Stuttering/starving at acceleration - ideas

[montaillou]

Some background:
The truck is at a mechanic getting some misc. work done. Right now I have more money than time, and some things are beyond my ability.
One of the things done was to swap a new hydraulic head as the old one had a leak (I sent him a link to how it was done here - also he referenced more stuff from here when he did the work). After the repair he took it for a test drive and everything was fine except the idle was higher than normal. Before the repair the idle was around 800 rpm, after it was 1300, so he adjusted it back down.
He then did a few other things, and took it for a last test drive before turning it back over to me, and now when accelerating the engine is stuttering.
He adjusted the idle back up in case that was the issue, it wasn't. My first thought was one of the fuel pumps, but I had the in-tank pump rebuilt 3 years ago and a new electric one put on at the engine - even so, one or the other could've just gone bad, so I suggested it. I've also suggested checking the fuel filters.

Can anyone else think of possibilities? It could just be a coincidental issue, I mean stuff happens...

 

[rustystud]

Did your mechanic adjust the "High Speed Screw" ?
Also the "Droop" adjustment plays a role as does the "Stop Plate" .

This might help.
View attachment Scan0181.pdf
View attachment Scan0182.pdf

 

[rustystud]

Does anyone know why my pictures come out as "attachments" or "Scans" ? The pictures used to come out, now you have to click on the link.

 

[fuzzytoaster]

Does anyone know why my pictures come out as "attachments" or "Scans" ? The pictures used to come out, now you have to click on the link.

They look to be .pdf files instead of .jpg or other photo types is why.

 

[montaillou]

Did your mechanic adjust the "High Speed Screw" ?
Also the "Droop" adjustment plays a role as does the "Stop Plate" .

This might help.
View attachment 784117
View attachment 784118

Thanks, I'll pass those along.

 

[cattlerepairman]

While it is possible that the issue is caused by adjustments made during the HH swap, it is also possible that the new hydraulic head now provides full fuel flow - as opposed to the defective old one. This can cause restrictions in the fuel lines to become more prominent. Filters are a good starting point, so are crushed or kinked copper lines.
I never thought that played that much of a role until I limped home with the engine losing power and shutting off every three or four minutes.....it was filters.

 

[Floridianson]

Yep when ever we have performance problems it should be listed first change all three filters even if you believe they are ok. Also believe a member just found trash in the booster pump inlet port that caused restriction. Then we go to fuel delivery pressure. We need a gage 0 / 100 psi hooked at the bleeder between the secondary and final fuel filters. 30 psi minimum at idle and 60 psi high idle minimum. This will tell us the booster is making the minimum pressure the system need plus if the secondary / final fuel filter pressure relief is stuck open or the over flow valve is stuck open / spring broke. Then if the gage shows low delivery pressures the performance will be bad. If all checks out with the IP and it's fuel delivery you might even have to look at the injectors for performance problems. Is you FDC bypassed? When we bypass the FDC the droop screw is no longer in play and all fuel delivery is now controlled through the twin nuts / main fuel adjustment.

 

[rustystud]

Is you FDC bypassed? When we bypass the FDC the droop screw is no longer in play and all fuel delivery is now controlled through the twin nuts / main fuel adjustment.

Not true. The "Droop" screw plays an important role. Just look at the "G" injection pump which does not have a FDC. It has a "Droop" screw and it needs to be adjusted properly (picture 2) .
Common sense would tell you if a screw is mounted to the main "Fulcrum" then it must have an impact on the fuel (picture 1).

 

[rustystud]

I covered a few of your potential problems on this thread. Post #27 .
https://www.steelsoldiers.com/showthread.php?192207-M35a2-Wont-start/page3

 

[Floridianson]

Not true. The "Droop" screw plays an important role. Just look at the "G" injection pump which does not have a FDC. It has a "Droop" screw and it needs to be adjusted properly (picture 2) .
Common sense would tell you if a screw is mounted to the main "Fulcrum" then it must have an impact on the fuel (picture 1).

