What is this on my Lehman?

[PennBruce]

Can anyone tell what function this serves?


This is a tap off the rear of the Lehman.



The hose runs to this pump. The pump has an on/off rocker switch to the left.



The pump then connects to these filters.



Thanks,

Bruce

 

[O C Diver]

I'm not a Lehman expert, but the 1st picture looks like the mechanical fuel pump. The other pump might be to prime the filters and / or be a backup to the mechanical fuel pump. Following the hoses should give you the fuel direction and path.

Ted

 

[PennBruce]

The hose runs from the engine to the pump then to the filters. I had assumed that the direction of flow was from the engine.

Bruce

 

[psneeld]

Ford Lehman mechanical (lift) fuel pump

 

[O C Diver]

Assuming the first picture is the fuel pump, where does the other hose go to? The injector pump?

Ted

 

[psneeld]

The little hose (maybe metal pipe) out the top foes to the secondary filters which are usually right above it.

 

[O C Diver]

Maybe someone mounted the secondary filters on the wall.

Ted

 

[PennBruce]

Two votes for it being a fuel pump. Your picture shows a much more robust fuel hose then mine.

Is the mechanical fuel pump drawing fuel from the filters on the bulkhead and feeding the injectors? If so, what is the purpose of the switched pump on the bulkhead?

I have lot to learn about the fuel system on this boat. It has two fuel tanks and a "day" tank.

I appreciate the input.

Thanks,

Bruce

Ford Lehman mechanical (lift) fuel pump

 

[SoWhat]

The first picture is the mechanical fuel pump. The lower hose comes from the tank manifold. The upper hose originally went to the dual primary/secondary filters mounted on the engine. A previous owner has modified the filters and top hose probably goes to the Racor primary filter now mounted on the aft bulkhead. Then to the secondary filter, and finally to the high pressure injector pump.

PO has also installed a switched electric fuel pump that is apparently used to prime the primary/secondary filters but a wider view photo would be necessary to figure out what PO has done. As mentioned it could be also be used as a backup pump or as a fuel polisher depending upon valve settings and hose arrangement.

The mechanical fuel pump should last forever, it's a $25 part. Failure mode is typically a leaky diaphragm, a $5 part. Electric fuel pumps also last forever. Failure mode is typically corroded connections. Inspect every inch of hoses with LED light and mirror. Replace if tiny cracks are visible.

Fuel can come from one or both tanks depending upon valve setting. Make sure the return valve is set the same way.

 

[PennBruce]

There is also a set of filters mounted on the engine near the top of the block. Next time I visit the boat I will check to see if they are plumbed into the fuel system.

The first picture is the mechanical fuel pump. The lower hose comes from the tank manifold. The upper hose originally went to the dual primary/secondary filters mounted on the engine. A previous owner has modified the filters and top hose probably goes to the Racor primary filter now mounted on the aft bulkhead. Then to the secondary filter, and finally to the high pressure injector pump.

What area should i photo?

but a wider view photo would be necessary to figure out what PO has done.

Thanks,

Bruce

 

[catalinajack]

The first picture is the mechanical fuel pump. The lower hose comes from the tank manifold. The upper hose originally went to the dual primary/secondary filters mounted on the engine. A previous owner has modified the filters and top hose probably goes to the Racor primary filter now mounted on the aft bulkhead. Then to the secondary filter, and finally to the high pressure injector pump.

PO has also installed a switched electric fuel pump that is apparently used to prime the primary/secondary filters but a wider view photo would be necessary to figure out what PO has done. As mentioned it could be also be used as a backup pump or as a fuel polisher depending upon valve settings and hose arrangement.

The mechanical fuel pump should last forever, it's a $25 part. Failure mode is typically a leaky diaphragm, a $5 part. Electric fuel pumps also last forever. Failure mode is typically corroded connections. Inspect every inch of hoses with LED light and mirror. Replace if tiny cracks are visible.

Fuel can come from one or both tanks depending upon valve setting. Make sure the return valve is set the same way.

Yes, the mechanical pumps do last a long time but when that diaphragm fractures, the risk is an oil sump filled with diesel fuel which will wipe the bearings in short order. That is a risk I was not willing to take. I installed a Walbro electric pump, rated for 18,000 hours of use, and removed the mechanical pump. The port in the block can be covered with a Big Block Chevy block-off plate, on-line for about $8.

Side benefit - priming on-engine filters with ease.

