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Old 05-13-2023, 12:31 PM   #1
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Ford Lehman 2728T losing power

I have a pair of Ford Lehman 2728T with 2500 hours. They both run smoothly at all RPMs. Neither of them smoke significantly. The port engine demonstrates power loss at all RPMs once it warms up. When cold it idles at 600 RPM and when put in gear it drops maybe 10 RPM. When at operating temp the idle increases to 800 RPM and drops 200 RPM when engaged. When run to the stop it will not go beyond 2200. The starboard engine performs normally and runs up to the manufacture specs of 2400 with no power loss along the way. All else is equal, engine temperature, drive ratio, propsÖ. Fuel filters clean. New engine mounts and recent alignment. Rebuilt injectors. The engine stop completely disengages. Fuel return line check valve at secondary filters is operating correctly.

I have had the boat for 3 years and had this problem since day one. I have no past service records. I have talked to Brian at American and pursued all his suggestions.

Not a major issue except when it occasionally stalls while dockingÖ. Makes it interesting.

Any ideas?

Thanks, Mike
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Old 05-13-2023, 02:13 PM   #2
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Sounds like the fuel filter may be plugged. Change it and see if it helps.

David
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Old 05-13-2023, 02:46 PM   #3
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Sounds like the fuel filter may be plugged. Change it and see if it helps.

David
And related, if there's a screen on the fuel tank pick up tube that may be clogged. If there's one there, cut it off. You don't need it. Had the same problem on a car once, took the mechanics a while to figure out out.
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Old 05-13-2023, 03:28 PM   #4
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Thank you both for the replies. I have changed all filters multiple times and back flushed the fuel pick up. No feasible way to get it out for inspection. By the way I have had the fuel polished and have put several thousand gallons through the tanks over the past three years. The problem seems to somehow be fuel and temperature related. Aside from what I described at a cold idle vs. hot, the only times it has shut down while docking is after a days run. I even tried opening the fuel fill thinking the vent was clogged and creating a vacuum. Thanks again, Mike
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Old 05-13-2023, 03:47 PM   #5
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Greetings,
Mr. E. Have you considered a collapsing fuel line? On 2 occasions I have experienced the inner layer of rubber line delaminating and collapsing under suction.
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Old 05-13-2023, 03:53 PM   #6
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Greetings,
Mr. E. Have you considered a collapsing fuel line? On 2 occasions I have experienced the inner layer of rubber line delaminating and collapsing under suction.
That is what I would look at. You may not be able to tell just by looking at it since it may take a vacuum to collapse. I would just replace the hose, it is relatively inexpensive.

RT got to it first, he is pretty fast…
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Old 05-13-2023, 03:54 PM   #7
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If it is a fuel tank screen on a GB you could feed to from there other tank and test it.

Fuel line makes sense, gets hot in ER then gets soft and collapses.

Does it restart easily?
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Old 05-13-2023, 06:54 PM   #8
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Yes, restarts immediately.

Good point! Will check the lines. I had that problem on an outboard once. Forgot all about it. Thanks!
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Old 05-13-2023, 07:55 PM   #9
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Thought some more. Probably not the fuel pick up. The Racor vacuum gauges stay within he norm. Not sure why the increase in RPMs at idle? I will replace the fuel lines from the Racor to the engine. That could be an easy fix. Thanks.
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Old 05-22-2023, 03:36 AM   #10
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The engine dropping revolutions when the gearbox is engaged sounds like a clue.(assuming that it is not just a momentary decrease) Am I correct in stating that setting the throttle position selects desired revolutions and fuel is supplied at the required rate/volume to maintain the selected revolutions independent of the load ?. From your description it sounds like thatís not happening.
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Old 05-22-2023, 04:42 AM   #11
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Fuel pump starting to go weak,

Idle adjustment or load adjustment was messed with on the pump prior? Any marks or evidence?

Get a oil analysis and check oil for extra fuel.

Check compression warm and cold.

