120 Lehman lift pump failure

[Randomwake]

I replaced my lift pump due to fuel dilution in the oil. The first new lift pump worked for 20hrs before the “foot” which rides on the camshaft sheared off. I thought it was an anomaly and got the pump warrantied. Installed the second new pump, installed easily and pumped 5psi like clockwork. 5 engine hrs later and the pump was dead due to the exact same failure. Almost looks like the edge of the cam sawed off the foot???

 

[Chuck34]

Call Brian at American Diesel and ask him about this.

 

[warfdog]

Interested - do you have a pic of what it’s supposed to look like? Is it this foot that sheered off ?

 

[Randomwake]

Yup, that’s the foot!

 

[boomerang]

Were you able to retrieve the broken piece?

 

[catalinajack]

And another reason why changing to an electric pump solves all these problems, including the fractured pump diaphram that dumped diesel into the oil sump. Get yourself a Walbro electric pump and cover the hole in the block with a Big Block Chevy block-off plate. The Walbro is an 18,000 hour product.

 

[Bmarler]

It looks like it snapped off from the stroke of the pump bottoming out before the cam was at its high point. Is there a spacer missing?
I don’t know if the pump is self regulated, or if a high pressure or high vacuum condition can cause that but also a possibility. Maybe check for a blocked return line?

 

[Redhook98]

Switch to Electric. Makes purging after filter changes easier too. The 18,00 hours between failures is a nice bonus too.

 

[socalrider]

Yup - I switched to Walbro pumps & they've been working great. One less thing to worry about.

 

[Bmarler]

For you guys that have switched to electric, what flow rate and psi did you select?

 

[socalrider]

I think these are the ones. Basically the lowest pressure and flow they make. FL120s don’t return much fuel so flow rates are low. A few psi is all you need for pressure.

https://www.go2marine.com/Walbro-Ma...GnLlsymx0a9Ku5e3vzeAAkmxLHxJFgtRoCp-gQAvD_BwE

 

[Mike GB32]

Thats the one I use. Walbro FRB-13

 

[Nick F]

The flowrate for a Lehman is extremely low. I have successfully run my engine using this pump which was installed for the purpose of topping up the filter bowl after filter change.

Mr. Gasket Micro Electric Fuel Pump

https://www.ebay.ca/itm/12569684102...mMnqnOV-XmCHdLFZfGG2sjk1GgmA0r7xoC_bAQAvD_BwE

 

[Caballero II]

I replaced my lift pump due to fuel dilution in the oil. The first new lift pump worked for 20hrs before the “foot” which rides on the camshaft sheared off. I thought it was an anomaly and got the pump warrantied. Installed the second new pump, installed easily and pumped 5psi like clockwork. 5 engine hrs later and the pump was dead due to the exact same failure. Almost looks like the edge of the cam sawed off the foot???

Can't quite imagine which part "sheered-off". Where did the sheered-off part go, and how does an electric pump fix/replace this problem. How does an electric pump help this and other fuel supply problems. I am very interested. Thanks.

 

[socalrider]

Can't quite imagine which part "sheered-off". Where did the sheered-off part go, and how does an electric pump fix/replace this problem. How does an electric pump help this and other fuel supply problems. I am very interested. Thanks.

The idea is that electric fuel pumps are pretty much indestructible. They just work. Replacing a mechanical fuel pump, which has multiple failure modes, eliminates a point of failure and leads to greater overall reliability.

There's also the advantage that electric fuel pumps make bleeding & priming much easier; no need to manually pump (which is inconvenient and doesn't work if the engine is in certain positions), or install a bulb. It's just overall a simpler and superior solution.

 

[Caballero II]

The idea is that electric fuel pumps are pretty much indestructible. They just work. Replacing a mechanical fuel pump, which has multiple failure modes, eliminates a point of failure and leads to greater overall reliability.

