Fuel System

[BigAl.NZ]

Evening fellow sailors,

We recently had our Perkins 4.108 die while motoring. Initially we thought it was the lift pump, but after pulling the lift pump off we decided to check the fuel line and discovered a blockage which is now cleared.

This is when the real mystery started - since putting the lift pump and fuel filter back on (we put a new fuel filter on since it was off) we cant get fuel to the lift pump.

The setup:

The yacht has two tanks:

1. fwd tank feeds the engine directly
2. aft tank which can transfer to fwd tank

I can siphon fuel from the tank to the supply hose as it enters the engine room. From there the fuel line goes through the primary filters and then to the lift pump.

If I try to siphon the fuel from the hose that enters the lift pump I can get air to come through but no fuel - almost like there is a leak somewhere - but I cant find it.

Manually pumping the lift pump didn't manage to pull fuel through either, even with the filters undone to bleed any air. During the removal of the obstruction the entire length of the fuel hose was basically emptied of fuel.

The actual setup is a bit more complicated as there are lines that go to the transfer pump (it is'nt just a pump between a line between the tanks) and obviously the return lines.

Next time I am at the boat I will draw a picture and post it, but interested in any suggestions in the meantime.

Also as the pickup hose enters the tank at the top and goes to the bottom of the tank, then the fuel line goes along the top of the cabin floor boards I am a little surprised there is not a boost pump - but the boat has been operating this was for many years so I guess the system is plumbed correctly.

Anyway thanks for suggestions in advance.

Al

[Attikos]

I once found a hiding leak by using a little electric fuel transfer pump at the pickup to pressurize the system.

[Bruce K]

Maybe accidently left the sealing O ring in when you changed the filter = 2 O rings = air leaks.

[BigAl.NZ]

Thanks for the input. I got a hand pump today and was able to take of the hose that connects to the fuel in side of the lift pump and suck fuel through.

Then, using the manual pump leaver on the lift pump I was not able to get fuel to come out of the filter before fuel goes off to the engine/injectors.

I have also drawn a diagram which is attached.

I think the perhaps secondary to the blockage the lift pump is now also broken or put back on incorrectly?

[Lepke]

The lift pump could have a bad valve, debris stuck in a pump valve or in the wrong position for lever manual operation. The lift pump is operated by a lobe on the cam. Depending on the position of the engine, the lift pump may be at or near the end of the stroke and the manual lever isn't able to move the diaphragm enough to flow fuel. Try turning the engine to a new position.
If you had blockage in one place, there could be other debris. The valves in the lift pump are small disks and a spring. They function as check valves. Even a little debris in the valve holds it open and the pump just sucks in and out without moving fuel.
The easy way to solve this is an 12v pump. Placed in the same line with the lift pump. Either pump can easily pump thru the other. If the hand pump worked then the 12v will quickly get fuel thru the lift pump and to the secondary filter and injector pump. Then you can bleed air easier and get your engine running.

[BigAl.NZ]

Thanks for all the suggestions.

I was wondering if it would work, as a function test of the lift pump, to connect the in hose to a container of diesel, and connect a hose to the outlet, and then see if I can pump any fuel?

Also, do I need to pour fuel into the new fuel filter to fill it?

Cheers

AG

[Wainui]

I had a small electric 12 volt fuel pump inline with the engine lift pump.
It was wired to the ignition switch and was near the tank pickup.
Try blowing back down the line into the tank. You should be able to hear air bubbling up in the tank.
You may have a blocked pickup tube.
By using the electric pump you should be able to find any leaks
Good luck

[BigAl.NZ]

Well a few more hours of investigation and I think this is the problem:

https://www.dieselpartsdirect.co.uk/...tary-valve.htm

We have this setup. I temporarily hooked up a hand pump I am unable to suck any fuel out of the OUT value of the racors. IN side of the racors has fuel.

I even tried taking the filter elements out and still unable to suck fuel through :-(

I have noticed the the handle which selects ALL OFF, FWD ON, AFT ON, ALL ON feels a little unusual. It only "clunks" in about the 1 oclock position and seems to spin with minimal resistance the rest of the way. Are these units serviceable or?

Cheers

AG

[kapnd]

Going back to your first post, the blockage you discovered is most usually a sign of a bigger problem in your fuel tanks.

[BigAl.NZ]

kapnd - yes that is probably part of the issue.

I took the racors off - they have dirt in the bottom of the glass bowls - so they are getting a service.

I also took the valve selector apart, as I said it didnt feel right when moving it. Here is a picture of it. Notice the metal pin isnt seated very well, the stem looks a little flared, and there is like a clear silicone gunk (marked by arrow).

Surely this is not normal?

[BigAl.NZ]

An update. We got the engine going today.

It looks like there was a blocked fuel line, AND secondary to that our dual racors FMX500 filter valve stem snapped in the shut position. So once we fixed that and bled the fuel system she started right away.

Same issue as here: http://www.cruisersforum.com/forums/...nt-205620.html

Thanks