99 f350 7.3 Powerstroke

Replaced glow plugs, now misfire on two cylinders. This is a new thread with all the new info and test results in one place.

when installing new glow plugs, out of cylinder test was preformed to ensure glow plug was working via the truck wiring harness. During the test
the number 1 glow plug wire smoked and burnt out its connection on the connector. New connector was installed and truck was re-assembled. After
first start the truck successfully started but ran rough and had excess white smoke coming out the exhaust, even when warm and while driving.

Inspection of the plug showed connector to glow plug 1 was burnt out agian. New uvch were installed on both sides along with another new plug on passenger side. Truck was fired and the misfired persisted. Truck was driven for 20+ minutes with multiple hard accelleration pulls to ensure no oil
in cylinders was left unburnt or air in fuel system.

Cylinder contribution test shows cylinder 5 and 7 low contribution. When unplugged injectors 5 and 7 no change to the trucks performace can be observed.
Upon unplugging each injector, the CEL will illuminate but will remain unlit when both are plugged in. All injectors can be heard firing evenly
when performing a buzz test. Here is a video of the buzz test : https://youtu.be/FipTASGaUTE
Buzz test throws these codes: "Cylinder 7,3,5 High to Low side Open (p1277,01273,p1275)", "High side open bank #1 (P1293), High side Open Bank #2 (P1294)

Tried Swapping injector 7 and 1 as well as 5 and 3, no change in truck performance. Misfire same cylinders.

Checked Fuel pressure at fuel bowl, just over 60psi while running. Video of that here plus startup and run: https://youtu.be/YihkAsCjN4c

IDM Swapped with used oem, no change in performance. Compression test on 5 and 7 cylinders showed 350 and 370psi respectively. Also tested #3, which showed 320psi.

Truck ran great before changing the glow plugs. Completed about 6 hours of driving just prior with no issue. Now the truck smokes and shakes
with notible loss of power. Any advice is appreciated, thanks in advance.

EDIT: Fixed. I am relieved and embarassed to say I had 5 and 7 wires switched when I replaced the UVCH connector.

Buzz test:
https://youtu.be/FipTASGaUTE?si=PctwsuYBFNbLyGOC

Video of truck runnining:
https://youtu.be/YihkAsCjN4c?si=wEmCo3z5ue8BJTP1

 

Did you change the valve cover gaskets also, or just the harnesses?

 

Man that fuel pressure sure is slow to build up. Have you checked for aeration? You can catch a sample from the fuel bowl drain with a section of 5/16 hose and a clear bottle or jug. Just open the valve and turn the key and see what ya get. X2 on the VC gaskets and I'll add a where did the harnesses come from?

 

If a glow plug wire is burning repeatedly either the glow plug is faulty and has an internal short in it, or there's a pinched wire somewhere.

 

Yes, UVCH gasket both sides and the connector on the problem side because it was burnt.

 

That problem was fixed after replacing the UVCH. No smokey wires anymore. Do you think there's anything else that could have been toasted by a short? Tested wires at idm, seemed normal, also tried a new IDM.

 

Aeration should work it's way out after driving the truck and beating on it a little, yeah? I've tried that and it has not changed anything. I'm embarrassed to say they are Dorman gaskets. From reading some other forums I've learned that isn't cool.

 

The pass through connections on the valve cover gasket cannot carry the load of a shorted wire. Nor can the conductor inside the plug that connects to the valve cover gasket plug. Been there. Had a glow plug wire running so close to the push rod that it wore through the insulation and shorted out the circuit. Burned out the pin on the outside plug and I had to repair that, along with new valve cover gaskets and wiring harnesses.

 

That would depend entirely on the cause of the aeration. The way the factory fuel system is designed there are at least half a dozen potential leak points between the fuel in the tank and the pump. Any leak from those areas means the pump is sucking air causing it to work harder to maintain flow and pressure, and that isn't going to work it's way out. It will just continue to churn up cappuccino and send it to the bowl and on to the injectors. Then depending whether you've already done the Hutch mod whatever gets sent back to the tank dumps into the "mixing chamber" still full of air to get mixed with more air and fuel and right back to the bowl and injectors. Either way the pressure is sluggish and something is causing it.