There's also the advantage that electric fuel pumps make bleeding & priming much easier; no need to manually pump (which is inconvenient and doesn't work if the engine is in certain positions), or install a bulb. It's just overall a simpler and superior solution.

So, how does it work? You change your fuel filters, and worry about how much air you've introduced into the lines. So you run the electric fuel pumps and then light off the engine? Or do you crack open the fuel supply nuts at the secondary fuel filter to get pure fuel with not air? Or do you do that and then crack open the bleed screw at the fuel injector pump and run all the air out there? I'm sorry to be dense about this, but I've never had to do it and so don't know. If bleeding it at the fuel injector pump, do I then do all the injector lines together, or shortest to longest, until I get solid fuel flow without air bubbles?

 

[Bmarler]

So, how does it work? You change your fuel filters, and worry about how much air you've introduced into the lines. So you run the electric fuel pumps and then light off the engine? Or do you crack open the fuel supply nuts at the secondary fuel filter to get pure fuel with not air? Or do you do that and then crack open the bleed screw at the fuel injector pump and run all the air out there? I'm sorry to be dense about this, but I've never had to do it and so don't know. If bleeding it at the fuel injector pump, do I then do all the injector lines together, or shortest to longest, until I get solid fuel flow without air bubbles?

Depends on what engine you have. All seem to have different venting procedures. But if unsure, and no manual showing vent screws, you can crack fittings instead.
So, open vent screw/crack fitting on filter output, run electric pump till good fuel comes out. If lucky, engine will light up. If not, I crack the two highest injector pipes, crank till I get fuel, or the engine starts to fire. Tighten pipes.

 

[socalrider]

On the Lehman as I recall you just change the primaries, and vent at the filter housing as the fuel pump runs. I don't think you'll need to bleed at the injector pump or injectors, but if you do, you just do them one at a time, I don't think the order matters.

 

[sunchaser]

I replaced my lift pump due to fuel dilution in the oil. The first new lift pump worked for 20hrs before the “foot” which rides on the camshaft sheared off. I thought it was an anomaly and got the pump warrantied. Installed the second new pump, installed easily and pumped 5psi like clockwork. 5 engine hrs later and the pump was dead due to the exact same failure. Almost looks like the edge of the cam sawed off the foot???

Was the new lift pump SN matched by Brian or sourced elsewhere? It would seem you installed a lift pump for a different model / SN engine.

 

[twistedtree]

I’m all for an electric pump, but at a minimum you now have a huge amount of metal in your engine. Hopefully it’s harmlessly dropped to the bottom of the pan. I’d drain it, and hopefully you have a magnetic drain plug. If not, I’d try to get a magnet in the pan to draw out all the shrapnel.

And it still begs the question of why these pumps are being destroyed. Is there supposed to be some sort of hardened cam follower like for the valves? Or does the pump arm ride directly on the cam lobe? What does the cam lobe look like? I wouldn’t be surprised if it’s totaled too.

 

[Redhook98]

I used these:


https://www.amazon.com/gp/product/B013U647IQ/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

 

[jleonard]

And it still begs the question of why these pumps are being destroyed. Is there supposed to be some sort of hardened cam follower like for the valves? Or does the pump arm ride directly on the cam lobe? What does the cam lobe look like? I wouldn’t be surprised if it’s totaled too.

I agree the cam lobe is now suspect. You should be able to see it with a flashlight or with a flexible borescope. If the lobe is scored, that would be why an electric would now make sense.

 

[sunchaser]

On most diesels the arm slides under the cam lobe. This means the lobe must be at its highest point when the pump is placed. A worn cam lobe would decrease the fuel pressure and or rate of fuel delivery. A fractured lift pump arm indicates either the wrong pump, cheap knockoff pump or incorrect placement in regard to the cam lobe.

But, a call to American diesel should solve the riddle.

 

[catalinajack]

It looks like it snapped off from the stroke of the pump bottoming out before the cam was at its high point. Is there a spacer missing?

