CUCV engine stalls on deceleration

[Power Giant]

Just like in the title, the CUCV engine stalls on deceleration, but otherwise runs good and starts easily. The TM says to look in the governor area for binding linkage or black residue from the governor weights? Didn't find either of those things upon inspection under the governor cover. Any thoughts on the matter?

 

[Power Giant]

I have a good, used injection pump on the shelf. I'm thinking of swapping it out. Do you think this is a good option?

 

[albersondh]

Assuming all the obvious stuff is g2g. Try turning in the idle adjust screw before swapping the pump. It should idle up as you turn in the screw. Turn the screw in just enough to make the stalling go away, try about 1/8-turn at a time (I could typicaly power brake and get the syptom to repaeat vs going for a drive, this speeds up adjustment). if the idle has to be so high that it slams into gear when going "D" or "R", swap the pump its a gov/cal issue and needs rebuilt and calibration. Or at this point you can throw caution to the wind and try an in-frame min/max adjustment, I have had pretty good luck doing this, but its realy a field fix and you should get a pump replaced at this point.

Note the original orientation of the screw or throttle lever angle before starting. If you find some other issue that is contributing later you can always return the lever to proper angle. Setting throttle angle is a part of the calibration routine.

 

[Power Giant]

I turned up the idle speed, and can make the engine not stall. It is faster than stock, but doable. I'm going to drive it awhile to see how it feels. Thanks for the advice albersondh.

 

[K9Vic]

I had the same issue on my M1009 project with stalling. I increased the idle slightly and it no longer stalls and seems to be OK. My IP on inspection with the top cover off did not show any fragments. But not to say there are other issues with the IP that cannot be seen.

 

[tvguy]

I was having the same problem and adjusted my idle also. So far so good.

 

[albersondh]

Blue = min-spring
Green = max-spring
Red = "min-max" governor adjusting nut
Purple = metering valve
Yellow = metering valve linkage
When you turn in the idle screw you are adjusting the position of the throttle shaft that is linked to the metering valve.
So pretty much moving the metering valve annulus grove into a position where more fuel can pass. This will raise the idle.
With the idle higher there is more RPM/centrifugal force working the governor weights. These weight sling outward and move a collar that is linked to a lever that pushes against the front of the min-spring. The min-spring is attached to a guide rod/stud along with the rest of the min-max assy. The min-max is linked to the metering valve via the metering valve linkage. When enough RPM is present at idle the min spring is depressed to a point where the metering valve linkage holds the metering valve in position to give adequate idle. I believe what happens is that when the min/max starts to wear and you are under load, snap out of the throttle (decelerate), there is an instant where the min spring is depressed enough due to high RPM low throttle position, to put the metering valve into no fuel position for just long enough to shut it down. For this reason I started adjusting the min-max nut to increase tension or lengthen the assy by turning the adjusting nut out just a tad. I had pretty good luck doing this but would consider it a "field fix" only. Once you touch this stuff the pump is out of cal. The adjusting nut also plays into the max spring adjustment (max RPM before fuel cut).

 

[HalfaLehman]

My M1009 had the same issue when I got it. I had tried adjusting the idle and such with no luck. A diesel mechanic friend of mine recommended that I fill the fuel filter with dieselkleen, start the truck and run it for a few minutes until the pump fills with cleaner, then let the truck sit over night. I tried it and when I got it started the next day the stalling problem was gone and I have not had any issues since.

 

[sturkopp]

I Have the same issue with my M1010, engine almost stalls when decelerating before turns.
It makes the same in "P" after reving it up quickly and idle goes up and down a bit.
Truck sat for 7 years, so I first put in a new fuel filter, checked all fuel supply and return lines with pressured air and replaced the lift pump.
After this all changed nothing, I gave the IP to a shop and they did a complete rebuild, calibration and test run, I build in the pump and still no change,
so I assumed only thing remaining where the injectors, I changed them with no result.
Since almost everything in the fuel supply is new or checked, what else can I look for??

 

[Power Giant]

I Have the same issue with my M1010, engine almost stalls when decelerating before turns.
It makes the same in "P" after reving it up quickly and idle goes up and down a bit.
Truck sat for 7 years, so I first put in a new fuel filter, checked all fuel supply and return lines with pressured air and replaced the lift pump.
After this all changed nothing, I gave the IP to a shop and they did a complete rebuild, calibration and test run, I build in the pump and still no change,
so I assumed only thing remaining where the injectors, I changed them with no result.
Since almost everything in the fuel supply is new or checked, what else can I look for??

Try raising the idle speed?

 

[sturkopp]

I already raised idle speed so it doesnt stall.
problem stayed the same, just at "higher" rpms.
it still goes up and down after reving it up
and return line goes empty for a about a second, then fills up again at idle (I replaced by a clear one)

 

[Recovry4x4]

Sounds to me like it's sucking air from somewhere.

 

[albersondh]

I would check for delivery at the IP. This will rule out sucking air and general delivery problems. I think I would even do a temp electric pump just as a trouble shooting tool. Verify delivery to the IP. If its good, and no leaks at any of the 8 output lines or injectors, I would question the rebuild. They say they did a rebuild, ask them what machine they used to recal, or better yet, get a spec sheet. You cannot do a proper rebuild of these DB2 pumps without a full recal and that takes very specialized equipment.

 

[sturkopp]

I could test run it out of a jerrycan, so I can eliminate everything from lift pump towards the IP.
I already questionned the rebuild, but i think his work is ok, he´s got the hole equippment from surplus and is specialized in CUCVs
plus I live 10 mls from him and can piss him off as often as I want, he wont do that, I can be really annoying....

 

[sturkopp]

Due to new job I had no time to continue... but as some questioned the rebuild I thought it could help to re-check everything from the beginning.
I finally found out that the litle return line valve on top of the IP was empty, the little glass ball was missing. I replaced from an old pump I had laying around and engine runs great now, no idle issues any more. Dont know why I didnt check that first, cause I know this can cause trouble, also why didnt the shop notice??
It always the little obvious things .....

 

[GREENMV]

About 3 weeks ago before we left our property In TN It was 15 deg and the symptom of stalling as I took my foot off the pedal just started. I thought It might be the cold, thanks for starting this thread so when I get back and have more time, I can check to see what's going on.

Subscribed

 

[Kawgomoo]

My dodge does this. no clue why. Ive tried and checked everything. it did have an airleak in the fuel line, which i found and fixed. But i dont know if driving it 3000+ miles with that air leak hurt the pump or not.

Ive tried raising idle speed, fuel delivery, all kinds of stuff. if i stab the throttle just right and let off it quickly the engine will stall everytime. i can catch it with my foot and stop it from happening. but no idea why it happens.

my engine sat for 6 years on the east coast. some tell me it may have grown algae somewhere in the pump or injectors. no idea if theres any truth to that.

id be interested to know how you fix this.