I know i have some major issues... since my truck won't get above 35mph on flat ground. Its a 96 3500 cab & chassis 12 valve with 300,000 miles. Original injection pump, original injectors, original lift pump. I'm going to start by taking the fuel pressure reading from the tank before the injection pump. I also know to check the fuel return valve as well. Anything else you guys can think of to start out with?

Thanks

 

Any smoke?

Original trans?

 

No smoke... transmission was replaced last year (NV4500). It idles great, rev's fine without a load, but on the highway in 4th, it won't reach 2000rpm. Engine is completely stock.

 

How long's it been doing it?

I'm assuming you've done the simple stuff so far....

Fuel filter?

Air Filter?

Will it freely rev over 2000 RPM's?

 

Yes.. new air & fuel filters.... its been low on power for a year or so now, which i attributed to the age & mileage of the truck..but here within the past 2 months have i really noticed it. Within the past 2 weeks, it has gone from a top spd of 60 down to around 40. Thursday i plan to check for fuel line kinks, do a fuel pressure test and check the fuel return valve. Any thing else ya'll cam think of so i can i eliminate parts as i go?

Thanks

 

Has been using any oil?

At this point I'm thinking a weak governor spring in the pump.

If it's not smoking, filters are good and when you check it if it has good fuel pressure, the next thing I'd be looking at is the pump.

There's not much else to go wrong on it to cause a loss of power.

 

It uses about a quart between oil changes (3000 miles Rotella). The rack has never been set, engine actually has never been open except to replace a leaky valve cover gasket.

 

Will it rev up to 3000 when it's in park or neutral and there's no load on the engine?

How's the coolant level? Is it staying normal?

 

I've never been close to 3000rpm ... i usually shift around 2000-2500rpm. Coolant level is fine.

 

The redline on it is 3200 and it's built to handle an overspeed of 4100 RPM's for 15 seconds from the factory. You need to see if it'll run up to full RPM without a load.

The governor springs in the P7100 will limit the RPM's to 3000 - 3200. They start pulling fuel back at 2600 - 2800. You're not going to over rev it.

If it won't rev up to redline, then more than likely you have a problem with the governor spring in the pump.

Without a load, slowly bring the engine up to to max RPM. If it won't come all the way up without load, that narrows it down.

If coolant level is okay, that takes the head gasket out of the question.

How do you drive it everyday? What I mean is, do you essentially baby it....shift at low RPM's....not load the engine down much?