Re: Hot start problems- 5kcstq

[Orin Eman <orin@wolfenet.com>]

Once vacuum leaks have been ruled out, and assuming compression
is good...

My '86 5kcsq was very hard to start after being left for a while
in hot weather.  The fuel pressure would drop too quickly
after the engine was shut off.

Injectors are the first thing to look at - pull them and check
if they leak after the engine is turned off.  If the car is
well on the way to 200k miles, it's best just to replace them
with the newer viton-tipped injectors.

The fuel pump check valve would be the next suspect - there is
a test in the Bentley if you can get a pressure gauge with
the right adapter.  If you end up replacing the check valve,
just replace the pump too... too much grief diving in the
gas tank not to.

Then I'd take a look at the o-ring on the fuel pressure regulator
in the fuel distributor.  This can leak pressure when it gets
old and hard.  Just setting system pressure back up to the
high end of spec and replacing this stopped an UrQ I had
losing pressure.

Then make sure the injector fan is working to prevent vapor
lock in the fuel lines to the injectors.  This can cause
strange effects as the fuel vaporises and pressure _increases_.

Orin.

> I used to think that too, but I rigged up a test to check.  I spliced in
> a 12 volt direct supply to my fuel pump via a dash switch (some of you
> are probably starting to wonder just how many extra switches does this
> guy have in his dash...but I digress) So before starting the car, I
> would run the fuel pump for a minute or two.  NO EFFECT AT ALL.  It was
> just as hard to start.  I once tried leaving the pump on for several
> minutes to build up pressure and same thing- no effect, still did not
> want to start and my battery did not appreciate it either.  I am almost
> convinced that this hot start problem is related to the air flow plate
> and/or the warm up regulator and that is where I am focusing my
> troubleshooting as well as still looking for any vacuum leaks.  When the
> engine is cold, the cold start valve primes the engine, which fires and
> creates enough vacuum to lift the air flow plate and open the injector
> plungers.  When the engine is hot, there is no priming from the cold
> start valve and if there is a big enough vacuum leak the airflow plate
> won't rise to open the fuel injector plungers.  I imagine it could be
> one large vac leak or many small ones (valve cover, cracked lines,
> injector seals, etc...)This is my theory anyway, but I am willing to be
> proven wrong.