reading without damaging the pins

[@ScannerDanner]

No damage to this one. And you can't touch the metal inside without shoving the lead in. I'll give you a T pin with a smaller diameter point would have been ideal

[@dat4211]

2008 Chevy Tahoe put in new fuel pump still wouldn't start unplugged connector and started working put everything back together had it running them it died will now just start for a few seconds do u think I need to replace the wiring harness going to the pump

[@ScannerDanner]

+Donya Kerby you need to do some voltage measurements to confirm where your problem is. It can be as simple as a bad ground eyelet on the frame.

[@cagonesss]

got a question.i just installed a new pump on my 96 explorer had to clip and connect the new wires to the ones coming out the top.my question is if a wire say hot wire comes apart from my connection and touches ground or the assembly metal can that cause an explosion will it spark or is it safe?im kinda scared driving it because i have that in my mind should i drop it and make sure its super tight?or am i ok and safe if it would disconnect and touch?maybe its desighn to not spark?thnks sir

[@ScannerDanner]

what is your fuel psi? is this a port injection system or throttle body

[@p0k7lm]

tnx 4 video ! donthave a scanner , but i use ohm meter to test continuity with power off drawing and figuring the circuit on paper , some times with battery installed taking voltage readings of wiring points and knowing how the relay is wired , using my own jumpers to power up fuel pump at the relay terminals .

[@ScannerDanner]

@roro560v8 Can you check for me to see if the sound is fixed now?

[@kg1016]

Thanks for this. Nice and thorough. But if I may ask, what if at arriving at the connecter there was no power. Where would you then start your search for the voltage loss. I have a 2001 Corolla and checked the relays as you show. but when I get to the tank there is no voltage when I turn the key to crank. 15 amp Fuse under hood not blown but when I removed it to check condition the radiator fan started.

[@kenbehr5501]

What would you do if you only had 5 volts at the pump?

[@ScannerDanner]

It could be a frozen pump and the 5v you're seeing is from a voltage drop from the power wire heating up. Do an amperage measurement to determine. If it is super low, you have a wiring problem on that feed wire. If it is super high, you need a pump!

[@kenbehr5501]

That's what it was thank you very much my friend I am so happy I found your channel. Amen

[@ScannerDanner]

@@kenbehr5501 frozen pump? What was your amperage? Bet it was 19 amps on a 20 amp circuit?

[@keithjohnson7311]

HEYYYY ITS SCANNER DANNER AFTER WATCHING U WITH ERIC CAME TO YR CHANNEL

[@tammymarglon-desmet984]

One more question. I don't have a scanner or help but do have a test light can I leave the test light in while manually jumping out and turning the igniton over to test it or am I gonna need another person to turn it on

[@bathtubrenew]

hi bud, nice video! i have a weird issue on my 99 chevy venture. van died on me, i couldnt hear the pump prime on ignition, i changed fuel filter, the relay clicks but i changed that as well, i replaced pump with a spectra after-market, it buzz's on ignition but dont not have any pressure, i even popped the fuel line off to the filter and zero fuel is present, its like the manufacture of the pump forgot to put in the impeller, i called supplier they told me possible bad pump, i removed and installed another new spectra pump, same darn thing again. i have now ordered an OEM pump, we shall see the results tomorrow. any ideas??? what type of voltage should i be getting out of the 4 pin plug that plugs into the pump unit? if the pump buzz's on 2 second prime does this mean the pump should be pumping??? did i get two bad pumps back to back. any help would be greatly appreciated!!!!

[@ScannerDanner]

@RJC3po If a power side switched circuit gets shorted to ground it will fry the computer driver. If a ground side switched circuit gets shorted to ground it just keeps the output on all the time. No driver damage. Being that every metal component on a car is ground, when there is a wiring problem a short to ground is common. I feel this is a major reason for ground side switching on cars. But I am no engineer.

[@victormendoza871]

What would you do if you had a confirmed good fuel reg. Good circuit and you can hear the fule pump run but no pressure anyway

[@ScannerDanner]

Change the pump

[@billyr9840]

Paul, I have a neat little trick for you, if your in a pinch and you don't have a adapter or as ( tompain111 ) suggested, a amp clamp handy. You can take a couple of pieces ( or as many as you need ) of insulated 18 Ga. solid strand wire, striped at both ends and wrap them around the relay terminals. Being careful of course, making sure they are not Touching/Shorting to each other. You can now plug the relay in and you will now have access to the terminals. It is not as good as an adapter/etc. but it works pretty well !

