97 Blazer Starting issues

[supermann236]

I have a 97 blazer that has starting problems, When cold it starts right up, no issues. Once I drive for a bit and shut it off, when I go to start it when its still hot, it will either just sit and crank or it will stumble. If it just cranks I have to cycle the key for a few times and then is will start fine. If it stumbles I can usually catch it with a pump of the gas pedal and the it runs fine. Once running no problems. While idling engine does seem to loop a bit, little throttle everything works fine....ANY IDEAS?

[old_master]

Check fuel pressure and leakdown. Key on, engine off, fuel pump running: should be 60psi to 66psi and remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. Post your results.

[supermann236]

Fule pressure with key on is 60psi...looks to be about 56-57psi while engine is running....and held 55psi for 5min with no sign of losing pressure.

[old_master]

Fuel pressure and leakdown are within specs. Unless there's an intermittent problem, fuel delivery is OK. Is the check engine light on? If so, have you retrieved the codes? How many miles since the last good tune up, (plugs, wires, cap, rotor, fuel filter) with AC Delco parts?

[supermann236]

tune up was all done recently. i did change the fuel filter (it was pretty gummed up) seemed to help. The engine light does come one every now and then, but i cannot get the codes because when i hook a scanner up it says there is now comunication with the computer. The truck also has a small draw on the battery. Kills the bat when it sits for 3 days. No sure if this is all related to the same issue or just small ones all at the same time. Any ideas on all that. I did order the multi port fuel injection conversion that I am also going to install and hopefully solve all fuel problems. Do you know if there is a common problem why I cannot connect to computer?

[old_master]

What brand of parts did you use on tune up? Several aftermarket manufacturers can't, or don't, manufacture parts that work well in the 4.3L engine. Bosch spark plugs and Autozone cap and rotors are especially poor performers. 97 has some known issues with the ignition switch which can cause symptoms as you're describing also. Have you checked fuel pressure when it won't start? Having to cycle the ignition switch could indicate a loss of fuel pressure, which could be due to a pump problem or the ignition switch is not supplying power when and where it should. I doubt if the CMFI conversion will help as it has to do with misfires and stalling, rather than a no-start condition. The fuel pressure and leakdown test that you did does not indicate a problem with the injectors or fuel pressure regulator. Be aware, the CMFI conversion is a step backwards in technology, and your fuel mileage may suffer after doing the conversion. If your scan tool or code reader can not communicate with the ECM, check the orange wire in the data link connector under the dash. It should show battery voltage at all times. If no voltage, check the fuse. Is the scan tool that you're using capable of testing the BCM, ABS, SRS, or transmission? If so, does the scan tool communicate with any of those modules? If the SES light comes on, there is a DTC stored in the history file and a capable scan tool can retrieve it, (not a code reader or scanner). Code readers, like the ones Autozone and Advance auto use, are not capable of retrieving history file DTC's.