1988 2.1L Engine Rebuild now Running Rich

[Landojin]

Last year I blew the engine out on my '88 Westfalia; after having the engine rebuilt, I'm now running into an issue where it's running rich.

It seems to run pretty nicely for about the first minute or two and then the exhaust turns black. I've read that the fuel injection system is probably the place to start, but wondering if anyone has seen this problem before?

Thanks,

Lando

[tencentlife]

If it restarts easily and runs OK for a short time then resumes the black smoke, it's probably a grounded O2 sensor signal line. Easy to find by searching here, it's very common.
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[Ahwahnee]

The signal line Chris refers to is the green wire in this photo:

It has a coax shield which is grounded... but if so much as one strand of that coax contacts the center conductor or the female connector it will send a signal to the ECU that things are too lean (causing rich running).

The clue is that it runs okay for a short time - that is the interval when the ECU ignores the O2 signal.

Fix is to just trim the coax back a bit then put some shrink tube on the end to keep it tidy & under control.