120 Lehman Stalls at Full Throttle

[jleonard]

A Walbro. Good pump. I had one in the polishing system I installed in my trawler.

I set mine up to have the ability to polish. All I needed was to add one hose.
But decided I never needed that feature.
This is typical of how my filter elements looked.

 

[Chuck34]

Greetings,
Mr. H. No need to run WOT to "clean" a Lehman, IMO. On rare occasions (maybe once or twice a year) I do run up to WOT for a very short time (less than 30 seconds) just to see if WOT is still achievable. American Diesel is a GREAT source for parts AND information. https://americandieselcorp.com/

Yes, you need to develop a relationship with American Diesel. They know that engine better than anyone and can diagnose problems over the phone better than most mechanics can sitting in your engine room.

 

[727Gold]

I had same symptoms, same engine, approx 3000 hrs. Checked all the recommended items in this thread, nothing came of it so replaced the lift pump which cleared the problem. Not hard to do, not expensive and therefore very unusual for a boat "issue".

 

[Tiffany]

The topic of running a diesel at WOT to "clean it out" often comes up, but with age and use most engines develop a hard carbon accumulation at the top of piston, leading to the rings becoming frozen and unable to move freely. This leads to oil consumption, loss of compression, increased wear, etc.

At the risk of appearing to be shilling for a company, I would like to suggest the use of Cost Effective Maintenance's FTC Decarboniser (https://costeffective.com.au/product/ftc-decarbonizer/). I've used this with my T6-354 Perkins, my neighbour's Lehman and my VW turbo diesel.

Marked improvement in power, oil remains cleaner, fast, cleaner starts, engine runs smoother. CEM has a US distributor. Their products aren't cheap but they work and are cheap in the long run.
Sorry for the ad - I just read so many people struggle with these engine predicaments with limited avenues for resolution. Cheers!

 

[Alisske]

I think the auxiliary pump recommendations are helpful.

I had the same problem when in a trip. Was offshore and the RPM started to “hunt” then she would just drop dead. Within 5-15 seconds, I cranked the engine just to get fresh water pumping (to cool her down since its a damn sin to shut down that engine without a low RPM cool down period) not start the engine. It fired up! Idles for a minute, so i dropped her in gear and 3 minutes later, same thing.

I had decent weather, so rather than limp back to port, i worked on her in situ.

Started with a bleed at injector, worked my way back to secondary, then to primary. When i popped the top, it “hissed” indicating there was a vacuum. Traced back further and found a prime pump that was plumbed directly in to the fuel system. Just cut hoses, by-passed it and i was on my merry way.

2 major points, never plumb directly, and have a vacuum gauge on your water separator. If it was not such a nice day, and the waves were “lapping” the hull, would have missed the hiss sound. Simple gauge would have prevented that and got me a 30 second diagnosis.

Just FYi

 

[JdaleH]

A diesel needs air and fuel. Remove the air intake filter to make sure it is not blocked. Already been there.

 

[DBrunes]

Hey Hutch, have you solved the issue yet?

I am probably the last guy to listen to... but it sounds like an issue I had with my genset. I'd run it, put some load on it and shortly thereafter, it would just stall.

Start and run fine again until I loaded it up for a while, then a clean stall again.

Turns out I was not looking at the temp gauge for the gen. It had a high temp auto shutoff.

Needed to clean and rebuild the heat exchanger.

I'm assuming you've watched your temp gauge?

 

[Hutch9900]

Hey Hutch, have you solved the issue yet?

I am probably the last guy to listen to... but it sounds like an issue I had with my genset. I'd run it, put some load on it and shortly thereafter, it would just stall.

Start and run fine again until I loaded it up for a while, then a clean stall again.

Turns out I was not looking at the temp gauge for the gen. It had a high temp auto shutoff.

Needed to clean and rebuild the heat exchanger.

I'm assuming you've watched your temp gauge?

No, it's not resolved yet as we couldn't go to the boat last weekend. Too many issues with kids starting school and whatnot.

I was watching the temp gauge closely. No issues with overheating. Water continuously coming out the exhaust as well.

 

[ronobrien]

And yes, sorry I should have mentioned FL120.

It was in the title of the post.

