P0087 fuel rail pressure low limp under high loads

[Mark Rinker]

Well, the second time this happened - only 1,500 miles into a fresh OEM Delco fuel filter - I knew there had to be something more going on, than just bad fuel.

No smoke at idle, none under load, but watching requested and actual fuel rail pressure showed exactly what was happening...when requested gets to 22k# the actual begins to fall behind, and when it peaks at 24K# or more, the ECM catches the variance and sets the code.

A helpful and knowledeable diesel tech at www.whitesmountainchevy.com of Casper, Wyoming verified that he has seen this before (P0087 with new fuel filter that is flowing properly) with trucks used to pull heavy equipment in the Wyoming oil fields. Said that unlike classic injector failure symptoms such as smoke at idle, this one initially had him 'scratching his head' until it became apparent that the weak injectors and/or weak high pressure pump caused the low fuel rail pressure code to be set due to their combined high return rates, rather than due to a restricted filter, which is usually the culprit.

In my case, it took a loaded trailer, Wyoming mountains, and hot engine temperatures.

They documented my situation at 101,500 miles - and I used my own ability to reset the code to continue the trip on to Salt Lake City. Code was reset about 12 times, total - always while climbing grades. Unloaded (empty) trip home was no problem.

[Duramaster]

Here is something to your P0087. We had a few trucks come in with the P0087 and went through the fuel filter routine and come to find out the P0087 would set 350 mile or so later. These particular vehicles were "HAULERS" as well. Come to find out, the flexible fuel lines at the engine and under the vehicle near the transmission would kink and cause the P0087.

Here is the bulletin.



2008)


Subject: Diesel Engine Fuel Line Repairs


Models: 2001-2007 Chevrolet Silverado Classic

2001-2007 GMC Sierra Classic

2007-2009 Chevrolet Silverado

2007-2009 GMC Sierra

Equipped with the 6.6L Diesel Engine RPO codes LB7 LBZ LLY LMM




--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A dealer may need to perform a repair on the rubber portion of the fuel supply (suction) lines. The rubber section of the line could become kinked or collapse. Fuel lines that kink or collapse may induce a fuel system restriction (high vacuum gauge readings) or DTCs P0087, P0093, and/or P1093 to set.

If a technician was to suspect the rubber portion of the fuel feed line collapsing or kinking, replacement of only the rubber line is acceptable.

Recommendation/Instructions:
Complete the steps below to repair the rubber section of fuel supply line:

•Carefully cut, split, and remove the OEM crimp from both ends of the flexible hose. These crimps can be cut with a small cut-off wheel. Split the crimp into two pieces (use your discretion on first cut location, then cut directly across from, or 180 degrees from first cut). Special care must be taken not to damage the flare on the end of the steel pipe that will be reused.
•Remove the OEM crimps and flexible portion of hose from the existing supply line.
•If replacing the rubber section of the supply line, a 1/2 ID hose meeting SAE specification 100R3 is suggested. Dealers may be able to find a local supplier for this hose, or can contact the manufacturer Parker Hannifin. The replacement hose would be a 1/2" diameter Parker part number 601-8 or H017-8. To find a local distributor the Parker website can be accessed at www.parker.com
•Use worm type hose clamps (use double clamps on each end) to attach the replacement hose to the existing pipe.
The locations of the flexible hoses are pictured below.





Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

[Mark Rinker]

Tech did a suction test while I was standing there. If fuel lines were crimped (much like a plugged filter) I believe that test would have shown the restriction.

There are clearly three injectors out of range, indicating high return rates. I failed to mention clearly that the tech wrote up his findings, and recommended replacement of all eight injectors...

Thanks for the TSB. I'll check those lines, anyway - just in case!!!

[Duramaster]

Those lines won't show much of a obstruction at idle or even at 3000 rpm's in the shop. It's more of a load thing (trailer, hill, WOT, PULL BABY PULL!)

[Mark Rinker]

Hmmm...duely noted.

I would sure like to get a fresh set of eight sprays, if possible, since the return rates indicate that as necessary, but...

The truck will certainly be up on the hoist looking into the other possiblity.

Thanks for taking the time to post. Possibly its the combination of the two.

[Mark Rinker]

Those lines won't show much of a obstruction at idle or even at 3000 rpm's in the shop. It's more of a load thing (trailer, hill, WOT, PULL BABY PULL!)

I also inspected the supply line with the truck on a hoist, it appears fine (no obvious damage or kinks) but may replace entire supply line anyway, to rule out the possibility of an intermittent collapse... which would be nearly impossible to see unless you are under the truck when the high fuel request was happening!!!

(BTW it doesn't take WOT to trigger my P0087. It does take a fair load (12K#), warm/hot engine temps, and a reasonable climb - one that would put the %LOAD at 95% or better on the OBDII data...)

[DmaxMaverick]

Have you given thought to a lift pump setup? Certainly not a complete solution, but could edge you across the threshold causing the fault. What's JK think about it?

[Mark Rinker]

Had thought about that ... hadn't taken it any further. I still have a NIB Delco inline lift pump from the 6.5L days, would that provide enough flow?