no start on a 95 Trans Am

Symptoms - cranks, does not run. Will sometimes try and start to run when fuel pedal is pressed to floor sending clear flood signal.

Has spark at plugs. Verified fuel at injectors - removed fuel rail and injectors pulse/spray fuel. 43psi at key on, will hold after turned off. Have drained and replaced fuel in tank with fresh fuel.

New plugs, wires, battery, ICM, coil, and blue Ford injectors.

I have had 4 optisparks on the motor. The current one has MSD cap and rotor (with loctight), and has been tested on an oscilloscope and verified as good. New harness for the opti to pcm test connector. Has also passed on the opti tests on shbox.com. Last time opti was installed I removed rocker cover and confirmed #1 cylinder was at TDC on compression stroke. The cam pin lined up in the slot on the #1 mark on the back of the opti.

Verified plug wires routed correctly and don't appear to be arching on anything.

No codes stored in ECM. I've removed VATS from the PCM and updated the tune for the ford injectors. I replaced the PCM ground connector near the coil as the old one had a crack and replaced the braided ground cable at the same connection. Tested the coil, it has 10,000ohms resistance, which seems a little high, but appears to be working ok. Verified each fuel injector has voltage and pulse. Tested temp sensor at water pump and it checks out ok.

Things I have not confirmed are: compression test, timing chain it could be off a tooth.

I'm starting to run out of ideas or things to check, and I'm just looking for suggestions at this point. This has been one of the most frustrating troubleshooting experiences I've ever had in my 20+ years working on cars.

Just to confirm is there is also a PCM ground that connects to the block just above the starter on the drivers side? What's the likely hood of there being an issue with the PCM?

Thanks, I appreciate any input you guys might have.

Kevin

 

Hey Kevin Welcome.

Do you have access to a scan tool? check and see what your coolant temp sensor is reading cold and make sure its accurate. Very common issue if the sensor is faulty (which doesn't throw a code) will cause a no start or hard start condition. Either doesn't add enough or dumping too much fuel causing a flooding issue.

Another thing to look at is your ignition switch on your steering column. Notorious for getting hot and burning the connector. When key is being cranked it may not be getting a good contact to send to the pcm to run.

 

OP

is this a M6 car?

if so, check NSS (neutral safety switch) on clutch pedal

 

Have you been through the fuse blocks yet? Check the in car and the under the hood one.

How did it drive when it did run before it got to the no start part? If you have spark and fuel you should have a running car. If those systems are checking out it seems like something electrical is causing it. Even a crappy starter could give you those problems.

 

Thanks for the comments guys.

I do have access to scan9495 and the coolant sensor reads ambient air temp when ever i've logged the car. Its connected to the harness, but not plugged into the water pump as I have the pump off just for ease of access while trying to get the car to run.

This is a automatic car, but good point about the nss sensor.

I've checked all the fuses relating to the PCM, ignition and fuel systems i can find. Swapped most of them out with other fuses and verified voltages at the block.

The car ran previously but the water pump leaked on the original optispark and it died. It hasn't run since.

 

so what kind of Opti is in the car now?

 

It has a rebuilt GM unit it in now with the mitsubishi sensor. I've had 2 oem GM ones in it, as well as a Chinese one, all produce the same results.

I also removed the EGR valve last night and tested that it will open and close under vacuum and isn't stuck.

 

Double (triple) check your firing order and that the correct opti port is going to the correct spark plug.

That narrows things down significantly. Unless you removed the timing chain and gear, there's no way for it to have jumped time due to an opti r&r. Same for compression test, unless there's another part to the story. That leaves electronics or fuel. Sounds like you've got fuel - so that leaves electronics. You said the opti tested good on a scope - was that scope a bench-test or an on-car test?

It ran before the opti work, so it is something associated with the work itself. Check every single wire that was touched during the r&r. Put your hands on each one and check for continuity. Check each connector and check for continuity.

 

well assuming the "rebuilt" AC Delco is not bad out of box.

If you have scan ability to see if hi or low res code is not present.

not saying this is your issue but an example of WTF could this no start be after checking what you have...for me after several optis just by chance (when it did start with a brand new dealer installed AC "new" Delco Opti back when) I just "touched the wires going into the long 4 pin connector going into the opti. Car immediately died.

Turns out the factory GM harness had 1 wire (brown) that was not "crimped" just "in" the pin just came out when I 'gently" tugged on each wire to check. Needless to say that was my "needle in the haystack"

my point is really check every wire associated with the Opti, ICM, coil. Sometimes all "looks" good but further inspection by unraveling tape/conduit you find small breaks in wires. 20+ year old wires laying on engine or near it finally crap

I doubt seriously your timing chain jumped a tooth.

yeah PCM can go bad. Not very common.

 

I know you said the cts is reading ambient temp, but I'd replace it just for the hell of it. Also, make sure you're getting 5 volts to it. That's really the only thing I can think of that has the no start, clear flood mode symptom. Also, wouldn't hurt to check the plugs again, because they become fuel fouled almost instantly with a bad cts