I have a 1998 5.9 24 valve cummins. I acquired this truck when I married my wife. It has 110,000 miles on it. The only things that have ever been done to this truck are oil changes and a tranny service. The truck seems to run good, however the fuel economy has gone down a little. She owned the truck since day one and towed a 10000 lb horse trailer with it consistently. I was wondering what major service items I need to perform on this vehicle. In addition, what problems or issues I should be on the look out for and address. Right now the truck has a couple of oil leaks and the ac doesn't work. Any help would be much appreciated.

 

There are alot of answers to your question. Best bet is to do a search on this site. Oil leak(possible KDP), low feul mileage(possible lift pump). Best bet is to search for specific questions, and some reading.

 

I believe the KDP problem was only with 12 valves

 

I think the kdp could happen until 99 or 2000. just my .002

 

Welcome to DTR, glad to have you here.
Is it just mileage you're noticing?
Is there any smoke, loss of power, or other symptoms you've noticed along with the loss of mpg's?

You mentioned that the truck has had oil and trans servicing, but I did not see in your post any mention about the fuel and air filter.

Also, your truck has an electronic lift pump. This pump picks up the fuel from the tank and transfers the fuel to the injection pump. These electronic lift pumps are a know issue on the 2nd gen, 24 valve engines.

So, without any more info available, check (or have checked) your fuel pressure and change fuel and air filters.
Also, the Cummins 1st and 2nd Gen engines need to have the valves adjusted from time to time.
The 12 valves are more frequent, but check your owners manual or maybe someone can help here. I dont know the interval for the valve adjust on a 24 valved engine.
Last, proper tire inflation. While this is minor, running low tires will affect mileage.

As far as major service on these trucks, its pretty simple and sounds like your already well on your way.
Check fuel pressure every other oil change (or more often).
Check/replace air filter and fuel filters regularly (depending on your climate conditions such as dusty roads and such).
Continue the upkeep on you tranny.
And, yes, the KDP issue has been known to hit some early 24 valve engines. Something you should probably check into.

Rich

 

I purchased my truck used and the milage was 17 highway & 12 city. I found this board and heard about the lift pump problems. I put a fuel pressure gauge on and my readings were 7 lbs. idle, 5 lbs. cruise & 0 lbs. at WOT. I change the lift pump and my milage went up to 19.5 highway & 14 city. I would find out what your fuel pressure is quickly because the injection pump will suffer with low pressure.

Mark

 

Does anyone know where I could get a lift pump and injection pump for a reasonable price? I would prefer oem, but will take something that is good quality. My check engine light had been coming on every once in awhile but is now on for good. I am guessing that the lift pump was going out and is taking out (or has taken out) the injection pump. I hope I could get away with just doing a lift pump. If I do a lift pump only, could the lift pump get ruined if the injection pump is bad?

 

Don't think Injector pump can hurt lift pump, but failing or failed lift pump will hurt injector pump. Injector pump = $$$$. Take the truck to autozone, get the codes read. If you get a 0216 it's the IP.

 

http://www.cumminsstuff.com/

This place has the best prices I could find, can purchase the pump with a 1 year warranty too.

 

the engine may need a valve adjustment,have heard that performance is improved.