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Discussion Starter · #1 ·
First time posting, long time reading. I have searched through this forum and any others I can get my eyes on and if my issue has been addressed before, forgive me but I can't find it.

Late 1999 F250 7.3 no mods except tuner. 175,000 miles.
Noticed at idle it had a slight knocking sound that was abnormal but that went away with rpm. Drove home about 40 miles and it drove fine but when I got home I noticed a slight raw fuel smell from the exhaust when I got out after shutting if off.
The next day it started but was stumbling and running really bad.
Now it doesn't start but wants to. Once in every couple tries it will start but shake bad.

-Ran buzz test. Passes. Crisp and even sound. Tach jumps to 3000 when all 8 buzz and to 2000 when each individual injector buzzes.
-No DTC's/no CEL.
-While it was running I disconnected the pass side UVCH and it didn't change much at all except for a slight buzzing when reconnected. When I disconnected driver side connector engine shut right down. Indicating only driver side seems to be firing.
-Ran cylinder contribution test. Indicated cylinders 1, 3, 5 consistently. Sometimes 7 with them.
-Performed resistance test from IDM connector. All injectors between 2.9 and 3 Ohms.
-Swapped CPS with known good. OEM Motorcraft.
-Swapped IDM with known good.
-Pulled ICP connector. No change in symptoms.
-Pulled all tunes and put back to stock. No change.
-Fuel pressure appears good. Replaced fuel filter just in case it was it. Fuel filter looked fine and fuel in bowl was clean.

Next plan was to pull the passenger valve cover and disconnect one injector at a time to see if an injector is taking down the whole bank. I read somewhere someone had that. Also will visually inspect for a bent pushrod etc. becasue I also read that one persone had a bent rod and it caused the whole bank to fail. Not sure how that works.
Just hoping someone else may have seen this.
Scouring the forums I did find instance where a guy had the same thing and he eventually replaced all 4 injectors on that side.
I know these are not original injectors. PO replaced them a few years ago. PO was a diesel mechanic and took care of engine meticulously. I just don't see how multiple injectors failed at the same time. I can't see how it is electrical but this is my first diesel. Been working on gasoline engines for 30 years so the concepts are clear to me, just don't have experience.
Thanks.
 

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Good, logical, troublshooting!

I had an injector solenoid fail and that one injector took down the whole bank.

On the other hand, it could be the Under Valve Cover Harness. Do you know if that was ever replaced?

I assume you ran it on the "stock" tune? But no DTCs? That is weird.
 

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Discussion Starter · #3 ·
Good, logical, troublshooting!

I had an injector solenoid fail and that one injector took down the whole bank.

On the other hand, it could be the Under Valve Cover Harness. Do you know if that was ever replaced?

I assume you ran it on the "stock" tune? But no DTCs? That is weird.
Thanks. I ran the buzz test many times and even ran it on my buddies rig just to make sure the sounds were the same, and they were. No dtc's any time. No cel. That is with all programming taken out and PCM put back to stock.
I don't know if the UVCH was ever replaced. I figured if the buzz test passed, no dtc's and ohm check was good that the UVCH wouldn't be it but then again I don't have experience with that so if that is a possibility still then I will definitely try it. Actually I will order a replacement set since at this point I don't think I can go any farther without pulling the valve covers and inspecting. I was thinking that maybe there could be a fuel issue to the passenger side only and if the injectors were firing without fuel that it could have caused them to fail? I've read its almost never the HPOP. I know the electric pump is at least coming on, and the issue seems to be just the right side. Wasn't sure if a fuel issue could have caused the problem, and dead injectors are now a result? It is definitely not leaking fuel though.
The coolant only smells like coolant and the fuel is clean so I figured the injector cups should be fine.
I just think once I heard that abnormal sound that maybe it was an injector, and then driving home 40 miles may have caused more to fail, especially if it was a fuel issue on that side. Then again, on the drive it ran good and I didn't feel any type of miss. Just smelled unburnt diesel from the exhause when I got out of the truck and the next morning it was just running like garbage.
I'll swap the UVCH's and see if fault swaps sides. Then if not, swap injectors from side to side and see.
I will respond with results once I change the UVCH's.
I appreciate your response and look forward to any other advice!
 

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Are you using FORScan to pull the codes?

It's really weird that there are not any. I definitely had a code on my failed injector. It was brand new, too!

#$%^&*( Chinese crap.
 

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Discussion Starter · #5 ·
Are you using FORScan to pull the codes?

It's really weird that there are not any. I definitely had a code on my failed injector. It was brand new, too!

#$%^&*( Chinese crap.
I'm using LAUNCH. It is chinese but its a higher end program that does a lot. It's worked perfectly on friends 7.3's and I trust that theres no codes. This weekend I pulled right bank injectors. 1 and 3 were relatively dry as far as oil as compared to 5 and 7 which looked like all the other videos i've watch. It was strange that injector 7 also had surface corrosion on the the bottom that goes in the cup. I bought it used a few months ago so I don't know the entire history of all the parts. So I juste went with new Alliant UVCH's and Alliant AC injectors that I will get a tune for. If that doesn't solve the issue then this really will blow my mind. I'm pretty sure the relatively dry 1 and 3 injectors at least indicate those failed.
As far as the surface corrosion on the nozzle barrel makes me wonder if there is a cup issue? I cant imagine with the oil pressure that coolant would be able to make its way into the cup, and even if it could it shouldn't corrode. I do know the truck sat for a few years, being started a few times per month for about half hour each time.
So I will respond when I have all the injectors back in. Appreciate it!
 
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