[T3] I think I found my stalling problem!
phil.hof at ostronic.org
Mon May 30 10:08:24 PDT 2022
I am posting this here and on the Samba.
I have been fighting a stalling/no-start problem when Clemmie warms up. I’ve replaced many components (like I tell others not to do!), and have had some temporary success, then a new problem.
But I think I have a breakthrough. I hooked up an engine bay remote start wire harness so I can crank it remotely. I added a fuel pressure gauge. I left the timing light hooked up. And I added a small harness so I could operate the cold start jet on demand. All this was to separate various potential fuel and spark issues once the problem shows itself.
And I think I have it!
I noticed the fuel pressure dropped near zero, followed by the sputter and stall. At first I assumed the pressure dropped BECAUSE of the stall, but it looks to be the opposite! One stalled, the pressure stayed low during cranking.
Faulty fuel pump? I jumped terminal 19 to ground, and the pump operated. I could see it stayed steady at 28 psi, and with the remote switch she started right away and was stable.
So AGAIN, the pump relay ground circuit, likely the output transistor, was failing when hot.
I had replaced my original ECU with a Bosch rebuilt unit from many years ago that I kept as a spare. It worked… for a while, then the warm stalling happened. The old one was a hard fail, this happens only when warm.
The odds are very small, but this is the likely culprit. I’ll have Jim Adney replace my old ECU’s transistor, and once done, maybe also the “new” one to again have as a spare.
But if the temporary jumper works consistently for the next week or so, I’ll take the chance that this is the real fault, and leave the jumper in place for the Invasion drives. I”ll want it to work correctly for safety’s sake, but this will be an acceptable risk to allow me to drive Clemmie, and not another non-VW vehicle in a couple of weeks.
I am excited, and I hope it’s not misplaced. I've had several “aHA!” fixes, only to have new problems. Fingers crossed this is the last one!
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