P0087 fuel rail pressure low limp under high loads

[JohnC]

Have you ever watched the fuel temp this closely before? Maybe the temp is normal and the pump can't keep up with the thin fuel...

[DmaxMaverick]

Curious....How are you reading "fuel return rates" on the roadside? Perhaps injector balance rates or PWM, but return rates?

Anyway, start looking for the cause of the fuel temp increase. A couple possibilities come to mind....HP pump bypassing internally (failing), or failed/failing FPR/sensor. Friction = Heat. This applies to all states of matter, including liquids. Either the pump or FPR/sensor can cause this condition, which increases fuel temperature. This can also cause a snowball effect, regardless of the suspect component: Component bypasses excess fuel at high pressure -> fuel temp increases -> fuel returns to component at a lower viscosity -> fuel bypass increases (due to lower viscosity) -> fuel bypass increases fuel temp -> lower fuel viscosity and progressively increased bypass condition push the pump's ability to develop pressure -> PCM unable to maintain desired fuel pressure -> DTC set.

This condition is not likely a restriction issue. Generally, a restriction rate will decrease as viscosity decreases. This is opposite the condition you describe.

The later lower temps and less load demand doesn't help much with the diagnosis. The lower ambient temp helps prevent higher fuel temps (increases the system's ability to shed heat), and the lesser engine load reduces the fuel volume demand (less foot-feed required). The condition may still exist under this condition, but doesn't exceed the pump/FPR ability to maintain the desired fuel pressure range. Because of this, you won't likely get a dealership or garage able to duplicate the issue. You'll have to get the tech with you on the road with a load on, or on a dyno.

[Mark Rinker]

>>> Curious....How are you reading "fuel return rates" on the roadside? Perhaps injector balance rates or PWM, but return rates? >>>

Sorry, wrong terminology. Reading injector balance rates, using Edge Evolution...

Today, completed boat delivery to Walker, MN with no further codes or issues. Fuel temps averaged 130-140 all morning... (Have NOT yet cleaned the fuel cooler, but plan to.)

REQUEST FOR ASSISTANCE: To any of you that haul trailers, 5'ers, etc. and have the Edge Evolution, Predator, etc. where you can monitor fuel temps - would you give me your averages for 60mph level cruise? Please include ambiant (outside) temps during your readings. Interested to know what you are seeing...thanks in advance!

[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