Face cam causing throttle to stick

[nairb]

Recently picked up an m1123 and have been going through and fixing all the issues I can find while waiting on my SF-97. This one has me a bit stumped and looking for some help.

I noticed when I picked it up I couldn't push the accelerator very far, barely above idle. I disconnected the throttle cable and attempted to move the throttle by hand. I can do it, but it gets hard to push past the halfway point, if I push hard I can, but then it gets stuck at the halfway point on the reset. I've tracked it down to the "face cam" on the injector pump. Part #8 on page 2-89 of TM 9-2815-237-34:



If I loosen the torx screw (#14) on it the throttle moves freely, if I tighten it I can't move the throttle much past idle. This is unfamiliar territory for me so looking for some ideas on what to try next. It looks like they painted everything in the engine black, is that maybe gumming up the mechanism? Something else to check?

 

[Mogman]

Have you tried penetrating oil? WD40?

 

[nairb]

I haven’t, but that seems like a logical next step.

What function does the cam perform? I can’t tell what it’s sticking on from above.

 

[nairb]

Looks like it pushes the rocker lever (#13) which is attached to something at the bottom of the pump. It looks pretty rusty down there because water collects in the valley and it has been sitting in Georgia for who knows how long with a clogged drain hole. Guessing I’m in for a new ip or a rebuild.

 

[Mogman]

I would try some lube, maybe RWH will chime in here, everything in moderation though, don't bust anything.

 

[AAVP7]

I would try some lube, maybe RWH will chime in here, everything in moderation though, don't bust anything.

That rocker lever actuates a little plunger which, as far as I recall, enriches the fuel flow when accelerating. The little plunger likes to rust in place, and / or start to leak diesel.
I´ve had to replace the plunger on all my current Humvees. Can be done with the IP in place, you need to use a modified (ground down) wrench. The measurements are in one of the TMs.

 

[nairb]

That rocker lever actuates a little plunger which, as far as I recall, enriches the fuel flow when accelerating. The little plunger likes to rust in place, and / or start to leak diesel.
I´ve had to replace the plunger on all my current Humvees. Can be done with the IP in place, you need to use a modified (ground down) wrench. The measurements are in one of the TMs.

Do you recall which parts you were able to replace without removing the IP? Looks like 16-21 are the likely culprits. Did you replace the parts on the left side as well (40-43)?

 

[AAVP7]

Do you recall which parts you were able to replace without removing the IP? Looks like 16-21 are the likely culprits. Did you replace the parts on the left side as well (40-43)?

View attachment 867314

The part usually causing the leak is the plunger no. 17, which often rusts heavily and then damages seal no. 18. Overhere, I only got that seal together with no. 19, so I swapped no. 17 - 20 indeed.
I didn´t swap anything from nos 40-43.

BTW: You have an M1123, so four-speed tranny, and a TPS (throttle positon sensor) on the right side of the IP. That TPS basically replaces cam no. 11, and also shaft no. 44 is different. Make sure you got the right diagramm from the TM; I´m not sure if nos 17-20 are identical between M998 and M1123.

 

[TOBASH]

Try Marvel mystery oil and then run a couple of tanks of bioDiesel.

 

[jake20]

@nairb brought this up in another thread, figured I'd post my injection pump results here since the thread is already more specific to it. Per the pictures I've attached, you can see that the bottom half of my pump is pretty much rusted away. I'm guessing my only options are to just get reman or new pump. If someone thinks I can still salvage this in a garage, know where I can source the small individual parts from?

 

[jake20]

One more thing actually, as I was browsing around, I couldn't help but notice that Chevy 6.5L injection pumps look extremely similar to what we have. Anyone have any experience with trying one of those? (They're about $400-500 cheaper is why I ask)

 

[nairb]

I bought a second pump for parts for cheap off ebay. I got the intake manifold and all the fuel lines off this weekend, should be pulling the pump this week as time allows and will update this thread with results. I’m expecting to have to have mine rebuilt. Yours appears to be in worse shape than mine but that’s the same spot mine rusted. The lowest fuel line was also corroded almost all the way through, would have been a leak soon.

 

[Coug]

One more thing actually, as I was browsing around, I couldn't help but notice that Chevy 6.5L injection pumps look extremely similar to what we have. Anyone have any experience with trying one of those? (They're about $400-500 cheaper is why I ask)

I would expect it to look the same, as it's basically the same engine except in 24V instead of 12V, and tuned to government specs.
I don't know if it's compatible or not as I'm not a fuel system expert, but physical appearance doesn't mean much when the internals can be tuned completely differently.

 

[TOBASH]

This is a question for the 6.5 GM Diesel section on truckstop.com

 

[jake20]

@TOBASH I think you mean https://www.thetruckstop.us/forum/ ?

I got a little confused when I went to truckstop.com and found broker services lol

 

[TOBASH]

Jake. You’re correct

 

[jake20]

I did some digging and found a company that can rebuild them for half the cost of a new one, will be pulling and sending mine off in a few weeks. I'll report back with my experience, costs, and other details once I get into it.

 

[Coug]

I did some digging and found a company that can rebuild them for half the cost of a new one, will be pulling and sending mine off in a few weeks. I'll report back with my experience, costs, and other details once I get into it.

you might want to post the name of the company if you haven't sent it off yet, as I'm sure at least someone on here has tried them and can give you feedback as to whether they do a good job or not.

 

[jake20]

you might want to post the name of the company if you haven't sent it off yet, as I'm sure at least someone on here has tried them and can give you feedback as to whether they do a good job or not.

The company is Huckstorf Diesel out of Wisconsin. I spoke to them over the phone a few times, they seem pretty knowledgeable and were able to answer my questions about the process pretty well. If anyone has any input on them, would definitely be appreciated.

This describes the service: https://www.hdiesel.com/P/5ChevyGMCDieselInjectionPump/1071

This is the gasket set I was going to get as well: https://www.hdiesel.com/P/LPumpInstallKit/742

They're a direct Stanadyne dealer, so they have access to the parts required I suppose.


The bizarre part is my actual pump model number, it's labeled DB2-831-5079 on my dataplate on the pump. According to that company's site, this is the description for that pump in the first link:

DB2831-5079

10224039

1993-97

214 Ton Cab-over (Military) - Turbo (200 hp)

Anyway, plan is to pull it in 2-3 weeks and send it off. They say the process takes 1-2 weeks and it should be done.

 

[zr2yz125]

I’m having this same exact issue with my M1123. Throttle was sticking at halfway and not returning to idle. I removed the screw #9 to keep the throttle from sticking while I get the parts and fix that plunger. I’m only driving it locally without that cam screw engaged - but it definitely feels low on power climbing hills.