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

2001 GMC 3500 8.1L engine with no fuel pressure. In this video I am showing how to test the fuel pump electrical circuit using a test light and scan tool.
Engine Performance Diagnostics chapter 16
Symptoms
- no start
- no fuel pressure
Fix
- replace faulty fuel pump
Tests shown
- how to measure fuel pressure
- how to test the fuel pump relay
- how to test for proper power and ground to a fuel pump
- how to test the transfer pump
- how to test for a proper ground on your test light
- how to command a fuel pump relay to turn on with a scan tool
- how to test the computers control of the fuel pump relay
- how to determine fuel pump wiring without a diagram
Tools used
- scan tool - Autel MS905 MaxiSys Mini Diagnostic System
www.jbtoolsales.com/autel-ms9...
- incandescent test light www.jbtoolsales.com/otc-3633-...
- back-probing tools - AES' Electronics Accupuncture Probes www.aeswave.com/cart.php?m=aff...
- S.U.R. & R FPT22 Deluxe Fuel Injection Pressure Tester Kit
www.jbtoolsales.com/s-u-r-r-f...
Playlist
- (Chapters 14, 15,16) Fuel Delivery and Fuel Pressure Testing
• (Chapters 14, 15,16) F...
Related videos
- How to test an electric fuel pump (1997 4.3L Chevy Blazer CPI)
• Fuel psi less than 50 ...
- Low Fuel Pressure from a bad fuel pump ground (Ford Ranger)
• Low Fuel Pressure from...
- How to test an electric fuel pump (no fuel psi testing) Ford
• How to test an electri...
- Fuel pump electrical circuit diagnosis (no fuel pressure testing) GM • Fuel pump electrical c...
- No Start No Fuel Pressure Troubleshooting
• No Start No Fuel Press...
- How to test fuel pressure, injector pulse and spark with basic tools • How to test fuel press...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[@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

[@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!

[@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

[@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 :)

[@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

[@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

[@csgorton]

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

[@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.

[@orlanmedina3693]

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

[@scottketchum2224]

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

[@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!

[@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.

[@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...

[@nigelstringfellow5187]

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

[@ScannerDanner]

Thank you Nigel!

[@jono0309]

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

[@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!

[@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

[@davidmcmurtry734]

Very informative

[@terrydavidmullins]

Great video! Thank you.

[@bassment03]

Good job man you explained that very well.

[@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!

[@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!

[@Darjan_Spasojevic]

As a professional parts shootah, this is great!

[@Mikeoscope]

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

[@SteveRobReviews]

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

[@ericheine2414]

Excellent, you're a teacher.

[@jonathanwest3656]

Outstanding work professor

[@doug2993]

Good video and knowledge, thank 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.

[@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.

[@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

[@slofr8dan]

Very well explained. Thanks.

[@nicholassmith4172]

Great video. Thanks for the explanation

[@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.

[@speckspeck]

very cool presentation, luv it

[@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

[@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

[@jparson3309]

Great video my friend thank you very much

[@shanebuckles9134]

Great vid life saver for sure thank u

[@codywaite3765]

Great video Helped me with a volkswagen.

[@ScannerDanner]

Glad it helped!

[@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.

[@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 .

[@driscry]

Awesome, thank you for the detailed tips. Very helpful.

[@mikehigby7897]

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

[@ScannerDanner]

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

[@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.

[@j.onofre6613]

Gracias compa por el detalle.. 👏👏👏

[@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.

[@dreamer2355]

Another great video!

[@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.

[@curtisjar]

Good video. Really helped.

[@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.

[@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?

[@TheWhisky81]

Hi Dan, great video here, just wanted to ask could you have gone straight to the pump and tested for power which would have saved you time testing relays and checking they have feeds to them cos if the pump has a good feed then all other parts must be working as i understand power must run through fuse first then the relay and then to the pump?? or was there a reason you went to fuse box first? thanks john.

[@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

[@ScannerDanner]

@PDSVIDEO1966 I just checked it and it is good on my end. Not sure what is going on?

[@ScannerDanner]

thank you Chris!

[@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!!!!

[@RJC3po]

@ScannerDanner Thanks for the response. I understand your point and I think it is a good one.

[@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?

[@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.

[@ScannerDanner]

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

[@lcsliao15]

thumbs up for the touch screen scanner :D

[@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

[@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.

[@george536]

In this case since it was a difficult spot to find ground, a power probe would be more beneficial correct? and awesome videos.

[@IntheBlood67]

Most Excellent!

[@ScannerDanner]

go to my website scannerdanner d o t c o m fill out your name and email and I will send you more information about the ebook. Thanks!

[@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

[@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.

[@ScannerDanner]

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

[@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.

[@nunya8866]

Before I replaced the fuel pump on my 94 silverado c-1500 2wd 5.0 the gauge would go way past the full mark and it would run out as soon as it hit the red for reserve on gauge. Ok now I had to replace the fuel pump and now my gauge isn't working at all and my headlights will go to flashing at times. Any ideas?? Thanks for any help!! Just hitting for any help I can get. Had some guy do the work now with this he seems to have left me high and dry..

