shauns@tekcad.UUCP (05/25/83)
#R:vax2:-54300:tekcad:13200004:000:3351
tekcad!shauns May 20 21:41:00 1983
Subject: Rabbit Warm-start Injection Problem
I have been having a problem with my 1977 Rabbit (fuel-injected)
since I have purchased it. After driving the car and the engine is fully
warmed up, if the engine is turned off for a few minutes (i.e. - to run
into a store etc.) and then restarted, it is very difficult to keep it
running. Racing the engine for 10 to 15 seconds seems to cure the problem,
but if it does die it is then very difficult to restart. The problem
appears to be more prevalent in warmer weather.
My local VW dealer claims the problem is due to vapor forming in
the injecter lines and should go away as "summer fuels" begin to be
distributed around the country. He also mentioned a possible fix that has
been tried on some models, consisting of a modification to the cold start
relay that pulses fuel even if the car is warm. He warned that this could
possibly cause flooding under some circumstances and would only help in
getting the car started, not in keeping it running.
Does anyone out there have this problem and know of a method to
solve it?
Howard Kaplan
John Fluke Mfg. Co. Inc.
Everett, Wa.
----------
The problem is partially caused by a very fast draining pressure
regulator on pre-1980 VWs. Fuel simply drains out of the lines,
and until the pump can catch up, the engine stumbles.
Another potential cause is the location of the fifth injector thermo
switch. It's mounted on the block, which doesn't cool off too quick -
however, the air in the intake manifold apparently does, with the
result that the engine starts up very lean in the conditions you
describe. Add that to the previous behavior, and you get an engine
that starts too strong on too few cylinders and then, because the
fuel pressure hasn't built up enough, runs out of fuel and dies.
I have a 1979 Scirocco that has exhibited this behavior for at least
a year, and have had the fuel system apart myself several times and
the car into my local Volkswagenwerk 3 times to try and cure the
problem.
So far, nothing really has done the trick. My mechanic says that the
cause of the hot start problem is almost impossible
to verify except by substitution of parts, and over the past few years
they have noticed that ANY part of the fuel system can cause it.
As above, fuel pressure seems a major culprit, and often they have
traced it to a fuel pressure regulator that's gone south or gotten
dirty. In my case, it appears that my fuel distributor is lunched,
though I'm not so sure.
Often just changing injectors does the trick - for a while. Don't
ask me why.
The 'summer fuels' argument doesn't hold water with my mechanic - he
sees about as many hot start problems in winter as he does in summer.
In general, the Bosch CIS fuel injection system is EXTREMELY
susceptable to contamination of any sort, including water in the fuel.
Too, after about 5 years of operation the moving parts tend to shellac
up, and unfortunately cleaning won't guarantee rejuvenation.
I've gotten so disgusted lately that I have been tempted to replace
the entire fuel system, but I'm not sure even that would work.
Maybe carburetion DOES have something going for it...
Shaun Simpkins
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