P0087 fuel rail pressure low limp under high loads

[Kennedy]

Mark,

I can't really say definitively, but in talking to my sources my gut is saying that you are seeing the injectors begin to fail in the ball seat area. This causes excess return rates and of course high fuel temps. I'm hearing more and more of this same complaint with the LBZ these days, but have yet to see one through to the end.

The big thing I am interested in is seeing a set of used injectors from a vehicle exhibiting these symptoms. Then we could test and look at whether it's an abrasive wear issue or a cavitation issue.

I have a notion it's time for another round of me harping: FILTRATION, LIFT PUMP, ADDITIVE...

[Mark Rinker]

"Gawd, with all this driving I've been doing - I hope I don't fail in the ball/seat area as well..."

JK - I switched to your tune earlier today. Going to run it for the next 5K miles at least, for the boats and destinations listed above. The next two boats are on their own trailers, with ~500 miles of empty truck/no trailer inbetween. Should be able to get a good read of unloaded cruising mileage at 65mph average.

I am starting to prepare myself for the reality that I will be buying and installing my first set of injectors for cash. Hopefully I can get through the spring push, first - and spend the money from savings, rather than throwing it on the AMEX and paying it off over the next few months. Its NEVER in the budget...

[Kennedy]

I don't know if you plan any vacation/down time, but if you do we could try to pick a pair of suspect injectors and have them tested. They'll be the hottest of the bunch. Not sure how well a guy could test with a IR thermometer if some similar device, but this should help narrow down to the worst offender(s)

[More Power]

A fuel pressure/vacuum gauge, like the one JK sells, would tell you in moments what the suction draw is, which is an indication of fuel filter life or if a problem might be with the fuel supply system (plugged sock in tank, crimped hose, etc.).

Jim

[Kennedy]

A fuel pressure/vacuum gauge, like the one JK sells, would tell you in moments what the suction draw is, which is an indication of fuel filter life or if a problem might be with the fuel supply system (plugged sock in tank, crimped hose, etc.).

Jim

I've done everything but hit him upside the head with the gauge so far and he still hasn't grasped the value when troubleshooting OR knowing when it's time to replace that expensive fuel filter.

[Mark Rinker]

LOL - however I don't see anything that points to a fuel system restriction, as that would be a more consistant problem.

What I am describing / experiencing happens only under very specific circumstances - i.e. heavy load + pulling hills + outside temps >75F.

Its definately fuel temp related, unless 180-190F fuel temps are considered normal...

[JohnC]

Its definately fuel temp related, unless 180-190F fuel temps are considered normal...

Or you can't get enough fuel through the system to control the temps...

Whack!

[DmaxMaverick]

LOL - however I don't see anything that points to a fuel system restriction, as that would be a more consistant problem.

What I am describing / experiencing happens only under very specific circumstances - i.e. heavy load + pulling hills + outside temps >75F.

Its definately fuel temp related, unless 180-190F fuel temps are considered normal...

Realistically, no. It isn't. You're talking to the wrong end of the horse. Cause <-> Effect. Your fuel temp is an effect, not the cause. It isn't a paradox. Something is causing the results you are seeing. Elevated fuel temperature is the result of a component failure.

180-190°F is not normal. On mine (2001, but it shouldn't be too far off), the highest temp I've seen is around 160°. That was ascending Pacheco Pass (several miles of 6%) with 22K+ on, and an ambient temp of 118°F. It was as hot as it was going to get.

[Mark Rinker]

Guys, I clearly understand that the fuel is getting too hot, as a result of SOMETHING. Certainly the fuel is getting its heat transferred from engine componants - injectors and/or injection pump, its not pumped into the truck HOT! LOL

Yesterday was a big heavy boat up the North Shore of Lake Superior. All the ingredients for setting a code - except one - ambient temps were in the 40s and 50s, so no issues and fuel temps were 130s-140s, max.

Load + outside heat + hills = high fuel temps, in my case. When it hits 180/190...BING! I get the code.

[Mark Rinker]

Or you can't get enough fuel through the system to control the temps...

Whack!

If I were short on fuel, I'd be short on power. Power is normal - even when turned up with JK's tune. Yesterday on a few hills, I downshifted to 4th and stood on it. My pump can maintain 24k requested and 24k actual fuel rail pressures, indefinately. Try that with a plugged/plugging filter, crimped fuel delivery hose, or plugged tank sock.

Sure looks like injectors to me, but I won't be replacing them until there are more driveability related problems than I am experiencing right now. Todays issue is the ECMs, and a theoretical one for members of TDP to digest. (No white smoke, no power loss, no knock, no oil dilution, etc...)

I am not concerned, under extreme circumstances, that my Requested and Actual FRP vary by >10%. In fact, this whole issue could be programmatically eliminated through a few tweaks with EFI-Live...there are probably many LB7 trucks out there running around with the same issue, but the ECM doesn't detect the variance and set a code. That is why an LB7 with restricted fuel filter will run until power is down, with no check engine light. LBZs with same filter restrictions will complain of low FRP...

[Mark Rinker]

I've done everything but hit him upside the head with the gauge so far and he still hasn't grasped the value when troubleshooting OR knowing when it's time to replace that expensive fuel filter.

Unless the gauges can be in-cab-mounted for observation during loaded, grade towing on hot days, I don't think they will be helpful in troubleshooting this problem.

Unless one of you guys wants to crawl under the hood, and go for a ride...

[JohnC]

If I were short on fuel, I'd be short on power.

My comment was based on the assumption that excess fuel flow is required to keep temps in check, like cooling the PMD. You may have enough fuel to produce the power, but nothing left over to carry the heat. Also, heat of "compression" likely contributes more the fuel temps than heat conducted away from engine components, but I could be wrong...

