Bypassing leaky Perkins 4108 manual lift pump

[MaungaMoana]

Hi everyone.

This may seem like a really silly and novice question but thought I would ask anyways.

We have a Perkins 4108 and sometimes the engine fails to start. We looked around and noticed that when we pump fuel (hand ball rubber pump at tank) there is a few leaks along the way to the secondary engine mounted fuel filter. This means that the engine can (and does) suck air in.

Most of the leaks we stopped but one of the major leak is at the manual lift pump on the engine (just before the engine mounted filter)

We can go out and order a direct replacement for the lift pump or we read that a lot of people just install a electric 12v fuel pump instead


My questions are...

1) if we bypass the manual original lift pump is it ok to simply stay in place on the engine as is?

2) should the 12v electric fuel pump be wired in to be on while engine is running (I assume yes)

3) should we put the 12v pump right before the engine mounted fuel filter or should it be after it? (Should the electric pump push the file into the filter or pull it from the filter?)

Thanks !

[Cheechako]

It will work fine on a 4-108.
Put it just before the old lift pump and leave that old pump in place if you want. Or you can put it before the big filter (between it and the tank, or where the hand ball is)
I like it so it "pushes " fuel through the big filter, rather trying to suck it through.
Pump on when engine running.
Have a switch to use the pump for bleeding and refiltering.

I fail to understand why you dont just fix the line leaks though.?

[C420sailor]

Just realize that if you have an alternator failure, the engine will stop running when your batteries die.

The beauty of [most] diesels is that they don’t require any electrical power once they get moving.

As such, I cast my vote for the proper fix...not that my opinion matters.

[Lepke]

Plumb the electric somewhere between the primary and secondary filters. Remove the plumbing from the old pump and it can stay. Or make a block off plate.
An electric pump makes filter changes and bleeding air much easier. The average battery will run a 12v fuel pump for days.

[MaungaMoana]

Thanks for the advise and suggestions of where to put the 12v pump!

Just to clarify the above, the old lift pump is leaking not from the connection but from the center which after doing research, I learnt this probably means ripped diaphragm.

We will probably leave the old lift pump as is (dont want to start risking loosing oil pressure. and install the 12v with an extra switch for bleeding (thanks for the suggestions)

[mabowers]

For what it's worth, an OEM Perkins lift pump is only $50-75 US, probably the most affordable part on the 4.108 engine. (That said, I also have an electric fuel pump that I only run for faster bleeding with less cranking)

[StoneCrab]

Originally Posted by C420sailor

Just realize that if you have an alternator failure, the engine will stop running when your batteries die.

The beauty of [most] diesels is that they don’t require any electrical power once they get moving.

As such, I cast my vote for the proper fix...not that my opinion matters.

Not to be a smart ass but the manual pump isn't being used once the engine is running, the engines own mechanical pump takes over, so don't overthink an electrical pump.

Bypass the leaky manual pump so you eliminate those leaks....or fix the leaks.

I'm a big fan of adding an electrical pump. Can't beat it when bleading the engine.

[Minggat]

A bad diaphragm can fail in such a way to fill your crankcase with fuel.
Get a new mechanical pump, install the electric upstream of your Racor. Putting it there does many things for you, including exposing any points you might be sucking air.

[C420sailor]

Originally Posted by StoneCrab

Not to be a smart ass but the manual pump isn't being used once the engine is running, the engines own mechanical pump takes over, so don't overthink an electrical pump.

Bypass the leaky manual pump so you eliminate those leaks....or fix the leaks.

I'm a big fan of adding an electrical pump. Can't beat it when bleading the engine.

You’re right, I’m mixing up my engines.

[AJ_n_Audrey]

a) Replace the lift pump (if that is part of the problem) - they're cheap.
b) Add electrical pump and while you're at it, dual Racors if you don't have them already.
c) I am re-powering with BetaMarine, because my 40 year old Westerbeke (which is basically a 4-108) has given up the ghost, but the guy at Beta warned me about over-pressurizing with an electrical pump, so I'm investigating that aspect. Something you may want to look into with the Perkins.

[c.K.]

I have the exact same engine, and changed the fuel filters 4 days ago and had to deal with the air bleeding of the fuel system
Could not get enough pressure (I thought) with that hand-crank fuel pump so I took it off (had to remove the filter assembly as well) and checked it by blocking the intake and pumping the lever it had plenty of suction remounted the thing but found out the connecting hose was leaking a bit, fixed that

tip for bleeding the fuel lines: I set a vise grip on the vent hose of the tank and just happened to have an airpump that had a nozzle that fitted in the diesel tank intake , few pumps kept plenty of pressure to bleed the fuel and restart the engine

[svfinlandia]

Originally Posted by MaungaMoana

Thanks for the advise and suggestions of where to put the 12v pump!

Just to clarify the above, the old lift pump is leaking not from the connection but from the center which after doing research, I learnt this probably means ripped diaphragm.

We will probably leave the old lift pump as is (dont want to start risking loosing oil pressure. and install the 12v with an extra switch for bleeding (thanks for the suggestions)

I have a Perkins and I have been told, though I have never dealt with it, that a torn diaphragm in the lift pump can cause fuel to be pumped into the engine deluting the oil. I would pull the engine dipstick and see what your oil looks like.
As someone else said, a Perkins lift pump only costs around $60 from a marine store, and since the Perkins engine is used in so many farm tractors you can probably get a new lift pump from a farm tractor dealer for a lot less.

Al, S/V Finlandia

[Svsumurun]

OP, sorry for drift , but a question for the others here.Our 365 has a westerbeke 40 that has the exact same issue , and I installed an electric pump mostly due to the lift pump being over $400. Yet, a 4108 is supposed to be the same engine and several people mentioned the pump being cheap?
Can the Perkins pump fit the W40?

[svfinlandia]

Originally Posted by Svsumurun

OP, sorry for drift , but a question for the others here.Our 365 has a westerbeke 40 that has the exact same issue , and I installed an electric pump mostly due to the lift pump being over $400. Yet, a 4108 is supposed to be the same engine and several people mentioned the pump being cheap?
Can the Perkins pump fit the W40?

I really can’t answer your question, but I did discover that there are at least two types of lift pumps for the Perkins 4.236. One is a 2 bolt and the other is a 4 bolt.
I think in your case I would remove the pump and take it to a tractor dealer and see if they can match it.

Al, S/V Finlandia

[Argyle38]

Originally Posted by C420sailor

Just realize that if you have an alternator failure, the engine will stop running when your batteries die.

The beauty of [most] diesels is that they don’t require any electrical power once they get moving.

As such, I cast my vote for the proper fix...not that my opinion matters.

I like this answer. The on-engine lift pump is good to have since it doesn't need an external power source. As others have said, if it's sucking air, it could also be leaking diesel in to the oil, so it'd be a good idea to check that. The best option is to replace the mechanical pump, it's cheap and easy if you have access, and install an electrical pump as a backup and to make bleeding that much easier. These guys stock the mechanical lift pumps for US$36.

https://www.parts4engines.com/perkin...lift-pump-kit/