7.4l Now no start

[smokymtn65]

Still dealing with no start issue, It has spark, drained fuel, put in fresh fuel but only had a couple minutes to try it, cranked a couple times no love. fuel pressure is 49lb after one hour drops to 38 after 3hours it was 25. When I powered the pump is sounded like fuel running (the hose trickle) sound I have read about. I do have a set of injectors (28lb) that came with the truck. I haven't put them in till i was read to do the 0411 upgrade & tune. All suggestions would be appreciated. Thanks Few more details under introduction thread.

 

[RichLo]

Usually fuel related problems end up being fixed with new ignition parts and vice-versa, lol. Have you checked anything with the ignition system yet?

 

[smokymtn65]

Usually fuel related problems end up being fixed with new ignition parts and vice-versa, lol. Have you checked anything with the ignition system yet?

Thanks for the reply, I have checked for spark I have spark. I am getting P0339 code .
I had cleared it before after a 15 mile drive i had P0339, P0401, P1153. Then sitting overnight it would start I cleared codes and the P0339 came back On the Tech 2 says passed but a newbi on using that too. lol

 

[RichLo]

p0339 is a crankshaft position sensor.

I'm sure that would cause a no-start condition.

 

[smokymtn65]

I had read or watched something on how to test it. Now to find it again..

 

[stutaeng]

Wait, how did you say you had a no-start and then you mentioned you were driving around? Is the no-start intermittent?

As far as the crank sensor: The easiest way to test that is actually at the ICM. If you are getting pulse, that can most likely rule out the crank sensor, as that's what generated the signal for the ECU to pulse the ICM. Also, the ICM is easy to test with a test light and is on top. The crank sensor is under the engine (and greasy!), and you have to turn the engine by hand to test it. You can test it with a scope and look at the waveform by cranking the starter also, but that's for like the Pro.

https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/how-to-test-the-icm-1
https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-crank-sensor-1

It's best not clear code(s) in my experience. I prefer to drive the vehicle after it is "fixed" and confirm the ECU has seen the problem corrected, then code goes away. Otherwise you find yourself driving the vehicle, then realizing the problem was not actually fixed and potentially getting stranded.

 

[smokymtn65]

Wait, how did you say you had a no-start and then you mentioned you were driving around? Is the no-start intermittent?

As far as the crank sensor: The easiest way to test that is actually at the ICM. If you are getting pulse, that can most likely rule out the crank sensor, as that's what generated the signal for the ECU to pulse the ICM. Also, the ICM is easy to test with a test light and is on top. The crank sensor is under the engine (and greasy!), and you have to turn the engine by hand to test it. You can test it with a scope and look at the waveform by cranking the starter also, but that's for like the Pro.

https://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/how-to-test-the-icm-1
https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/how-to-test-the-crank-sensor-1

It's best not clear code(s) in my experience. I prefer to drive the vehicle after it is "fixed" and confirm the ECU has seen the problem corrected, then code goes away. Otherwise you find yourself driving the vehicle, then realizing the problem was not actually fixed and potentially getting stranded.

I had it do this once before, after long cranking it started, A couple days later fired right up no issues, drove it about 30 miles in total. got home at 9pm , at 6 am next morning it would not start. The 3 codes mentioned were what came up during to 30 mile drive. It fires some but no start. It does read RPM output on TechII I had cleared the codes after snapshot, then during multiple crank attempts it has the P0339 again. I hope this in more clear. LOL

 

[stutaeng]

Ok, gotcha. Sounds like you are losing fuel pressure and it's flooding the engine. That's one problem. I believe if you press the gas pedal all the way down it holds back injecting fuel and you should be able to start it that way. I think injectors are common problem on the 7.4 based on what I've read here.

I had a 4.3 that had the crank-no-start under wet/damp conditions. Never solved that one, after checking everything. I think that issue is distributer related. At some point I was able to start it after like 2 minutes of straight cranking, LOL.

Looks like the other 2 codes are O2 and EGR related. That needs to be fixed, but likely unrelated to the no-start.

 

[smokymtn65]

I have a set of 28lb injectors that came with the truck, I guess i can put those one and see if it runs, they were going on anyway but hadn't planned to do this till i did a 0411 swap. The truck has been cammed by PO with CC XR-270-HR-13 cam

 

[smokymtn65]

Got it going, here is the link to other thread .
https://www.gmt400.com/threads/98-k2500-ecsb-l29-nv4500.52740/