Intermittent power loss - fuel starvation?

[cattlerepairman]

LDS engine

• starts as soon as you touch the button
• Ran fine all year, she is being driven a lot (when not down for upgrades or maintenance)
• Yesterday, four hour trail ride, no hiccups
• On the way home, in 5th at about 1700 rpm it suddenly felt as if I lifted my foot off the throttle completely. No power. In fact, depressing the clutch sees the engine shut right off. After a few seconds (5-10) of coasting in gear, keeping the engine spinning, depressing the fuel pedal causes the engine to respond normally, as if nothing ever happened.
• Repeat episode, seemingly at random.
• 5th gear at 1700-2000 rpm seems to "trigger" it more, 4th at governor....not one episode. Not sure if that means anything.
• When she runs, she runs like a bat from ****. More power than you'd need.

I was thinking "fuel starvation". That is why I kept her coasting in gear....keep that IP spinning. I was not sure if she would re-start if I pulled over to the side of the road.

- spin on primary and secondary fuel filters, new this Spring
- gap between HH and IP body is moist; I guess I will be doing O rings in the future. But would a hardened O-ring at the HH alone cause such symptoms? Normally it is just fuel leaking out, isn't it? Changing the O-rings is a job I do not want to do unless I have to. Done it at the previous engine. I just do not like the HH.
- no fuel leaks that I can see
- running #2 diesel only
- new aluminium A3 fuel tank last fall; squeaky clean; cleaned in-tank-pump at the same time, it is running. I did not replace the pump hose, though.


I searched for similar issues - and found some posts, so this does happen to others - but there was no conclusive evidence as to what the cause was (or it was a cause that does not apply here, such as rusted, dirty canister filter).

Any thoughts? Recent power steering install...maybe I kinked a fuel line? Gotta check...

 

[rustystud]

To bad you don't have a fuel pressure gauge installed. That would tell us immediately if it was fuel starvation. Since you know the Hydraulic Head is leaking fuel that is where I would start.
Also when you had the fuel tank pump out, did you replace the rubber fuel hose then ? They can develop pin hole leaks once they get old. Then they are sucking in air not fuel. Since this condition only happens when your putting the engine under load (overdrive) that can be a culprit. So many variables here, you just need to start at one end and work your way to the other end.

 

[Floridianson]

For now with the weeping little bit of fuel from the Head and IP. Loosen one and retorque that one Head nut to 18/20 foot pounds then in x wise pattern loosen one of the other and retorque. Then the other two in x wise pattern. Weeping I do not believe will cause your problem. Guess you do not have the room to drive it around your property to see if you can make it act the same again. Road test is not the best here if she stalls out you might be stuck. Easy troubleshooting pressure gage installed between secondary and final for now. 30 psi idle 60 psi high idle. Catch and drain all three water traps with just the in tank running. Check all linkage and that includes under shut down cover for correct movement. Check all copper lines for leaking fuel and rubber line from copper line to booster pump for leakage with just in tank running. Pain but yes could be air from in tank so pull in tank pump is on the list if problem is not found before hand.

 

[Floridianson]

Was thinking last night about fuel pressure loss. We already know the motor will idle/run with the pressure relief valve on the secondary open or even removed. Now to check the relief valve you would have to disconnect both fuel lines from the T fitting where the relief is. The one from the Head and the tank return. Then you would have to connect them together leaving the valve output open and run the motor at high idle and see if the valve leaks. The only other way I can see maybe just run the Head return line into a bucket to catch the moving fuel from the Head. This is to much work and it would seem to be so much easer just to remove the cap from the relief valve and check / clean the valve itself. The one on mine was just a spring and slug type. The other valve that maintains pressure is the overflow valve on the Head. Just trying to think of more troubleshooting things that do not take long to check. Hope you find the problem quickly.

 

[N472AF]

I am having the exact same issue on my Deuce. Ran fine for a while then stumbles, shut off while coasting for a couple seconds, turn on, press start and back to normal for a short time. Limped it home and trying to trouble shoot. Tank pump is working, filters all 3 changed.

