Bad ECU? Part 2 of the saga...

[calo1956]

Well I replaced the wiring harness, thanks Kyle from Kyle Automotive Specialties!I wanted peace of mind, that old and brittle harness could have many gremlins and after 38 yrs was time to change it, and I'm glad i did. I hoped that might have been my problem, but also knew it might not, either way i won't have to worry about it down the road.
So it wasn't my problem, and i can't get it to start. I have 28 lbs fuel pressure, i can smell gas, I have spark, but it won't start. new t2 , new double relay, changed the cap and rotor, checked the points, tried changing the coil, changed the fuel filter. all new fuel lines, new injectors. The thing is it ran fine till it craped out after i did the exhaust. it always started, ran ok, timing was set and checked while it was running many times.Ive looked for any wires that might be loose or broken . Could the ECU have gone bad? That and the AFM are the only things i haven't changed. I don't mind replacing them, if there was a consensus that they could be the problem. Im the original owner, and I have restored just about every system, fuel, suspension, etc. I just want it to run, so i can continue on to panel replacement. Some things I'm good at, but diagnosing issues like this isn't my area of expertise, changing parts and up grades I'm good at.Thanks to all who have posted suggestions in the past.

[MarkWard]

What year vanagon? I would start with a basic compression test. If compression is good and even, you can narrow it down to spark problems or fuel mixture. I ask about the year, because the earlier vanagons did not use the ECU to fire the coil. Only the later ones.
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[shagginwagon83]

My mech thought ECU was problem. It was not. It was Idle stabilizing unit.
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Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan

[calo1956]

Thanks Mark,its a 1980. i can do a compression test, but from what i have read about doing them, the motor should be warm, does that matter? The motor ran fine before i got stuck doing a test drive after installing the new exhaust. FYI the motor has only 500 miles on a rebuild. What do you think would be causing the spark or fuel mixture problem, if the compression checks out? like i said, the only 2 things i haven't changed on the EFI system are the AFM and the ECU

[calo1956]

Thanks Shaggin, i don't have one of those, but i defiantly have a issue somewhere!

[Ahwahnee]

You do not need a warm engine to get a compression test that is 'good enough' for your purposes here. The engine will run with low compression - not so much so with no compression.

Have you looked at the spray from the injectors with the engine cranking?

That is the real test for 'getting fuel'.

If you have fuel spraying and your spark test was done at the plugs then I would be looking at timing.

[calo1956]

Thanks Ahwahnee, Ill do the compression test,after tomorrows snow! Do you have to do it with the throttle plate wide open, or that doesn't matter either? And why would there be a sudden lack of compression?Im only asking because I don't know. I haven't checked for spray at the injectors, i can only say that i smell plenty of fuel when i crank it, and i have 28 lbs oh fuel pressure, and the injectors are new, I realize that doesn't guarantee anything. I tried rotating the dist. both directions yesterday,after marking its current position with a pointer. i got a tiny kick once, but that was it, and i have spent much time making sure the timing was spot on before this episode.

[MarkWard]

Air cooled vanagons had a 5th injector or cold start valve. You could be smelling the fuel from it. It is not controlled by the ECU like the injectors are. It has an an external thermal time switch. You say it ran fine before you did the exhaust. You may have pulled a vacuum hose loose say on the brake booster supply or the intake boot. A large vacuum leak has the same symptom of no fuel.
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[calo1956]

Thanks Mark, I am aware of the cold start valve and that surely could be my source of smelling fuel.Im really diligent on vacuum leakes, and hunted down and fixed them all. I have a super clean engine compartment, and didn't see anything disconnected up top, or below. But i surely could have missed something i haven't looked for

[Vanagon Nut]

[MarkWard]

Did you mix up the wires at the coil? The lead for the ECU is on the - side of the coil. It uses that as an rpm signal. Easy mistake to make. Not sure what color wire the replacement harness wire is. Without it, the injectors won't fire. The sparkplugs don't like getting continuously soaked with fuel.
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[calo1956]

Thanks Neil, you are correct about not needing any welding on the exhaust, not to say that I haven't done a lot of MIg welding on the van over the years, but it didn't affect the old motor, to the current rebuilt motor. Good food for thought though, i think unplugging the ECU, and the battery would be a good practice. Thanks for pointing me in the direction of the cold start valve, I will look at posts here on that. As always, thanks for your time and input.

[calo1956]

Thanks Mark, that wire is where it belongs on the coil. this problem started a few weeks ago, and i still had the old harness, I was hoping that the new harness may have been the answer to my problem, but it wasn't.After our major snow storm we have coming tomorrow, Im going to look into some of the things you and others have suggested trying. What about the AFM, do you think that could be the culprit?

[Vanagon Nut]

[MarkWard]

I don't believe the air flow sensor can prevent the engine from starting. Another member described using the fuel pressure gauge to determine if the injectors are working. I'd go ahead and remove them from the intake and visually watch them spray. If the injectors are pulsing, it has to start assuming spark is present. It is rare, but I have seen one injectors short internally which will spray the injectors continuously. That will quickly flood the engine. I would pull the dipstick, check the level, but also smell it.

To condemn the ECU, you need to verify everything else is good. Through process of elimination you will determine if the ECU has failed.

Welding on the chassis with the ECU connected is a no no. High charge rates are bad as well for the ECU.
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[Marshj]

Have you confirmed you have spark?

Additionally one method that has always proved success for me, if something stops working after I do work on a vehicle - consider the cause likely to be from something you changed and track back through that. So any connections related to the exhaust you removed, etc.

[calo1956]

Thanks Mark for your knowledge and input. I can't take back years of welding,but will unplug the ECu, and battery in the future. As soon as the weather improves, i will check if the injectors are spraying, and check the oil as well, and pull the plugs and see if they are wet. So when i have checked for spark, i pull a wire, put a plug on it and lay it to a screw on the block. I see spark, but is that sufficient? I don't know how strong or bright the spark should be..

[calo1956]

Thanks Marshj , like i just posted to Mark i have seen spark, but don't know what constitutes a proper spark. I have had the van up on the lift and checked and checked again for anything that might have been affected by the exhaust install. The only area that i may have disturbed could have been the starter wires, as the heater hose from the heater control was right in that area. But i checked them several times. Im no expert mechanic by a long shot, but it seems to me that something electrically must have gone wrong, I can't imagine that a major motor malfunction took place, but again, I'm no expert.

[danfromsyr]

I imagine that when you installed the Kyle electric harness you hooked the starter trigger wire to the harness. this is the wire that plugs into the solenoid from the double relay. it tells the double relay to turn on the fuel pump while you are cranking the key in the start position.
then
once the engine fires up when you release the key from cranking to run.
the fuel pump is operated by the contact points in the AFM cover.
once the engine fires up and breathes in the AFM flap moves and makes the points contact. but it has to fire while cranking 1st.

so double check that the wire from the ECU harness to the starter solenoid is plugged in and happy.

or
use a small clip and tie the AFM contact points together, effectively bypassing all of that to force the fuel pump to run.. you should hear it..
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[danfromsyr]

Double relay demystified by Colin.
http://www.itinerant-air-cooled.com/viewtopic.php?t=5459
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