 

[ronobrien]

Hi everyone! My name is John and I just purchased a 1982 Marine Trader 34 DC. We are super happy with the boat so far and cannot wait to absorb some of the knowledge in this community. We have owned two other boats, both I/O (one a cuddy and the other PC). I have never owned a diesel before.

So, we took the boat out this past weekend and enjoyed a wonderful cruise of about 20 NM. I did slowly increase the throttle to full and after a minute the engine died. It would fire right back up and all temp and oil pressure was fine. As long as I stayed at 1800 rpm or below it would not stall. Has anyone ever heard of this problem? What is the typical performance should I expect (max rpm, best economical cruise, etc.)? Thank you all in advance for any information!

If you have 2 tanks, that would seem to eliminate the possibility of an obstruction. If you only have 1 tank there may be something in the tank that gets sucked up to , and blocks the pick up tube under high fuel flow, then drops away as the suction stops when the engine stalls. I have seen this in trucks. Anything is worth investigation when all else fails.

 

[JdaleH]

Check to make sure the air intake filter is not partially collapsed. Remove to check.

 

[catalinajack]

If you have 2 tanks, that would seem to eliminate the possibility of an obstruction. If you only have 1 tank there may be something in the tank that gets sucked up to , and blocks the pick up tube under high fuel flow, then drops away as the suction stops when the engine stalls. I have seen this in trucks. Anything is worth investigation when all else fails.

A Lehman 120 is not a high volume fuel draw, no more than two gallons per hour with almost no return flow so this is not likely the problem but I guess it is possible. As for air supply, that is not a likely cause either. A Lehman 120 uses a very course foam sock as a filter. Continue to look for a fuel supply problem. A collapsed hose would not be visually evident. I would start with replacing all rubber hoses. If that doesn't work, replace the lift pump. If it were I, I would replace it with an electric pump. A Walbro has a service life of 18,000 hours and, with it, no more using that pump lever actuated a million times to bleed air. By the way, if that mechanical lift pump has failed there is a chance that its diaphram has fractured and is putting diesel fuel in the oil sump, a very bad thing for an engine.

 

[JdaleH]

Although the air intake is unlikely to be the issue, as a previous owner of a 120, I can attest to it being a possibility. You can't tell until you remove it.

 

[old-School]

I agree. FL 135 are 1800 engines as well.

 

[Hutch9900]

A Lehman 120 is not a high volume fuel draw, no more than two gallons per hour with almost no return flow so this is not likely the problem but I guess it is possible. As for air supply, that is not a likely cause either. A Lehman 120 uses a very course foam sock as a filter. Continue to look for a fuel supply problem. A collapsed hose would not be visually evident. I would start with replacing all rubber hoses. If that doesn't work, replace the lift pump. If it were I, I would replace it with an electric pump. A Walbro has a service life of 18,000 hours and, with it, no more using that pump lever actuated a million times to bleed air. By the way, if that mechanical lift pump has failed there is a chance that its diaphram has fractured and is putting diesel fuel in the oil sump, a very bad thing for an engine.

Would you happen to know the model number of the fuel pump you are referencing? This sounds like an upgrade I want either way. I didnt know you could replace the fuel pump with an electric one but that sounds like the way to go.

 

[catalinajack]

Would you happen to know the model number of the fuel pump you are referencing? This sounds like an upgrade I want either way. I didnt know you could replace the fuel pump with an electric one but that sounds like the way to go.

FRB 13-2

walbro.com/fr-series-fuel-pumps

 

[Hutch9900]

FRB 13-2

walbro.com/fr-series-fuel-pumps

Thank you! Does it mount the same as the original mechanical pump? I know I would need to get the 12v power there, but just wondering if this unit needs to be installed remotely of the mechanical pump?

 

[catalinajack]

Thank you! Does it mount the same as the original mechanical pump? I know I would need to get the 12v power there, but just wondering if this unit needs to be installed remotely of the mechanical pump?

No, the pump mounts in any other convenient place. The mechanical pump can be removed and the port covered with a block-off plate for a big block chevy gas engine.