 

[Flyingvan911]

I wonder if you knocked some junk loose in the fuel system and clogged the primary fuel filter. You might try changing your fuel filters again.

 

[cattlerepairman]

Was thinking last night about fuel pressure loss. We already know the motor will idle/run with the pressure relief valve on the secondary open or even removed. Now to check the relief valve you would have to disconnect both fuel lines from the T fitting where the relief is. The one from the Head and the tank return. Then you would have to connect them together leaving the valve output open and run the motor at high idle and see if the valve leaks.

I have a spin on secondary filter with its own base and did not retain the original filter base. I don't think I have this valve but will check.


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[cattlerepairman]

...the Hydraulic Head is leaking fuel that is where I would start.
Also when you had the fuel tank pump out, did you replace the rubber fuel hose then?

Nope. Hose "looked ok" so I put it back on. Smart, in hindsight....not.

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[cattlerepairman]

Took it out for a drive to reproduce the problem.
It takes at least a half hour, until everything is good and hot, to start seeing the problem.
Until then, running at full power (up to 2400 RPM, boost up to 12psi) is fine.

Here is a video. You can hear the boost vanish at 0:08. It is unspectacular, just like lifting the foot off the pedal.

https://www.youtube.com/watch?v=lJmpadWIQu0

 

[frank8003]

torque peak is 1820 RPM
What are you describing
The future con rod hole in side of block?
Just an opinion and they are like holes

 

[cattlerepairman]

torque peak is 1820 RPM
What are you describing
The future con rod hole in side of block?
Just an opinion and they are like holes

It's an LDS, I installed the 12 point upgraded rod bolts, stock max RPM is 2800 and mine has the governor turned DOWN to allow 2400 RPM max. If it still throws a rod, I can't help it.

 

[Floridianson]

I have a spin on secondary filter with its own base and did not retain the original filter base. I don't think I have this valve but will check.
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If no pressure relief then the other is the overflow valve on the head that maintains the correct pressure in the Head. As said an in cab fuel pressure gage would tell if it is a pressure drop off. So that or some restriction is happening and closing off the flow if fuel pressure is the problem. You don't have to make the in cab gage fixed if you don't want to or just to troubleshoot.

 

[N472AF]

Changed all 3 again and it fixed all my issues. I only had about 20 miles since doing filters and really didn’t believe it was going to help it but all is good. For now.....

 

[cattlerepairman]

10-4. Fuel hose for in tank pump on order. Filters on order. HH re-torqued as per Floridianson (no more moistness in this area). Will change these items and report back.

 

[Floridianson]

The more I strain my little brain on this I am now leaning to air in the system. I say lean because I can tilt pretty far before I fall down. It's James to you sir.

 

[cattlerepairman]

Update:
- primary and secondary filter changed. Both had gunk in them.
- in-tank fuel hose changed.

The in-tank hose looked ok but was in fact shedding its outer layer. The hardened plastic shreds went through the in-tank pump and ended up in the primary filter. The filter was likely clogging (I did not cut it open; did not want the mess)

90 min test drive - Queen Lola did not miss a beat and had tremendous power. No moisture around the HH. Re-torquing was a good step.

If two filters, a hose and a clamp fixed it, I will not complain. Thanks to everyone that chimed in!

 

[rustystud]

Update:
- primary and secondary filter changed. Both had gunk in them.
- in-tank fuel hose changed.

The in-tank hose looked ok but was in fact shedding its outer layer. The hardened plastic shreds went through the in-tank pump and ended up in the primary filter. The filter was likely clogging (I did not cut it open; did not want the mess)

90 min test drive - Queen Lola did not miss a beat and had tremendous power. No moisture around the HH. Re-torquing was a good step.

If two filters, a hose and a clamp fixed it, I will not complain. Thanks to everyone that chimed in!

Glad to help. Remember that fuel tank hose gets a lot of people. They don't last forever. In fact I remember reading somewhere that the military recommended they get changed every two years. I last replaced mine 5 years ago, so I better heed my own words and replace it again. This new diesel is not the same as our good old diesel from the past.