jerking at partial load, where to look?

[arno]

Experts,
I have brought home my 1969 M35A2 on monday. Although it pulls with a lot of strength (I can pass other trucks uphill easily, when I run it at partial load (cruising at constant speed), it starts jerking a lot (regardless of engine RPM). I am quite sure it is related to the fuel system because sometimes one can even hearing the turbo whistle change in tone...
I am running diesel fuel.
Where should I start looking?

Greetings, Arno

 

[rosco]

Change the fuel filters.

 

[gimpyrobb]

Yeah, change fuel filters and then if that doesn't cure it, have the injectors pop tested and adjusted.

It gets expensive after that.

 

[greenjeepster]

Clutch problem.

 

[daytonatrbo]

I noticed both of my trucks got a little bouncy/jerky when going up steep hills in 3rd gear, 2000 RPM (tach straight up and down).

Granted the guy I bought them from was bragging about how he had done zero maintenance in the 8+ years he owned them.

i'll be changing a lot of fluids and filters before i get to worried about it.

 

[arno]

Hey Folks,
I ordered a set of fuel filters and will change them as soon as they arrive. Will also check everything visually, maybe the problem is also related to the link between accelerator pedal and injection pump as the linkage hat a lot of play - maybe it is assembled incorrectly... one never knows with a truck that is 46 years old. Pressure checking the injectors is also a good hint, will do that maybe next week when I have access to my pressure tester...
I cant imagine the clutch is at fault - the truck pulls fine at full load and there is no hint of slipping, whereas the jerking appears at partial load - cruising at 30 or 50mph...

Greets

Arno

 

[arno]

fixed...
Thanks to all, the problem was cured by changing the fuel filters. I have never before seen a comparable amount of dirt, water and rust in a fuel filter... all three filters were contaminated. It is surprising that the truck ran at all...
Sooooo, next question, how to clean the fuel tank?
And in the next few weeks I will work my way through other parts of the truck, it is quite likely they show the same signs of neglect. Changing motor, transmission, axle oil is next on my list...

Greets
Arno

 

[gimpyrobb]

Unscrew the drain bolt in the fuel tank to drain.
Take electric plug off top of fuel pump.
Undo fuel lines
Unbolt straps holding tank to saddle.
Pull out and clean.

 

[arno]

Hi gimpyrobb,
maybe I should have been more specific, the obvious stuff is exactly that, obvious...
Can you recommend a good way to clean the tank? Chemically? Or with gasoline? Steam cleaner? How about rust treatment? Maybe I ask the guys at the local farming machine garage...
There are tank cleaning sets available, but those seem to be made for mostly motorcycles and, in the amount needed for the deuces' tank, cost around the same as a nos tank...

Arno

 

[tommys2patrick]

Arno,

I did not see an introduction from you so Welcome to Steel Soldiers from Colorado. Fuel Filters--glad it was a relatively simple fix.

 

[gimpyrobb]

I'd wait till you get the tank off and look in it to decide what to do. Mine just had some varnish in it. I dumped 2 gal of old fashion carb cleaner in it and sloshed it around in the bed of my pickup truck for a week. I made sure to turn it on its side every once in a while to get all surfaces. It worked pretty good.

I have heard others take them somewhere to have them dipped in caustic baths like at a radiator shop.

 

[arno]

@tommys2patrick,
thanks for the welcome, I just made an introduction at 'Members' Rides'....

Thanks to all the others for their hints and to the Owners of Steel Soldiers for running such a great forum.

Arno

 

[rustystud]

Hi gimpyrobb,
maybe I should have been more specific, the obvious stuff is exactly that, obvious...
Can you recommend a good way to clean the tank? Chemically? Or with gasoline? Steam cleaner? How about rust treatment? Maybe I ask the guys at the local farming machine garage...
There are tank cleaning sets available, but those seem to be made for mostly motorcycles and, in the amount needed for the deuces' tank, cost around the same as a nos tank...

Arno

If you have access to a steam cleaner ( a real steam cleaner, not a hot water pressure washer) that will do a good job of cleaning out the gunk. As far as the rust goes, you can use some rust removers like "evapo-rust" or "metal rescue" .

 

[bonedoc]

I cleaned out mine with a cleaner called Marine clean. It is made by POR-15 and is now called POR-15 cleaner/degreaser. Works great!! I used it as a kit to clean, etch, and seal the inside of my fuel tank. Worked great!!

 

[tankie88]

Do you all get bio diesel added at the refinery like we do over here? EU law over here 5% bio diesel is mixed in with normal diesel at the refinery.Trouble is the bio diesel "grows" in your tank after being stood for long periods.Had to change all my filters a few months ago.

 

[frank8003]

Deuce fuel filter one each

Put a real filter at the tank and make re-circulation line back to the tank. I used the boss {drilled&tapped} for the arctic heater as a return
It will filter all the fuel all the time the in-tank pump is running. It is cheap. It can be run for hours and hours with truck off {hook up a battery charger} .
One must try to save the hydraulic head rotating element, which is the purpose. Filters and filter head and a new in-tank pump are inexpensive.
...................and pictures for the General.

 

[rustystud]

Put a real filter at the tank and make re-circulation line back to the tank. I used the boss {drilled&tapped} for the arctic heater as a return
It will filter all the fuel all the time the in-tank pump is running. It is cheap. It can be run for hours and hours with truck off {hook up a battery charger} .
One must try to save the hydraulic head rotating element, which is the purpose. Filters and filter head and a new in-tank pump are inexpensive.
...................and pictures for the General.

View attachment 571476View attachment 571477View attachment 571478View attachment 571479View attachment 571480

That's a nice set-up you have there Frank. I see you also like the "PTFE" stainless steel Teflon hoses too.

 

[Aussie Bloke]

G'day everyone,....


If your fuel tank is half as bad as your filters were I'd consider also cleaning the fuel lines as well.

Just my thoughts,...



Aussie.

 

[arno]

Yes those suggestions make sense... what I will do next is (after running the tank empty to less that 25l) drain the tank, filter what I have drained, clean the tank, disconnect the fuel lines and clean with compressed air and probably change the filters (at least the primary) one more time...
In the mean time, another problem has arisen - when changing the oil in the transfer case, on the magnet I had not only the ordinary metal debris but also pieces from a ball bearing roller cage. So I dont drive the truck a lot and will remove the transfer case very soon - it is leaking at the seals anyway...

Greetings

Arno