6.5L TD Stalls and Missfires Stumbles

[kpgary]

Problem (1) I just purchaced this truck, When cold I wait until the glow plug light goes out and crank it and it starts, 10sec later it will die and I wait for the glow plug light to go out again and it cranks for 15-20 sec before it will start again and then it runs great.

Problem (2) I was stuck in traffic after driving 15 miles or so,
once the traffic started going faster I would press on the pedel and it would stumble and fall on its face. later this afternoon I was waiting for a long light and it did the same thing. any help would be appreciated.

Kevin

P.S New to the site. I have already learned alot about the 6.5's thanks to every one that spends time on here helping others.
__________________
1995 Chevy 3500 6.5T Dually 4x4 124000Mi

[Robyn]

A warm welcome to you. :D

be sure your electric fuel pump is working and that thye filter is clean
Pump located under the drivers seat area in the frame rail.

Poor or no fuel pump pressure will do just what you describe

Let us know

Robyn

[N9Phil]

Kevin, you have come to the right place for info on your
Problem.

My guess would be your OPS (oil pressure switch). I just had the same problem two days ago on one of my burbs.

You are fortunate because the 95's allow you to check the fuel pump without much trouble. With the engine off, put the gear shift into R or D. Then turn the key to start the engine wont start while not in park or neutral but you will be able to hear the fuel pump run (it is located on the frame under the drivers seat) If you don't hear the pump run, it needs to be replaced.

If it stalls on you and you run the above method to run the fuel pump for 10 or 15 seconds the engine will start with a lot less cranking. I have found that when my OPS goes bad, I can get by if I stay below 1500 rpm until I get rolling. When you punch it, the injector pump needs the fuel pump to supply the added demand of fuel. If you take it real easy, the injector pump will supply enough fuel to keep going.

I would recommend that you do a search on this forum for "OPS", "Fuel pump" and "engine stalls".


This will not only keep you busy for a while, it will help you learn a lot about your vehicle.

N9Phil

[kpgary]

I want to thank both of you for your input, it has put me on the right track,

I found the fuel pump was not running. I checked for power and found no power. I checked the relay and it was was not working. I found I had no power on circuit 86 but I had ground on 85.
I pulled the relay and it works fine. I took the relay cover off and pushed on the contacts and I can hear the pump run fine. until it pressures up and slows down until it stops.

So I need to find out where does circuit 86 get its power??

THIS IS A GREAT SITE>

Thanks.

[bbtlr3]

If your pump runs and the relay is functioning then your Oil Pressure Switch (OPS) is bad. The OPS is located at the back of the drivers side head angled toward the centerline of the engine. These are a common problem on these engines, poor contacts and too much current from my understanding, they do make kits to put a relay on the OPS so the relay takes the current load for the fuel pump instead. Haven't heard if they work well or not though. But for now, IMO the OPS needs replaced.

[kpgary]

Put in a new OPS and It runs great, But now my Oil Pressure is around 4 lbs at idle after the engine is warm. The other guage was never that low.
I will check the actual pressure with my master guage.

Again Thanks to every one for your help!!

Kevin

[redsuburban]

[QUOTE=kpgary]Problem (1) I just purchaced this truck, When cold I wait until the glow plug light goes out and crank it and it starts, 10sec later it will die and I wait for the glow plug light to go out again and it cranks for 15-20 sec before it will start again and then it runs great.


I've been having the same problem. It showed up out of the blue one morning. Engine turned and fired, ran for ten seconds and then quit. The symptoms are identical to yours. LP runs like a champ, but when I changed the fuel filter this morning, the fuel housing was nearly dry just from sitting overnight (no obvious leaks). I filled the housing half way with fresh fuel, installed the new filter, hit the key and it runs great. Never have a problem once it gets going.
LP was replaced in Dec 06 with a new GM unit. Check valve problem??? I have a new OPS but I need to wait until my patience factor is high enough to attempt a change out. I'm no electrical genius so I don't no how to check the relay to see if it is OK. Need to drive to Tampa in the morning - hope I make it back.

[simon]

Just fixed same thing today, look in post a little down.
I put a gauge on the drain valve, opened the cock, started the engine, had 5 lbs of pressure till the ops was supposed to take over running the liftpump.
the pressure dropped to zero and engine died. bad OPS.

Because of the difficulty and agravation to get the OPS out, I installed a 1/8" grease gun hose 8" long with a 1/4" adapter in the block's oil port. I took the long T adapter out to . Then put a 1/8" elbow on the other end with adapter to fit new OPS. Now the OPS is wth a 90 degree angle right above and in front of the glow controller. Next time the damn thing fails it will be a 10 min job instead of the 4 hours it took this time.
The wiring harnass is plenty long to reach, you will have to bring it from behind and over top of the main harnass.

I am planning to change the elbow to a T and put a universal pressure switch in the other end of the T and use that one to run the liftpump.
OPS is to expensive at $ 75.- can.

[tommac95]

Simon-
Your part price was too high. Try one of the TDP advertisers , or :
www.rockauto.com/. They have a great site , and good prices.

[redsuburban]

I was able to track down my problem this weekend.

Measured voltage at LP with key ON. 11.3V dropping to 10.1V when glow plug relay cycles. This told me that the LP relay was operating. Correctly, I assume.

Primed fuel bowl, installed filter, hit key. Started on the first go. Measured voltage again at LP. 13.8 volts. OPS is apparently working OK. Had LP unplugged and truck idled great.

Removed filter, drained fuel bowl. Turned key to ON. LP running like a champ but pumping NO fuel. Nada. Nothin'.

I replaced the new GM pump that I had installed in Dec 06 with an old pump that was in the bottom of a box of junk. Plugged everything in and primed fuel bowl. Lots of pressure.

I talked to my GM parts guy this morning. NO replacement on LP. Electrical parts have only a 90 day warranty. Apparently the LP can run and vibrate but pump no fuel. I guess I'll be running on a old LP for the time being.

[tommac95]

Redsub-
The LPs are capable of sounding good , & not pumping. Dirt in check valves MAY be problem(?) , one reason some of us added a filter pre-LP.

They are also capable of premature demise (not sure why) . They not infrequently crap out about when FSD/PMD does same.

They typically make throbbing noise initially , and soon quiet down , as pressure is established.