huffhound

I'm having one injector that will not fire. I have checked continuity , spark , swapped injectors, changed PCM's ran a jumper wire from PCM to injector, ran jumper from 12V supply to injector, verified grounds. I even swapped the pins and injector plugs between #1 and #3. The problem seems to be with the #1 PCM negative output. It's a 6.0L , PCM # 12589462. Could this be caused by the crank position sensor or cam position sensor? This is driving me nuts....Any suggestions?

stevieturbo

If you changed PCM/ECU....it would seem hard to understand how both could be faulty.

Are you saying the engine runs fine on all other cylinders, just that cyl 1 has no signal going to the injector from the ecu ?

I cant see any scenario where the crank/cam sensor would cause such a problem

huffhound

I am saying the engine runs fine. Just a dead or very weak cylinder. When i swapped wires so it was #3 cylinder, swapped on PCM and injector, the problem followed. That rules out mechanical problems. So i'm thinking maybe something is telling #1 not to fire.

I'mreally having a hard time with this one

stevieturbo

So is the injector getting a signal from the ecu ?

huffhound

I have 12V to the injector. I checked resistance of all 4 one that side. They are all the same. I swapped the injector plug and wires on both the ECU and the injectors from #1 to #3. The problem moved from #1 to #3. I am going to get a noid light now. I get spark but i'm thinking the ground signal from the ECU is not being sent. I cannot figure out why. The truck has been running great until this. About 6 months since last dyno tune. It's driving me crazy.

Thanks for your input. Anything at this point will be a great help

stevieturbo

Hence why I asked...are you getting a signal from the ecu at the injector.

And it sounds like you havent tested this ?

Whether noid, LED, multmeter, scope...really doesnt matter. There are many ways to test and none need to cost money and it will only take a few seconds.

huffhound

I have signal from the ECU. I checked them all. Seems the same strength. Bulb not bright but lighting on all.

I am going to try swapping injectors. That's the only thing I know to do now. I don't have a fuel pressure qauge but since the others seem to be operating as normal...I think I can rule that out

stevieturbo

If there is a tigger from the ecu at the injector...

either pull the injectors out of the intake, and crank the engine to physically see if fuel is spraying from the injectors during cranking, or unbolt intake and lift of engine and do same

or do a compression test, check rockers etc to ensure they are opening/closing the valves on that cylinder

huffhound

Injector is spraying. I have turned the engine over with the valve cover off and all seems well. Remember that i swapped the #1 and #3 injector plugs ECU. The problem went from the #1 cylinder to the #3. I guess the next thing is to put a pressure gauge on the fuel rail. I can't see why the other cylinders seem ok.

I'm going crazy with this. I feel that all I am doing seems right but I still cannot find the problem

stevieturbo

So the injector is spraying fuel, same as all other injectors ?

Really...that dont make a lot of sense.

I dont see how fuel pressure will be an issue here, especially if you've proven fuel is being injected.

And also...history leading to this problem ?

huffhound

I just noticed a little misfire so I changed the plugs. It was not even close to the mileage needed but I did anyway. Seemed to get a little better but that could have been just me thinking it was gone. I swapped the coils then swapped injectors around....no help. Compression check, manual turn over of engine with valve cover off...then all the other things I already described. I noticed it with my temperature gun on the headers.

This is so frustrating. I don't know where to look now.

stevieturbo

You need to run the engine, and with either a meter or scope ensure there is a valid signal at the injector, when you are sure the cylinder is not firing.

Do likewise for coil to ensure that coil is charging/firing as expected.

That should rule out any electrical aspect.

Any tests with the engine not running, are clearly not adequate here.

Monte4ever

iTrader: (2)

See if there's a short going from the #1 injector to the main harness. I had this problem but it was all 4 injectors on the right side (2-4-6-8).