I don’t know if the pump is self regulated, or if a high pressure or high vacuum condition can cause that but also a possibility. Maybe check for a blocked return line?

You probably wouldn't know this, but a Lehman 120 returns virtually no fuel.

 

[catalinajack]

For you guys that have switched to electric, what flow rate and psi did you select?

I used the Walbro marine-rated #13 model. I forget the rated PSI, but it has run fine for more than a thousand hours.

 

[catalinajack]

Can't quite imagine which part "sheered-off". Where did the sheered-off part go, and how does an electric pump fix/replace this problem. How does an electric pump help this and other fuel supply problems. I am very interested. Thanks.

How does it help this problem? The mechanical pump is removed and the mounting port is covered with a block-off plate.

 

[catalinajack]

So, how does it work? You change your fuel filters, and worry about how much air you've introduced into the lines. So you run the electric fuel pumps and then light off the engine? Or do you crack open the fuel supply nuts at the secondary fuel filter to get pure fuel with not air? Or do you do that and then crack open the bleed screw at the fuel injector pump and run all the air out there? I'm sorry to be dense about this, but I've never had to do it and so don't know. If bleeding it at the fuel injector pump, do I then do all the injector lines together, or shortest to longest, until I get solid fuel flow without air bubbles?

You bleed te system in the same manner as you would with the mechanical pump's silly lever that must be actuated dozens and dozens of times. Merely turn the electric pump on and bleed away.

 

[sunchaser]

For many of us old style mechanical engines with lift pumps are to be appreciated. That doesn't mean that a 12 volt electric pump can't be installed for backup or filter changes.

There is no mystery to mechanical lift pumps. But they are cheap and should be properly replaced every 5-10 years or at around 2,000 hours. I just replaced for the second time my two, pre-emptively. They are cheap - I paid about 60 bucks each.

As a corollary, changing out a lift pump is no more difficult that replacing a alternator belt. For many diesels, an electric lift pump is driven by the alternator. So if you lose that belt your engine stops.

Like many things on TF, maintenance 101 answers a lot of questions.

 

[Comodave]

So, how does it work? You change your fuel filters, and worry about how much air you've introduced into the lines. So you run the electric fuel pumps and then light off the engine? Or do you crack open the fuel supply nuts at the secondary fuel filter to get pure fuel with not air? Or do you do that and then crack open the bleed screw at the fuel injector pump and run all the air out there? I'm sorry to be dense about this, but I've never had to do it and so don't know. If bleeding it at the fuel injector pump, do I then do all the injector lines together, or shortest to longest, until I get solid fuel flow without air bubbles?

Our last boat had Lehman SP225s in it. I put Racor 12 volt pumps in the main Racor filters. They had a bleed screw in the top of the Racor filter. The kit with the pump came with new tops for the Racors if I remember correctly. If I changed both the Racor filters and the secondary filters too, I would crack the bleed screw on the Racor and run the pump until fuel came out. Then tighten the bleed screw on the Racor and loosen the bleed screw on the secondary housing. Run the pump until you got fuel out of the bleed screw on the secondary housing. Tighten the bleed screw on the secondary and start the engine. Simple and took a couple of minutes. Much better than using the hand pump on the lift pump.

 

[catalinajack]

For many of us old style mechanical engines with lift pumps are to be appreciated. That doesn't mean that a 12 volt electric pump can't be installed for backup or filter changes.



There is no mystery to mechanical lift pumps. But they are cheap and should be properly replaced every 5-10 years or at around 2,000 hours. I just replaced for the second time my two, pre-emptively. They are cheap - I paid about 60 bucks each.



As a corollary, changing out a lift pump is no more difficult that replacing a alternator belt. For many diesels, an electric lift pump is driven by the alternator. So if you lose that belt your engine stops.



Like many things on TF, maintenance 101 answers a lot of questions.

A Walbro electic pump is rated for 18,000 hours. Cheaper and more reliable in the long run and never a worry about a fractured diaphram dumping disel into the oil sump.