Stalls while warming up

[BIGTPM73]

I just bought a 98 6.5L TD. The truck is in great shape, but I got a really good deal on it because it has 200,000 mi and the tranny was bad. I had the tranny rebuilt and it runs great execpt two problems.

1) it starts up no problem at all, but then in the 1st few minutes, as it is warming up, it stalls out. Idling or driving. It will spudder, and sometime catch, and sometimes stall completely. Then after it completely warms up, it runs fine. The Check engine light does not come on, so I am assuming there are no codes for my mechanic to diagnose. Does any body have any idea what this could be.

2) One of the reasons I bought a deisel was for good fuel economy, but after running a couple of tanks of gas, I am only getting about 12mpg. Does anybody have any suggestions to improve this. Thanks

[trbankii]

1) it starts up no problem at all, but then in the 1st few minutes, as it is warming up, it stalls out.

After starting, does the glow plug light cycle? It should come on initially when you turn the key, wait for it to go out, start the engine, and then it should flash on again a few more times as it starts up. I was having problems with starting when I first bought my "new" used truck - including something similar to yours - and replacing the glow plug controller did the trick.


2)I am only getting about 12mpg. Does anybody have any suggestions to improve this. Thanks

First, need some more information... C or K? 1500? 2500? 3500? What rear end ratio? Towing? Empty? Running empty, my K2500 listed below is getting over 20mpg mostly stock.

[Kenneth]

This sounds like a common oil pressure switch failure. Try checking this. Start the truck and let it warm up. Then go to the front of the motor, and find the fuel filter drain valve. Open the valve and check to see if fuel comes out of the drain line. If the motor dies and no fuel comes out, the pressure switch is bad. This switch is what turns the lift pump on which pressurizes the injector pump. If it is bad you can get these oil pressure switches anywhere. Try to get a ac/delco or a standard. Don't get a cheap one from checkers or autozone the electrical part on them fails prematurely. I found and ac/delco at a dealer for like $28. They are cheap. But, try this test to check your oil pressure switch. You never know, maybe the problem is something else. But I would try this first this is a simple test and if it is the problem you lucked out.

About your fuel mileage. Check your air filter, fuel filter. Those are probably the first thing to check, beings as your mileage is kind of crappy if you are running an empty load there is a possibility that there is some other problem. Try running the grey Power Saver fuel additive in your next couple tanks, and then check your mileage after a few tanks of the additive. Mine is a bone stock 94 6.5 TD 2500 HD ext cab, long bed, with 3.73 gears and I get around 17-19 miles on town/highway driving and 18-22 on just highway miles. Good luck.
BTW, good buy on your truck. These are great trucks.

[BIGTPM73]

Thanks for the tips. I am checking into these possibilities this week end. How do I tell what my gearing ratios are? My truck is a 98 6.5LTD K2500 4x4 4L80 OD Trans. On Monday, I could call the guy who rebuilt my tranny to see if he knows, if it is something not easy to tell. I don't have the owner's Manual.

Also, I have used it to tow my 4500lb Dump trailer, and it pulled it so well, I at times forgot I was pulling the trailer, so I suspect I may be the lower gears. I don't tow the trailer that often, and I live and drive quite often in the city of Philadelphia, so I if it is not too expensive, can I change the ratios. Also, I have a small diameter stock muffler. It is actually smaller than the muffler on my 93 Gas 350 K2500. Will changing this to a 3 or 4 inch diameter muffer make any difference on fuel milage. Thanks in advance for more tips. Tom

[a5150nut]

Most likely you have 4:10s. There should be a lable on the inside of your glove box lid with all the production codes to how the truck was put together at the factory. If it has been changed you can juck up the rear and turn one rear weel one full turn and count how many times the driveline turns.

As for the exaust, open up the entire system from the turbo back. At least from the CAT back. You will notice a big difference in the hills just by opening the exaust.

Oh, and welcome to TDP! You will learn much here, lots of very good advise.

[drewkeen]

2) One of the reasons I bought a deisel was for good fuel economy, but after running a couple of tanks of gas, I am only getting about 12mpg. Does anybody have any suggestions to improve this. Thanks

I would advise to stop putting gas in your truck as it will lead to very bad things :p

[BIGTPM73]

I will make a mental note not to put gas in the truck. Sorry, I am new to the diesel world.

As for the stalling, I still haven't figured it out. It only does it right when it just about reaches operating temperture. It will do this for about 2-3 minutes, then, stops and runs fine. I had the fuel filter changed and my mechanic performed the Oil Switch test, and he can't find anything wrong. I may just change the switch and the lift pump if its not too expensive and seee what happens. Any other ideas?? Thanks. Tom