View attachment 784208View attachment 784209

The question was is you "FDC" bypassed? When a "FDC" is bypassed the servo in the "FDC" no longer moves to change the wedge stop plate that the droop screw rides on that is connected to the "Fulcrum".
If you have "ever" bypassed a " FDC" you will know we must then readjust the main fuel / twin nuts to decrease or in some cases increase the fuel to get the "EGT's" correct. If you then did anything to the droop screw it would change the main fuel adjustment and throw off what you just did to get the main fuel / twin nut setting and EGT's correct.
The main reason for this whole forum is to spread "knowledgeable" information about our military vehicles not hear say or old outdated information. I would hate to see someone go messing with there fuel control not feeling comfortable what they were doing and understand they might decrease performance if not done correct.
Maybe you should put down your TM's because there is nothing in them about the FDC bypass and what it affects when we bypass it.
There is more to bypassing the FDC then just rerouting some lines. We need to install a pyrometer to get the best performance but not burn up the pistons but apparently you have not done one yet. If you did then you would have seen that the droop screw will then change the main fuel adjustment we just adjusted after we got the Temps right. Just what we do not want!.

 

[Floridianson]

My first thought was one of the fuel pumps, but I had the in-tank pump rebuilt 3 years ago and a new electric one put on at the engine - even so, one or the other could've just gone bad, so I suggested it.

Had to reread you post again. What and where did you put a electrical fuel pump on the motor. You bypassed the IP booster pump?
The in tank pump was designed to be able help clear air from the whole fuel system by circulating fuel from the tank through the IP back to the tank. Not being a geared pump if it failed it will no cause a restriction to the booster pump on the IP. That is why if the in tank pump fails and we do not open the fuel delivery system the truck will still start but we loose a very small amount of performance. If this electric pump you installed somewhere does not free flow in might be able to cause some restriction for the booster pump. Even if we read the trouble shooting manual they have us check fuel pressures before we go digging into the guts of the IP and trying to guess the problem. The only other thought, the "Mechanic" has never really done any work on a running installed Deuce IP.

 

[rustystud]

The question was is you "FDC" bypassed? When a "FDC" is bypassed the servo in the "FDC" no longer moves to change the wedge stop plate that the droop screw rides on that is connected to the "Fulcrum".
If you have "ever" bypassed a " FDC" you will know we must then readjust the main fuel / twin nuts to decrease or in some cases increase the fuel to get the "EGT's" correct. If you then did anything to the droop screw it would change the main fuel adjustment and throw off what you just did to get the main fuel / twin nut setting and EGT's correct.
The main reason for this whole forum is to spread "knowledgeable" information about our military vehicles not hear say or old outdated information. I would hate to see someone go messing with there fuel control not feeling comfortable what they were doing and understand they might decrease performance if not done correct.
Maybe you should put down your TM's because there is nothing in them about the FDC bypass and what it affects when we bypass it.
There is more to bypassing the FDC then just rerouting some lines. We need to install a pyrometer to get the best performance but not burn up the pistons but apparently you have not done one yet. If you did then you would have seen that the droop screw will then change the main fuel adjustment we just adjusted after we got the Temps right. Just what we do not want!.

If you had read the original complaint you would have seen this mechanic had "messed" with the injection pump. Did he try and adjust the "Droop" screw ? Who knows. What I had wrote about was a valid troubleshooting option. As far as having my nose in the TM's and having never worked on an injection pump before, who has worked on these things for a living for the last 4 decades.
I rebuilt four injection pumps just in the last two years. Total rebuilds. When was the last time you "totally" rebuilt an injection pump ? James quit the squabbling and lets help this guy. Your constant trying to "undermine" everything I say has gotten to be quite ridicules. Now your even trying to justify your incorrect answer about the "Droop" screw having no effect when the FDC is bypassed. I mean really James.
I said in the other post to "DeleKEngineer" that a gauge installed after the filters would help solve a ton of questions. That is a valid troubleshooting option which needs to be looked at here. Of course even if the pressures are good that still does not eliminate the possibility of a stuck "Bypass" or "overflow" valve. Remember I had the answer to that problem months ago that you and another guy had with his truck down there in Florida. I said check the "Bypass" and "Overflow" valves.
Turned out the "Bypass valve" was stuck.
Of course this is all speculation as the mechanic could have installed the Hydraulic Head incorrectly. Where assuming he did it right.
So the first thing that needs to be done is install that gauge and find out the actual pressures. After that is determined we can look at other potential areas that would cause the problem.

 

[montaillou]

The only other thought, the "Mechanic" has never really done any work on a running installed Deuce IP.

Yeah, he's a mechanic, he's just never worked on this type of truck before. Most of the work he's done for me hasn't involved the engine, once you get past the engine it starts looking like some other trucks (albeit, older ones).

