M1009 dies if I let the throttle off too fast

[btmurph]

So I'm trying to get my M1009 running reliably after it sat for 7 or so years... I've finally gotten the motor running but if I let off the throttle too fast the motor shuts off like I turned the key. When I let the throttle off gradually it won't die, just keeps on running. I even took it around the block a couple times and if I do it right the motor won't stall but I needed to brake for a stop sign and it died on me. Starts right back up in neutral with barely a turn of the key and I'm on my way... but I can't do this in 20 miles of stop and go traffic.

I've seen a couple of mentions of similar symptoms and one exact match using search but there was no resolution in that thread. The TM's also didn't have the exact symptoms I'm having. Drives fine otherwise, revs up nicely and when I drove it around I got up to about 35ish and it shifted to 2nd just fine.

Some facts:

When I got it I pulled 15 gals of nice clear diesel out of the tank (old of course, but it wasn't cloudy or anything and smelled like diesel). I could have and would have pulled more but I only have 4 jerry cans and 1 had 5 gals of fresh diesel in it! I added a Napa brand diesel treatment and then added the 5 gals of fresh diesel in.

I put on a new fuel filter and proceeded to prime the fuel system (and screwed that up by not pulling the IP wire at first but got that handled )

Tank gauge currently shows about an 1/8th of a tank.

I'm not sure how to proceed here and my $*@(@$(&@(_$%&%(%@)$ Durango is having computer issues (I HATE computer controlled vehicles!) that I can't really look into until the CUCV is running at least somewhat properly. Thank you ahead of time for any input you might have.

 

[doghead]

Are you sure it is on the idle screw, at idle?

Does it stall the same when it's on the high idle stop too?

 

[Naqeeb]

I had a very similar problem and replaced the fuel filter, that didn't fix it. Then installed a new mechanical fuel pump, still didn't fix it. Replaced the injection pump and that fixed it.

 

[btmurph]

Are you sure it is on the idle screw, at idle?

Does it stall the same when it's on the high idle stop too?

doghead, I am NOT sure... I will check on that tonight when I get home from work. The fast idle system is currently non-functional as well. I was planning on troubleshooting that on Sunday when I can work in the daylight (I'm working on this in my driveway as the CUCV wouldn't fit in my 1940 garage even if I had the room ) maybe a droplight and some cold fingers are in order...

Naqeeb, I'm trying to avoid IP replacement at this time but I'll do it if I have to... I've got a new mechanical IP mounted on a rebuilt 6.5l at my shop that will probably be going into the CUCV at some point (when this 6.2 isn't reparable) but I'd prefer to wait a bit on that

 

[porkysplace]

doghead, I am NOT sure... I will check on that tonight when I get home from work. The fast idle system is currently non-functional as well. I was planning on troubleshooting that on Sunday when I can work in the daylight (I'm working on this in my driveway as the CUCV wouldn't fit in my 1940 garage even if I had the room ) maybe a droplight and some cold fingers are in order...

Naqeeb, I'm trying to avoid IP replacement at this time but I'll do it if I have to... I've got a new mechanical IP mounted on a rebuilt 6.5l at my shop that will probably be going into the CUCV at some point (when this 6.2 isn't reparable) but I'd prefer to wait a bit on that

The only way to get cold fingers in 50 degree temps is from a cold beverage.

 

[btmurph]

The only way to get cold fingers in 50 degree temps is from a cold beverage.

It IS dropping into the 40's at night... of course, that's probably shorts and t-shirt weather for you poor folks in Michigan

 

[ranchhopper]

Turn the idle screw up it cured mine when that was happening.

 

[mp_tx]

I had same issue on my mechanical 7.3 IDI. The injector pump got sticky and gummy inside. Ran a bottle of ATF through the small fuel tank, drove it on the small tank, and it fixed itself. I would try that or Seafoam (or the like) before replacing the injector pump.

 

[danoscooter]

If you got a rebuilt motor laying around I would just put that in. Thats what I ended up doing with my 09. The swap is pretty easy and you can tear into the old motor and really check it inside out.

 

[Karl kostman]

I am not to familiar with the diesel motor that is in a 1009 but I had a 72 GMC pickup in high school that had like an electric plunger the carb linkage ran up against and all it was for was to slow down how fast the carb linkage could close the butterflys and it stopped working at one time and if you just took you foot off the gas completely the engine would shut off, I replaced the unit and hooked the two wires back up to it and all was well again. The component was called a "DASHPOT" bear in mint this was a 350 ci gas engine not any for of a diesel!
KK

 

[btmurph]

Thank you all for the responses! I got sucked into indoor chores by the wifey last night and just got home tonight so I'll probably be working on this on Sunday. First thing will be to turn up the idle screw and then troubleshoot the fast idle circuit. I'll be sure to post back with updates.

@ danoscooter, swapping motors would be problematic and is only a last resort at this time... I'd rather pull the IP than swap motors. EVENTUALLY I'll do it, but if I can wait a year or 5 I will

@ Karl, my other motor is actually mounted in my grandpa's old '70 Chevy C10 (part of a failed diesel conversion I ran out of money and then time for). I put over 150K miles on that truck, first with the 307 with the old 2 bbl and finally with a 350 with the edelbrock performer rpm top end... Lotta fond memories there

 

[danoscooter]

Yeah I hear you. I had my 6.5 in the garage almost two years before I decided to put it in the 09. Where did you score a rebuilt 6.5 at? I picked mine up on gov liquidation about a year after I bought my blazer from them too.

