Cat fuel problems

If it is an older truck, it can be fuel lines collapsing....

 

How about boost pressure sensor. I have had trucks that will not get out of there own way with no codes. Will not fuel with out the ecm seeing air. Did he check fuel pressure? Also check vac reading on output of the primary fuel filter should not be higher than 5 inhg. My not be filter but something that is stuck in pickup or fuel line. Also put sight glass at input of primary and look for bubbles may have rubbed small hole in suction line.

 

How about telling everyone what engine you are talking about? Year, Model, Spec?

 

We had that trouble with a C-7, they replaced a turbo boost sensor and it ran like new for about six months, then same thing, replaced again and ran like new, now it is starting to loose power again. This is an Acert as well. I don't know any more than this.

 

You just have to love people that diagnose buy the ripping and tearing method, The boost sensor, you check that while you are checking the CAC. Fuel preasure, that you have to run around the truck 4 times, clockwise of course. sorry I just could not resist.
An engine needs AIR, you check the CAC and while hooked up, the boost sensor reading, the intake manifold, you look at the exhaust ,on a school bus the tip is it bent over, seen that. The turbo if it has a waist gate, plumbing leaks, and operation. Has anything gone through the turbine and it it free. The air filter, If it gets wet, then drys, some will really restrict the flow of air.
Fuel, like suggested, a vacuum guage in the primary outlet, and preasure under load.
When it is running listen with a bar on the head for abnormal noises, pull the cover and check the set and look for broken springs, injector and valves, is the cam OK everything is working as it should.
The throttle is it going to 100%
You really want to give as much information on the unit as posible.
Just a thought!

 

if it is a c-7 acert.they are by far the worst engines for having "touchy" injectors.any slight amount of contaminant in the fuel (water,gasoline,wrong additives etc.) will kill the injectors.does not mean it is your problem.should diagnose properly as john said.check for desired/actual icp at idle and loaded.since heui pump has been replaced,sounds like injectors to me,but "check twice,replace or fix once"good luck.

 

There's quite a few diagnostic steps to do before throwing all those parts at it. Actuation pressure test would be my first. Also a manual oil pressure gauge to verify oil pressure is good. Many HEUI engines don't have an oil pressure sending unit at all. They will not run without oil pressure, so was optional. Low oil pressure will make it run crappy. Low oil level can make it run bad. Has the oil been changed recently? Thin or dirty oil is bad for HEUI engines.

What tests did he run so far? How did the computer tell you that it's a fuel related issue? What exactly did it say?