 

[Scooby5959]

This is not complicated I have probably owned around 10 120 Lehman‘s here’s my recommendation ,I’m always right so don’t argue. The electric lift pump is a very good idea that’s the first thing you should do. After that Inspect your fuel line from your fuel tank to pump, hopefully a straight line with no Tee or other fittings, if not make it so. A switch for a manual run of the fuel pump is necessary. A good or a new line from the output side of your fuel pump to your fuel filter ,scrap the stock fuel filters that are mounted on the side of your engine the ones that take insert type filters or cartridges I guess.Install a filter housing with a bleeder screw on top of it. The type that will take a screw on filter. I use a 2 micron combination fuel water separator filter standard in the trucking industry.Next have a fuel line made to go from the output side of the filter to the input of your fuel injection pump get rid of that problematic steel line. Now you are good to go you will never have a problem again if the motor starts running bad or dies it will always be a plugged fuel filter it takes less than five minutes to change the filter . open up the bleeder valve on top of the filter housing flip your pump on and pump fuel into your filter until fuel comes out with no air bubbles in it that’s it you’re done at the very outside you may need to bleed your injection pump that is the same process , crack the bleeder screw on your injection pump flip your switch on for a second and watch for clean fuel with no air bubbles you will never have a problem again if you do you’re sucking Air somewhere. if the fuel lines are good that will never happen . None of that complicated multi filter multi valve fuel polishing gimmicky stuff for me a single two micron filter is all you will ever need .I have owned a lot of diesel trucks and equipment They were operated that way ,you do not want a complicated system trust me you will regret it if you do . I run thousands and thousands of gallons of diesel . Some of it pretty questionable from sources you cannot trust. Stop on the side of the road takes less than five minutes and you’re up and running again if you’re worried about changing a filter while underway then just change it every once in a while , I don’t worry about it .Don’t ask me what I think about the Ford Lehman .A motor that shakes and rattles your whole boat and you can’t stand to listen to it run other than that it’s OK

 

[TJM]

I have taken that bleed step one farther and painted the tops of the bleed screws a unique color with nail polish, green and yellow actually. I also painted the corresponding box wrenches and have them hanging in the engine room. Last week I had to bleed both engines in rough seas and I was done in about 3 minutes. Awesome with an electric priming pump, a little different set up then what Scooby5959 says, but close to it.
I might ponder switching out my old lift pump to the FRB that was discussed. Thanks for the info.

 

[catalinajack]

This is not complicated I have probably owned around 10 120 Lehman‘s here’s my recommendation ,I’m always right so don’t argue. The electric lift pump is a very good idea that’s the first thing you should do. After that Inspect your fuel line from your fuel tank to pump, hopefully a straight line with no Tee or other fittings, if not make it so. A switch for a manual run of the fuel pump is necessary. A good or a new line from the output side of your fuel pump to your fuel filter ,scrap the stock fuel filters that are mounted on the side of your engine the ones that take insert type filters or cartridges I guess.Install a filter housing with a bleeder screw on top of it. The type that will take a screw on filter. I use a 2 micron combination fuel water separator filter standard in the trucking industry.Next have a fuel line made to go from the output side of the filter to the input of your fuel injection pump get rid of that problematic steel line. Now you are good to go you will never have a problem again if the motor starts running bad or dies it will always be a plugged fuel filter it takes less than five minutes to change the filter . open up the bleeder valve on top of the filter housing flip your pump on and pump fuel into your filter until fuel comes out with no air bubbles in it that’s it you’re done at the very outside you may need to bleed your injection pump that is the same process , crack the bleeder screw on your injection pump flip your switch on for a second and watch for clean fuel with no air bubbles you will never have a problem again if you do you’re sucking Air somewhere. if the fuel lines are good that will never happen . None of that complicated multi filter multi valve fuel polishing gimmicky stuff for me a single two micron filter is all you will ever need .I have owned a lot of diesel trucks and equipment They were operated that way ,you do not want a complicated system trust me you will regret it if you do . I run thousands and thousands of gallons of diesel . Some of it pretty questionable from sources you cannot trust. Stop on the side of the road takes less than five minutes and you’re up and running again if you’re worried about changing a filter while underway then just change it every once in a while , I don’t worry about it .Don’t ask me what I think about the Ford Lehman .A motor that shakes and rattles your whole boat and you can’t stand to listen to it run other than that it’s OK

Perfect. Pretty much, Scooby, that is the setup I have on my Lehman 120s, including the 2-micron filter. Exception. I have the spin-on adapters for the stock double on-engine filters. I use a 3-mocron to a 2-miron. My primary filters are a 20-micron to a 10-micron.