[@ScannerDannerPremium]

For sure. Done that many times myself. I just don't teach it because of how easy it is to cook the computer driver with those bare wires :)

[@billyr9840]

Can't blame on that ! Just thought I'd pass it on, know you would! Take Care!

[@MrHrivera28]

No matter what some of these nuckle heads say, some of us appreciate your time to show what you can thanks keep up the great work.

[@billyr9840]

What are these knuckle heads saying ?

[@ScannerDanner]

+Harry Rivera thank bro

[@FreeThoughtCrime]

@ScannerDanner Why would there only be a few mV going through the light if the ground is good? I thought that voltage would be the same through all branches of a parallel circuit. Am I missing something?

[@ScannerDanner]

@jose6788 I just check it, seems ok on my end. I guess someone else has an issue too since I got a thumbs down already.

[@stevepooran2240]

Hey quick question does it matter which way the relays go in 85 can be bottem right or top left witch is correct?

[@ScannerDanner]

it really doesn't in most applications. There is a de-spiking diode on some of these, while others just use a resistor and even though there is information out there saying otherwise, I've never once replaced a computer driver where the failure of the driver was due to a relay being installed "incorrectly" to a circuit

[@RJC3po]

@ScannerDanner I agree… Test lights can be deceiving sometimes. I recently switched to using the Power Probe II. I do not know how I have been getting by for so long without one! The Power Probe would have made this job go a lot quicker.

[@angelf9800]

Question If the test lead turns red with power but it won’t come on with ground means you have a bad fuel pump

[@ScannerDanner]

What type of test light are you using? If it is an LED type light, they can be misleading. Use an incandescent style like I am here. Carry the tests out when the circuit is loaded (relay energized) and then yes, that is correct

[@p0k7lm]

can also test motor for resistance compared to new one , and test for open , short and to casing 👍🔩🔧

[@ScannerDanner]

the problem with resistance measurements is, when it tests bad, it is bad, but when it tests good, it can still be bad. The ohmmeter, while useful at times, is the most overrated and misleading tool in your toolbox

[@YoungerPrice]

so if i was using a test light without the scanner i would have to crank the truck to check for power correct?

[@jono0309]

Thats correct

[@bensmith2466]

blown5.3 And if you're lonely, can't see the test light, use a jumper wire, connect to pin long enough to reach cab. So you can see ?

[@tammymarglon-desmet984]

Question.. someone put something in mine and it stretched it so my relay doesn't connect right and sits in there loose. And I also have a prob w my new fuel pump I put in something electrical . So 2nd time having to drop my tank.

[@ScannerDanner]

You can tighten those pins with a very small pick or pin

[@tammymarglon-desmet984]

Ty so much! I'll give it a try. And ty for the video on how to test my fuel pump u rock!

[@justin6296]

good spark fuel pump turns on. but im only gettin 11 psi. could it be a bad relay or bad pump

[@ScannerDanner]

Thank you very much! I've gotten better at shooting and editing of videos since this one was done, so sorry about that but at least the content was still good.

[@HowlerWelding]

Rather than pick apart what you did any further, it will be faster to explain how I do electrical diagnostics. This will be specific to a normally open, power side switching relay controlling a power source being applied to a load. I grab an LED Circuit Tester and check the fuse then move on to the relay base. I check for power and ground in the control circuit, then for battery power at 30 and a load at 87. If all this is good, I can either test the relay or substitute in a known good one...

[@strattuner]

if you're fixing cars and trucks you're doing it right,don't worry about what people think,most can't hit their asses in the dark,and they own the ass

[@TheReptilianman]

Hey, I have a 95 Astro van it has 0 fuel pressure. I replaced the fuel pump and strainer, icm, and filter. It cranks but won't start. I know I have spark, itll turn on with starting fluid but then shuts off after.

[@chucklaneChuckylane]

I have a 94' GMC Sonoma and can't locate the fuel pump relay. Unlike a Lumina I owned, there is no box under the hood w/ all of the relays. Could you tell me where they would be located or the one for the pump anyway? Nothing under the dash even looks remotely close to a relay.

[@ScannerDanner]

+chuck lane (Chuckylane) sorry, not off hand. You'll need to do a google search

[@chucklaneChuckylane]

+ScannerDanner thanks, I'll try that.