Dave Pannabecker Posted January 13, 2022 Share Posted January 13, 2022 (edited) Evening Folks - Pulling my hair out over a cylinder misfire,looking for help. Job started out needing head gaskets (coolant leak at the front edge of the rear head) and had intermittent codes for EUP’s cylinder #3 & #5 for FMI/8. I did the head gaskets and also replaced the EUP’s & 3 and 5. Got it back together and had a miss on #4, can crack the high pressure line and it has no fuel pulse whatsoever nor does the engine tone change at all (all other holes firing). At that point I assumed despite how clean I was disassembling and reassembling it I must of got a chunk of crud in the EUP in the process of the head gaskets and changed the EUP (and pulled the tappet and visually checked the EUP cam lobe - both good). New EUP - still has the miss - nothing changed. At that point I pulled the V/C and rechecked valve lash - it’s OK - right where I left it. I then rechecked the harness for continuity, Ohmed out perfect but also load tested it with a headlight and actually found an issue with #3 cylinder (but # 4 tested good). Changed the injector harness - same problem #4’s dead - nothing changed. At that point I thought maybe when I installed the high pressure fuel line in the head I may have pushed crud/rust into the nozzle blocking it and causing premature failure of the new EUP so I pulled the nozzle, disassembled it and blew it out and found nothing more than 2 of the 8 (think that’s how many holes the tip has) were blocked. Been fixing trucks for 35 years and this has me kinda stumped. Any helps appreciated. P.S. All EUP’s are Bosch remans, all other parts are dealer sourced. Edit : 2 items I forgot: when it’s running with #4 misfiring it has no active codes. I also checked for an electrical pulse @#4 EUP with an LED light and the ECM is firing the EUP. Edited January 13, 2022 by Dave Pannabecker Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted January 14, 2022 Share Posted January 14, 2022 Sounds like an injector, especially since you said there was dirt in it. Have you tried swapping it to another cylinder to see if your problem moves? Also are you using new fuel lines and to the correct torque? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted January 14, 2022 Share Posted January 14, 2022 I hope i'm following correctly... Did you swap a known good EUP with #4 to see if the issue follow's the EUP? jojo Quote Link to comment Share on other sites More sharing options...
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