Archived '03 Defuels at 2500 RPM's

[lcaad1249]

I'm trying to help a buddy diagnose a problem with his '03 with 48RE with 60,000 miles. Every time he hits 2,500 RPM the truck defuels. If the AC is on it hits around 2,000. Been happening for about 4 months now. He's changed the fuel filter and there's no codes. Any ideas? He's had an EZ on it before but since the problems happened he took it off. I had him disconnect the battery's last night and haven't heard if it helped or not. Any other ideas?

 

[lcaad1249]

Any ideas?

 

[Pawpaw]

I was hoping someone more knowledgeable would chime in.



Are you sure it's de-fueling and not just running out of fuel? It could be his lift pump is getting weak.



Just a guess, I'm afraid.



Bob

 

[lcaad1249]

I appreciate any input. I'm not sure. That's a good idea. He's been running it for around 4 months by now. Wouldn't a lift pump have given out by now if it was going bad? Is there an easy way to insert a gauge in the system?

 

[Pawpaw]

The one thing I've learned in 30+ years of working on electronic and electro-mechanical equipment is that they don't always fail in a predictable manner. Yes, you would think it would have died by now, but who knows? Since it can't keep up with demand, it's actually doing less work.



I wouldn't worry too much about the pressure, it's the flow you're interested in. Back in the day, we used to unhook the fuel line from a carbureter and let it pump into an old coffee can to check flow. I don't see why you couldn't do the same thing with the lift pump.



Unhook the line from the CP3, then bump the starter to get the lift pump running.



Again, I'm guessing.



Bob



On edit: Did you check for codes before disconnecting the batteries?

 

[lcaad1249]

Yep there were no codes at all. Also theres white smoke when it happens.

 

[Rams-n-Hogs]

Does he have any mods done to the truck, and does he have any gauges?

 

[lcaad1249]

He had an EZ which he took off after the problem started. He said the EZ actually helped get more RPM's.



No gauges.

 

[scootergmc]

I've heard of/seen this once before on an '03 (not a buddy or friend) and it ended up being the lift pump. Similar symptom.

 

[Peter Campbell]

I second with lift pump. The in tank new module or an aftermarket pump right by the tank might be what is needed. THere is the possibility of a high pressure relief going bad on the common rail. I don't know how to tell that is the problem.

 

[silverram03]

Is his trucks lift pump making a slight buzzing sound? Mine was making it ever so slightly. I know when mine went I was leaving a stop light and I felt it stumble right around 2,500 rpm and turned the corner to go to work and she finally gave up the ghost and left me on the side of the road. The dealer replaced the lift pump with the in-tank pump. I would strongly recomend changing the fuel filter. I can tell you one thing in the four years I've been changing my fuel filters some were cleaner than others and I change them every 10,000 miles. Oh yeah when you drain the filter and clean out the bowl and W. I. F. sensor with a clean rag and DON'T forget to make sure the valve is closed before priming. I can now say for sure that the new pump will put out what seemed like 5 gallons of diesel in less than 30 seconds all over the ground. I guess everyone has a bad day every now and then.

 

[lcaad1249]

He changed the fuel filter after his problems started.

 

[sag2]

Pull the inlet line to the CP3 and bump the starter. You want at least 400 ml in 10 seconds. This checks lift pump and fuel filter. Or open the filter drain and measure from the drain hose, but I believe you are not getting filtered fuel doing it that way, so only do it if your sure the filter is not plugged.

 

[lcaad1249]

My friend finally got the problem figured out (by Chrysler). It was one of those things he was embarrased to admit, but it was a clogged air filter. Truck runs great now. Filter was supposed to have been replaced 2 oil changes ago.