Low power when pulling grades or trailer

[memrys]

I apologize if there's a thread for this. I couldn't find it.



I have a 92 D250, 5. 9 auto, all stock. 250K miles. seems to run great. If I wait for the "wait to start" light to go out, it'll start before the engine has turned over a full turn when warm, and about a full turn when cold. It doesn't smoke at cold startup, not even a puff, and it doesn't seem to smoke when pulling a grade or pulling the trailer.

The only issue I can find is that the rear seal leaks, but even that uses about a quart of oil per change.



But when pulling the Cajon pass with a car trailer, even only hauling an AMC hornet (not exactly a heavy car), I can barely make 45 mph. I still don't see any sign of black smoke in the rear view, but that's floored flat out. It even seems to be having trouble with the trailer empty. And it's getting worse.



Yet when it's empty, just driving my wife around town, it seems mostly ok. not as much get up and go as I might like, but decent.



my old 91 D350 hauled a car trailer as thought it wasn't hauling any weight at all. it behaved pretty much the same with or without the trailer: 70 mph flat ground or up a grade.



I do not have a pyrometer or boost gauge in the truck.



I have no idea where to begin to look for the issue. Any ideas?



Thank you,

 

[Simplysmn]

I sent you a Message let me know if you need help .

 

[NIsaacs]

The first gens. stock, were all under powered in my book, especially the autos. The difference between your two trucks was probably axle ratio. Have you owned the truck long enough to see a decrease in power? If so, it could be a number of issues but we need more info. Without boost and pyro it will be hard to determine what it might be. If all is normal then a pump adjustment will make a big difference, after guages.



Nick

 

[mweiman]

Check the AFC diaphram on top of the fuel pump, it may have a hole in it and not letting the pump fuel as hard as it should. It will be on top of the fuel pump, somewhat round, with 4 screws holding the top plate on and a small line bent in a U coming off the head. There will a rubber diaphram with a pin and spring underneath it. Check the condition of the rubber diaphram.
Matt

 

[Bob4x4]

Pulling cajon with 160 HP at 45mph sounds normal with a trailer

 

[memrys]

Thank you all for your replies.
I'll check the AFC as soon as I can get the truck from my wife and I'll see about getting some gauges installed.

It's subjective, but it does seem like it has less power than it did when I bought it a year ago. Definitely less than the d350 I had, but it is possible it has different gearing. I need to check into that. I know the D350 was 4. 10:1. Not sure what this ohe is yet.
it also gets only 16 mpg in town and the D350 got 18, but that hasn't changed.

 

[HHhuntitall]

Has the fuel filter been changed? Is the transmission slipping excessively? Is the air filter clean? Has an intercooler boot gotten a hole in it? Just things to check on before you take it all apart.....

 

[JDerrig]

Dodge

Well with my '92 Cummins W250 auto with 3. 55gears, towing truck/trailer about 6000lbs up Lookout Pass on I90 in Idaho (6% grade @ 4700ft elevation) I have to run 1st gear at 2200rpm @ 25mph or so. 2nd gear just got the transmission warm so just stayed in 1st and took my time! Learned to not be in a hurry with a stock 1st gen. Was with a newly rebuilt auto with stock torque converter, which are pretty "loose" with motor @ 84K miles. Still got ~15mpg going 1700 miles. .



-J

 

[cerberusiam]

After making sure all the filters are clean and the trans good check again.

However, Cajon pass with a stock 92 and that load 45 mph is about right. Unless it used to pull the same load on the same hill faster it is probably just starting to weak in the fuel delivery area. If you have not turned the AFC pin and the full power pin its set conservatively.

You might want to check to make sure you are getting full throw on the throtttle assembly. The cables stretch and pretty soon you can't get all the throttle open. Backing the hihg idle screw out and resetting the linkage to get full throw sometimes makes a huge difference.

 

[Bill Stockard]

Well with my '92 Cummins W250 auto with 3. 55gears, towing truck/trailer about 6000lbs up Lookout Pass on I90 in Idaho (6% grade @ 4700ft elevation) I have to run 1st gear at 2200rpm @ 25mph or so. 2nd gear just got the transmission warm so just stayed in 1st and took my time! Learned to not be in a hurry with a stock 1st gen. Was with a newly rebuilt auto with stock torque converter, which are pretty "loose" with motor @ 84K miles. Still got ~15mpg going 1700 miles. .