 

[btmurph]

Got it off a guy on eBay... The one that used to advertise $400 running takeout motors (for all I know he still does, all those repower 6.2's the military put on the market). He was having employee issues when I ordered my rebuild and it took something like 3 months to get the motor. I was really patient with the guy and he gave me some upgrades for free to make it right: discount on it being bored up to 6.5 (I verified after I received the motor that the block casting was good for that) and I got a new IP instead of a rebuild. Got the motor 12v and with the humvee pan (which I shouldn't have as that caused fitment issues with the 2wd crossmember!). Added a flywheel and clutch for an SM420 and it's sitting bolted in my C10 and that's where I ran out of money.

Holy derailed thread, Batman! Sorry folks, the next post I make will be the results of my troubleshooting the idle system!

 

[btmurph]

OK, the good news is, I adjusted the idle screw in and got it to stay running. The bad news is, the screw is now bottomed out against the spring. If I have to can I temporarily (and I do mean temporarily and not semipermanently) remove that spring to get more travel?

I also noticed some wet around the throttle mechanism (class 1 leak or maybe 2 in TM terms I guess) so it looks like I've got a leak out the throttle shaft. Does this sound like I need a new IP? Can I likely limp things along for a month or 3 till I can replace this IP?

Thanks again for all the help!

 

[cpf240]

Magic 8 Ball says "maybe" - it may run that way for a long time, or it may not.

Throttle shaft seal leaks are fairly common, and can be fixed by replacing the seals. Some here have done that while the IP is on the truck. With the other problem it is having, I think I'd have the pump rebuilt rather then just fixing the throttle shaft seals.

I don't know enough about the way the IP operates, or its internals, to answer the question about the idle spring.

 

[btmurph]

Thank you for your response cpf! I think I'll be swapping IP's in a couple months after things settle down here and then rebuild the old IP as a spare. Anyone know if I can remove that spring off the idle adjustment screw if I need to?

 

[Keith_J]

Common problem with the injection pump. It meters fuel by varying pressure in the feed to the plungers. The plungers are held in the bottomed out position by spring force. Assuming a linear spring force, length of compression of the spring is a linear function of pressure. By varying the pressure, a linear variable injection quantity is obtained.

Now, what makes this intermediate pressure? A vane pump. The vanes are subject to wear but more likely in your case, it is sticking vanes. When you let off the throttle, this intermediate pressure is vented but also, the engine speed drops reducing the speed of the vane pump ( the vane pump spins with the injection pump, half crankshaft speed). When worn or sticking, the pressure falls too fast and the plungers (there are two) fail to charge).

You can try automatic transmission fluid or Power Service silver bottle to see if it is gummed vanes. Or you could bite the bullet and go with a rebuilt injection pump.

That spring on the idle stop screw? It is a friction lock to preserve the setting. Sure, it can be removed but you will need it once the injection pump is overhauled.

 

[cucvrus]

When all else fails change the injection pump. They are less then $300. rebuilt. And they pick up and deliver for free. I have put several of them on. Several hundred as a matter of fact. It is a common issue and the pumps working correctly make the whole machine a more enjoyable item to own and drive. Other then that keep tearing into it and trying mystery methods to fix the dying injection pump. Put a new lift pump on also while you tear into it. It is your choice but I would not bother putting on a used pump or a home rebuilt one. It is not worth the effort. These pumps are precision pieces and need to be cared for as such. Clean fuel clean filters and not a lot of additives. This has always worked out for our team I hope it helps sway your decision. Good Luck.

 

[btmurph]

Common problem with the injection pump. It meters fuel by varying pressure in the feed to the plungers. The plungers are held in the bottomed out position by spring force. Assuming a linear spring force, length of compression of the spring is a linear function of pressure. By varying the pressure, a linear variable injection quantity is obtained.

Now, what makes this intermediate pressure? A vane pump. The vanes are subject to wear but more likely in your case, it is sticking vanes. When you let off the throttle, this intermediate pressure is vented but also, the engine speed drops reducing the speed of the vane pump ( the vane pump spins with the injection pump, half crankshaft speed). When worn or sticking, the pressure falls too fast and the plungers (there are two) fail to charge).

You can try automatic transmission fluid or Power Service silver bottle to see if it is gummed vanes. Or you could bite the bullet and go with a rebuilt injection pump.

That spring on the idle stop screw? It is a friction lock to preserve the setting. Sure, it can be removed but you will need it once the injection pump is overhauled.

THIS was what I was hoping for! An explanation of what the heck is going on... the why if you will. I plan on trying the bottle of Power Service at the next opportunity. Thank you Keith!

@ cucvrus: I definitely plan on replacing the IP with the new one I have (see posts #4 & 13 above) if a cleaning additive doesn't help/fix things. The effort of replacing the throttle shaft seals only and trying various hillbilly "fixes" (apologies to HillbillyWizard ) versus replacing the IP entirely doesn't make sense to me either. The truck WAS sitting for at least 7 years (and maybe as much as 10) so I could very much see that it could be just sticking vanes. Thank you for the response!

 

[btmurph]

Update: the bottle of Diesel Kleen fixed the issue! Dumped the bottle in at the next fill up, ran through 20 gallons, at next fill up I turned the idle screw back down and no more engine stalling

My apologies for taking 7 months to post this, I can only claim work and a 3 year old as my excuses... That and fixing other issues with the 09