lly surge

[Mpsoldier]

Ok so as many know i am not home just but we have a lly in the shop that my best friend is working on he's a amazing mechanic and fabricator, but for some reason i don't think the problem with this truck is the injectors. So here's the story truck is locally owned with 98k on it two injectors where bad so replaced them now the truck is surging at lower rpm's. Next step taken was ramping up rail pressure to 26k only 13k came out of the pump. He was thinking another injector but i was thinking cp3 or fpr what do you guys think? BTW this just gives me something to focus on while i am here and i am sure he will figure it out. Truck has 98k on it and all stock.

 

[Fastorange]

did they test the balance rates again? i know with efi live something was messed up with the balance rate test.. so there is a chance that they replaced the wrong injectors

 

[Evan@InglewoodTrans]

It was the DVT function to shut injectors on and of that was wrong as far a know.

 

[jc1843]

Many LLY engines have a weak FPRV, and that can bleed off high rail pressure. Best to do a "Bottle Test", that will confirm if the FPRV has a problem.

 

[DieselmafiaLLY]

x2 fprv, also check fpr those also go bad on LLY. I would rather buy a 180$ fpr and some .02$ ss washers and shim your fprv then replace cp3 or injectors...fyi if you change the fpr put in an LBZ one

 

[Mpsoldier]

Tech 2 was used yes balance rates are in check. I have heard of the efi live problem but usually i use the tech 2 anyway for diagnosing problems on stock vehicles.

 

[DieselmafiaLLY]

is the truck tuned?

 

[Devon]

Probably the fpr? I switched my bad one out for a lbz Fpr and even after tweaking the tune I get a low acceleration surge at low rpms.. Nothing to irritating though.


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[Mpsoldier]

yeah just trying to get fuel pressure back thats what i though it was as well fpr not injectors i am going to let him know. Also the truck is stock as stated in the first post and staying that way as per the owner...

 

[adeso]

if he isn't paying for labor I would shim the FPRV first, then try the FPR. If he is paying for labor I would just do both at the same time

 

[Mpsoldier]

going to go ahead have him shim the rail first then fpr sense i think i got like 6 or 7 in the shop in working order thanks guys

 

[BobbyBDirtyMax]

My truck did the exact same thing and just last weekend I replaced my stock LLY FPR with a new one for an LBZ which I bought off All Season Diesel. Stopped my low idle surge and added a bit of RWHP too. The next day after testing it without flaws, I put on the LBZ duramax turbo mouthpiece, a PPE ported fuel rail fitting and modified my banks LLY intake so I didn't have to get my MAF remapped and OMG after the computer tuned itself to what I'd done.....My mostly stock LLY is a monster. Good luck just figured I'd help if possible

 

[quinton]

Mine is surging also going with the Lbz fpr soon and gonna port the fuel rail.

 

[Mpsoldier]

yeah doing a return rate test seee what that brings up then doing shim then fpr