My truck has been not starting, stalling, and running like ****.
sometimes it won't start, just crank, crank, and crank. Leave for an a hour or more and it'll start.
Sometimes it'll start, then five minutes later it'll stall.
Sometimes it'll start and run fine then it'll stutter and sputter give it gas and it goes nowhere. I mean absolutely no response from the peddle. As if the trucks not even running. But it is. Then it'll cut the **** catch itself and run fine until I shut it off again
i had a few codes bad ignition coil, O2 sensor, and two evap codes a large leak and small leak detected. I fixed the small evap leak and that code went away. Then I replaced the ignition coil the code stayed so I cleared all the codes to see what would come back ( the truck was given to me because two mufflers exploded and my brother didn't want to deal with it.
I'm still having the starting and stalling issues however no codes have come back yet even though I've been driving it here and there. ( Tired of it being unreliable)
ive checked the fuel at the fuel rail and there's fuel there. No I haven't put a pressure guage on it yet.
So I went to harbor freight and bought a spark tester. I hooked it up and as the truck cranks and cranks and cranks there's no light on the tester. But once the truck finally does starts the spark tester has light.
My question is shouldn't that tester have light as Its cranking even before it starts?
So this should mean it's not starting because there is no spark?
This truck is driving me nucking futs

 

Is it a true spark tester, or just a timing light?

Most timing lights will not trigger until around 250-300 RPM at best. The one we use on the dragster is a cheap generic one, it won't light at all until well above spinning speed (400-500 RPM).

 

Thanks for your reply. It's an actual spark tester. Not a high quality one though. I may hook it up to my girls van and pull the fuel pump relay and see if it lights up as it's trying to start. I need to know why this truck isn't starting and stalling. I bought this tool hoping it would show me wether or not I had spark. Originally I was told that if it wasn't the ignition coil then it was the computer. However I've since learned that in these trucks there's two wires that go to the ignition coil one is power from the computer the other is a signal from the crank position sensor and the cam shaft position sensor. So, if it doesn't have spark it may not be the computer, it could be not getting a signal from either of those. Anyways here is the spark plugs tester that I got. Thanks again

 

Yea, those inline style arc-gap testers are usually good enough for what you are doing.

On the coil, orange is constant 12V from the ASD Relay (also supplies power to fuel injectors). Black is a pulsed ground from the PCM, which i pulsed based on the signals from the crank and cam sensors. The sensors aren't connected to the coil directly.

 

Yeah I saw a video where they hook a test light up to the orange wire to see if it's getting power from the ASD relay. Then they hook an LED light up to the black wire to see if it's getting a pulse from the pcm based off the signal from the two sensors. So that my next step. Also for ****s and giggles I'm gonna try to replace or swap that ASD relay.
This thing keeps back firing once in a blue. Some pretty loud ones too. I do believe it's what killed the mufflers. I also believe it's from not getting spark then getting it again. Now my question is if timing was off would this thing run? Because sometimes it starts and runs great. Then it'll go back to stalling and not starting again. I would think that if timing was off it just would start or it would stall right away.

 

The PCM has a roughly +/- 10 degree injector timing window before it screams bloody murder and shuts down. But it takes a DRB3, MT2500, or similar scan tool to read the injector sync. Usually beyond +/- 6 degrees, there will be odd/rough behavior but it will still run.

That LED method is actually a great way to test for the coil signal from the PCM. You'll want something like a 200 ohm resistor inline with the LED ideally. You can also use the same idea at the fuel injectors.

 

So I went and picked up a test light so I could check to see if the ignition coil is getting power from the ASD relay. The only one they had was this LED style. So I'm wondering if I can check the pulse signal from the PCM using this since is LED? Or do I need to buy an LED light, some alligator clips, and rig up my own LED light with the resistor as you mentioned? I've saw a video where they were testing the PCM for pulse with a home made LED light, so I get what you were saying. However since this test light is LED would it work???
Also why does the light to check for pulse have to be LED???
Thanks

 

That will work perfectly fine!

LED is required because the human eye cannot discern the rapid flashing of an incandescent bulb. Think of an old incandescent timing light, but at 8 times the speed for the coil, and the same speed for the injectors but without a nice target to aim at.

 

Well after going back and forth and trying to figure out why this truck was speradically not starting, stalling, and running like crap. I dropped it off at the shop this morning. They just called me to inform me they Diagnosed the problem. The computer is bad. They said the part is obsolete, so Monday they're gonna call around and try to find a used one so they can install it and program it to my truck. Hopefully they can find one and it doesn't cost and arm and a leg. I asked for a rough price and he said if he can get one probably 6 to 8 hundred.

 

So I've looked on the web and found a few computers for around 200 to 300. You give them the VIN and they flash and program to your vehicle then send it off to you. From there it's plug and play. Has anyone had any experience with this? Or am I just better off letting the shop doing it and paying a little more??