Bypassing leaky Perkins 4108 manual lift pump

[c.K.]

on bypassing the lift pump
I have a shop manual that shows how to disassemble this pump, it says you have to mark the parts for re-assembly you should be able to get a new membrane for it , my pump is attached with 4 bolts to the block
And no, I did not replace the gasket on the block, was still fine and so far no oil leaks.

[Lepke]

I have 2 generators, a Perkins and Onan, and twin Detroits. All have a 12v electric pump inline. They are only run to bleed or fill filters. DDs don't need bleeding, but filling the filters means less cranking on the starters. And if I have a fuel pump failure, I flip a switch and I'm back in business w/o hunting for a spare. When the manual pumps on the generators go, I'll block them off. I've had zero problems leaving a 2nd pump inline and turned off.

Blocking off the old pump doesn't involve oil pressure. If you leave it and forget about it, mechanical parts could fail. And if the mechanical parts fail, it could damage the engine.

https://www.parts4engines.com/perkin...lift-pump-kit/ has 2 and 4 bolt manual fuel pumps for $35 if that's what you want. They do disassemble, but you probably will have to find the material for a new diaphragm. I don't know anybody that sells a ready made diaphragm any more.

Several new generators I've looked at come with 12v pumps and no manual pump.

[jimbunyard]

Originally Posted by Lepke

I have 2 generators, a Perkins and Onan, and twin Detroits. All have a 12v electric pump inline. They are only run to bleed or fill filters. DDs don't need bleeding, but filling the filters means less cranking on the starters. And if I have a fuel pump failure, I flip a switch and I'm back in business w/o hunting for a spare...

Not relevant to anything but my curiosity, but do your Detroits still have their 'lift' pumps? Those things are serious, positive displacement pumps more akin to engine oil pumps (which technically they are) than to the electric lift pumps common on most modern engines. If I remember correctly operating pressure is somewhere around 50-60 PSI?

[c.K.]

repl;y to Lepky
I think you are right my pump has an internal connection inside the block and does have a funktion beyond just a priming

[sharkdiver84]

Originally Posted by Argyle38

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/

I also have a Downeaster 38 and it is indeed leaking fuel into my oil. I'm having difficulty accessing the bolts to remove the lift pump. I'm not good at this mechanic gig, but it would seem to be that bypassing or with electric should eliminate that problem, since the fuel would no longer be paying through it. Am I correct I'm that assumption or am I overlooking something?

[c.K.]

Originally Posted by sharkdiver84

I also have a Downeaster 38 and it is indeed leaking fuel into my oil. I'm having difficulty accessing the bolts to remove the lift pump. I'm not good at this mechanic gig, but it would seem to be that bypassing or with electric should eliminate that problem, since the fuel would no longer be paying through it. Am I correct I'm that assumption or am I overlooking something?

I was told that the hand lift pump could be a source of fuel lkeaking into the block
it is not that hard to take that pump off and test it , access with small socket wrench
My brand new punp was not leaking so only 2 other possibilities fuel pump or injectors
Just to get an answer, I'm having my injectors tested the fuel pump ?? bit too expensive to have that done
Besides I'm getting a new engine and don't want to sink more money into this pitt
Good luck

[sharkdiver84]

Originally Posted by c.K.

I was told that the hand lift pump could be a source of fuel lkeaking into the block
it is not that hard to take that pump off and test it , access with small socket wrench
My brand new punp was not leaking so only 2 other possibilities fuel pump or injectors
Just to get an answer, I'm having my injectors tested the fuel pump ?? bit too expensive to have that done
Besides I'm getting a new engine and don't want to sink more money into this pitt
Good luck

I hope everything works out for you. I'm in the same situation where the injectors would be far too expensive. I'm lucky the engine wasn't killed entirely on that runaway. So hopefully it's the fuel pump diaphragm.

For some reason I can only get the socket to grip two of the four bolts to remove it because it's up against a wall and the pump body itself interferes with the shaft of the socket extender. And I feel like the potential of a leaky diaphragm to completely kill the engine in a runaway is too much of a liability. Hopefully the electric works.

[c.K.]

Originally Posted by sharkdiver84

I hope everything works out for you. I'm in the same situation where the injectors would be far too expensive. I'm lucky the engine wasn't killed entirely on that runaway. So hopefully it's the fuel pump diaphragm.

For some reason I can only get the socket to grip two of the four bolts to remove it because it's up against a wall and the pump body itself interferes with the shaft of the socket extender. And I feel like the potential of a leaky diaphragm to completely kill the engine in a runaway is too much of a liability. Hopefully the electric works.

There ate 1/4 inch socket shafts {May be slightly bigger ) they do the job

[CaptTom]

I'm following this, one of my Perkins engines (T6.354) showed a little high on the dipstick last time I checked. Maybe I over-filled on the last oil change, but my suspicion is a leaking diaphragm is the more likely culprit. A new lift pump ($40 on line) is on its way.

