Mercruiser Electric Fuel Pump Leaking

[eldplanko]

I'm hoping someone can provide some advice on this. I have a 1998-2001 Mercruiser 4.3L 2BBL (Service Manual 25 engine) that is leaking gas from the electric fuel pump. I haven't been able to determine where it's leaking from. While on the boat, I've gone through and tightened all the fittings (inlet and outlet flare fittings at the fuel pump; and the o-ring sealed "adapter" fittings that convert from the flared fitting to the fuel pump fittings (3/8-24 and 5/8-18), it still is leaking. I pulled the pump off the engine, and inspected the fittings, no obvious cross threads, o-rings looked fine.

My question, does anyone know if the pump could be leaking internally (i.e. between the brass part and the aluminum metal housing)?

 

[eldplanko]

Thought I'd add a bit more context after some use of the search function here...

This is marine pump (assume oem, it has the mercury part number on it).

 

[alldodge]

I'm hoping someone can provide some advice on this. I have a 1998-2001 Mercruiser 4.3L 2BBL (Service Manual 25 engine) that is leaking gas from the electric fuel pump. I haven't been able to determine where it's leaking from. While on the boat, I've gone through and tightened all the fittings (inlet and outlet flare fittings at the fuel pump; and the o-ring sealed "adapter" fittings that convert from the flared fitting to the fuel pump fittings (3/8-24 and 5/8-18), it still is leaking. I pulled the pump off the engine, and inspected the fittings, no obvious cross threads, o-rings looked fine.

My question, does anyone know if the pump could be leaking internally (i.e. between the brass part and the aluminum metal housing)?

If this is a new pump it needs to be returned for another. Now if this is an old one, then the pump needs to be replaced. Marine pumps have an bleed vent which should be sending the fuel that leaks to the carb. If it is leaking at the fittings then again it needs to be replaced

 

[Bondo]

I'm hoping someone can provide some advice on this. I have a 1998-2001 Mercruiser 4.3L 2BBL (Service Manual 25 engine) that is leaking gas from the electric fuel pump. I haven't been able to determine where it's leaking from. While on the boat, I've gone through and tightened all the fittings (inlet and outlet flare fittings at the fuel pump; and the o-ring sealed "adapter" fittings that convert from the flared fitting to the fuel pump fittings (3/8-24 and 5/8-18), it still is leaking. I pulled the pump off the engine, and inspected the fittings, no obvious cross threads, o-rings looked fine.

My question, does anyone know if the pump could be leaking internally (i.e. between the brass part and the aluminum metal housing)?

Ayuh,.... I've run across those pumps, that when the hi-lighted fittin's are over-tightened, the aluminum housin' gets a linier crack in it,....

Even though I myself have welded one up before, for all intents, 'n purposes, it's junk,...

 

[eldplanko]

Ayuh,.... I've run across those pumps, that when the hi-lighted fittin's are over-tightened, the aluminum housin' gets a linier crack in it,....

Even though I myself have welded one up before, for all intents, 'n purposes, it's junk,...

Thanks for the advice; I'm doing some inspecting of the parts (they are old not new) and don't see anything out of the ordinary with regard to cracks. For the adapter fittings w/ the o-ring seals I did the old soapy water and blow in in trick: no bubbles with mouth pressure, it's probably not enough to really test it though. For these fittings, I could easily see how one could overtighten and crack it... they can be turned all they way down until metal (brass adapter) hits metal (aluminum or brass housing). On mine, I could do this finger tight.

 

[Bondo]

Thanks for the advice; I'm doing some inspecting of the parts (they are old not new) and don't see anything out of the ordinary with regard to cracks. For the adapter fittings w/ the o-ring seals I did the old soapy water and blow in in trick: no bubbles with mouth pressure, it's probably not enough to really test it though. For these fittings, I could easily see how one could overtighten and crack it... they can be turned all they way down until metal (brass adapter) hits metal (aluminum or brass housing). On mine, I could do this finger tight.

Ayuh,.... For a Carb, 4 to 6 psi is all there is,....

Wish I could help, but I've only seen the one leaker,.... mine,....

Maybe try hookin' it up on the bench, 'n run it deadhead to see the leak,..??
that'd be max pressure, just like against the needle valve in the carb bowl,...

Maybe abit of perfect seal on the threads under the o-rings,..??

 

[eldplanko]

Ayuh,.... For a Carb, 4 to 6 psi is all there is,....

Wish I could help, but I've only seen the one leaker,.... mine,....

Maybe try hookin' it up on the bench, 'n run it deadhead to see the leak,..??
that'd be max pressure, just like against the needle valve in the carb bowl,...

Maybe abit of perfect seal on the threads under the o-rings,..??

I just put everything back into the boat, that bugger is a pain to get to with the freshwater cooling in the way. Figured I'd invest my effort with a good flashlight and inspection mirror to try to figure where it's dripping from. The service manual did say to put liquid Teflon (no tape!) on the threaded (ie not flare) fittings. I didn't yet as it wasn't there when I took it off. If it's still leaking, will probably try that next, I don't mind off and on a few times to properly diagnose.

 

[Bondo]

I just put everything back into the boat, that bugger is a pain to get to with the freshwater cooling in the way. Figured I'd invest my effort with a good flashlight and inspection mirror to try to figure where it's dripping from. The service manual did say to put liquid Teflon (no tape!) on the threaded (ie not flare) fittings. I didn't yet as it wasn't there when I took it off. If it's still leaking, will probably try that next, I don't mind off and on a few times to properly diagnose.

Ayuh,.... Does yer phone take pictures,..?? it'll fit where yer head won't,....

 

[eldplanko]

Just wanted to close this one out... I finally got around to finishing up the job. As of the last update, I had reinstalled the pump fittings etc... Today I finally fired up the engine, stuck my head dangerously close to the serp belt, and noticed it was still leaking.

Shut it down, and pulled the pump again. I set it up to bench test, figured I'd at least do this before I threw $250 at a new pump. Basically I attached 3/8 barb/flare fittings to the inlet and outlet of the adapter fittings on the pump. Pulled the weatherpak connector apart so that I could hook jumper wires onto the pump terminals. Hooked up the wires to a battery and some clear tubing and let her rip on a can of gas. All was fine, no leaks, even after pinching off the outlet hose to simulate the back pressure of a full carb bowl.

On reinstalling, I added the teflon thread seal paste to the connectors (adapters to pump, not the flare fittings). Also, I noticed that these connections barely took any torque before they bottomed out. My thinking, was that previously, it was really easy for these to loosen up as I was putting the pump back on the engine. On reinstalling this time, I snapped the pump into the bracket. Tightened the two adapter fittings against each other. Then connected the outlet flare fitting and loosely tightened. Connected the inlet flare fitting and loosely tightened. Retightened the inlet and outlet adapter fittings, as they worked themselves slightly loose. Then did the final tightening on the flare fittings. Fired her up... no leaks.

Thanks everyone for your helpful suggestions on this.

 

[alldodge]

Appreciate it much coming back to close the thread, many don't do it and keeps us hanging.

Sure hope the leak never starts back up but I am concerned, from your mention of "barely took any torque before they bottomed out". All that said sure hope you have a problem free of many seasons of fun. Happy boating