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Discussion Starter · #1 ·
My PSD has a miss. Took the valve covers off to determine which cylinder wasn't firing. #6 cylinder no change in the sound of the engine when I pull the injector wire off. The rest of them caused the engine to stumble even more when I pulled the injector wire off. I replaced the under valve cover harness on both sides with the newer style with integrated harness. Then ohmed the injector and that was good. Checked resistance from #6 all the way to the ECM with no breaks in the wire. Now I'm stumped. The rig only has 102K miles on it (motorhome) so I'm leaning away from a bad injector. Any thoughts?
 

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You can measure the armature gap. Is the injector is spitting oil when running? You can always swap the injector with an other one to see if the problem follow the injector or stay on the same cylinder.

Do you have a powerstroke capable scanner?


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Discussion Starter · #3 ·
I'm not familiar with measuring the armature gap. What's that? I don't recall if it was spitting oil. What would it tell me if it isn't. My next step is to swap injectors but was holding off on that because of the pain in trying to suck the oil out of the cylinders.
 

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Discussion Starter · #4 ·
Update: I've got oil coming from every oil spout (including #6) but #6 continues to be the only cylinder that doesn't cause the engine to stumble when I unhook the wire. What does this mean?
 

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It means it's either not getting a signal to fire or not acting on it.

What did you get for solenoid resistance? Should be between 2 and 5 ohms IIRC. Did you check it against any other injector solenoids? They should all be in the same range.

To check the armature gap, you need to remove the solenoid and slip a feeler gauge between the plate and injector body. If it's closer than about 0.0015", then it's probably worn. But the fact that it's spitting oil means that the solenoid is activating the pilot valve (armature) in the injector.

You might have a low compression issue that's causing the fuel being injected not to combust. Could be valves or a cracked piston or ring.

A PSD capable scan tool would allow you to do a buzz test to check the electrical side of the injectors. The buzz test buzzes all the injectors and then in sequence, 1-8. Listening for differences in the sound during the sequence, will sometimes identify a bad injector.

The scan tool will also do a Cylinder Contribution Test, but that will only tell you which cylinder isn't contributing to engine power at idle. It won't differentiate between an injector problem and base engine problem (such as low compression) though.

You could follow up with a compression test, using a gauge that attaches thru the glow plug holes. If you have good compression on all cylinders (lowest within 25% of the highest meets service spec), that would pin it down to the injector itself.
 

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Discussion Starter · #7 ·
Thanks for the responses guys. It turn out to be a wiring issue. I swapped a couple of injectors and the misfire continues to be at #6. I can't explain the earlier test where I checked continuity all the way back to the ECM. My next step is to swap out the UVCH plug. I just hate to do that because it creates a lot of splices.
 

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You should never splice the UVCH, just replace it.
If you meant the outside harness connector, it's done all the time. No problem unless you can't make a good splice (solder recommended.) Stagger the splices within the harness so they still fit inside the loom.
 

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Discussion Starter · #9 ·
Yes, I meant splice in a new plug on the outside which I did and it didn't fix the problem. Is there a way to tell if the ECM is sending a signal to the injector without doing a buzz test? I don't have any fancy tools like that.
 

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One issue might be corroded pins on the valve cover gasket itself. You might eyeball them closely. If they're corroded it will increase the resistance and decrease the voltage delivered to the injector. In a worst case situation you might need to replace the valve cover gasket. To check the circuits, you just need a multimeter. On a good circuit, you should see less than 2 ohms end to end.
 

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Discussion Starter · #11 ·
Alright, finally found the problem. Hole in the #6 piston. Have cracks in all of the other pistons. #6 is the one that burned through first. Time for a rebuild. BTW, pulling a PSD out of a Class C motorhome (van cab) wasn't as bad as I thought.
 

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yap that would do the trick LOL

glad you got that under control
 

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I would sure get a EGT gauge on it after the rebuild if you don't have one. That engine must have been run really HOT to do all that piston damage. Running at or over 1250*F for an extended period of time will do the damage you have. Motor Homes are heavy, never ever lug them, always down shift, that keeps the EGT's down. Mountains are a *****. LOL

The EGT sensor should be installed in the exhaust manifold between #6 & #8 cyls.
 
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