Hot outside, she cuts out

[ChuckZ]

I have a 2006 LBZ, with only 186000 miles, my 04 has 320,000. I pull rv's for a living. When the outside temp. reaches above 90, and I have a 12000+ trailer on, going up a hill, she will not hold cruise and will cut back to 15 or 20 mph, it has not died completly. After changing 3 fuel filters in Nevada last week and only going 2 miles, I determined in my wisdom, that it wasn't the filter. I'm stubborn, I have changed 4 since. After setting overnight or just running in cool weather she runs fine. The DTC each time has been P0087 (3times). The fuel filter gets so hot, I blistered my finger on the second filter. The tranny temp runs around 200 to 210, with the engine staying around 210. neither way to hot. Since the first decrease in power I have pulled 7 trailers, but each one where the outside temp was over 90 she cut back to a limp mode. My dealer disconnected the fuel heater thinking that it might be on all the time, no luck. It will start right up, if you shut it off. What's up??

[jbplock]

Have you checked the fuel cooler? It's on the frame in front of the fuel tank.

[ChuckZ]

Yep, it seems OK, no clogs or bugs. Had tranny shop do a flow, everything was OK there also.

[Duramaster]

:confused: How about checking the air flow through the CAC/ Radiator/ Condenser/ Trans cooler assy? :confused:

[Duramaster]

It would be nice to know what the actual fuel rail pressure is when this happens. You could possibly have a defective fuel rail pressure limiter valve.

[ChuckZ]

AAmco checked the flows after they serviced the tranny, after the first failure.They said everything was good. I had called them hoping to add a tranny cooler. The rail pressure, at the dealer, after letting it run and driving it for 4 hours, dropped to 20,000psi.

[killerbee]

I will make a guess here.

It sounds to me that you are running into heat induced FPRV bypass. I have not studied the LBZ, but if it has the same FPRV as we do, it is popping. And it does self reset when pressure is removed.

Suggest to the dealer to replace the FPRV

One other thing it could be, cavitation. If the fuel gets hot enough to start to vaporize in the suction area of the pump, gas will form and the pump is crippled. If fuel is staying under 200, then it probably is the former.

[Rabbler]

Have you checked the fuel cooler? It's on the frame in front of the fuel tank.

Did aamco flow check the trans or fuel cooler?
Like jb said the FUEL cooler is mounted on the front of the primary fuel tank (looks like a tranny cooler) As it's under the vehicle it is prone to clogging from mud. gravel etc and overheated fuel will definitely cause driveability problems.

[ChuckZ]

Didn't check fuel cooler, but will now, thanks

[ChuckZ]

It appears there are (4) injectors not up to snuff. They are letting to much fuel bypass and when called upon for power can't put out. Now if the diesel shop can only find injectors!!