Hey folks. First time posting here and i'm in need of some help. It won't start. It will turn but won't ignite at all.

I've done spark plug tests: Working and like new.
Fuel: We have 55 PSI fuel and plenty of fuel volume coming through the lines. I think the issue is that the injectors are not firing at all. If they were clogged surely at least one would shoot a little gas and the engine would backfire or something. But no. I'm convinced that something (i.e. a sensor or computer) is telling the injectors to not work.

Does anyone have an idea of what sensors might cause this or perhaps another possible explanation?

Thanks!

 

Your truck has the CPI fuel injection system which stands for Central Port Injection. This system uses a single large fuel injector mounted into the fuel injection spider that delivers fuel to the individual intake runners. The connection at the injector can sometimes fatigue over time and lose contact resulting in a no start condition.

I would pull the plenum and test the wiring at the injector itself using an injector pulse test light (a.k.a. noid light). You can alternatively test the resistance of the circuit by disconnecting the wiring outside the plenum or testing at the ECU itself.


I believe that wiring diagrams have been posted for the CPI engines in the past, but don't have the time at the moment to find them.

 

Wow. What a quick and well thought out question. Thanks!!

I was thinking that might be the problem. Can you explain what exactly the "Plenum" is though? I previously owned a 98 c1500 with the v6 as well and i've taken it apart but as far as I remember the only thing you can do is take out and inspect are the injectors "Spider legs" and the fuel pressure regulator.

I will look up a wiring diagram. No problem.

 

The CPI engines and newer SCFI (used in the 96+ trucks/suvs) engines have two piece intake manifolds. On the CPI engine, the plenum is the aluminum upper piece of the manifold. It will have bolts around the perimeter. You may want to pick up a new gasket prior to pulling things apart just in case you damage the old one.

You can test the coil resistance without pulling the plenum. I seem to recall the injector resistance should be around 1.4 ohms to indicate a good injector and can be slightly higher depending on where you are measuring, but you may want to check on that.


If the circuit comes back as open, you have a bad connection.


If it comes back as continuous with a resistance higher or lower than specified, you will want to pull the plenum and test both the injector itself as well as each of the wires in the circuit for resistance. Resistance on a single wire should not be very high at all with a high resistance meaning there is a problem with that wire somewhere.

 

I am going to take a look sometime today or tomorrow. I hope you advice helps me find something. Thanks a lot Swartlkk!