96 ram 2500 cummins low power/economy


Old 07-27-08, 02:00 AM
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96 ram 2500 cummins low power/economy

Hello! I have a problem with my truck and hope you can help me with it.

I recently bought a 96 ram 2500 cummins with auto tranny, 4:10 rear, club cab, and 150k miles. I have put a few thousand miles on it, and have some problems. For one, my economy stinks. I am getting 14-15mpg in town and 17-18hwy (hand calculated). The guy I bought it from said he got 25.5mpg at 55 mph, and 22mpg at 70mph. I am consistently reading that folks are getting high teens and low 20s in town and low to mid 20s on the hwy. I personally know of several similar trucks that are par with that.

I have tried driving with a light foot, then with a heavy foot, and actually got about 1 mpg better with the lead foot.

Another thing, and it's probably related and may help diagnose the problem. I have a small single axle trailer...about 1000 pounds. When I hook it up, the truck turns into a dog. I can't pull out into fast moving traffic without fear. It doesn't want to pull the trailer up to speed. At 45-50 mph going uphill, the truck will barely pick up any speed at all even if I floor it. If I can get the truck running at 2000 rpm, it does ok, but at 45-50, it's at 1700 rpm and bogging. If I lock out overdrive, the engine revs, but falls flat on it's face at 2300 rpm. I know this 1000 pound trailer should be an insignificant load on my truck. As it stands, my 23 year old chevy 1/2 ton with a 305 engine can pull the trailer quicker and easier than the dodge.

The turbo bearings feel tight (tolerance-wise) and like they should be. I feel the turbo kicking in once the engine revs up, and it sounds like a turbo should...so I know it's working, although I don't know if it's at full potential. A quick visual inspection of the turbo boost hoses showed nothing unusual.

The engine runs good, and idles well. The truck lopes a little (I get a little "hop" feeling in the seat at idle), but I don't hear it in the engine speed...it's more like a reverberation in the truck frame from the vibrations of the engine. Maybe that's normal? This is my first time owning, but not driving a diesel.

If anyone has any suggestions, I would be grateful to hear them! I like the truck, but I'd love to feel like I'm getting everything I was expecting. Thanks!
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Old 07-27-08, 02:59 AM
Join Date: Mar 2006
Location: NE Wis / Paris France{ In France for now }
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I have few diesel powered truck in fleet and with the Dodge with automatic it should be little more higher on mileage.

Really sound like you have some issue with the injector pump and AFAIK dodge cummins do redlined at anywhere from 2500 to 2800 rpm depending on which type of injector pump it have.

With my older ford diesel truck I have the same gearing as you have but only diffrence is that I have is 5 speed manual and I get about 19 ~ 23 on the road { yeah this is a 4X4 }

did the previous owner tell ya when the last time the engine did have valve adjustment ?? most cummins need a valve adjustment at every 60-90 K miles { they are not too hard to do that they are mech valves no hydrallic valve lifter in cummins engine }

First try to change the fuel filter first if that will clear up or not if not clear up check the max rpm in netual { don't be afraid to wind the engine WOT in netual due the engine govener will redlined useally at 2500 to 2800 rpm or so + 200 to 300 rpm over just like you work on small gasoline engine govener set up so expect to wind up just shy over normal max rpm }

if reading too low like 2300 rpm then there a trick i can get the rpm up more.

One of my service truck have IHC DT 360 engine that wind up red lined at 3000 rpm { rated at 2700 RPM } and my larger service truck IHC also but larger engine DT466 that redlined at 2600 RPM { rated at 2300 RPM }

Oh yeah some of the cummins engine do have wastegate so check that out as well.

And I know there is other member in this forum he have Dodge diesel also IIRC I think he will chime in also

Old 07-27-08, 07:02 AM
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have you installed a new air filter? that sounds like a restricted air filter, also the waste gate is a good place to look. last what are your trans shift points. if the trans is upshifting to soon that could cause the problems with the load.

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Old 07-27-08, 08:12 AM
Join Date: May 2006
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We had fourteen of those engines in a fleet operation in Des Moines. It'll deliver great performance. We would pull 29,000 GVW's with them. They were in our Dodge trucks as well as the FL50 Freightliners. We've since gone on to L9's in full grown semis.

That engine has a torque peak at about 1400 rpm so it'll pull a lot at low rpms. One of the problems Dodge had when they put it in light trucks was coming up with a manual transmission that could handle the torque at take off. It would lay gears flat.

