I have fuel pressure at the rail. I have replaced, fuel pump, 2 relays behind stereo, fuel filter, and have moved around all relays in engine compartment. still wont start after sitting for a couple hours. but it will start all day as long as I don't let it sit too long. it does have spark, this is how I start it after working 12 hours. starting fluid spray in the airbox. I have a crankshaft position sensor that im gonna try tomorrow.


I have an XL version and it doesn't have the THEFT light. I don't know what PATS is?
projectSHO89

 

You have to SPECIFICALLY identify what you're working on. We're not psychic. You posted in the V8 engine section, but the modular V8s covered almost 20 years of vehicle models.

If it was a bad CKP sensor, it wouldn't start or run on the spray can, either. Dead end. Besides, the CKP sensor is buried behind the compressor and is tough to get to. You don't want to screw with it when you're only guessing.

The correct question to be answered is HOW MUCH pressure is generated by the normal pump priming cycle.

 

If you have no theft light turned on, then you don't have to worry about it.

It sounds very much like electrical problem. Something might be expanding when you warm up the engine, and then contracting after it cools off, which then shorts something out. It sounds like the crank/camshaft sensors are working, because if they were broken, I would not think that they would fix themselves and start working again. It could however be the lines to those sensors that are causing the problem. If you are going to troubleshoot the crankshaft position sensor, just trace the wiring harness around for that and make sure it isn't wrapped tight around anything. I think my problem was in near the back of the valve cover on the passenger side where the harness/wiring for the crankshaft sensor turned and headed towards the drivers side of the engine compartment.

So, when it's cold and doesn't start, how do you know there's pressure at the fuel rail? Depress the pin valve on the rail, and have someone crank the engine at the same time. Does it squirt out with good pressure, or does it just bubble out? Spraying starting fluid into the intake and cranking the engine at the same time does nothing when it's cold?

 

I suspect your PCM's assessment of the engine temperature is off. It needs to richen up a lot to run when cold, and the ether solves that.


This is very very easy to check and free (and that is why it's always good to suspect this). You simply hook up to OBDII and look to see what temperature the PCM thinks the engine is.

 

it turns out that it was the crankshaft position sensor! I replaced it and has been fine ever since. its been a couple weeks now.