M35a2 fuel cutoff rod springs back to firewall 5 o'clock position when cover removed

[rockbronco]

I'm a Brand new member please be kind if I posted wrong please educate me I'm still learning about this forum.

I am the proud owner of 1975 M35A2 with the Hercules 1D turbo multifuel engine, I have had the truck for about 9 months and it has always started and run flawlessly until recently.
The issue I am having is the truck runs great above 1000RPM but will not idle if I am not lightly feathering the gas pedal, also up until now I have never had to touch the gas pedal or throttle pull cable to start the truck , now the only way to start the truck is pedal to the floor as I crank it over and it starts immediately but will not hold idle as I said unless I lightly feather the gas pedal. (even after warmed up)
I removed the cover to the IP fuel cutoff rod and noticed the fuel cutoff rod springs back to firewall 5 o'clock position when cover removed, I can push it to the 7 o'clock position with very little effort but when i let go it returns to the 5 o'clock position on its own very quickly.
I have reviewed lots of posts on this forum and have viewed dozens of pictures of the injection pump with the cover removed and the lever seems to always be in the 6 or 7 o'clock position on working pumps.

What would cause the lever to return to the 5 o'clock position?


I have done the following work on the truck over the course of the last two weeks.

1.replaced all fuel filters (4 filters total, 1 on frame rail passenger side, 2 on engine last one was for intake flame starter)
2.checked lift pump(in tank) screen it is clear
3.checked lift pump preasure without engine running (stays between 5-7psi)
4.checked all fuel filter bleeders are free clear and produce a steady stream when lift pump is powered on.
5.checked turbo spins free clear
6.removed cover on IP for fuel cut off rod found rod/lever to be in 5 o'clock postion. (lever moves freely but always snaps back to 5 o'clock when cover is removed, also found about 2 oz of motor oil behind cover)
7.checked all cylinders with IR thermal gun to be sure all were firing and running consistent temps.
8.Air filter clean.
9.checked all injector lines on top of engine produce fuel when they are cracked open.

 

[gimpyrobb]

Sounds to me like your hydraulic head is going bad. Might want to find a back up HH.

 

[gimpyrobb]

Have you had the HH apart at all?

 

[rockbronco]

I have not done anything to the HH at this point, I stopped when I noticed the lever under the shut off rod cover was in the 5 o'clock position, also I forgot to mention when I removed the cover to look at the lever mechanism I noticed there is no retaining clip where the rod goes through the lever like all the pictures show. I was going to remove the lever next but was hoping someone may know why the lever is springing back towards the firewall before I dug to much deeper.

 

[gimpyrobb]

I would say its either a tarnished plunger, or more likely, from what you just said, someone has been in there and not put it back together correctly.

Any chance of you posting a pic?

 

[rockbronco]

I will try to get a pic if its still light out when I get home from work. Thank you for the the tips

 

[gimpyrobb]

No problem. If it gets complicated, I'll just call, or send you my number.

 

[rockbronco]

 

[rockbronco]

 

[rockbronco]

So while I was out taking these pictures I made sure again that I could move the lever both forward and backward with little pressure needed but again it will always spring back towards the firewall to the 5 o'clock position.
I noticed when I press the gas pedal or pull the hand throttle the internal rod attached to the lever behind the cover will move the lever forward and it returns when released.
I replaced the cover and started it up still have to hold pedal down while cranking (turns over quick)to start and very lightly feather gas pedal to idle at 900 rpm feels fairly smooth, any speed below that stalls immediately.

 

[rockbronco]

I forgot to mention in my initial description the FDC was bypassed when I got it, I have only removed the cover from the fuel cut off rod no modifications have been made to fuel rate , idle , mixture, droop ect.... to my knowledge.

The truck has 18,000 miles on the odometer.

 

[gimpyrobb]

Well, I hate to say it but this is a new one!

The fact that the safety wire is still in place leads me to believe that no-one has been in there.


Just some background, the lever back towards the firewall is the fuel "off" position. That would be why it doesn't want to keep running. The lever forward(7 O'clock position) is "WFO" so to speak. That lever needs to float forward and back freely so the governor can do its thing.

There is a metal rod that sticks through the fuel lever. This rod is what "should" push the fuel rod forward to the WFO position. Would you be scared to remove the FDC and look down in there?

Its basically 4 bolts and the unit should slide straight up, mind you there is some fuel lines and maybe safety wire that might need cut.

 

[rockbronco]

I am willing to remove the FDC , I don't think it has any fuel lines installed in it there is a brass plug threaded into the inlet side. Could be a couple days before I can pull it.

 

[gimpyrobb]

No prob. PM headed your way.

 

[m-35tom]

if it won't run under 900 rpm likely HH is worn. soon it won't run under 1000 then 1200 then it just won't start.

 

[rockbronco]

Thank you for the suggestion, on that point I have been researching the HH and symptoms related to it as well as replacements and have had little luck finding a distributor in the US.
Do you have any suggestions where to get them at a reasonable price?

 

[Jeepsinker]

Looks to me like the retaining clip is still on there. You may have something loose or damaged in the fuel metering portion of the injector pump( the section toward the firewall). Try this; remove that little retaining clip from the rod you see, slide the rod out the back of the lever ( this will take some finagleing) then see if the shutoff lever acts as it should. Make sure the governor rod isn't touching the shutoff lever when you try it. Be extremely careful not to lose that little clip.

 

[gimpyrobb]

if it won't run under 900 rpm likely HH is worn. soon it won't run under 1000 then 1200 then it just won't start.

Tom, if you look at his fuel lever, its not where its supposed to be. I don't think its a worn HH, I think its a spring issue in the back of the IP.

 

[gimpyrobb]

Looks to me like the retaining clip is still on there. You may have something loose or damaged in the fuel metering portion of the injector pump( the section toward the firewall). Try this; remove that little retaining clip from the rod you see, slide the rod out the back of the lever ( this will take some finagleing) then see if the shutoff lever acts as it should. Make sure the governor rod isn't touching the shutoff lever when you try it. Be extremely careful not to lose that little clip.

I'd wait to do this till after we see under the FDC. I'm thinking maybe the spring in there broke.

 

[gimpyrobb]

6.removed cover on IP for fuel cut off rod found rod/lever to be in 5 o'clock postion. (lever moves freely but always snaps back to 5 o'clock when cover is removed

This is the part that makes me think its in the back of the unit.




huh huh, he said unit.