Weekly waveform 14 - Fuel rail pulse test

[@macdonaldsmotorworks]

this was a really good vid Chad (like all of yours honestly) but I have to say that my "go-to" test is to monitor the fuel pressure on the rail with wps 500 and manually trigger the injectors with my scan tool or stand-alone injector tester. That way I can see with full fuel pressure what each injector does. This test doesn't let me down, assuming it's not a huge PITA to get to injectors, turn the fuel pump on etc. Nice work once again!

[@billyyoder8171]

Thank you Chad and Val. Have a blessed and safe week.

[@bartscave]

Great video Chad! KY home garage utube channel has good videos of experiments with the pulse sensor on fuel rails. Faults looked more obvious when he divided up lines for cylinder events.

[@jhauna1]

Nice vid bro, I tried this test on a few vehicles and I basically came up with similar results. It largely depends on the location of the pressure regulator, the size of the regulator and some cases the length of the test hose. On another note, you sync from the ignition which fires at compression while the injector fires most likely during the exhaust stroke so tht should be taken into account. Great demo anyway keep it up!

[@ThunderbirdRocket]

Excellent lesson ! Thanks !!

[@Jpilgrim30]

You have three pulses with the ignition disabled during cranking. It looks like the ecm is firing the injectors in pairs on companion cylinders during cranking until it establishes which cylinder is at TDC of the compression stroke. They typically do this to allow for a faster start up vs having to wait for a full cycle to establish which cylinder to fire. With the WPS500 it’s best to use with the pico scope when using it like you would a pulse sensor. On the pico you can crank up the scaling like an enhanced zoom feature.

[@spelunkerd]

I had to watch this one a second time since I was confused by the vacuum port method, and because I was scratching my head as to why the pressure wave begins dropping before the pintle opens (only if the engine is running). When cranking without starting, the wave is nicely synchronized to pintle opening. Maybe the pulse sensor is showing how pressure in the rail is being filled up with fuel, causing a declining rate of positive pressure change even before the negative drop when pintle opens. With so many factors, it is hard to make definitive conclusions unless everything looks fine.

[@ThePracticalMechanic]

I agree with you on this one Dave. I wanted to include this test in the weekly waveforms primarily to start a discussion about the test since I see people asking by about it from time to time in the forums. I have yet to find a vehicle that the test performs well on.

[@lovetolearn5253]

I have a question if you dont mind. I diaged a 05 Jetta with no reverse the other day. It ended up being a siloind sticking. My question is if I ran a amp clamp around each siloind and bidirectional turned them on would I see a difference in the stuck one on the scope? Omhs law says no because all me resistance was the the same. On the other hand yoy can catch a injector by the little hump sometimes.The only reason I ask is to find a faster way to diagnose the problem Without dropping the pan. I never thought to scope it to see if there's a difference.

[@ThePracticalMechanic]

Let me check for some captures I took off my 2005 TDI. It had no second gear shift until warmed up. I tried testing the solenoids the same way I would a fuel injector and got mixed results. It seems like the transmission had 7 or 8 solenoids and I only got a pintle hump on 4 solenoids. I replaced the valve body but never checked the new solenoids with scope. I think it may depend on the solenoid design. If the solenoid is a variable flow with a duty cycle control the hump may not be visible. Many of these solenoids don’t hold up well to constant power so I’m afraid to test them with a jumper and the pcm/tcm often time won’t have by directional controls for them.

[@lovetolearn5253]

@@ThePracticalMechanic awesome just let me know. I just hate I had to tear down the valve body on a hunch and I didn't have proof. Experience lead me down the path but it would be nice if we can find a better test method.

[@sargetester99]

Some of us own the snap on pressure sensor but have no idea how to hook it up to the scan tool. Please show us how to hook it up.

[@theGADGETSplaylist]

This is one I pursued Chad , in a quest to find an alternative to injector balance test ( firing each injector one at a time and measure rail pressure drop method), to no avail. Even toyed with pressure transducer connected to fuel rail, fuel pump disconnected and capturing waveform as rail ran dry. Yes, that was silly. Tough nut to crack.

[@mike-yp1uk]

It looked good on pulse sensor but not enough accuracy to conclude much.

[@Howardtripper]

Can you please tell us again where we can get a break out box

[@ThePracticalMechanic]

I don’t remember a breakout box in this video but I have several of them. My first breakout box was from PICO and I like it the most but you cannot use shielded banana jacks with it. It can with two leads that are unshielded for use with the pico BOB. I now own a generic Amazon breakout box and a couple of GOdiag breakout boxes. AESwave is probably the best place to buy them since they make a nice cable for connecting to ECMs on the bench

[@ttstang43]

i believe just about everything should be in the arsenal but at the same time, you need to know what works properly but also for you.. i know using the transducer with fuel pressure drops on each injector would be a good way to do it .. seen eric o do that..

[@Lambros_Stefaneas]

very nice.

[@brasileirocanadiando504]

Hey there, could I get authorization to translate your videos to Portuguese to make them more accessible to my Brazilian friends? Stay health. Thanks.

[@sargetester99]

Invert the green, its upside down