Fuel Pressure Issues

[Wildcat18]

I have a LBZ Duramax and I am having an odd fuel problem. While cruising at around 70-75mph fuel rail pressure around 13.5k it'll jump any where from down to around 3k psi to 23k psi usually more around 8k to 18k psi and you can feel the truck lose and gain power as the pressure fluctuates but my speed will remain the same and only the actual pressure will jump around. It will do it at lower speed with a lower rail pressure also. (Almost sounds like it's backfiring coming out of the exhaust) The fluctuation is usually less frequent and less of a big jump, under full throttle it seems fine as well and doesn't seem to lose rail pressure also it doesn't have a problem at idle and sounds normal at idle. My rpms are not jumping and seem normal.

I recently replaced my fuel filter housing as well as replaced my airdog filters and just put in new thermostats. I haven't replaced my fuel pressure regulator yet but not sure that is the issue.

Do you have any suggestions?

 

[Chevy1925]

Moving over our posts from the other thread you posted in...

 

[Chevy1925]

its generally a FPR issue but you need to line out your symptoms, what you have done and your truck information. Start a new thread so we can start fresh with your issue.

 

[JoshH]

Did you ever find out what the problem was? I am having the same issue.

It's unlikely you will get a response from him since he hasn't been on the site since 2018, but can you give us a little more info on your problem? What are the mods on the truck, and what steps have you taken to diagnose it?

 

[Fingers]

Most likely the FPR shuttle sticking. But don't rule out a bad electrical connection.

Seems to be common after rebuilds when the engine/pump has sat for a while. Remove the FPR, remove shuttle, clean everything with carb cleaner and back together.

 

[Wildcat18]

My symptoms are the same as his. Fuel pressure fluctuates mainly around 8-10k psi. It comes and goes and it is not throwing any codes. I have a 2006 LBZ. I have an airdgog 165 lift pump and an HSP Max airflow bundle on it but that is it. I just recently replaced my thermostats and my fuel filter housing.

 

[Wildcat18]

Most likely the FPR shuttle sticking. But don't rule out a bad electrical connection.

Seems to be common after rebuilds when the engine/pump has sat for a while. Remove the FPR, remove shuttle, clean everything with carb cleaner and back together.

I should have clarified that I did not do a rebuild.

 

[Chevy1925]

My symptoms are the same as his. Fuel pressure fluctuates mainly around 8-10k psi. It comes and goes and it is not throwing any codes. I have a 2006 LBZ. I have an airdgog 165 lift pump and an HSP Max airflow bundle on it but that is it. I just recently replaced my thermostats and my fuel filter housing.

did any of this start at the time you installed the airdog lift pump or not long after installing it?

 

[Wildcat18]

did any of this start at the time you installed the airdog lift pump or not long after installing it?

Nope. It has been on for over a year. I did just change the filters on it though.

 

[Chevy1925]

Miles on the truck? when is this fluctuation taking place? decel, under light accel, backing trailer up, need more details.

 

[Wildcat18]

Miles on the truck? when is this fluctuation taking place? decel, under light accel, backing trailer up, need more details.

333,000. Happens mainly on the hwy. It will be running just fine then start happening. It gets bad then all of a sudden it's fine. It will fluctuate and feel like it is sputtering but it maintains speed.

 

[Chevy1925]

Sounds like its the FPR then. Make sure you buy a legit bosch one. there are 30-40 dollar cheapies and its a toss up if they hold up over time. i believe a legit bosch one is around 150-160 bucks