OK I have a 93 with 375,000 miles on it, I started it up and left it ideling to warm up and went into the house, about a minute later I heard it surgeing so I went out and reved it a few times and it still went back to the surge, after it warms up it will idle but just lately its doing the surging thing all the time, even when warm, it runs fine otherwise, no loss of power or performance, this was 2 months ago and I still haven't found out what's going on. So far I have added a throttle cable so it will idle, I replaced the fuel filter, blew back into the fuel tank to make sure the screen wasn't cloged, added electric fuel pump,( its getting plenty of fuel ) turned idle adjustment screw up, gutted FSS and added shut off cable, checked for any fuel leaks, there's none, still no change, is it possable the govenor spring is weak or is there something else in the pump that would cause the surge at idle, this my friends is driving me nuts because it runs just fine going down the road. What's your thoughts???Thanks, Wayne

 

Tired pumps can surge at idle, most of the time turning the idle up will help. I'd also make sure you are not sucking air into the supply side of the fuel system. Weak injectors can also cause a surge. How much of an rpm surge is happening?

 

The surge is so bad that kills the motor, turning up the idle did help, and after it warmed up it went away but here lately is starting to do it all the time, I don't see any leaks in the fuel system any where, thanks for the come back

 

Cold fuel.....

 

I'm here in FL it 's not that cold, you are right tho cold fuel will make some of them surge, but usually that's up north in the cold, maybe the pump is going, you would think if the pump is wearing out it would just idle faster not surge, the old Detroit diesels from the 60's used to surge at idle but I never new what caused it. Do any of you think a weak govener spring would do it??

 

Have you run the main fuel-screw in any? What, if anything (other than that above) has been done to the IP that you know of?

WELCOME to our forums BTW.

 

Dying pumps start showing those signs of poor or no idling when they warm up. They'll run just fine when cruising though. When the motor is up to normal operating temperature, you can try pouring a glass of warm water over the pump. If it quits surging and idles as it should, there's your answer, unfortunately.

With the way the governor functions, I can understand the possibility of a weak spring but I've never heard of that being an issue. I'm not sure at what point the governor spring can stretch and become weak over a period of time, if it can at all.

 

BC847, yes I did run the fuel screw in a turn and a half hoping that might help, it increased my power conciderably but didn't help the surge any.
Answering the other fellows question it runs fine when warm and surges when cold so poring hot water on it after its warm would be no help! It is starting to surge some even when its warm now so I think its probably just the pump getting old, time for a new one I guess, thanks everyone, Wayne

 

Is the smoke out of the tail pipe just black? You mention a electric lift pump, what is it putting out at the injection pump? Where is your timing at? I'd be sure the problem is the pump before you go off and replace it.

 

Yes just black smoke out tail pipe, getting 13 lbs at pump, that should be plenty. Would timing have anything to do with the surging??? I have moved it full circle, I mean all the way against the head to all the way down and seen no differance in the way it ran, any idea's on that??? You would think there should be some differance in the way it ran, the pump doesn't move very far tho so I don't know, 1/2 inch maybe.
I wonder what maks them surge when they get older?? you would think if anything it would just idle faster, things like this bug me to no end, not knowing why its doing what its doing. I had a whole P pump setup from a 95 cummins, injectors, lines, gears and all but I sold it, now I'm sorry I did as they are better pumps from what I hear?? The last 44 I had when it went bad it wouldn't idle at all, as soon as you let off on the fuel it would stall, it never got a chance to surge.

 

375,000 miles that's what I call running on good maintenance and borrowed time.

Wayne go find yourself a GOOD local Bosch injection, Cummins shop.

 

I've got considerably more miles on my original pump than that. Probably 425k if I could guess. The curiosity for me lately has been, "how much longer will it last?" I think the first couple grand of cash I can save up, I'll invest in a newly rebuilt and well-tuned pump from Giles .

 

My pump pump died at 315k IIRC

When H&H rebuilt it they gave me a bag with all the old springs, plates, cams, etc etc.
They even took the time to show me ware in the old compared to new parts.

 

That's why I feel that my pump isn't quite 100% and that my power numbers would be higher if it were. My truck was bone stock, with the exception of the Banks I/C, when I got it 4 years ago. Even then, I didn't actually turn the fuel screw until about a year and a half ago.

 

I do have a good injection pump place in Pensacola but they want $675 to rebuild a pump, why so much I don't know, rebuild kits are only $30, I know its not easy to rebuild one and I don't think I could do it because I don't know what to look for when doing it, I wish I knew what causes the surging or stalling when a pump goes bad, is there a part that always should be replaced when doing one to correct it??, I'm retired and on a fixed income and try and do all my repairs myself, but I just might have to bite the bullet on this one.UGH Thanks guys.