P0087 fuel rail pressure low limp under high loads

[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!

[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...

[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]

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...