Perkins 4-108 1983 Fuel Pump

[Boracay]

I took the fuel lift pump from my Ford 2402E to my friendly local truck supplier. They looked through their catalogue, found the one that matched and ordered it. Arrived a week or so later.

Works fine.

I also tried an electric lift pump but it gave up the ghost after about an hours running. I took it back and got another one which I have plumbed in but do not use. I would use it for bleeding or emergency use.

The engine did not run as well on the electric pump as it did on the mechanical, but it was a cheap generic pump.

[AnchorageGuy]

With Sea Trek's original 4-108 we ran with the dead fuel pump in line without a bypass and using just the electrical pump for 4 years. Don't try to use an automotive electric fuel pump, they just can't stand up to the use on a boat.

[jimisbell]

Originally Posted by Chris31415

I took the fuel lift pump from my Ford 2402E to my friendly local truck supplier. They looked through their catalogue, found the one that matched and ordered it. Arrived a week or so later.

Was this for a Perkins 4-108???

[CSY Man]

I installed an electric fuel pump for the 4-108.
Kept the old lift pump after I "overhauled" it.

The electric pump is a heavy duty one. (And should be @ $140.00)

It makes bleeding the engine much easier and will also be a "go-home" pump if case the mechanical pump fails.

Did not bypass the lift pump, but rather installed it between the filters.

[never monday]

I prefer the mechanical pump atleast have the ability to be bypassed.
When the diaphram in the mechanical pump fails.You'll use the electric pump. This can give a high potential to filling the crankcase with diesel.

[CSY Man]

I prefer the mechanical pump atleast have the ability to be bypassed.
When the diaphram in the mechanical pump fails.You'll use the electric pump. This can give a high potential to filling the crankcase with diesel.

Hmm, good idea.

I will look into doing just.

Should be easy enough to disconnect the fuel line and bypass the lift pump if that happens...
(The boat is full of spare lines, hose clamps and other goodies)

[jimisbell]

I would think the time to bypass the mechanical pump would be before the diaphram breaks! Then use the electric pump as the main pump and if it fails, THEN "un bypass" the mechanical pump and use it as the backup.

If you do it the otherway you could have a crankcase full of diesel and a dead (permanently) engine from lack of lubrication before you were aware the diaphram had broken!!!

[CSY Man]

Yeah, but the lift pump is still going to "running" and wearing out as long as the engine is going even if ya bypass it and run the fuel through the electric pump on a permanent basis?

If the lift pump fails, the engine will stop and ya know what happened...Hopefully the crankcase will not be full of fuel right away?

That being said, when I bought this here boat, I had the engine oil analyzed and we got an urgent fax from the analyzing folks saying there was 6% diesel in the engine oil...Do not operate the engine....

Found the culprit to be a leak in the lift pump and the previous owner replaced the pump before we completed the transaction.

Since then I have had the oil checked a couple of times looking for abnormal wear or potential problems...Just in case. (So far, perfect results)

Can't remember seeing a overhaul schedule for the lift pump, does anybody know what the life expectancy is for the diahgram in the lift pump?
I would be happy to replace it now and then just to be safe.

[jimisbell]

Thats why I plan on using the mechanical lift pump while its good and putting the electric in line but not powered up unless I am using it for priming the system. If the mechanical pump fails I will then just move the hose from the electric pump from the input to the mechanical pump to the input to the filter thus bypassing the bad pump that might have failed because of a broken diaphram.

[CSY Man]

Thats why I plan on using the mechanical lift pump while its good and putting the electric in line but not powered up unless I am using it for priming the system. If the mechanical pump fails I will then just move the hose from the electric pump from the input to the mechanical pump to the input to the filter thus bypassing the bad pump that might have failed because of a broken diaphram.

Uh, that is what I intended to do as well, but for some reason I thought ya were advocating the oposite?

I would think the time to bypass the mechanical pump would be before the diaphram breaks! Then use the electric pump as the main pump and if it fails, THEN "un bypass" the mechanical pump and use it as the backup.

Maybe I am just really confused and should really be sailing more and not think too much....

[jimisbell]

No, I think it may be me that is confused. I thought someone was planning on having them both in series and then using the electric pump to push the fuel thru the mechanical pump after a failure without bypassing it. That would work, but if the failure was a busted diaphram it could be disaster.

[CSY Man]

I thought someone was planning on having them both in series and then using the electric pump to push the fuel thru the mechanical pump after a failure without bypassing it.

Well, my electric pump is indeed in series, but it has an on-off switch in additon to the 12 V breaker.
Therefore it stays off unless needed.

Clear as mud..?

[Sand Dollar]

The mechanical lift pump on my 4-108 failed about a year ago - a two bolt model. I bought a rebuild kit for it. The manual showed a shaft that passes through the pump body and the rocker pivots on that shaft. However in my pump model the shaft does not pass through the pump body, it is supported by steel U-shaped pieces at each end (same shaft though apparently). Anyway, the U-shaped pieces had deformed and damaged the aluminum pump body (guess that is why they changed it).

The replacement U-shaped pieces solved the problem (they came in the rebuild kit) but since the casting was slightly damaged these pieces eventually deformed again. Now I know the diaphragm is new in the pump since I replaced it a year ago. So I put in a NAPA electric fuel pump ($40) and it pumps fuel right through the mechanical pump as others have posted. It works just fine and I carry a spare electric pump. But I can still operate the manual pump if necessary - it just does not pump enough to keep the injector pump supplied with the bit of slop at that pivot shaft. Eventually I will replace the mechanical pump. If you have a fuel pump with a recessed pivot shaft design I would recommend replacing it.

I mounted the electric pump away from the engine just before the primary filters - even if the engine is not running, I can run the fuel pump and fuel circulates through the filters and returns to the tank. If I have concern about contamination of fuel, this is a useful feature.

[jimisbell]

First post to this thread in over a year.

I replaced the diaphram in the lift pump and it worked fine. But now I have a new problem...air leak in the fuel system that makes bleeding before every start a nessesity. That sucks.

I found the leak today, its a cracked fuel filter housing! I am looking for a replacement.

Its a pretty stock looking thing with two mounting bolts on 2" centers on the back/top, two line fittings on either side and two fittings on the top, one bleeder screw and one banjo fitting for a return line. BUT it doesnt look like anything in the manual.

Any one have one to get rid of, or know which one a 1983 4-108 should use?

[Chief Engineer]

How did you ever get the USCG to tow you?

They don't do that around these parts....you are left to the pirate towers of the Chesapeake....unless you have insurance.