DieselDog5.9 Posted September 10, 2022 Share Posted September 10, 2022 Catching up on some maintenance, changed the exhaust manifold gaskets due to a leak, replaced the radiator, belt tensioner and belt. As part of this process had to remove the fuel jumper lines from the unit injectors to the cylinder head, immediatly put plastic covers on the unit injectors. Job went fairly smoothly however primined the fuel system, and got the truck to fire, definitly missing on No4, we cracked the line, checked the wires, no4 manifold cold, crack the line and no engine droop, definitly have a miss. I have done this job on multiple other trucks and they fire up and eventually work the air out. This spring I changed the fuel pressure regulator and took a few minutes for it to clear out. So not sure if I have an issue, with the unit injector or just need to let the truck run longer and work the air out. Quote Link to comment Share on other sites More sharing options...
fjh Posted September 10, 2022 Share Posted September 10, 2022 1 hour ago, DieselDog5.9 said: Catching up on some maintenance, changed the exhaust manifold gaskets due to a leak, replaced the radiator, belt tensioner and belt. As part of this process had to remove the fuel jumper lines from the unit injectors to the cylinder head, immediatly put plastic covers on the unit injectors. Job went fairly smoothly however primined the fuel system, and got the truck to fire, definitly missing on No4, we cracked the line, checked the wires, no4 manifold cold, crack the line and no engine droop, definitly have a miss. I have done this job on multiple other trucks and they fire up and eventually work the air out. This spring I changed the fuel pressure regulator and took a few minutes for it to clear out. So not sure if I have an issue, with the unit injector or just need to let the truck run longer and work the air out. It some times takes a test drive to work the air out! Try it! 2 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted September 10, 2022 Share Posted September 10, 2022 you can pull #4 and swap it with another EUP, and see if the issue follows the EUP.. jojo 1 Quote Link to comment Share on other sites More sharing options...
DieselDog5.9 Posted September 11, 2022 Author Share Posted September 11, 2022 I had run the truck for a while, longer than it should have taken, we were cracking injectors looking for cylinder contribution, and fuel started dripping out of the turbo exhaust. 😬 I had thought about swapping the eup's, was concerned about damaging the O-rings. Unfortunatly the truck really needs to run Monday, I have aranged a hired truck for monday if I need it. I had a spare set of injectors from an AI400 that went to the Mack Garage and was turned up to 460 when it was new, I swapped the injector in Cylinder no 4, runs alot better, cylinder is coming up to temp, still have a miss, cracking the injectors Cyl 4 has engine droop 5 does not and has a ton of air, almost like it is being pushed back past the injector. I will be tearing into it again, swapping 5,6 injectors with the spare ones I have. 1 1 Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted September 11, 2022 Share Posted September 11, 2022 (edited) Sounds like dirt/rust got into the injector. Can happen pretty easily. Edited September 11, 2022 by Onyx610 1 Quote Link to comment Share on other sites More sharing options...
DieselDog5.9 Posted September 11, 2022 Author Share Posted September 11, 2022 Cracking injectors it acted like combustion was backfeeding through the injector line. 2 injectors and we are back in buisness. Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted September 11, 2022 Share Posted September 11, 2022 Stuck open, probably why you had fuel coming out the exhaust. 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted September 11, 2022 Share Posted September 11, 2022 (edited) was there a sealing washer at the bottom of the injector bore that was missed and they got doubled up with the new injector? FYI.. If you miss it, then put the inj. plug back in, and you see 3 + threads showing, it will miss-align the injector line, and well?? ..... pull it and look again... jojo Edited September 12, 2022 by Joey Mack poor sperring.. 1 1 Quote Link to comment Share on other sites More sharing options...
DieselDog5.9 Posted September 13, 2022 Author Share Posted September 13, 2022 On 9/11/2022 at 6:51 PM, Joey Mack said: was there a sealing washer at the bottom of the injector bore that was missed and they got doubled up with the new injector? FYI.. If you miss it, then put the inj. plug back in, and you see 3 + threads showing, it will miss-align the injector line, and well?? ..... pull it and look again... jojo Truck ran into the shop just fine, Changed the exhaust manifold and radiator now a miss, this all came before I touched the injectors. There is a specification of 14.34mm between the top of the cylinder head and the top of the injector when installing the injector but before putting the caps on, this is a check to make sure there are not double washers. After changing the injectors ran fine. It was before the injector change that it had a miss. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted September 13, 2022 Share Posted September 13, 2022 I read back a few posts.. seems like it's fixed. Good deal.... Bad injectors?? Jojo Quote Link to comment Share on other sites More sharing options...
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