I will freely admit that I am no mechanic. I research and figure stuff out, some stuff I can do, some stuff I pay others to do. I'm really, really good at research, it was part of my major (history) at college. I have passed along a few things in this thread, and he said he'd take a look at it on Monday. I'm thinking it's possible that maybe the high speed idle is the problem based on how he described how the first test drive went ok but the idle needed adjusting and then the second test drive was the new problem found. Of course it could be something else. Another mechanic friend also mentioned how maybe the throttle handle might've played a role, so I mentioned that as well. It's not well marked in my truck and again, the guy is unfamiliar.
If the things I've mentioned don't pan out on Monday, I'll refer him to this thread and maybe he'll be able to glean more from what's been written here. I don't know as I could adequately pass along some of these posts (beyond what I have already).

 

[Floridianson]

If you had read the original complaint you would have seen this mechanic had "messed" with the injection pump. Did he try and adjust the "Droop" screw ? Who knows. What I had wrote about was a valid troubleshooting option. As far as having my nose in the TM's and having never worked on an injection pump before, who has worked on these things for a living for the last 4 decades.
I rebuilt four injection pumps just in the last two years. Total rebuilds. When was the last time you "totally" rebuilt an injection pump ? James quit the squabbling and lets help this guy. Your constant trying to "undermine" everything I say has gotten to be quite ridicules. Now your even trying to justify your incorrect answer about the "Droop" screw having no effect when the FDC is bypassed. I mean really James.
I said in the other post to "DeleKEngineer" that a gauge installed after the filters would help solve a ton of questions. That is a valid troubleshooting option which needs to be looked at here. Of course even if the pressures are good that still does not eliminate the possibility of a stuck "Bypass" or "overflow" valve. Remember I had the answer to that problem months ago that you and another guy had with his truck down there in Florida. I said check the "Bypass" and "Overflow" valves.
Turned out the "Bypass valve" was stuck.
Of course this is all speculation as the mechanic could have installed the Hydraulic Head incorrectly. Where assuming he did it right.
So the first thing that needs to be done is install that gauge and find out the actual pressures. After that is determined we can look at other potential areas that would cause the problem.

Taking apart a Deuce IP that you bought, took it apart cleaned it up pretty and put it back together and never installed, wow. I sent you parts free so you could do it. I also gave my Son a whole one to take to his high school shop class so they too could take it apart multi times just to get hands on an IP. If you like you can ship yours to me and I can take them apart and make sure you did it right. As far as you working on Deuce IP's for 40 years I do not think so!. I have been here since you joined Steel Soldiers and seen you schooled / spanked on the IP more than once. Try working on a IP that is still in the truck but has problems like changing a head or bypassing the FDC and adjusting the fuel. Yea I do not rebuild them because most every one I have needed to work on the problem is in the Head so no need to remove the whole IP for that. When I remove an IP from parts trucks I take them apart for parts and give not sell them to other members to help them get back up and running. As for the droop screw like I said how many on the truck IP have you bypassed the FDC and then adjusted the fuel? Last time I saw a pic of you IP your FDC was still hooked up because you liked it. You liked it leaking fuel into the engine ok. As said we do not want to mess with the droop when the FDC is bypassed as it changes the main fuel we worked so hard to get right. What I said the droop screw is no longer in play meaning when the FDC is working the fulcrum and where the droop screw rides on the plate move. When the droop screw is not in play we can now longer control the excess fuel at the lower rpm scale till the turbo starts to kick in and clean up the exhaust. That is why when we bypass the FDC every truck will smoke more on take off then it should clear up at high idle. Any adjustment on the fuel from then on should be make at the main fuel adjustment. As far as the TM thing meaning is gives us no information about adjusting the IP after FDC bypass, this comes from experience. As far as helping the OP I believe I am trying and point being if the mechanic does not know what he is doing he should leave the droop screw alone. Even when the FDC is not bypassed the droop screw setting is not that easy to get right. As anyone guessing the problem a broken clock is right twice a day.
I still would like to know to help out the OP what is this electric fuel pump installed by the motor and is the booster bypassed. For the OP maybe the best thing here since you are not the one working on it and things can get lost in translation is to down load both TM's and take them to your mechanic so he has a full idea of what is involved with trouble shooting the Deuce IP. All we can really do is play a guessing game and that can sometimes take longer than to just read the trouble shooting manual and find the problem faster.

