Hello all. I recently bought a 2001 Sierra 2500hd. 175k miles. As far as I know all parts in fuel system are factory. Also has a tuner installed, however I rarely use it other than looking at engine info, codes, and injector balance rates. It has a severe fuel problem. No smoke at exhaust and when it's called for power it sounds like it is going to fly apart. No power at all. Sometimes worse than others. Seems like it's worse when it gets to operating temp. After it cools off there are times that it runs fine. I do think that I have a couple bad injectors but how do I diagnose the FPR and injector pump?
2001 lb7 duramax fuel issues.
- Thread starter Arlo75
- Start date
I have a buddy bringing a scanner later today to check those rates. What should I look for? And the balance rates on the injectors are all within spec. The highest ones are almost 3.0. There are 2 that read near that. The rest are under or close to 1.0
When it's running at its worst it sounds like a machine gun. It's awful. Would that be injectors starving for fuel?
balance rates are half the info, you need to look at main injection fuel rate as well. post all teh balance rates and the main injection rate when he looks it over.
OK. Thanks for the info guys. Will get back to you later. But one more question. While I'm waiting for him would it be a step in right direction for me to do a return rate test and in doing that could I determine whether the FPR or CP3 need replaced? Sorry guys. Kinda new to diesel engines. Learning here.
They are good to do to help judge the health of the pump and injectors. It's another piece of information to help in determining what the condition of the fuel system is in.
Thanks for all the info guys. However I've found the problem. Was the MAF sensor. Truck runs great but still has a knock. I think and I'm hoping it's the flex plate. At least that's where the noise seems to be coming from. Cheers all. 
Whatttttt lmao we ask for all this info and you think the maf sensor is gonna fix itThanks for all the info guys. However I've found the problem. Was the MAF sensor. Truck runs great but still has a knock. I think and I'm hoping it's the flex plate. At least that's where the noise seems to be coming from. Cheers all.
Lol. I've replaced the MAF sensor and it runs like a top. Just has one knock now. Was knocking everywhere. Lol. Never did get a code for MAF sensor but I'm guessing that the oil from KN filter was causing problems. Runs as good as it did when I bought it. Just the one knocking sound now.
BTW. I did look at the mm3 rates. At idle they were around 7 and under load I seen them go to around 100
Calculated fuel rate. And it was around 7 in park. Update also. Engine seems to be running fine all except the knock when under load and at operating temp. Transmission has been heating up and started slipping today. I've read where bad MAF sensors and cam shaft sensors can cause both a knock and trannie problems. This is killing me. I also seen on You Tube a guy changed everything from torque converter back and ended up being an injector. Any of you close to me?? I'll buy the beer and cook the steaks.
The truck runs great. Sounds fine in park or drive at idle. Gets knock under load and after it warms up but engine still seems to run fine. Don't notice a miss at all. Runs 100% better since I changed the MAF sensor. Seems I've been chasing several problems or one prob has led to another and another.
Let me rephrase that. The truck runs like shit. The engine runs great. I've been a Chevy/GMC man my whole life. Have had prob 10 diff trucks and never any issues besides the normal things. This truck has been a nightmare. Truly testing my loyalty.