-J

Yep, I learned to be patient when towing with my formerly owned '92 D350, automatic, 3. 54 gear ratio towing a 11,000-lb fifth wheel trailer. Like you I ran in 1st gear many times climbing 6% or steeper grades and without an exhaust brake I was cautious on the down grades. I towed our fifth wheel trailer for over 100k miles all over the western US. It would average 12-mpg towing and as high as 21-mpg running solo. It was economical and dependable, but slow pulling grades.

The CTD did a much better job towing than the '84 Ford F250 w/6. 9L diesel with a Banks Turbo, automatic, 4. 10 ratio that it replaced.

Bill

 

[Bob4x4]

Think of it this way... ..... torque gets you up the hill,horsepower determines how fast.

 

[NIsaacs]

Yep, I learned to be patient when towing with my formerly owned '92 D350, automatic, 3. 54 gear ratio towing a 11,000-lb fifth wheel trailer. Like you I ran in 1st gear many times climbing 6% or steeper grades and without an exhaust brake I was cautious on the down grades. I towed our fifth wheel trailer for over 100k miles all over the western US. It would average 12-mpg towing and as high as 21-mpg running solo. It was economical and dependable, but slow pulling grades.



The CTD did a much better job towing than the '84 Ford F250 w/6. 9L diesel with a Banks Turbo, automatic, 4. 10 ratio that it replaced.



Bill

You have way more discipline than I have, as soon as I burnt the paint off my exhaust manifold I had the screwdriver out



Nick

 

[HHhuntitall]

Yep, I learned to be patient when towing with my formerly owned '92 D350, automatic, 3. 54 gear ratio towing a 11,000-lb fifth wheel trailer. Like you I ran in 1st gear many times climbing 6% or steeper grades and without an exhaust brake I was cautious on the down grades. I towed our fifth wheel trailer for over 100k miles all over the western US. It would average 12-mpg towing and as high as 21-mpg running solo. It was economical and dependable, but slow pulling grades.



The CTD did a much better job towing than the '84 Ford F250 w/6. 9L diesel with a Banks Turbo, automatic, 4. 10 ratio that it replaced.



Bill

That's one of the biggest reasons Dad and I went to the Cummins in '91. The then-current Ford 7. 3 offering was ok, compared to the 460ci or pathetic 351ci offerings. Chrysler's gas offerings were equally pathetic, but better on mileage with the throttle body fuel injection systems (built by Holley). The fuel mileage of the first two '91s we had was outstanding. And power was phenomenal when compared to anything else offered in a pickup!! That, combined with the ever increasing emissions restrictions, the outlook for big gas power looked pretty dismal, so an alternative needed to be found... . Somewhere along this time we'd had several fires from catalytic convertors, so the realization that they had to be removed, but it was illegal, was coming to light... . Enter the Cummins Turbo Diesel on the Market scene.....



I had a built RB "wedge" in my 73/84/88 CabChassis, and mileage was pretty dismal... . but gas was just over a dollar..... Dad had previously experimented with an '86 F250 6. 9... . it was okay, but my 440 would walk off and leave it on a good day that ended in "y"... ... Interestingly, right around that time, we also had come across a '78 Dodge D250 that had the Mitsubishi diesel engine in it. It was better on mileage than the Ford, but rather gutless..... we looked at turbocharging it, but scuttlebut was that they wouldn't hold up with the turbo on 'em..... Without a turbo and overdrive transmission, it quickly became a dependable work truck, but didn't leave the ranches much. Certainly started well in cold weather, and barely used any fuel when left idleing while patching fence or in 2nd gear along pasture roads (I regret selling it now, but at the time it was the best alternative we had)... . A few months later, Dad left in his '77 460CI F350, and came home with his first '91D350 CabChassis... . in the months that followed, the '78 D250 Diesel, the '86 F250 6. 9L, an '86 D250 5. 9V8 were sold, and shortly after, another '91 W250 came home. A true love of Diesel was found, and the rest is history... ...



How sad is it that now I am looking at gas engines due to the idiotic emission restrictions on our beloved Diesels? :sigh: :depression: I certainly miss how simple those first trucks were. At the time, I remember how much power we thought we had! And then we discovered the tuning and fueling mods!!!!!! WOW!!! We had died and gone to turbo heaven!!

