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Discussion Starter #1
hello,

I am new here and looking for help. I know its difficult to troubleshoot over the internet like this, but finding a classic vw repairman/shop in the baltimore, md area is proving futile.

Does anyone out there know of any mechanic in Maryland that knows anything about the 1979 fuel injected models? (preferably within 50 miles of Baltimore)

thanks
 

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sorry for delay, thanks for responding. i found shop and have been busy getting her to it. not sure if they'll find the problem either. i have a feeling i will be getting her back unfixed and undiagnosed. she's stalling out upon starting and sometimes backfiring. i assumed vacuum, timing, electrical and/or fuel issue, but i have been through everything! well, obviously not everything, but i've hit a wall and don't know what else to check. again, i know these things are difficult to discern over the internet without seeing them in person. any advice as to where else to look or what else to check would be hugely appreciated.:)
 

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Tight tappet or burnt valve is possible.

Are the valve clearances correct and have you done a compression test?

That fuel system hates having a less that perfect vacuum.
 

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Do you know if there are any problems with grounding injector wires to engine? One manual said it was ok. After about 1,000.00 of diagnostic work, my 79 still won't run properly. The problem was narrowed down (I thought) before i ran out of expensive mechanic money - number 1 and 2 cylinders weren't firing. There was sufficient power coming into to the injectors but the circuit was apparently not being completed. Unknown if the wiring back to ecu was good. I figured I could save several hundred more bucks I don't have at the moment by grounding #26 and #27 to the engine block myself - bypassing the ecu altogether. Now she won't fire at all. She turns over strong enough and I was assured that everything else was double checked. I thought if i was wrong and grounded 3 and 5 inadvertently, she would at least still fire on the two good cylinders like she has been. I heard the fuel injected models were trouble. but this is really the only time this model has stumped the crap out of me.
 

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The injectors are supplied with power all the time and are activated when the control unit grounds them so you should have flooded it grounding them, not advised.

Test the continuity of the wires to the ECM. Ideally use an oscilloscope and probe the ECM outputs.

The fuel injected models are fine until they play up, due to not having readable codes it makes diagnostics a bit of a chore because you have to test everything manually although a scope speeds it up alot.

If it's a convertible and leaks the ECM might have water in it.

Bare in mind it's old, wires and terminals corrode and break.
 

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Discussion Starter #7
Thanks Dubsy,

sorry for the delayed response - i have been working on her nonstop. yeah, shes only running on two cylinders it seems. i'll be checking the continuity of the wires next. they are all exposed and look ok - no corrosion. the garage tested both of my ecms and said they tested fine. they even used one of theirs in the troubleshooting process.

thanks again for your advice.

jon
 

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im testing them in the head. power in is good and i am getting continuity in the ground back at the ecm. new injectors, new pigtails, opened the wiring loom all up to check for cracks and corrosion. soldered wire connections at the pigtails. checked all grounds, fuses and even looked for possible loose connections behind the fuse box. still feels like she is only running on two, maybe three cylinders. im really stumped. thanks for your constant feedback. although i have tested both of my double relays, im wondering if its that. if not, maybe its nothing electrical at all, but maybe something more fuel related.
 

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im testing them in the head. power in is good and i am getting continuity in the ground back at the ecm. new injectors, new pigtails, opened the wiring loom all up to check for cracks and corrosion. soldered wire connections at the pigtails. checked all grounds, fuses and even looked for possible loose connections behind the fuse box. still feels like she is only running on two, maybe three cylinders. im really stumped. thanks for your constant feedback. although i have tested both of my double relays, im wondering if its that. if not, maybe its nothing electrical at all, but maybe something more fuel related.
You really need to find that out first, feel the exhaust manifolds just after starting, working cylinders soon heat the manifold, once you know which you test for compression and spark, if they're good it leaves fuel, if it has a port on the intake squirt in fuel to confirm it is a fuel issue, then remove injectors and test on the car but off the head, test electrical and pressure.
 
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