Spark, Fuel and Compression still no start '95 Grand Am quad4


#1

Help!!! I’m banging my head against the wall trying to figure this one out. I purchased a 1995 Grand Am for my son and installed a good cylinder head on it. It ran fine for about a month now it wont start. New coil housing, plugs, crank sensor, tried new fuel pressure regulator, tested ignition module at NAPA, checked for a shorted sensor, took readings from sensors (crank, cam, map, maf, mat, temp, tps) checked resistance on injectors. I seem to have plenty of fuel squirting out of the injectors and good strong spark at all of the plugs. I am thinking too much fuel or spark and fuel at the wrong time. But when removing injectors and plugs then cranking, it seems to be going through the proper sequence. I did scan the PCM with an Auto x-ray scanner and got a code 34 (Map, Maf) but I dont think this would prevent the engine from running. Even with starting fluid it wont pop off at all. I thought water in the gas or plugged converter/tail pipe but that seems ok as well. I did reset the PCM too and that did not work. The engine has 150 psi in each cylinder. Which is what it was right after head replacement. Ughh, Someone smarter than I please help!


#2

Which sensor/circuit would prevent the engine from running? What does the MAP do? What does the engine (ECU) do with the information it gets from the MAP. Does it set fuel flow?
Maybe, the engine is getting too much fuel, rather than, too little. Hold the pedal to the metal while cranking to start. This will help to un-flood the engine, if it is flooded.
Backprobe (don’t pierce) at the ECM connector wires for the MAP circuit. Check for voltage. Check continuity of the MAP circuits at the ECM connector.


#3

In this case you need to go back to the beginning and start with some basic diagnostics. It sounds like parts are being thrown at a problem without proper diagnostics.

In ALLDATA there is a diagnostic chart called… A-3 engine cranks but will not run, part 1. It gives you step by step instructions on how to proceed and what to check.