 

[Bob Beauchaine]

Passes vs Performance



Deadman Pass 3573':



AKA Cabbage Hill between Pendelton and LaGrand OR east bound lanes snake up to summit I found that some of these turns slowed me down to 45mph but I could easily hit 60 - 65 on the straights.



In 1999 the east bound lanes were closed and all traffif was routed to west bound lanes - had no trouble maintaining 60 - 65 and hit the top at 65.



Lookout Pass I90 4725'



Also 1999 I had no trouble on this pass.



Summit I80 8640'



1998 I could easily maintain 60 - 65. We stopped at the Lincoln Memorial to site see.



All these were run towing 8000 lbs (across the scales) with the truck at 6500 lbs again across the scales. The only mods I had were Bosch 185s and new silicone boots turbo to intake and 14wg hot side. My truck has always loved towing at altitude. These are just some of the passes I have run.



Bob

 

[Bob4x4]

Passes vs Performance



Deadman Pass 3573':



AKA Cabbage Hill between Pendelton and LaGrand OR east bound lanes snake up to summit I found that some of these turns slowed me down to 45mph but I could easily hit 60 - 65 on the straights.



In 1999 the east bound lanes were closed and all traffif was routed to west bound lanes - had no trouble maintaining 60 - 65 and hit the top at 65.



Lookout Pass I90 4725'



Also 1999 I had no trouble on this pass.



Summit I80 8640'



1998 I could easily maintain 60 - 65. We stopped at the Lincoln Memorial to site see.



All these were run towing 8000 lbs (across the scales) with the truck at 6500 lbs again across the scales. The only mods I had were Bosch 185s and new silicone boots turbo to intake and 14wg hot side. My truck has always loved towing at altitude. These are just some of the passes I have run.



Bob

Injectors and the tighter housing make a good difference

 

[HHhuntitall]

And new injectors make a HUGE difference if you currently have a poor nozzle or seat spring, as it burns the fuel soooo much more effeciently. Higher mileage trucks can benefit greatly from this fairly simple mod. Seen it many times... .

 

[NIsaacs]

Passes vs Performance



Deadman Pass 3573':



AKA Cabbage Hill between Pendelton and LaGrand OR east bound lanes snake up to summit I found that some of these turns slowed me down to 45mph but I could easily hit 60 - 65 on the straights.



All these were run towing 8000 lbs (across the scales) with the truck at 6500 lbs again across the scales. The only mods I had were Bosch 185s and new silicone boots turbo to intake and 14wg hot side. My truck has always loved towing at altitude. These are just some of the passes I have run.



Bob

In '94 I pulled Cabbage eastbound with 26,000 gcw with my old Ford at 40 mph in 4th & under. The engine is a factory 180hp/457tq, with just a fuel screw mod, it dynos 240hp/650tq, like yours it likes to pull. Before the mod, it was sick:-laf



Back in '90 when I did the conversion, there were very few pickup trucks that didn't see it's tail lights, but now days with all the big power, it mostly stays on the porch



Nick

 

[JHumphries]

In '94 I pulled Cabbage eastbound with 26,000 gcw with my old Ford at 40 mph in 4th & under. The engine is a factory 180hp/457tq, with just a fuel screw mod, it dynos 240hp/650tq, like yours it likes to pull. Before the mod, it was sick:-laf

Back in '90 when I did the conversion, there were very few pickup trucks that didn't see it's tail lights, but now days with all the big power, it mostly stays on the porch

Nick

That's a BIG porch!

 

[RSchwarzli]

A few thoughts not the original post.



1- are you sure your 350 was stock? Did it by chance have a pump screw adjusted at somepoint without your knowing it?



2- Gearing. 3. 54 to 4. 10 will be day and night for the power band



3- Was the old truck a intercooled 91 or not? I find the non IC trucks a bit zestier.



4- Surprised no one mentioned it but the 1992 had the 21 cm turbo. The 1991 would have had a 18. That can make a difference as well for you.



5- Gauges. These will be your friend in diagnostics for sure! I can't stress enough to people how important they are. Best money you can spend on the truck!! Did you have them in your old truck? If so what were the numbers?



And almost forgot, welcome to the TDR!!!



Robert

 

[Bill Stockard]

You have way more discipline than I have, as soon as I burnt the paint off my exhaust manifold I had the screwdriver out



Nick

There wasn't a TDR forum back in those days offering helpful suggestions for improving power.



Bill