turnerracing354

My car was hard starting for about a week but once it got started it ran perfect. Then i went out to start it yesterday and it just crank and doesnt fire. It almost seem like it out of timing.

I changed spark plugs
The fuel preasure 45 psi
It has spark
It had a code 15 and 18 but when i cleared them they wont come back on.

Any idea would be appreciated.

Chet1185

If you have fuel and spark then that leave air. Is your elbow on all the way? Did you do anything with the opti?


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jloshotz

Engine coolant temp sensor (code 15) and injector circuit problem (code 18). Not sure the bearing the ECT code would have on your problem, but the code 18 would certainly be suspect. Fuel pressure at the rail test port is good, but I the injectors aren't firing...well. The opti does send injector pulse signals to allow the injectors to fire, (low res) have you verified the injectors are receiving voltage with a multi meter or noid light?

Injuneer

The injectors always have 12V on the pink wire in the harness connector. The PCM supplies a ground to fire the injector. Check for 12V at the pink wire in each connector with the key on - there are fuses for the injectors. The only reliable way to tell if the PCM is supplying the ground is a 'noid light. If you have 12V at the pink wire, with the connector off the injector, measure the resistance across the two terminals of the injectors. Should be 12-15ohms.

The coolant temp sensor (CLT) is important to startup. If the engine is cold, and the CLT sensor is not telling the PCM the engine is cold, it's going to be harder to start. And if the engine is warm, and the CLT sensor isn't telling the PCM it's warm, it's going to be harder to start. But it should not prevent the engine from starting.

turnerracing354

OK I have power to the injector. I'm going to go pick up a noid light to check if the pcm is supplying the ground. the injector all have 14 ohms. The coolant temp sensor wire was broke right were it went in the plug, so im going to get a new pigtail and that should fix that problem.

turnerracing354

I checked my injectors with a noid light and they all checked out. I'm getting 1.6 volt at the white wire on the ICM plug with the engine cranking and with the key on engine off im getting 11.3 volts to the pink and black wire and the white and black wire.

Do you think it could be my optispark?

rangers458

Test your Throttle Position Sensor. I just had the same problem, thought it was a fuel pump. Test voltage between the blue and black wire, should be between .5, and .9V at idle. It did not throw a code until I disconnected it, and reconnected it.

Try starting it with a generous amount of starting fluid. I got mine to run this way, and held the throttle open up just a little bit before replacing.

turnerracing354

I tried starting it with starter fluid and it still wouldn't fire. Is there anyway to check the throttle position sensor without it running?

rangers458

3 wires, blue, gray, and black.

Gray and black should be 5 volts.

Black is ground. Gray is 5 volts from PCM, Blue is signal back.

Closed throttle should be .5 - .9 Volts. Mine did not throw a code, and this is what the problem was. Open throttle should be 4.9.


Part 1 -TPS Test: GM 4.3L, 5.0L, 5.7L (96-06) P0121, P0122, P0123.

turnerracing354

Someone told me to unplug the mass airflow and then try to start it but it still didnt fire. I also checked the tps and it all tested fine.

Injuneer

You had DTC 15, which indicated that at some point in time, the PCM was reading the coolant temp sensor on the water pump as indicating -56*F, for 2 seconds. You fixed the pigtail. Even if the code does not come back, I would check the coolant temp sensor and the wire again.

Does it smell rich when you try and start it? If so, could be the temp sensor telling the PCM the engine is cold. Adding starting fluid to an already rich engine wouldn't help it start.

4th Gen LT1 F-body Tech Articles

slick1hunting

might be a good idea to recheck fuel pressure and look to see if it bleeds down quick(sticky injectors or leaky fpr). Might be worth looking at a couple of plugs and verify spark again. Im guessing your air filter isnt plugged too or was off when trying the starting fluid. Just thinking of a combination of problems like restricted airflow with a rich condition and leaky injector and wet plugs. Might even be worth a couple tries with gas pedal fully depressed(clear flood mode).


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rangers458

Wish it was an easy fix as mine was. Sounds like the same symptoms.

DirtyDaveW

Had you done anything to the car/motor just prior to this behavior? Any upgrades or maintenance? Just wonder if you accidently caused this condition.

Some quick notes:

• Your TPS sensor voltage should sweep in a linear fashion from .6'ish volts to 4.5'ish and back as you slowly depress and release the gas pedal. Use a multimeter or a scan tool. If the voltage jerks all over the place, the TPS sensor is bad.
• Is your altenator in good condition? My factory one was fine for years, then, just driving down the road, It started running pig rich and would just barely stay running. These computer managed cars depend on the quality and quantity of the voltage/amps. Mine had been deteriorating and slowly depleting the battery. Once it got to that point of no return it made my computer(PCM) go crazy. You should have around 13.5 volts show up at the battery terminals when the engine is running via your multimeter.
• Have you verified that the injectors are pulsing? I had a recent self inflicted issue where I toasted my PCM injector drivers. They all had voltage but they never 'opened'. I replaced the PCM (and I'm NOT recommending this as a starting point since it's almost never the PCM) and the car started up immediately and ran great. What was so frustrating about this incident (a week or two ago, btw) is that it drove fine that day. I went here and there. Then went to the local hardware store, parked it, took out the key and walked in the store. After 15 minutes, I came back out and the damn thing didn't hit once during 8 tries of extended cranking. I had a noid light with me(paranoid to drive a turbo car w/o tools, hahaha) so I found the injectors were closed full time. Assuming I'd fried the injector box (long story of why I would jump to that conclusion) I replaced the PCM and it fired right up.
• Have you verified you actually have a spark by pulling a plug, grounding it and cranking to view the spark?

Good luck friend. I love my car but jeez, it sure loves to have me under the hood and engine searching for the latest malady.

turnerracing354

The car been hard to start but once started it ran great. I put a noid light on it again and im not getting any injector pulse. The tps sensor seem to be working fine. The ect sensor is working know also. I checked it with data master and them to sensor seem to be in good working order. But I dont have any injector pulse what could cause this. I have 12volt and the injector pink wire and all injector range from 14.8 to 15.2 ohms.