Truck turns over but will not start

Hello,

This could be a problem with your crankshaft position sensor. Your vehicle's Crankshaft Position Sensor (CKP) is responsible for letting the Power-train Control Module (PCM) AKA, "computer" know where the engine is in it's four stroke cycle. Specifically, it keeps track of number one piston and let's the PCM know when it is at Top Dead Center of the compression stroke. The PCM keeps track of everything else from there. If the CKP is not working, or has intermittent failures due to a bad connector, or frayed wiring the PCM can't keep track of the engine's cycle and therefore won't start.
I have included a few links down below for you to go to.

https://www.2carpros.com/articles/how-a-crank-shaft-angle-sensor-works
https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor
https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

I have also included a diagnostic troubleshooting flowchart for the CKP in the diagrams down below. Please go through the guides and flowchart and get back to us with what you find out.

Thanks,
Alex
2CarPros

Well, I replaced the Crankshaft Position Sensor and while doing so found that my vibration damper was shot, so I replaced that too. As soon as I put it back together it started right up and continued to start the next two to four times I tried but just now I needed to use it and it refused to start again. It is acting just as before where it turns over good but won't fire. I tried to scan it for codes with an inexpensive scanner and it failed to link over and over if that tells you anything. I am getting real frustrated at this point as I thought I had it. Any more help you can provide will be appreciated. Thanks

Hello again.

This could be a problem with your Camshaft Position Sensor (CMP) as well. It sounds to me that given the intermittent nature of the failure that if it is the CMP it will definitely be heat related. I have included a diagnostic guide from the factory to test the CMP on your vehicle in the diagrams down below. Please go through it and get back to us with what you find out.

Thanks,
Alex
2CarPros

I just tested the CMP and the resistance is 1043 at 55°. This is within spec you provided so I assume that isn't my problem. Any more ideas?

Hello again,

Okay, let's get down to the basics. An engine needs three things to start, fuel, spark (delivered at the right time), and compression. If it has these three things it really has no choice but to start. So lets start with spark and make sure your vehicle is getting that. I have included a link below for you to go to:

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Please go to this guide and get back to us with what you find out. We will be able to continue either way from there.

Thanks,
Alex
2CarPros

I have spark as it started ten minutes ago but who knows if it will start next time or when it won't start when I need it. It runs fine when it starts and never shuts off or runs bad. It's all about if and when it will fail to start. When it won't start it turns great but doesn't even try to start. It may start again after I leave it alone or it may not. Of course it always fails if I really need it bad.

Hello again,

I know, don't you hate that. If you take it into a shop, guaranteed it won't do it when you guys go for drive to show the mechanic what's wrong. Given the intermittent nature of the no start it is either going to be the CKP or the CMP sensor or the wiring to each that is going out but not quite there yet. The sensors usually when they are going bad will work great when they are cold but will start to fail when get hot. I have included in the diagrams below the wiring diagram with the CKP and CMP sensors on it. Check the wiring going to them and get back to us with what you find out.

Thanks,
Alex
2CarPros