M109A3 Idling bad

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fpchief

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Truck has all new filters, new HH O rings, FDC bypassed, injectors have been tested. I just cant win with this truck I got taken to the cleaners with....Got it running for the first time in a while (just got my tank back on from having new bottom put in it). Has a surging Idle when cold and somewhat clears up when warmer. I can hit the throttle and It will throw black smoke and clear up real quick to a really good sounding motor and exhaust. I let off the throttle and it just about goes dead. Everything I am reading I THINK points to a IP issue. I do not think it is anything to do with the droop screw since the rpm's are fine at idle, just surging and of course just about shutting off when I let off throttle. I can not put it under a load due to having the cab still mostly torn town, etc. etc...

It is a 1988 rebuild.
 

Floridianson

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Yep now that your FDC is bypassed the droop screw does not act the same because the FDC wedge plate is no longer moving. Now every change comes through the twin nut main fuel adjustment. If you did change the setting on the droop now you are just changing where the main is set to. Did you read the other thread that is having the same problem?
 
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fpchief

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Yep now that your FDC is bypassed the droop screw does not act the same because the FDC wedge plate is no longer moving. Now every change comes through the twin nut main fuel adjustment. If you did change the setting on the droop now you are just changing where the main is set to. Did you read the other thread that is having the same problem?
Yea I think so. It is what led me to think it is the IP. Just can't find anything else wrong. It has a small leak at an injector line but as the other posts state it is unlikely for that to cause this.

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fpchief

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I have no oil in the transmission. I want to crank it and let it sit there and run for an extended period to see if this may change something. If the truck is in neutral and clutch is not pressed, is there anything freespinning in the transmission? I don't think so but I have to ask.

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frank8003

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Deuce jackshaft moving

and I have the question of How much fuel have you put thru her since you been working on it?

About all the gears and such...............It is all moving
Put some straight 40 W motor oil in the transfer and transmission cases.

Study your jackshaft

https://youtu.be/CC5ybVZrO5s
 
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fpchief

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and I have the question of How much fuel have you put thru her since you been working on it?

About all the gears and such...............It is all moving
Put some straight 40 W motor oil in the transfer and transmission cases.

Study your jackshaft

https://youtu.be/CC5ybVZrO5s
Not much fuel at all since it has had alot done to it. . Will go ahead and get the oil back in transmission and let it run for a good while.

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Floridianson

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Oil good fire bad. If you can get it running I like the LDS troubleshooting manual. Seems like most of the time it's said to check pressures at the bleed screw. That might be a nice place to start if she will run.
 

fpchief

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I let it get up to operating temp. Released throttle and it shut down and would not crank back up. Will see if it fires up after cools down completely. Still have pressure at bleed valve.

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fpchief

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Replaced my in tank pump with a Parker. Had it a while and decided to go ahead and do it. The original one is getting louder so I am sure it is on its way out the door. The in tank pump was not the problem but now I know it is a good pump.
After sitting back and thinking what I have done, I decided to check to make sure the two screws holding the little U shaped bracket for the fuel shutdown were not too tight. Read somewhere that if they are even just a tad too tight, they can impede free movement. Took the cover off (only oil in there best I could tell) loosed each screw maybe one turn...fired it up and no more surging.

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frank8003

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Do not put 100% "new flavor" pump diesel fuel in it

Thing needs to run with a load on it at 1800 RPM. Put homemade Seafoam in it or buy some commercial stuff but use it.
Put a couple of quarts of straight motor oil, cheapest new stuff you can get, into the fuel tank.
The "new" diesel fuel is not for that engine as it lacks lubricity.
Do not run it for hours and days just sitting there. It will wet stack.

https://www.steelsoldiers.com/showthread.php?145704-deuce-blowing-blue-smoke
 
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davidb56

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I tried to copy/paste the whole research with results but failed. So I'll post the condensed version ....based on a 26gal tank. Opti lube XPD...319 micron improvement @ 4.75$ .....Walmart superrich TWC3 for Outboard..162 micron improvement @ 1.07...Stanadyne Lubricity..157 micron (this was a shocker to me). and then Used motor oil shell rosella 15/40 (used in a deuce too)......only 2 microns improvement... there are another dozen results, but most cost more per dosage, or had actual negative results, including Lucas, which has been on my shelve for oil additive and Marvel mystery oil, for gas treatment. Both are good for what they are designed, but don't add lubrication properties to the IP.
 

davidb56

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A few more results...Optilube Summer blend (best value) 189 micron improvement and only uses 1.1 oz dose per 26 gal....as opposed to Walmart TWC3 at 15oz dose. Stanadyne uses 3 oz dose.... these are rounded out numbers. Based on what the price is in your area, you can pick which additive is cost effective for you.
 

frank8003

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I want you to know that the multi-fuel will run just fine on 100% new motor oil. I recommend 40-50% with "new" diesel fuel.
One is not allowed to toss containers in the trash with residual oil in them so I made a container drain for my mechanic and I get all the new container drained motor oil, so that is how I know. Also ran it constantly thru a 3 micron filter to the engine and back to the tank. Parker pump allows that due to considerable output volume. Probably cleanest fuel and tank around with nothing bypassed on the engine.

my filter invention IMG_4242.jpg
 
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Floridianson

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Just going through the tm's and found this again minimum 0.023. Trying to understand why some fuel control unit assembly's are sticking after install if everything else is not sticking. We know why they are sticking because of the varnish stain / crud in fuel. Now that would be the fuel control unit assembly or the plunger sleeve sticking on the plunger causing the whole fuel control to seem sticky / stuck. Now install torque 18-23 inch pounds is just for the screws and would seem as though the control unit can not go any farther when it hits the head. As said is there some how some way if the fuel control is not sticking but on install it is going too deep and binding us up. One would think if the unit has never been taken apart the tabs on the nut would keep it from ever changing and everything thing the same. Is there a change we are not seeing?
 

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fpchief

Active member
Steel Soldiers Supporter
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Bay Minette, Al.
Just going through the tm's and found this again minimum 0.023. Trying to understand why some fuel control unit assembly's are sticking after install if everything else is not sticking. We know why they are sticking because of the varnish stain / crud in fuel. Now that would be the fuel control unit assembly or the plunger sleeve sticking on the plunger causing the whole fuel control to seem sticky / stuck. Now install torque 18-23 inch pounds is just for the screws and would seem as though the control unit can not go any farther when it hits the head. As said is there some how some way if the fuel control is not sticking but on install it is going too deep and binding us up. One would think if the unit has never been taken apart the tabs on the nut would keep it from ever changing and everything thing the same. Is there a change we are not seeing?
Not sure but I will say that after re-installing my HH, I went by the specs on those two screws and my pump obviously did not like it. Just a frogs hair width of difference in the screw made all the difference in the world. I am just very relieved I found the problem and hope others can hopefully read this and not think they have a bad HH or pump when it is simply the screws on too tight.
 

fpchief

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Bay Minette, Al.
A few more results...Optilube Summer blend (best value) 189 micron improvement and only uses 1.1 oz dose per 26 gal....as opposed to Walmart TWC3 at 15oz dose. Stanadyne uses 3 oz dose.... these are rounded out numbers. Based on what the price is in your area, you can pick which additive is cost effective for you.
That is excellent info....I think I may actually have some opti I had ordered a while back....and I believe it was from reading a post you made.
 

davidb56

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I found Stanadyne at Walmart for 71$ a gallon. that will treat 2560 gallons of diesel, and bring the IP lubrication to specs. That is the most Research Proven, cost effective way for me.
 
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