 

[rustystud]

Taking apart a Deuce IP that you bought, took it apart cleaned it up pretty and put it back together and never installed, wow. I sent you parts free so you could do it. I also gave my Son a whole one to take to his high school shop class so they too could take it apart multi times just to get hands on an IP. If you like you can ship yours to me and I can take them apart and make sure you did it right. As far as you working on Deuce IP's for 40 years I do not think so!. I have been here since you joined Steel Soldiers and seen you schooled / spanked on the IP more than once. Try working on a IP that is still in the truck but has problems like changing a head or bypassing the FDC and adjusting the fuel. Yea I do not rebuild them because most every one I have needed to work on the problem is in the Head so no need to remove the whole IP for that. When I remove an IP from parts trucks I take them apart for parts and give not sell them to other members to help them get back up and running. As for the droop screw like I said how many on the truck IP have you bypassed the FDC and then adjusted the fuel? Last time I saw a pic of you IP your FDC was still hooked up because you liked it. You liked it leaking fuel into the engine ok. As said we do not want to mess with the droop when the FDC is bypassed as it changes the main fuel we worked so hard to get right. What I said the droop screw is no longer in play meaning when the FDC is working the fulcrum and where the droop screw rides on the plate move. When the droop screw is not in play we can now longer control the excess fuel at the lower rpm scale till the turbo starts to kick in and clean up the exhaust. That is why when we bypass the FDC every truck will smoke more on take off then it should clear up at high idle. Any adjustment on the fuel from then on should be make at the main fuel adjustment. As far as the TM thing meaning is gives us no information about adjusting the IP after FDC bypass, this comes from experience. As far as helping the OP I believe I am trying and point being if the mechanic does not know what he is doing he should leave the droop screw alone. Even when the FDC is not bypassed the droop screw setting is not that easy to get right. As anyone guessing the problem a broken clock is right twice a day.
I still would like to know to help out the OP what is this electric fuel pump installed by the motor and is the booster bypassed. For the OP maybe the best thing here since you are not the one working on it and things can get lost in translation is to down load both TM's and take them to your mechanic so he has a full idea of what is involved with trouble shooting the Deuce IP. All we can really do is play a guessing game and that can sometimes take longer than to just read the trouble shooting manual and find the problem faster.

First off, completely taking apart a mechanical device and "replacing" or "repairing" damaged parts. Then putting it all back together is called "Rebuilding" !
That is what I did. As far as never installing them, you know this how ? Why in the world did I do this if I didn't need it for one of my trucks ? By the way it is still working fine.
About me getting "schooled" here on injection pumps. As I remember it I schooled you many a time here. Show me where I got schooled.
Now about never bypassing the FDC. I did that last year, even though it "never" leaked a drop of fuel. I just did it to be safe when I finally can go on the "Great Alaskan Adventure" with my son. I don't post every little thing I do on my trucks here. In fact there are several things I have done to my trucks that will never get posted here. Especially after I had a month off from this site after certain people complained about me and got me banned.
Now I have never seen you post anything about "rebuilding" an injection pump. Ever. Anyone with a little mechanical aptitude can tear something apart. It takes a mechanic to put it back together and have it run correctly.
You did send me a housing that you had gutted, which I thanked you for. Even though after cleaning it up I found the housing was cracked and the stuff you left inside was unusable. Did you need payment for that ? Let me know.
Now here's the real point of all this. You "now" say to leave the "Droop" screw alone after removing the FDC, but here in five posts you say otherwise.

See post #6
https://www.steelsoldiers.com/showthread.php?82760-Fuel-screw-droop-balance

See post #6
https://www.steelsoldiers.com/showthread.php?29221-Droop-screw-questions

See post #8
https://www.steelsoldiers.com/showthread.php?146681-How-to-turn-up-fuel-on-a-M35A2

See post #37
https://www.steelsoldiers.com/showthread.php?59840-FDC-bypass-question/page4

See post #25
https://www.steelsoldiers.com/showthread.php?24388-IP-Pump-Calibration-For-Economy/page3

There are many more where you state over and over again how to adjust the "Droop" screw after removing the FDC.
What happened ? What changed your mind ? Or was it just because I mentioned it here and your saying "no" to my "yes" ?

