dying on the freeway?

M

mcmotorsports

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Mar 6, 2008
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My friends 99 cummins is having problems, almost shutting down after long durations at freeway speed.

List of mods:
100hp injectors
100hp chip
Super B turbo
BD intercooler
Holley puller pump
OEM lift pump
45hp injection pump
ATS exhaust manifold
cold air intake
stacks

Is there a way to tell a bad injector from the injection pump? I already took him to a local shop that I work with, at that time it was only stumbling on the freeway, they said if the check engine light isn't on, don't worry about it??? It's getting worse, to the point it almost stalls. But if he goes full throttle, it will straighten out for a while.

Already replaced the lift pump, puller pump pushes pleanty of volume, I doubt that's the problem, verified that myself.

His mechanic said either the injection pump, or an injector. Could one injector cause this? And how do you tell the difference?

Thanks,
MC
 
dying on freeway

If it were a bad injector, you can crack the lines at the head. Most of the time when you crack the line it will change the sound of the engine. If you crack one and it doesn't change the sound then most of the time that is the culprit. A lot of times though, you will have a dead miss at idle if it were an injector. Something almost exactly like this happened to mine. Fuel pressure would bounce around at about 70mph on the freeway, truck would cut in and out, push in the clutch and it would die. I dropped the fuel tank and I guess I got ahold of some bad fuel cause the screen at the bottom of the fuel tank was clogged with dirt. Cleaned it and its been fine ever since. Hope this helps you.
 
I'd check the MAP sensor connectors and look for corrosion (usually will light the CEL, but who knows) if the ECM loses this signal, it will derate the engine and you'll see no more than 5 PSI boost.

Also could be the APPS starting to act up
 
No fuel pressure gauge, runs smooth at idle, I'll tell him to start checking the wiring and sensors, atleast eliminate that.

Thanks guys, good starting points. He keeps thinking its the injection pump, we'll see what happens,
MC
 
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