RE:5KCSTQ Hot Start Problem...the saga continues

[Russ Southelrin <russell.s.southerlin@lmco.com>]

Phil,

> This is the exact same problem I had with my '87 5TKQ.  I tried the fuel
> check valve, injector cleaners, pressure regulators etc.  The problem
> persisted.  The fix?  The dealer tested and replaced all 5 injectors. 
> They were all leaking down.  It was expensive - about $500, but the car
> starts immediately every time, hot or cold.

If you blindly replace parts this is what you have to do.  If you check
the system, control and residual pressures this will tell you if the
check valve, press. reg., warm up reg. are O.K. 

>That's why we recommend checking the check valve (about $15) first.  But, at 
>the end of the day, the injectors are one of the most _likely_ causes.  Just 
>unfortunately the most expensive.

>And as a comment to a half-forgotten thread - you can't test Viton-tipped 
>injectors with air.  In fact, the factory manual specifically states that you 
>can't perform _ANY_ meaningful tests after they've been out of the car for more 
>than an hour.

Is this because of the temperature?  I have tested injectors with air
and have not gotten very good results.  They seem to open at about 60psi
and with soap suds on the ends they would "leak" (bubble) down to
55psi.  I tried all 8 of the spare used ones that I have and all 8 did
the same.

In the hopes of finding a better way of testing for leaking injectors, I
have also rigged up a pressure gage on the injector line itself and
found that at idle they were at 55psi and would increase to 60psi just
off idle and then would settle at about 60-65psi as the throttle was
opened.  This agreed pretty close with the results I got with air (even
though I could not conclude if any one was actually leaking with air). 
When I had the injector pressure gage hot soak for 15 minutes the
pressure went up from 45psi to 48psi.  I was hoping to find that one or
more injectors lost pressure during the hot soak but I guess mine were
all good.

Just my .02 worth.
Russ
87 5KCSTQ
Littleton,CO