When I got this truck a month or so ago, it would do 88-90 MPH out on the freeway if you really stood on the pedal. Now, all of a sudden, I can barely keep it going 65 and heaven forbid I come across a hill... then it drops to somewhere between 25 and 35. Something is very wrong.

I don't really know where to begin trying to diagnose this problem. The truck seems OK up to about 20 or 25 MPH, then levels off and the tranny does some weird shifting every once in a while. I don't really think it's the tranny, though, because when I am able to get it up to 60 or 65 (with the help of a downhill) the tranny is fine, while the truck speed then just gradually decreases because of lack of engine power.

For some reason I'm thinking this could be the pump. I had a leaky throttle shaft seal not too long ago, which seemed to fix itself. It is a 235,000 mile truck, and I don't think the pump has ever had any attention paid to it.

Does pump failure seem likely to you guys?

I don't feel like I have the time or expertise to diagnose this problem, so....
Do I take this thing to a Dodge dealer? (Do they know how to work on the diesels there?) Or to a general Diesel mechanic? Or to a Cummins service center? (There's a Cummins service center near me.. I'm only afraid that they will be expensive... and if for some reason it is a trans problem, it will be money and time wasted at the Cummins place...)

Thanks,
CR

(Maybe I should have gotten a manual trans....)

 

Are you making any boost? Check the simple things first like a blown innercooler boot or a plugged fuel filter. A transmission problem would most likely be shown by high engine RPMs and low ground speed. If the engine isn't reving when you're standing on it going up a hill at 35, it's probably not the transmission. After the filter, I'd check for the IP sucking air (cracked or loose line).

Let us know what your RPMs are doing going up that hill and when the last time was that you changed the fuel filter and we'll go from there.

BTW, if it was me, I'd go to Cummins before I'd go to Dodge.

 

Boost is normal..
RPMs are on the low side of normal...
Temps are OK, EGT maybe a little high...

(Sorry, but what's the IP?)

Will change fuel filter later today and report back.

CR

 

By the sounds of it you have no overdrive and are just running it in 3rd gear all the time.

IP=Injection Pump

 

Actually I do have overdrive.

The performance has been decreasing steadily, and when the performance was just beginning to slide, I was going into OD all the time, no problem.

On downhills or sometimes on flats I can feather the accelerator and I can still get it to slip into OD around 55-60.

CR

 

sound like lack of fuel to me... plugged filter, lift pump, air in lines, injection pump.

First and easiest change fuel filter. if that does not help look for cracked loose lines and if you have a fuel pressure gauge you could check that too.

Good luck,
Michael

 

Change the fuel filter. That should be the first thing looked at when trouble shootong low power.

 

When you say boost is normal, normal should be near 15lbs for a stocker. When you say rpm's lower than normal, when you put the transmission in neutral and stand on the accelerator are you getting at least 2500 rpm's?

 

Check to make sure you are getting wide open throttle. Have a helper stand on the pedal, and you look at the lever on the pump and make sure it travels all the way to the WOT stop.

 

Since you say EGT is a little high, take a look at the air filter element as well as the intercooler boots.

(I was gonna say to check the throttle linkage but torquefan beat me to it )

 

HOLY FRICKIN' FUEL FILTER, BATMAN!!!!!

What I didn't mention was that this was occurring during a long distance drive, one which should have taken 13 hours and took 19 hours instead.

I was going THAT slow.

Changing the fuel filter fixed the problem! Thanks guys!

I've owned quite a few cars and trucks, but I think I already know more about this one than I did any of the others. And most of that is thanks to this forum. This is an invaluable resource... I'll say it again, Thank you very much fellas. Saved me a lot of money.

For all you newbies out there (like me), Change your fuel filter. Now.

CR

 

I think I need a fuel pressure gauge.

CR

 

Glad it was that simple and glad that we could help.

That's why my spare fuel filter (and I always buy another one as soon as I use my last one) rides behind the seat. Never have had to change one alongside the road yet but always nice to know that I have one if I get a fuel flow problem.

Did you get a Fleetguard from Cummins (my personal preference) or what brand filter did you put on?

 

I am having the same problems, after calling 4 different diesel shop from coast to coast you guys have said everything they told me. Ya'll rock. I mpg is down to like 14.5 and last tank it was 19.5, Can the filter cause that kind of problem? By the way what do you think of this idea. On the banjo fitting going from filter to IP there is a air bleed screw. The line going from the lift pump to the filter doesn't have an air bleed. Is it possible or even logical to go to cumming and get the one with the air bleed and replace the one the doen't have it. Then I want to replace both bleed screws with fuel pressure gauges for pre and post filter, this would help to determine whether the filter is the cause.

 

A lot of 24valve guys do that but for us just do what the other guy said and carry a spare filter, I do, and if you have problems change it!! But if you want gauges it''ll work. IMO a spare filter isn't that expensive to have or to even change it every few oil changes or at least once a year as PM