Hi!
My -89 5,7tpi will not start when it's warm (at operating temperature.)
It always starts right up when cold, and if i imedetly do a "key of" it starts again, and again so the problem isn't the WATS.
It cranks, it got spark and fuel pressure and "pulsations" at the injectors.
when the no start situation apears the sparkpluggs is always drye.
It also ping/knocks at load, but the timing is right at the spot and "everythig" in the ignition is new.
I realy do need some good advise..
Where to start / what to lock for?
sorry for the bad spelling, im from sweden
//Lars

 

Checl fuel pressure hot and cold.

Is the ignition module and pick up coil new? Testing them doesnt get them near hot enough to eliminate all possible failures.

Bad block ground will also do strange things, as will a bad or failing ignition switch.

Also failing injectors will cause the inj driver to overheat in the ecm yet start when cooled.

later
Jeremy

 

Only tested fuel pressure cold so far....
The ignition module and pick up coil is almost new (only 80 miles)
and spark is present when in "hot no start" condition, does this fact eliminate the ignition switch?
sparkpluggs are always drye when in "no start"
Ater start from cold one only has to wait at idle until temp is "normal" and it vill not start. (it apears earlier, but im not sure at what temperature)
but it will run untill fuel tank is empty, if no one tuns the key off...
//Lars

 

This is a long shot, but check the Air Temp. Sensor, and the Coolent Temp. Sensor. Mine had almost the same thing (it would start and within 2 min. it would not start until it was cooled off) It was the Coolent Temp. Sensor.

Welcome to Thirdgen, hope this helps.

 

sounds a lott like my problem.......
the air temp sensor, is it the sensor at the underside/ downside of the plenium?
i think i will change them both just to be sure...
thanks! ...btw. it seems like you and i joined thirdgen,org about the same time (Join Date: Jul 2005)
//Lars

 

post back to let us know

 

changed both temp.sensors (GM#15326386)
the old coolant sensor reading at 70*F was 11000 ohm in stead of 3400...
but the change onley made things wors, now it has to be realy cool to start.
i will not put the old one back in as it is not right and will not solve the problem.
if i give the intake a shot of ether /"startgas" it fires rigth up and then runs when ever so hot.
but the gut feeling is its running werry, werry lean.
the detonation when fast "flicking" the trottle in park is still there - timing is at the spot. and of corse it detonates at load in drive.
fuel pressure is always pressent cold and warm (running 48psi adjusted with vac. hose disconected)
there is onley the #12 code from SES ligth "
"3.8TransAM Bad block ground will also do strange things"
Where more exactley is this ground located?
//Lars

 

Lars,

Read through these postings at this link. May possibly help you.

https://www.thirdgen.org/forums/tpi/...locations.html

 

Read it, found them all (i think) cleaned and remounted them, but the problem still there...
...the problem seems to appear after ecm gone in to closed loop, anyone had a bad oxygen sensor (O2) make this problem?
(as far as i know the normal / common bad oxygen sensor result is a rich condition)

 

i foud the problem to be 7 of the injectors sqeeesing when "hott"
replaced all 8 and newer had this hot starting problem again.