Restart on warm engine causes start-stall

[Nabeel Rahimpour]

Hello!

I have a 1988 VW Cabriolet, Manual, with over 300000 km on it, with the Bosh mechanical continuous fuel injection system.

Recently, the car will start and run fine, but after it warms up, it becomes hard to restart after you shut it off.

Usually on the first start it will crank, and seem like it’s going to start like normal, and just stall immediately afterwards.
After that, the crank times increase, and it becomes harder to start.

Starting with my foot to the floor, it will start easily and rev up, and which point I let go of the gas to not over rev the engine, but then it falls below the idle RPM sputters and chugs a bit, and sometimes stalls, other times will clear up and go away after a while of struggling.

When it struggles, it almost sounds like some of the cylinders have a dead miss, but once it clears up they all seem fine.

If I can keep it from stalling, and snap the throttle a couple times, it will clear up and go back to normal.

It almost sounds like it’s throat is clogged and needs to be cleared out, if you will.

I’m thinking it’s leaking injectors, and it’s flooding the intake manifold and, then the engine when I try to start it. And if the plugs get soaked, wouldn’t they have trouble igniting, thus causing that miss? Dom’t know how off base or on base that is…

Any suggestions, how should I start diagnosing this?

Just to add; when I park this car for a long time, I pull the fuel pump fuse, so I can crank it for a bit before starting it go get the oil flowing, before I let it light and run.
Their have been times, that the engine has actually tried started for a revolution or two, without the fuel pumps running. This is yet another reason why I think I have leaky injectors, because with no fuel pressure, it shouldn’t ever run, right? Unless the fuel in the lines was leaking into the intake?

Thanks,

Nabeel

Topic

[Andrew Phillips]

It sounds like you are on the right track with the injectors. They should probably be replaced if they are suspect. Most injector service companies will not work on them. Pull one of the spark plugs when you have a no-start condition and see if it is wet with fuel.

[Nabeel Rahimpour]

Is it safe to do that when the engine is warm?

[Andrew Phillips]

Yes, as long there aren’t any sources of ignition (such as a cigarette or open flame).

[Chris Orlando]

Check these videos for some general CIS troubleshooting and seeing what sensors to take into account and what should be doing what.

https://www.youtube.com/watch?v=yBwVfpPqSRM

The number 1 cause of hard hot starts in a CIS system is a bad fuel accumulator.

It really helps to have a high pressure fuel pressure tester when doing anything on these systems. If you have a pressure tester, you will pinpoint problems like this in just a few moments Vs. testing / replacing components haphazardly.

[Nabeel Rahimpour]

I was more worried about the engine block rather than my personal safety, haha.

[Nabeel Rahimpour]

Wow, those videos are great, thanks!

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