Ford Lehman 120 fuel pump

[Marin]

For those of you with boats with the Ford Lehman 120 diesel, we've been having an interesting discussion on the Grand Banks forum about removing and replacing the fuel lift pump.* As I discovered last week when we thought we might have a failed pump on one engine (we didn't) even if you have a full set of conventional (Craftsman, etc.) wrenches on board you will probably not be able to remove the pump if you ever have to.* The pump mounts on a pair of studs threaded into the engine block and is held in place by small nuts on these studs.

The issue is the clearance, or lack of it, needed to remove the rear nut.* A typical, off-the-shelf box or open-end wrench will be too thick and have jaws too wide to do it.* So you need to either thin down and narrow a cheap off-the-shelf wrench or find a thin, narrow walled wrench (like a tappet wrench) that will fit onto the rear nut in such a way that will still allow you to swing the wrench.* The forward nut is no problem because there is sufficient clearance ahead of it to use an open-end wrench.* You cannot use a socket because the pump body overhangs the mounting nuts, and there is apparently not enough room behind the rear mounting nut and the big flange on the rear of the engine block casting to fit a crow's foot.

The fuel hose connection on the bottom of the pump can also be a problem and should have a "reworked" wrench to properly tighten the fitting.

So for those of you with FL120-powered boats, don't assume that because you have full sets of wrenches on board that you'll be able to remove and replace that pump if you need to on a cruise.* Make sure you have a wrench that will actually fit before you head out.

 

[billsteele]

Interesting - I took mine off today with a cresent wrench!!!

 

[Daddyo]

Interesting - I took mine off today with a cresent wrench!!!

Wow big difference. Please explain?

 

[RT Firefly]

Greetings,
Mr. Marin. Point well taken regarding specialty tools but to the best of my memory, I've not needed a "special" wrench to remove my fuel pump. It was a bit of a wiggle and a squirm but I used the regular stuff from the tool kit. What I DID find was that when I dropped a nut into the drip pan (5/16-24 ??) I didn't have a spare on board to replace. Got 6 now.
The ONE I do remember needing a "special" for is removing the expansion tank to change the thermostat. I think I had to cut down a 9/16" ?? shorter.

 

[bobofthenorth]

Marin you can get that nut with a really good set of combination wrenches but its not pretty. The ideal wrench for the job is an offset wrench. I know this because I borrowed one from my slipmate and have been searching for a set of offset wrenches ever since. I finally found a tool store that knew what I was talking about and they have ordered a set for me which should be waiting when I get home from the boat show. On my boat you would not get that nut with any form of a crescent wrench. Offset wrenches are sometimes called ignition wrenches in the smaller sizes but finding a set that goes above 3/8" has proved to be a challenge. YMMV

 

[Capn Chuck]

Bob, I used offset wrenches and I have used ignition wrenches, but they were very different. Chuck

 

[bobofthenorth]

That may be Chuck but what I call an offset wrench and what I call an ignition wrench looks exactly the same except that the offset wrench comes in larger sizes. Here's an image which I shameless stole off the interweb.

 

[psneeld]

offset wrenches are bent in the handle (offset) so you can clear obstacles/other bolts/nuts...at least that's my experience... and what I see when I look up "offset wrench"..

 

[Capn Chuck]

That's an ignition wrench. An offset is a box wrench bent at both ends. I just didn't want someone to go out and buy the wrong tool if that is the one that works for the fuel pump. Chuck

 

[Marin]

The recommendation from our diesel shop, which has a lot of experience dealing with FL120s, is that the best tools for removing/replacing the aft mounting bolt for the stock fuel lift pump are a tappet wrench or a conventional wrench which has been ground down thin enough to fit, which is what a machinist friend made for us.

 

[Capn Chuck]

tappet wrench or a conventional wrench which has been ground down thin enough to fit, which is what a machinist friend made for us.

How about photo, there are lots of ways this could be interpreted. Chuck

 

[bobofthenorth]

The offset wrench I posted is available to 1.25" (maybe larger). The catalog that we ordered my set out of identified it as an offset open end wrench. What was previously posted is an offset BOX wrench. The 1/2" open end version is all you need to remove the lift pump on a 120 Lehman. I've never worked on an ignition that required a wrench larger than 9/16". BICBW

As I posted previously, you can replace this pump with a couple of good sets of combination wrenches. You may need to switch back & forth between the 1/2" combination wrench from two different sets but it can be done.