1999 Chevy Astro 6 cyl Two Wheel Drive Automatic 106000 miles
My '99 Astro has had various intermittant problems over the past few years, culminating with a no-start
condition. The engine burbles and hiccups, but will
not start. This has happened occasionally over the past
few years, mostly on cold days when the car has not
been used for a while.
AT THIS TIME
* The starter motor cranks energetically
* There is good fuel pressure ( 60PSI ) measured at the rail.
* There is good spark
* I scoped the output to fuel injector 1, and
there are no pulses. Well, there is an occasional
pulse ( accompanied by an engine burble ). It seems
clear to me that the no-start condition is caused by the
ECU not supplying a pulse train to the injectors.
I have verified the following sensors:
* TPS - it was worn, I replaced it.
* MAF - numbers during cranking seem reasonable
* MAP - tested it with OBDII and a hand vacuum pump
* CKP( crankshaft position) - tested it with a scope and
a digital dwell meter. Chevy spec is 40% to
60% duty cycle, measures 51%. Nice pulses.
* IAT ( intake air ) - reading seemed reasonable - 64F -
via the OBDII
* Coolant temperature sensor - also reasonable via OBDII
I am thinking that the reasonable thing to do now is to replace the ECU, but
My question to you at this time is:
What is the short list of sensors that must work in order to START THE CAR? At this time, I only care about
the no-start. I believe that leaves out the oxygen sensors, because the car has to be able to start before they warm up.
If I replace the ECU, there are rebuilts available for modest cost. As a professional, do you have experience with these? Do they work well, or result in a lot of callbacks?
- Jerry Kaidor
have the same problem?
Tuesday, January 19th, 2010 AT 11:26 AM