[DmaxMaverick]

I don't think it's injector(s). The possible return rate for an individual injector is minimal, and not of consequence compared to the return rate of the remainder of the system in regard to heat. If all 8 injectors were returning excess fuel to the point your fuel temp increases to the rate you are seeing, AND the rail pressure can't maintain, you would have a noticeable condition not limited to the conditions you are seeing. The PCM would be throwing a fit and you would have DTC's across the board. The injector parameters are monitored very closely. No way I can see it could return enough fuel to cause the issue and go unnoticed. It is a matter of likelihood, and I don't see it as likely. What's the likelihood of all 8 (or enough injectors) to fail in the same manner at the same time? Your odds are better at winning the lottery.

I'm still thinking pump or FRP regulator. The conditions you create may very well be pushing the fuel flow rate beyond what the system can maintain, while just under the envelope is sustainable. Pumps do not make pressure. They ONLY provide flow. A restriction is what causes pressure to develop, and pressure is maintained or limited by the amount of restriction. If the FRP or pump is bypassing, not by design, the maximum pressure attainable will be less. Fuel flow is friction, and friction is heat. At 24K PSI, this can be substantial. In any case (during your episodes), the pump is unable to develop sufficient flow to maintain desired pressure. This is either a failed pump, or a component responsible for maintain restriction. IMO, the FRP is the only component capable of flowing enough fuel to cause all the conditions you are seeing, assuming the pump is able to provide sufficient flow otherwise.

[Kennedy]

Cause-effect as Dmax Mav stated is my inclination.

It goes like this:

High loads due to head wind causes you to run deep into the tables and at a higher fuel pressure. Higher fuel pressure with ball seat issues will mean more flow and when the fuel passes it gets HOT.

The restriction gauge IS handy to verify the filter condition. This can change in one fill up or less. It will generally show at idle, but I have had guys add a hose to my gauge and clip iunder the wiper to observe.

[Kennedy]

I have fielded 4 calls from LBZ owners already today and it's not even noon.

1) Had P0087 codes and others. Replaced pump no cure. Replaced injectors and his fuel pressure issues went away. Now he's chasing boost codes. Totally stock truck

2) Has 4 Dmax trucks pulling RV's 2) 2007 LBZ, 1) 2005 LLY and 1) 2004 LB7. The 2007 LBZ's are the only ones giving grief. P0087 both trucks, sudden onset. Totally stock I believe

3) 350k and no fuel pressure problems. Running TS MP-8 (jacks fuel pressure) and called regarding different issues.

4) 2006 LLY (actually LBZ) 300k+ hauling RV's now getting P0087. Has Edge with monitor and uses it to clear codes.


I'm thinking this is still injector related (caller #1 supports this, BUT I also think this may be one of those things like the 2001 where we can do some programming changes to address this. Unfortunately not enough of the fuel psi info is available to do this at this time.

[Mark Rinker]

I recently received communication outside TDP from another 2006 LBZ owner who also hauls cargo (trailers) commercially. He had been experiencing the same P00087 low fuel rail pressure code (with limp) when the truck was fully warmed up, and while running loaded in the hills. Recently, the problem had been occuring more frequently, with less load...all symptoms identical to those I have been experiencing.

Their GM dealer had previously recommending 8 new injectors due to 'high return rates'. They did perform the physical return rate test with tubes and graduated cylinder. The truck was exhibiting no other symptoms of injector problems - no smoke, no oil dilution, etc. and had 215K miles on the factory set.

They were not convinced, were not willing to spend 4K uneccessarily, and kept on digging for answers.

Finally, another GM dealer they found on the internet had pointed out GM bulletin PIP4526 which deals with collapsing rubber fuel lines, on the draw or supply side. They replaced a section of hose per the bulletin, and have had no further issues with similar loads over similar mountains.

Hope this helps someone scratching their head over P00087 codes, with a fresh new filter and no other driveability problems. I have yet to repair my truck, but am confident this will address my issue, too. Possibly a GM tech reading this could cut and paste the contents of the bulletin in this thread.

[Kennedy]

Hmm, I wonder if a fuel system/filter restriction gauge would be helpful in diagnosing this???

[Mark Rinker]

The gauges would have to be mounted in the cab - not under the hood, so you could monitor restriction under high loaded fuel demands, while driving uphill, loaded with trailer.

Also, the lines would have to be tapped pre-filter, and then somewhere between the tank and the restriction, which in the case described was somewhere near the transmission.

Honestly, not knowing what we now know of the line collapse under demand and resulting restriction - there would have been no reason to install the gauges in these locations.

[Kennedy]

Actually for the benefit of those who may encounter a similar condition, step 1 is to measure fuel filter restriction. It is not neseccary to measure at any place other than the factory test port at this stage.










Step 2 would be to measure restriction under load provided Step 1 test is passed. Now this gauge has a fixed mount to simplify operation, BUT a hose can be easily added and the gauge placed up under a windshield wiper (standard practice) while the truck is driven.

When troubleshooting something like this the first suggestion I typically make is measure filter restriction. Maybe I need to rephrase this to: Measure fuel system restriction as it seems there is an assumption that a new filter fils this operation. While a new filter CAN, it is never a given. I've seen filters load in as little as a couple hundred miles. Mdrag has not been here in a while, but he and I had this converstion some time back. Out came his restriction gauge, filter verified as loaded and problem solved until it loaded again...

[Mark Rinker]

Got it! That will really help the next time I am troubleshooting fuel related issues while hauling big oversize boats across the US or Canada!!!

Thanks, John!