No smoke at all?
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Old 05-22-2023, 05:58 AM   #12
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Thank you both for the replies. I will follow up.

The rpm drop is not momentary. No significant smoke or color on either engine. No change in oil level when running. Both engines equally use less than a half quart of oil every 20 hours or so.

Two additional observations. In my original post I misstated the power loss occurs after it warms up. Correction: When first starting the engine idles smoothly at 600. Engage the gear and there is virtually no rpm loss and little to no change in the vacuum gauge on the Racor. Over the next 5 minutes (engine still relatively cold) the rpm gradually increases to 800 and now when engaging the gear there is a 200 rpm loss and the needle on the vacuum gauge on the Racor drops about a 1/4 inch. Not sure what that means.
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Old 05-22-2023, 09:45 AM   #13
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To reaffirm some things already mentioned:
- change out the lift pump. They are cheap.
- suspect fuel lines so disconnect feed to racor and suck from a fuel jug placed above the normal tank level
- how old is the injector pump
- is the on new engine filter of different type than old one
- Disconnect your return tank line and install a new temporary one

What things were done to engine or fuel system prior to problems arising?
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Old 05-22-2023, 11:34 AM   #14
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I had this exact problem on one of my 2728T.

After a partial overhaul, new turbo, new lift pump, we were left with rebuilding the injection pump.

It solved the problem.

When you do so, tell them to NOT adjust the calibration settings, per Brian at American Diesel.
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Old 05-22-2023, 12:38 PM   #15
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Thanks to you both.

Sunchaser: No service records came with the boat


Hytedin: Good insight. Just talked to Brian a few minutes ago. He suggested confirming the check valve on the injector pump is not stuck open. Had already checked the one between lift pump and the secondaries. Iíll let you know what I find.
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Old 05-22-2023, 01:43 PM   #16
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The INCREASE in idle RPM from 600 to 800 is counter to a fuel restriction, and suggests a governor issue. Similarly, an increase in droop from 50rpm at first start up, to 200 rpm a while later also suggests a governor problem.


I think I heard that Lehmans (or at least some of them) have separate oil reservoirs in the injection pumps? Has that oil been checked and changed? Beyond that, I agree that it's time for a pump rebuild, with special focus on the governor and associated springs and mechanism.
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Old 05-22-2023, 02:49 PM   #17
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What kind of shaft seal. If old style, packing could be tight. Also alignment could account for 200 rpm.

Since you have 2 engines, switch fuel items between the engines and look for differences. Swap the injectors, later the injector pumps, etc.
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Old 05-22-2023, 03:34 PM   #18
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Engine air filter? Remove and inspect. Blow it from the inside to the outside.
Tank vent plug up??? Blow it from the outside to the inside, catching the fuel in a container for inspection.
Does the engine lose RPMs with the fill cap open?
Mud dabber wasps seem to like that environment and my chain locker.
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Old 05-22-2023, 04:48 PM   #19
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The INCREASE in idle RPM from 600 to 800 is counter to a fuel restriction, and suggests a governor issue. Similarly, an increase in droop from 50rpm at first start up, to 200 rpm a while later also suggests a governor problem.


I think I heard that Lehmans (or at least some of them) have separate oil reservoirs in the injection pumps? Has that oil been checked and changed? Beyond that, I agree that it's time for a pump rebuild, with special focus on the governor and associated springs and mechanism.
The 120s have a separate oil reservoir in the pump and the oil gets diluted with fuel. Recommend starting oil change at 50 hour intervals and if it isnít diluted then increase the hours between oil changes per Bob Smith.
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Old 05-22-2023, 05:18 PM   #20
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Thanks all.

Trying to eliminate all the other things before pulling the injector pump for a rebuild. (These pumps do not have their own oil reservoir.) I have checked the vents, run with tank cap off, had the injectors serviced, made sure the shut down solenoid fully opens, rebuilt the dripless seals, new motor mounts and alignment, etc. Going to blow out all the return line check valves and swap them between engines next.
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