[@mattdloughy5369]

So, the relay is computer controlled. If I were to want to know circuit design by looking at a wiring diagram, the wire that didn't go to the computer would be a ground right? Telling me the circuit is power side switched? I get so confused with input and output differences

[@fehronation8310]

Good job

[@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

[@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]

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.

[@lwh7301]

My 2001 Mercury Sable is experiencing sporadic non-priming of the fuel pump, and the car won't start. I wait awhile, and it would prime and start. I measured voltage of 12.6 v at the relay, same as the battery voltage. But at the connector to the pump, I got only 11.75 volts. (I used the battery negative terminal as ground.) Is this normal or is there a wiring problem somewhere? But since the car starts OK when it feels like it, is it the pump that's causing the sporadic non priming? Thanks.

[@ScannerDanner]

@PDSVIDEO1966 can you double check the sound for me on your end? I think it is good now.

[@deviouscarma]

My Fuel pump is constantly priming whilst the ignition is on, i have a CEL light for a code that just comes up as a fuel pump circuit error, im thinking it might be a ground wire or a relay issue, not sure where to go

[@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.

[@alitheballoonguy3036]

I have Acura MDX 2002 crank but doesn't start and the fuel pump doesn't work.i pulled out the electric cable from the fuel pump and it has 5 pins and checked the voltage in every one.only one give 11.5 voltage and the others give zero voltage .is that normal do I have to change the pump or it is electrical issue.thank you

[@justin6296]

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

[@mikeswgr13]

I have a 99 f150 5.4 that wont start if you turn the key on the pump won't run but if you keep cycling the key on and off the pump will come on and run it starts and run fine when you shut it off on it won't start back up the other thing I notice when I checked the fuel pump relay circuit when you turn the key on to prime the light stayed on should that go out in a few sec. any idea of what it could be thanks

[@jackmarks8607]

How many wires should have power at the pump mine has power at 1 wire new pump and only runs on starting fluid Truck sat for 3 years and ran prior now it won't also I don't hear the pump kicking on Could a fuel filter make it not run If it was clogged?

[@oscargutierrez8180]

Good video

[@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.

[@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.

[@gregscrap]

Have a 88 s10 headlights won't work and half the fusebox not working for computer ect acts like half the fuse box not working just curious if you might have lead.also no power to relay

[@cesnep]

Great video. I'm trying to diagnos my trucks fuel pump. The last test you did, doing the ground to ground voltage drop test, I found that my test light is lighting for this one. Does this mean there is a short somewhere?

[@ScannerDanner]

+Well if your test light was connected to ground and the ground wire for the fuel pump motor is lighting your light? You have a bad ground wire. Make sense?

[@cesnep]

+ScannerDanner as in it's not grounded well or it's shorted out?

[@ScannerDanner]

+Well open ground is what you have not a short. Fix your ground wire and or the eyelet where it bolts to the frame

[@cesnep]

Thank you sir. I just finished watching your video on the 99 Ford Ranger low fuel pressure. That helped tremendously. Keep up the great work! Thank you for your time and sharing your knowledge.

[@michaelpearce8661]

I have had a similar problem with my 94 GMC fuel pump on my 94 GMC Sierra 7.4 engine. Parked to do some shopping and came back to the vehicle and it wouldn't start. Changed over the pump relay and no change. Had no good ground either under the hood. Cleaned up the grounding wires and tried to start it and still no gas to the TBI. I ran a test with a multimeter at the wiring link at the fuel pump and it had continuity. I reconnected the link at the gas tank and had examined the wiring at the harness. Not sure what was the cure for the no start but the engine started up like the problem never happened.

[@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

[@felplayvina]

Mr Paul Danner where do you get the T pins?

[@jroman23]

Hi! I very like your videos. There are no much Tech guys out there with that knowledge or do the diagnosis the way you do. I am a Auto Technician and I learn a lot from you, so thank you. I'm curious about or if you can tell me, It is more easy to use the Test Light for this or similar kind of test? What about a Logic probe like "Power Probe"? Do you use it or you prefer a test light instead a Logic probe or other tool? Thanks in advance! My best wishes...

[@ScannerDanner]

I use my power probe at times, but never use or trust and LED type light or logic probe for this type of testing. Just a regular incandescent test light or a voltmeter test with the circuit loaded

[@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

[@ericheine2414]

There's nothing like a nice box. Iron American Dream on KZbin. Guns and Harleys.

[@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?

[@wyattoneable]

Love tests a DIY'er can do.

[@markdivin458]

Help. I have a 2003 mustang new battery but was sitting for a year. needs a jump and starting fluid to fire up. Not getting fuel. fuse is good and no noise at relay. switched with wiper relay and same thing,nothing. Where is the power to the relay coming from. No noise at pump, think it's something easy. please help