Back to the OP's issue, I notice there's been a lot of talk about the "manual" lift pump. My engines don't have these, but I know some Perkins engines did. Obviously if those develop a leak you can just cap them off and ignore them.

I think maybe what we're talking about here is the mechanical lift pump. Yeah, that's a problem when it fails. Just so we're all talking the same language.

I've been toying with the idea of an in-line electric lift pump for bleeding and as a back-up to the mechanical pump. I've run a couple of boats which had this, and actually used one once. Seems like cheap insurance to keep you going when making the repair would be inconvenient.

[skipperpete]

Originally Posted by CaptTom

I'm following this, one of my Perkins engines (T6.354) showed a little high on the dipstick last time I checked. Maybe I over-filled on the last oil change, but my suspicion is a leaking diaphragm is the more likely culprit. A new lift pump ($40 on line) is on its way.

Back to the OP's issue, I notice there's been a lot of talk about the "manual" lift pump. My engines don't have these, but I know some Perkins engines did. Obviously if those develop a leak you can just cap them off and ignore them.

I think maybe what we're talking about here is the mechanical lift pump. Yeah, that's a problem when it fails. Just so we're all talking the same language.

I've been toying with the idea of an in-line electric lift pump for bleeding and as a back-up to the mechanical pump. I've run a couple of boats which had this, and actually used one once. Seems like cheap insurance to keep you going when making the repair would be inconvenient.

I’m curious to know how you prime the fuel system after a filter change with no manual lever on your lift pump, do you have gravity feed from an overhead day tank?

[Cheechako]

Originally Posted by skipperpete

I’m curious to know how you prime the fuel system after a filter change with no manual lever on your lift pump, do you have gravity feed from an overhead day tank?

You dont normally need to "prime" after a filter change if you nearly fill the filter with fuel. I used an electric or a squeeze bulb i had installed on a few boats for filling the last bit of the Racor just to avoid issues. (lid loose or off). Never in 40 years have I needed to use the manual lever for just a filter change. However, you may need it for bleeding the injectors after having some of the sysem apart after the lift pump or injection pump. Or use an electric pump or squeeze bulb.
PS: I found some squeeze bulbs go soft after some time with diesel.

[skipperpete]

Originally Posted by Cheechako

You dont normally need to "prime" after a filter change if you nearly fill the filter with fuel. I used an electric or a squeeze bulb i had installed on a few boats for filling the last bit of the Racor just to avoid issues. (lid loose or off). Never in 40 years have I needed to use the manual lever for just a filter change. However, you may need it for bleeding the injectors after having some of the sysem apart after the lift pump or injection pump. Or use an electric pump or squeeze bulb.

PS: I found some squeeze bulbs go soft after some time with diesel.

What you just described is “ priming the system” , you just do it with a pump other than the one provided by the engine manufacturer. Bleeding or venting is the same process but usually applied after the engine has run out of fuel and often requires that the engine be cranked to purge the injector pump and HP pipes. The only engine I encounter that has no priming pump is Detroit diesel 2 stroke in all of its iterations other than the wretched “fuel pincher” 4 stroke.

[CaptTom]

Originally Posted by skipperpete

I’m curious to know how you prime the fuel system after a filter change with no manual lever on your lift pump...

My mechanical lift pump has a lever on it to manually pump if you need it to prime. There is also a manual priming pump on some motors, but it's not what we usually call a lift pump.

[capt jgw]

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?

That's Westerbeke. They don't make engines or anything else. They take off the shelf industrial or agricultural engines and add off the shelf parts to make them marine engines. Then they take parts from those engine builders, put a new label on the box and raise the price 10x. If it's a Perkins engine, then yes the Perkins pump or any other part will work. Same exact part at 1/10 the cost. Don't EVER buy anything from Westerbeke.

[Lepke]

Originally Posted by jimbunyard

Not relevant to anything but my curiosity, but do your Detroits still have their 'lift' pumps? Those things are serious, positive displacement pumps more akin to engine oil pumps (which technically they are) than to the electric lift pumps common on most modern engines. If I remember correctly operating pressure is somewhere around 50-60 PSI?

I have 671 naturals. All Detroits have a gear fuel pump. Mine pump 35gph at about 35psi. Turbo DDs have what looks like the same pump but with wider gears and pumps about 70gph. Excess fuel returns to the tank. Detroits were designed in the 1930s based on engines a decade older. High pressure oil or fuel isn't their thing. The fuel pressure needed for injecting happens in the injector. There's a plunger inside the injector that makes the high pressure need so no injector pump.

I have an electric fuel pump inline that is normally off. I use it to fill the secondary filter. I could leave it on and it wouldn't make a difference. The gear pump will act as a metering pump. My generators also have an electric pump for bleeding.