Can I test the CPS or is it a replace? So, back to my original thought. If I turn the key on and the CPS is bad, will it not let the fuel pump energize? I just cleaned and dielectric greased the battery connections and it would still start. Okay, so I let it sit for a day now it won't start ...again. The CPS issue doesn't make sense to me, but I have no clue about that...
I don't think the CPS would cause an intermittent no-start, but never hurts to check. Here's a way to test the crankshaft position sensor: https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-crank-sensor-1
Okay, is it possible that lots of oil would cause the crank sensor to be hit and miss? Also, wouldn't it kit a code if it was bad?
Um, not likely. My 4.3 engine I just pulled is a nasty crud. Oil leaks and gunk everywhere. I did replace the CPS engine a long time ago, but because it was leaking a bit from the connector, based my mechanic's advice, but the sensor never malfunctioned. And later on I had a timing chain oil leak. Again CPS sensor never malfunctioned. I believe it works off Eddie Currents, which is an electromagnetic field, so I don' think it is impacted by either oil or water. Think about it, the sensor is right at the bottom of the engine, right under the front of the crankshaft...lot of oil. So you still have the problem? Why don't you test your ICM? If your ICM is getting pulsing signal, you can eliminate the CPS, because the ICM signal is based on the CPS producing signal. No pulsing signal means your CPS is dead (or more rarely the ECM is faulty.) It's easy and all you need is a test light. https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/how-to-test-the-icm-1 Testing the CPS requires you to get underneath and turning the motor by hand...not as simple as it sounds.
I haven't checked for spark when it happens, but I have checked fuel pressure. When it happens, there is none. It did this again last weekend. Every day or so, I would try to crank it. Same issue. I thought maybe it was a voltage thing since I'd been trying to start it a lot with no luck. Hooked up cables to my other car same thing. Nothing. It's been cold and or raining here lately so I wasn't going to mess with it at that time. Was leaving Tuesday morning for an appointment, but tried it anyway. Bang, fires right up. No misses, no bad idle...just normal.Someone suggested a damaged wire that might not be making contact when cold, but when it's warm expands to make contact. Plausible, but I haven't checked that yet too.
But on mine, when it won't start there is no fuel in the line....which is before it gets to the regulator. Doesn't seem to matter the temperature or the weather conditions. It's worked or not, hot, cold, rain... don't see a pattern..
If the fuel pump won't prime, it's not the ignition module. If the fuel pump won't prime, and won't provide pressure when the engine is cranking, you've got at least one fault in the electrical circuit which could include the pump itself.
