Insights into Fuel Problem

[LB74ever]

Fuel filter on my truck physically failed. I knew it was time for a change so I already had a replacement in hand. Switched it out. Afterwards a P0088 code for high fuel rail pressure appeared. It has been accompanied by the following caveats.

After I start the truck, it idles rough. If I reset the code, the code immediately reappears. However, if I let it idle for 15 minutes and reset the code, it does not reappear. At that point the engine is also idling smoothly.

If I take it out to drive, it runs smoothly at low speed. However, it is clearly stuck in “limp” mode. Will not go over 25 mph. As a reference point, the truck did not demonstrate any performance problems before the fuel filter failed.

Hoping someone can offer some actual expertise to help me remedy this problem. Truck is old but solid and meets my current needs. Have searched for information on the internet but seems like partial and/or questionable information predominates. Thanks for any help provided.

 

[TheBac]

Lift pump? Have you ever replaced any fuel system parts in the past? Would really help to know more particulars of the truck.

 

[LB74ever]

Lift pump? Have you ever replaced any fuel system parts in the past? Would really help to know more particulars of the truck.

No lift pump. I did not buy the truck new but it is completely stock as from the factory as far as I know based on driving, maintenance, etc. over the last 8 years. What particulars would you like to know? Had the injectors replaced spring of 2019. Have driven it across country pulling trailer and equipment numerous times (work related) during the time I have had it. In fact, bought it for that purpose. Other than the injector failure and a line rupture have never had a problem.

 

[Ron Nielson]

Fuel filter on my truck physically failed.

Please explain this. What year is your truck?

 

[LB74ever]

Please explain this. What year is your truck?

As I am sure you know, there is a float that screws in at the bottom of the fuel filter. My understanding, it is a water fuel separator. On the old filter, the housing had collapsed (rusted?) resulting in failure of the structural integrity. Upon removing the filter, I attempted to unscrew the separator and the filter housing was so weak it actually gave way leaving the threaded portion attached to the separator. My guess is there was some water in the filter and the unusually cold weather we had in the area recently froze the water, expanding it, and augmenting damage to an area already challenged. Subsequently, bought a new separator for use. In fact, I replaced the entire unit, housing, filter, and separator. Had read online the housings had a tendency to fail on older trucks in cold weather. Thanks for the attachment. Anticipating it is applicable. My truck is a 2003, 4WD, crew cab, 6.5ft bed.

 

[2004LB7]

I'm going to guess that the failed filter let debris into the fuel and that may be messing with the regulator on the pump. A stuck or sticky regulator will have a hard time maintaining the correct pressure and you can get that code.

You can try pulling the regulator and cleaning it. But if you're going through the work to pull it, might as well put a new Bosch regulator in. Don't skimp on the brand or cheaper one. They won't last and you'll be back at it on a short time

 

[LB74ever]

I'm going to guess that the failed filter let debris into the fuel and that may be messing with the regulator on the pump. A stuck or sticky regulator will have a hard time maintaining the correct pressure and you can get that code.

You can try pulling the regulator and cleaning it. But if you're going through the work to pull it, might as well put a new Bosch regulator in. Don't skimp on the brand or cheaper one. They won't last and you'll be back at it on a short time

Think that is a reasonable possibility. From the research I am continuing to do, things seem to be pointing towards the regulator. I have read certain scanners have the capability to control fuel pressure. In fact, that was referenced in the pdf Mr. Nielson posted. Do you know of a scanner having that capability for the LB7? Would like to have as much confirmation as possible before tearing into it. Have seen videos stating replacement is a 4-5 hour job for the experienced. That roughly translates into a couple of days for me. Have also seen different disassemblies suggested as to the best approach. Most do concur with your assessment of not skimping on the regulator.

 

[2004LB7]

You need a bidirectional scanner. There are many. Hard to recommend any particular brand. I use a V2 for mine. But an old V1 would work for yours.

Let's see what others say for a current bidirectional scanner

4-5 hours seems high. That sounds like the number for the inexperienced.

 

[LB74ever]

You need a bidirectional scanner. There are many. Hard to recommend any particular brand. I use a V2 for mine. But an old V1 would work for yours.

Let's see what others say for a current bidirectional scanner

4-5 hours seems high. That sounds like the number for the inexperienced.

Looked around at the bidirectional scanners and there is quite the selection. Some seem to be bidirectional but do not have all test and control functions of others. The wide selection was the basis of the question. Is the V2 you reference the D7 by Xtool? Xtool has a wide selection just within their brand. Certainly, will appreciate any additional perspective in regards to scanners. The time number is quoted off a video on Youtube. I think it is grounded in whether one takes off the A/C, alternator etc. From what I have watched that would seem to make the regulator physically easier to get at. However, every video I have watched states it is located in a difficult spot and one is working blind in regard to the bottom torx screw since it is underneath the regulator itself. Another guy just took out the blower shoot/horn and got to it that way but the components mentioned did serve as an obstruction. I am fairly mechanically inclined but do not do such repairs every day. In addition, seems like every job I start (yard, house, vehicle, you name it) turns into three of four along the way. Have learned to include a large time buffer just in case.

 

[2004LB7]

V2 as in EFI live V2

The regulator is in the valley of the engine attached to the CP3 and pointing towards the firewall. The CP3 is near the front of the engine. The intake horn can be removed for more access. I've done it both ways. Depending on your assortment of tools, one may be better then the other.

 

[2004LB7]

This looks like a decent write-up

[Guide] LB7 Fuel Pressure Regulator Replacement

Introduction: This guide will demonstrate the procedures to install the LBZ/LLY fuel pressure regulator in the LB7 duramax. The time taken to accomplish this was around 1.5 to 2 hours. If you don't have all the tools listed below it may be slightly difficult to accomplish in that time frame...

www.duramaxforum.com

 

[TheBac]

Find a 4-6" long torx bit. makes that job a whole hell of a lot easier.

 

[2004LB7]

Find a 4-6" long torx bit. makes that job a whole hell of a lot easier.

This set of ratchets, specifically the hex bit ratchet has saved my but many times and taken hours off some jobs. It reaches and swivels where other wrenches can't. Combined with the 4-6" hex bits Tom mentioned and it can pull that regulator without needing to remove a lot of the other parts

 

[TheBac]

A-feakin-men, brother!