1995 Chevy S-10 6 cyl Two Wheel Drive Automatic 135000 miles
Truck developed a problem with stalling after 15 minutes of driving. If starting fluid is sprayed in intake truck will start momentarily. Ignition was checked with spark tester and blue spark. Last part replaced was PCM. After replacing PCM truck was driven 2 hours before failure. When symprom starts to appear truck will start surging or bucking. Feathering of throttle seems to keep running until about 5 additional minutes when truck completly stalls. Letting truck cool down for 10 min will allow a restart and can be driven for a couple of min before stalling again. Fuel pressure guage was left installed and showed 60 psi a time of failure. I have a OTC 2000E scan tool but did not think to leave hooked up. Do not know what I would look for at time of failure. I really thought PCM not pulsing injector was going to fix issue. I have heard that the TCC solonoid in the transmission or other solonoids could intermittently short and cause PCM to go bad or maybe cause intermittent failure. Would not know how to diagnose. I am fairly skilled in Automotive diagnosis and trouble shooting to componet level and would like to stop swapping and pin point failure to componet. Parts replaced fuel pump, fuel filter, distributor cap and rotor, Ignition pickup, PCM, Spyder injector and fuel rail. Previous responses in other forums lacked any valuable troubleshooting advice. I appreciate any help. I know this is a weird one and most difficult to diagnose. Thank you!
Make sure you are reading the correct fuel pressure
as if it start and run after stalling and by you using starting fluid its an indication its a fuel problem
two things very common fuel pump failure and or injector
7 out of 10 its the fuel pump also check the connector wire at the fuel pump top of tank
also after it stalling was the injector pulse checked?
Do a fuel pump flow test
June, 12, 2009 AT 1:53 PM
The fuel pump pressure is 60psi while running and key on after stalling. Voltage drop at connector at tank is visibly fine and voltage and voltage drop indicate no issues. Flow test indicate no issues and since pump is brand new I suspected it would be ok. This is a CPFI fuel injection. The injector is underneath the plenum and I would not know how to check whether it is being pulsed when it fails since the noid lights I have need to be plugged into the injector connector. I believe the injector is not being pulsed which is why it will run until the fuel I spray into the intake is exhausted. Issue is why is the injector not being pulsed? I need some new ideas to diagnose. It is not the fuel pump or the connector or the fuel injector assm (it was also replaced). It is not the PCM unless it is new defective and suspiciously has the exact same issue. I have seen several posts in this forum with the exact issue on the same vehicle but never past the original answer which is the same answer I was given here. I have seen the throttle position sensor mentioned as a suspect. That a wide open throttle position would shut down the injector. Does theis make any sense? I should be able to see this on a scan tool should'nt I?
June, 12, 2009 AT 5:57 PM
The big square black connector on top middle is the injector wires
unplugging it will allow you to access the injectors wiring and check for injector pulse
TPS if you have a scanner check TP volts it should be under 1 volts
if higher than that TP at fault
also check coolant sensor
June, 14, 2009 AT 2:45 PM
The failure has become more consistent 10 min of driving. I replaced the Throttle position sensor and temperature sensor. This did not fix. I was wiggling the wires for the 5 connectors at the PCM and it appeared to be influence the problem. One time the truck shut off while I was wiggling the wires. I pulled all connectors and inspected for backed out connector pins and corrosion and found nothing. I looked for poor crimps and found othing. If I knew the pins that might be suspect for pulsing injector or inputs that would keep the PCM from firing the fuel injector it would allow me to proceed further. I need some specific theory on the functioning of the PCM in relationship to the Fuel injection system. It always shuts down after it is hot 10 min and when allowed to cool 5-6 hours it will run for 10 mins.
June, 15, 2009 AT 6:24 AM
Fuel Pump Oil Pressure Switch (Back-Up Circuit)
To test fuel pump oil pressure switch back-up circuit, start engine. With engine running, disconnect fuel pump relay. If engine stalls, fuel pump oil pressure switch is faulty. If vehicle continues to run, switch is okay.