Now about the TM not giving any advice on a injection pump without a FDC. Really ? What then is a "G" pump then ? Is it not a injection pump without a FDC ?
So it stands to reason that you would set the "Droop" screw to the specifications of a "G" pump. Very simple.
Again I will mention that since the "Droop" screw is installed into the "Fulcrum" it is "in play" no matter what you think. Anything that moves the Fulcrum will effect fuel.
So what slur are you going to come up against me with now ? No experience ? Don't know what I'm doing ? Don't read the TM's ? Read the TM's to much ?
Just because you have been on this site longer then me doesn't make you an experienced mechanic. Just means you've read what others have done longer then I have.
Of course during that time I was actually rebuilding injections pumps for vehicles that went down the road hauling freight and passengers.
Also for those who are still reading this, the "Droop" screw advice was just one of many different things I said to check. I was giving advice for this fellows "mechanic" to possibly check out if the "fast idle adjustment" I said to adjust didn't pan out.
Out of all the possible things I said to check, James latches onto this one to drag me around with. Even though I have proven it is a valid thing to check.
So lets end this stupid discussion on the "Droop" screw. Or is it your intention to badger me until I get angry at you James so I will get banned again ?

 

[montaillou]

Certainly it's possible that a repair made 3 years ago could have a bearing on this situation, however I would like to first look at things that are likely to have happened related to the installation of the new HH and the adjustment of the idle. In short, check the most likely suspects and widen the search from there. In the past 3 years, I've put about 3k miles on the truck without any problems such as what has just happened. There has been a fuel leak out of the HH all this time, hence the replacement, but it wasn't a really fast/bad leak.

At this point, I don't have any new information. The shop is in another country and about an hour's drive away. It's expensive to call and I know this guy is working on my truck when he can, and that it takes a back seat to his real bread & butter and I don't mind because it's **** hard to find any mechanic who will work on one of these and does not charge a fortune. There are things I need to do on the truck when I get it back, but frankly it's been so cold here (Rusty can back me up on this, he lives nearby) that I wouldn't be doing much as I don't have a covered work area.

Also, I appreciate any help, but maybe keep the pissing match to private messages?

 

[cattlerepairman]

I am looking forward to hearing what the problem turned out to be!

 

[rustystud]

Certainly it's possible that a repair made 3 years ago could have a bearing on this situation, however I would like to first look at things that are likely to have happened related to the installation of the new HH and the adjustment of the idle. In short, check the most likely suspects and widen the search from there. In the past 3 years, I've put about 3k miles on the truck without any problems such as what has just happened. There has been a fuel leak out of the HH all this time, hence the replacement, but it wasn't a really fast/bad leak.

At this point, I don't have any new information. The shop is in another country and about an hour's drive away. It's expensive to call and I know this guy is working on my truck when he can, and that it takes a back seat to his real bread & butter and I don't mind because it's **** hard to find any mechanic who will work on one of these and does not charge a fortune. There are things I need to do on the truck when I get it back, but frankly it's been so cold here (Rusty can back me up on this, he lives nearby) that I wouldn't be doing much as I don't have a covered work area.

Also, I appreciate any help, but maybe keep the pissing match to private messages?

The Hydraulic Head being changed could effect not only the idle, but the fast idle too. Every Hydraulic Head is just a bit different then the other even though they are suppose to be exact replacements.
Could it make this much difference ? Who knows. Was your Hydraulic Head completely disassembled and cleaned ? Even NOS Hydraulic Heads can have crap in those passages. I had two that had "cosmoline" in them. That stuff gets extremely hard over time. There are several passages in them that can harbor debris. Also the infamous "Fuel Delivery Valve" could be sticking too. As could the "overflow" valve on the side of the Hydraulic Head.
Then there is the whole injection pump "Booster pump" issue to check out. They can cause quite a messy can of worms all on their own.
To bad it takes two to three hours to get to your place (depending on traffic) . I'd be over there trying to help out, and yes it has been cold here. It was getting down to 21 degrees at night for about a week. I know you guys back east are getting hit with extreme snow, but out here with the low temperatures and rain it can make it really miserable to work outside.
It has threatened to have "freezing rain" lately too. That stuff is horrible.


Also sorry about all the "drama" lately. Trust me, it was not my intention to start it.

 

[montaillou]

Ok, so the guy was busy all week and got back into to it today. He tried a few things and in the end replaced the filters & cleaned a fuel line at the same time and the problem went away. So, I guess there was debris somewhere.

It'll be good to get it back, my neighbors are probably sighing with relief that it's "finally gone".

 

[rustystud]

Ok, so the guy was busy all week and got back into to it today. He tried a few things and in the end replaced the filters & cleaned a fuel line at the same time and the problem went away. So, I guess there was debris somewhere.

It'll be good to get it back, my neighbors are probably sighing with relief that it's "finally gone".

The look on their faces should be priceless when you pull in with your Deuce again !