 

[Gdavid]

On some old school mechanical engines (non-common rail), the engines idle smoother when an electric fuel pump is plumbed into the system, providing a more consistent pressure to the injector pump. To my knowledge, most of these pumps will allow fuel to pass through them just fine when not energized, so you don't have to use them all the time, they can be reserved only for priming the filters or whenever you see fit. Someone fitted one to my perkins that is controlled by the oil pressure sensor, this turns it off when the engine isn't running, otherwise it might keep pumping if the key is left on.

 

[SteveK]

Yes, the mechanical pumps do last a long time but when that diaphragm fractures, the risk is an oil sump filled with diesel fuel which will wipe the bearings in short order. That is a risk I was not willing to take. I installed a Walbro electric pump, rated for 18,000 hours of use, and removed the mechanical pump. The port in the block can be covered with a Big Block Chevy block-off plate, on-line for about $8.

Side benefit - priming on-engine filters with ease.

Since the pump failed how does the sump fill with diesel. Siphoning from the tank if fuel is above pump. did not think membrane failure opens it to spill into block. I thought there was a weep hole at bottom to indicate failure.

 

[C lectric]

Weep hole or not they can dump fuel into the oil sump.
My BIL had this very problem.

It may well have been a siphon but regardless the source of the fuel was a failed mechanical pump. A new pump stopped the fuel entry.

This is not a new problem for these engines.

There are other sources such as a cracked or loose fuel return line under the valve cover.

 

[SteveK]

Weep hole or not they can dump fuel into the oil sump.
My BIL had this very problem.

It may well have been a siphon but regardless the source of the fuel was a failed mechanical pump. A new pump stopped the fuel entry.

This is not a new problem for these engines.

There are other sources such as a cracked or loose fuel return line under the valve cover.

This is a concern I have not had...... Until now. Thanks

 

[koliver]

Your picture shows a much more robust fuel hose then mine.

I bought fuel hose from a hose store. the only 1/4" ID diesel hose they had was fat like that on the outside. I asked for something a little slimmer (less expensive) and learned that they only sell the fat stuff, as it is fire rated.

 

[jleonard]

Electric fuel pump for priming, fuel polishing, or as a backup to the mechanical pump.
I only used mine for priming but it was ready for the other tasks if need be.

 

[High Wire]

Looks like fuel comes from the fuel tank (assumption), through a large single Racor, then over to the engine mechanical fuel pump, then through the bulkhead mounted black electric fuel pump in series with the mechanical pump, then over to dual secondary Racor filters with metal bowls, then back to the engine.
Then again there are a lot of valves over by the dual Racors that need to be traced out. Start at the tanks and follow the path to the injection pump. There are some labels hanging off the hoses.

 

[catalinajack]

Since the pump failed how does the sump fill with diesel. Siphoning from the tank if fuel is above pump. did not think membrane failure opens it to spill into block. I thought there was a weep hole at bottom to indicate failure.

Because a partial tear can continue to supply enough fuel to keep the engine running while still putting fuel into the oil sump.

 

[mainer]

Fuel polishing?

Can anyone tell what function this serves?


This is a tap off the rear of the Lehman.

View attachment 122503

The hose runs to this pump. The pump has an on/off rocker switch to the left.

View attachment 122500

The pump then connects to these filters.

View attachment 122501

Thanks,

Bruce

Looks like it may be a homemade fuel polishing system system. The other purpose could be a fuel bleeding system that uses the rlectric pump rather than the mechanical lift pump.

 

[rgano]

On some old school mechanical engines (non-common rail), the engines idle smoother when an electric fuel pump is plumbed into the system, providing a more consistent pressure to the injector pump. To my knowledge, most of these pumps will allow fuel to pass through them just fine when not energized, so you don't have to use them all the time, they can be reserved only for priming the filters or whenever you see fit. Someone fitted one to my perkins that is controlled by the oil pressure sensor, this turns it off when the engine isn't running, otherwise it might keep pumping if the key is left on.

This is kind of what I was thinking when I first viewed this lash up, but there is no way to us really knowing. You must start as the supply valves on each tank and follow the system to the injector pump intake with a sketch pad in hand. ALSO, follow the return fuel line coming off the aft, right hand side of the engine's head to probably the day tank.

When following the line out of that Walbro-looking electric pump and through any downstream filters look for any added valves and the possibility of a return to the various fuel tanks (polishing system).

 

[jlhegland]

I can’t really see it being this complicated but my CHB has a Dickenson heater which is plumbed so that fuel can be pumped from the heater supply into the lift pump in an emergency. I’ve never had to use it so I don’t know if it is a good or a bad thing.