has spark wont start

[craig0407]

i have an 03 gt, recently got it, replaced leaking coolant elbows. runs great. however i is ignorant when it wants to start. sometimes it fires right up, others it wont start regardless of how long you crank. leave it alone for awhile chances are it may start. i replaced the camshaft sensor, cleaned the tb and maf. and the check engine light went away. car started up multiple times for 1 day perfect, now im back to it not starting. i checked for spark, its there. it has fuel pressure at the rail. im stumped. the trac off light has always been on too, wonder if the crank sensor is bad? but you'd think it wouldnt spark if that was the case.

[Tech II]

It's always, spark, fuel, compression? Has to be checked when it WON'T start....

Spark on all cylinders, using a spark tester?

Fuel pressure with a gage? Just depressing the schraeder valve is not a true indicator....

When it won't start, and you have spark, what happens when you spray cab cleaner into the intake? Does it start and run as long as you spray?

You say CE light was on....what was the code?

Since it intermittantly doesn't start, we can rule out compression....you either have it or you don't....

Also check vac line to f/p regulator for fuel and if it won't start, disconnect the MAF and then try to start it....

[craig0407]

It wasn't starting last night, still had spark. And like i said; tonight after I get home from work I'll try and start it and it probably will. Then I'll shut it off and it probably won't start again. I sprayed it with starting Fluid and it fire for a sec bit then nothing. The ce is back on and I'll check the code tonight. The first time it sai camshaft error 0341 or something. But when it does start it runs like a top. It just starts only when it wants to. I pulled bac to fpr no leakage: disconnected Maf no difference

[craig0407]

Didn't start tonight, fired up an fluttered for a second. Then just cranked. I replaced the fuel pressure reg tonight. Made no difference. Sprayed some fluid in intake and it started for a second. The pressure at the Schrader valve with the key on seemed weak when I depressed it. Think it's the fuel pump that's bad?

[Tech II]

I don't like using starter fluid...a little dangerous....

I prefer carb cleaner.....need a second person to crank vehicle while you spray carb cleaner into the intake when it won't start....if it runs as long as you spray, either low on fuel pressure, or the injectors are not firing(if you have good spark on all six cylinders).....like I said before, you need to put a gage on that schraeder valve.....should be around/above 40psi....

[craig0407]

Alright I'll put a guage on it tonight, I had one on it few days ago. When it was running it was 45 psi, but engine off and key on it int read anything, but there was pressure at valve bc it sprayed out when I released it. I thought the guage was bad. I'll also check for injector pulse. Could a bad crank sensor prevent injectors from firing? I'm still somewhat convinced its bad just because the trac off light is constantly on and is not related to abs

[olopezm]

You say you have fuel pressure, but is the fuel pump priming every time? Can you hear it prime while you turn the key to the run position?

How about it priming it 4-5 times before you actually start it. If it starts, you know for sure it's a fuel pressure problem. If you can't hear the pump priming, then inspect the relays at the fuse block under the hood.

Oscar.

[olopezm]

Originally Posted by craig0407

Could a bad crank sensor prevent injectors from firing? I'm still somewhat convinced its bad just because the trac off light is constantly on and is not related to abs

Crankshaft position sensor has nothing to do with ABS or Traction control; these are triggered only by bad ABS sensors (mounted at each wheel hub) or a bad ABS module.

Oscar.

[craig0407]

Found out today there's no injector pulse.

[olopezm]

If spark is OK then the crankshaft position sensor is OK.

Fuel injectors are triggered by the camshaft position sensor under the water pump. One more thing I would check is to disconnect the TPS sensor and try to crank the engine.

If it starts with the TPS disconnected, then you've found your problem. A bad reading will make the PCM "think" the gas pedal is all the way to the floor and will keep the injectors from firing (clear flooded engine).

Oscar.

[craig0407]

It has spark. I replaced camshaft sensor last Saturday and it was running great all day. Sunday back to no start crap. I replaced it because it came up camshaft error 0341 I believe on scanner

[olopezm]

In that case you might have a bad out of the box sensor. Inspect the wiring to make sure everything is OK.

I would do the TPS test just in case and check for 12v between each terminal at every injector plug and ground at KOEO.

I think that if you disconnect the camshaft sensor and try to run the car it would run as well; that will definitely confirm if your problem is the sensor (or wiring) or not.

Oscar.

[craig0407]

Disconnected tps no luck. Same as Maf. Noid light tested the injectors no power. Checked the wiring to crank and cam sensor they looked ok. I'll try to disconnect the cam but I'm not very optimistic at this point.

[Tech II]

Bad cam sensor won't prevent an injector from firing.......what will happen is the computer has to guess the correct time to fire the injectors.....there is a one chance in six, that the injectors will fire at the correct time.....won't prevent the engine from starting, but it could feel rough because they are not firing at the correct time......cam code can be caused by the sensor....can also be caused by a missing magnet on cam, bad harness connection to sensor/ICM/PCM, bad harness wire, bad ICM, bad PCM, etc.


this is a 3.8, correct? After replacing the cam sensor, were all codes cleared? Which codes returned? Were body, or "B" codes checked or just "P", or PCM codes?

If the injector doesn't fire, take a look at the SECURITY light.......there are two starter schematics to the starter, one uses the BCM, another doesn't.....

When you go to start the car, just turn the key to on.....don't crank.....look at the SECURITY light......it should go out after 3-5 seconds......if it does, attempt to start the vehicle....if it cranks but doesn't start, and there is no injector pulse, you need to check if there is a fuel enable signal being sent to the PCM(need a scan tool capable of reading BCM and PCM data).....

If the SECURITY light doesn't go out, and it cranks and doesn't run, then you know you have a THEFT DETERRANT problem.....

Like I said, your problem may be that you are not having BCM codes being read....average scanner can't read BCM codes.....

[craig0407]

When I bought it she said someone the prior owner it needed a fuel regulator, I had the codes read, 0341 camshaft error and 0440 evap malfunction. I replaced cam sensor, cleared codes started up. Started not starting again that afternoon, I had some issues with the key so I ripped out the latch solenoid under the column ad it seemed to have fixed it, as it started numerous times after that. Next morning no starting again. Ce light came back on and the evap is back.

I'll check security later today