Symptom: engine running fine, losing power for a few seconds, then running fine

[cattlerepairman]

I have a super running refreshed LDS in my truck. During the refresh I had peeked into the fuel shutoff and down the holes in the HH and it looked clean. I did therefore not mess with it.

The weird thing that is happening is that I drive along, engine giving me full power, accelerating fine, levelling off....and then it feels as if I was pulling the shutoff. No fuel. No reaction to fuel pedal. Panic, count 21, 22, 23...look for place to coast to a stop.....boom, power's back as if nothing ever happened.

Even weirder is that this has happened only twice in about a month, each time after running flawlessly for about 100 km (70 miles). Both times it happened on the exact same, straight and level stretch of road. I start from a stop sign, accelerate and shift briskly up to highway speed and everything is fine - then this episode happens. It does not feel gradual, like a fuel flow restriction would. It feels like a shutoff.

I also tried to provoke it...accelerating with the pedal to the floor, running full power...nothing. I have not identified the exact circumstances that make it happen.

I need to do O-rings on the IP anyway (started seeping) and I am curious as to your opinions of what can cause this behaviour. I have a spare, used, LDS IP of unknown condition. Maybe I should swap the head in?

Oh, tank is clean, primary and secondary are spin-ons, new, and no crud when draining from the drain port. Truck pulls like a champ all the way to governed rpm (which a very sensible motor pool SGT had set to 2400 rpm on the LDS and I left it there). That is 60mph with my OD

 

[kc5mzd]

The first thing that comes to mind is air getting into the system. How is your in tank pump running? if it is turning off for dome reason then it would allow air into the system. Thought about temporarily putting a small 24v light on the electric fuel pump to see if it is turning off?

 

[JDToumanian]

Sticky governor? I'd run some fuel additive, like a heavy dose - maybe a gallon or two - of 2-stroke oil. If it's a new pump, nice and tight, it probably doesn't appreciate the lack of lubricity in modern diesel fuel.

Jon

 

[cattlerepairman]

In-tank is running fine, hose attached, building pressure. A sudden string of bubbles would perhaps explain the power drop.

 

[cattlerepairman]

I can add diesel fuel lubricant.

 

[frank8003]

If you look up seafoam MSDS and see what it is you might just go to the depot and get a gallon of Naptha and dump it in the tank but I can not find in this string what fuel you are using, what fuel?

 

[frank8003]

A new in-tank pump from a Bradley goes right in. Cheap, not to worry but the idea of wiring a lamp into the circuit is interesting. I will send you a 24VDC LED for the postage if you want.

The first thing that comes to mind is air getting into the system. How is your in tank pump running? if it is turning off for dome reason then it would allow air into the system. Thought about temporarily putting a small 24v light on the electric fuel pump to see if it is turning off?

 

[kc5mzd]

If it is a sticky governor you should be able to duplicate the problem by accelerating to 55 or so then slide your foot off the accelerator pedal so it is suddenly released. Then let the truck slow to about 50 or so without touching the accelerator again. Then put the clutch in - if the engine stalls then it might indicate a sticking governor. Once you get it to stall it should be fairly easy to duplicate. You will have to remove the cover plate and carefully spray cleaner / lube onto the lever and shaft. I think there lots of threads on how to clean it as it is a fairly common issue and easy fix.
Good Luck!

 

[Floridianson]

The in tank can have power and sound like it is working but the only way to tell is it making pressure. So light no gage yes. The truck will run without the in tank making pressure but if there is a hole in the pump tank line yes it could let in air.
The governor is oiled bathed not fuel bathed and in the tail shaft of the IP. The outside of the fuel control on the head that you see when you remove the shut down cover is also bathed in oil not fuel. The inside of the fuel control assembly where the little pin goes into the plunger collar does get some fuel.
I am still thinking about the OP's problem.
Just thinking if the fuel control was to stick while driving it would be like cruse control and hold a given fuel amount not just shut off. The fuel control would have to go back to the 4 o'clock position to shut down or act like it just shut off. OP says it happens when at running open throttle right?
Still thinking.
Does it shut down with throttle applied and driving or when you take your foot off the peddle and not come back or act like no fuel when throttle is applied?
Only remember one case where the fuel control rod that comes from the governor was broken at the fulcrum inside the governor housing.
Still thinking maybe check the fuel control assembly for ease of motion as others said above to start with.
Just because the foot throttle goes to the floor does not mean that the fuel control assembly is moving.

 

[cattlerepairman]

Thanks for the thoughts.
What I can do, if/when it happens again, is to let go of the fuel and hit the clutch. If the engine stalls, it is a no-fuel situation.

I will put a pressure gauge on the secondary filter and see what the in-tank pump delivers.

 

[Floridianson]

Check the fuel control for the free movement. Motor not running should be a around 7o clock and with finger it should easy move to about 4 o clock then snap back to 7 when you let go. If you were driving and you took you foot off the fuel peddle and the fuel control assembly stuck in the idle position then it might feel like no fuel because it's stuck at idle. If the motor died then the fuel control went to far passed idle and went to shut down position. That might be a governor / linkage problem.

 

[rustystud]

Check the fuel control for the free movement. Motor not running should be a around 7o clock and with finger it should easy move to about 4 o clock then snap back to 7 when you let go. If you were driving and you took you foot off the fuel peddle and the fuel control assembly stuck in the idle position then it might feel like no fuel because it's stuck at idle. If the motor died then the fuel control went to far passed idle and went to shut down position. That might be a governor / linkage problem.

I'm with you on the linkage idea Floridianson. I think it would be a good idea to take the FDC off and look inside at the governor assembly. Either a broken linkage or binding problem. One of the pumps I rebuilt had a broken fulcrum lever. Something like that could cause this problem.

 

[cattlerepairman]

I'm with you on the linkage idea Floridianson. I think it would be a good idea to take the FDC off and look inside at the governor assembly. Either a broken linkage or binding problem. One of the pumps I rebuilt had a broken fulcrum lever. Something like that could cause this problem.

Can I just take the FDC off without removing the IP from the truck or will I immediately lose several irreplacable parts as they fly off in all directions?

 

[rustystud]

Can I just take the FDC off without removing the IP from the truck or will I immediately lose several irreplacable parts as they fly off in all directions?

You can easily take the FDC off. In fact you don't even have to remove the fuel lines if your careful and have enough slack in the lines.

 

[kc5mzd]

Just bypass it. You don't have to remove any parts. Most of mine were bypassed by the military before I got the trucks.

 

[rustystud]

Just bypass it. You don't have to remove any parts. Most of mine were bypassed by the military before I got the trucks.

He wants to open up the injection pump to see inside. Not bypassing the FDC.

 

[cattlerepairman]

No updates, yet. It has been raining constantly. I worked days under a tarp a few weeks ago to do the axles but have little motivation to do it for less essential stuff.....

 

[rustystud]

No updates, yet. It has been raining constantly. I worked days under a tarp a few weeks ago to do the axles but have little motivation to do it for less essential stuff.....

I totally understand ! Out here in the "Pacific Northwest" we are used to rain but the old injuries and busted up joints don't care for it much ! I'm working on a few projects, but there all inside the cab or better yet inside the shop ! I just installed my "winter" heater in the deuce today. It will help to keep the condensation from forming on all that metal. I really hate to have it raining on me on the "inside" of the cab !