Over a ten year span we replaced about a dozen lift pumps and had a couple of injection pumps reworked. About five turbos went out. Really nothing but routine. We would put about 275,000 on them.

During those years there was a changeover in the engines we had from a conventional diesel setup to the electronic injection, more like a current automotive gasoline system. I believe the HP went from 155 to 225 with that changeover. You can use computer diagnostics on the electronic injection.

If you're not getting excessive smoke the turbo is building boost, but it could be coming on late = some dogging until the rpms get up. But if you're at 1700 and it's not jumping to pull, you have a performance problem. That engine likes to pull.

I'm sure you've already checked and replaced fuel and air filters. That would leave the injection pump and the fuel you're using. We've found the Biodiesel gets less MPG while the # 2 diesel will do the best for you. We would see about 3 to 4 miles per gallon difference in the smaller trucks.
Old 07-29-08, 12:18 AM
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Thank you for the replies. I just noticed that this forum is cars only, so if this needs to be moved to another forum, then ok. I'm good with it either way.

French- this one redlines at 3000 rpm. I plan on checking the valves soon. I replaced the fuel filter today. I don't know when it was last replaced, but I know now. The fuel filter wouldn't affect mileage though would it?

Speedwrench-I checked the air filter and it wasn't very dirty. It's a K&N filter, and today I bought the cleaner/recharge kit and cleaned the filter. It's drying now, but I'll run it tomorrow and see if there's any noticeable difference.

I put some pressure on the wastegate activator hose and it worked. That doesn't necessarily mean the wastegate is 100%, but it is opening/closing with pressure on the boost line.

The transmission does sometimes seem to be shifting a little soon. I haven't looked at it much, but it appears to be something like the old chrysler 727. How do you adjust shift points? I think it has a kickdown cable, but does it have any other controller that acts as a modulator?

Marbobj- I'm using regular #2 diesel with a cetane booster additive. I'm geting no excess smoke. In fact, I don't see smoke at all unless I take off pedal to the metal from a standstill. Then I see a little whispy black smoke from the tailpipe, but not a lot.

Thanks again for the replies, and for any further ideas. I will let you know what kind of performance I get with the changes I made so far, if any. I probably won't get a chance to check the valves until the weekend. I put upper and lower ball joints in it this past weekend. Wasn't too bad of a job.
Old 07-29-08, 12:38 AM
Join Date: Mar 2006
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Ok now we are getting somewhere .,,,

Ok the valve adjustment on cummins is not that hard to do almost the same way what you been doing with Briggs engine X 6 cylinders lol .,,

Anyway when you do the valve adjustment there is a barring { manual turning } on the flywheel housing and you willneed a half inch rachet { trust me on this one } and turn the engine over until you get the #1 CYL TDC then do cyl #1 and #3 and IIRC #4 as well and adjust the valves IIRC the specs are .018 on exhaust and intake either .010 or .012 one of the two do that when the engine is cold so you don't burn your hand from the exhaust manfold then turn the engine over a full 360 then do the rest.

If that truck did not have the tune up kit you can stop by one of the Cummins dealership or large truck centres they should have the kit on hand I think about 100 ~ 150 bucks but it worth to have it.

BTW did you check the exhaust manfold if any cracks there I know few cummins engines do crack from time to time it will be most common at between the #3 and 4 exhaust ports right next to the turbocharger flange { it did happned to my IHC twice and the manfold for mine IHC was not bad price at all }

Check the intercooler for any air leak and any hose popped off it will happend from time to time and if you heard like jet engine take off a good chance that the hose is loose.

The earlier Dodge automatic is 727 and the other verison with overdrive and there is a govner linkage AKA throttle valve you will see a soild tubeing from the transmisson to the injector pump throttle lever { some models will have cable as well } and all the Chryser automatic do not have any vaccum modation valve at all.

If you feel your engine still sluggish my suggest is get the pressure gauge and tapped between the ariond and intake manfold to read the boost pressure you should be getting at least 18 or more PSIG at full power if reading too low then you have issue with fuel injector pump or lift pump { yeah they do have some issue with it and once the lift pump go out it can restrict the power }

My IHC truck I get over 20 psi at full power with 900 F exhaust temp { post turbo }

your Dodge engine should get pretty close the same power level as my IHC dish out.

If need more question just holler we will help ya


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