1995 4900 with DT 466 and low power

Hi - I just found this forum and need some advice. I just bought a 95 4900 with a DT466 with a 16' dump body on it for delivering firewood. The truck seems to run well but has no power. It just dies on the hills, even empty. On some of the steeper hills on I91 in Vermont I was down to third gear and 35mph. Empty! It almost acts like its running at half throttle even though the pedal is down to the floor. In its past life the truck was a Ryder rental, would there have been something done by Ryder to limit the power output of this engine? I have a 79 with the same engine and it has way more power.

The accelerator cable linkages seem to be in order, when the pedal is bottomed out the whatchamacallit on the injector pump is up against its stop, so its going through the complete range of motion. According to the tach the max RPM is around 2700. Is this too low?

The truck has 233K miles on it, but I don't think the engine is worn out because it fires right up even when cold. Starts better than the 79.

Anyway, that's most of the story, thanks in advance for taking the time to read this post and respond.

 

Not yet, I'm heading to town in the morning and plan to pick one up then.

 

Thanks for the replies -

Truckon - I don't know what the rear end ratio is, but I guess it's pretty high. Truck goes right along on the highway on the flat or downhill.

Heavyd - I'll try putting pressure in the air line to the diaphragm and see if it holds pressure.

 

So I finally got a few minutes today to take another look at the engine, and it sure looks different from my 79. Looks like the intake manifold is part of the valve cover on top of the engine, and the air goes through a radiator after the turbo (the air to air exchanger darknight mentioned??) and into the intake. Is that right? And the aneroid diaphragm is on the rear of the injector pump and the short line (maybe 6" or so with what I call banjo fittings on each end) that goes from there to the engine is the one heavyd suggests I put 20 psi of pressure to and see if it leaks down, correct?

My question is that since the diaphragm is known to fail, and since it might take some finagling on my part to come up with adapters etc to do the pressure test, would I be better off just replacing the diaphragm anyway? Or is the diaphragm expensive and/or difficult to replace?

Oh and I don't think there's a computer in the truck so I don't think there are any codes to be read.

Thanks in advance for you time