fuel pump bad?

[acalabro]

Hello all, I recently purchased a 89-91' force 50hp. Previous owner and I not sure because serial isn't legible.
First time out it ran like a champ, no problems at all, except when we got back to flush it out, I found out fast that it must be flushed in a barrell and the cowling had a crack in it which let saltwater in so I cleaned it the best I could and checked impeller for damage and it was fine.
Second time out the motor idled fine then when giving it a little throttle was fine until I proceeded to give it more throttle up to WOT (idk rpms no tach). The motor would go up in rpms then drop then up then drop until bogging down, immediately I reduced to neutral and it sounded rough throttling down. and I ended up idleing the whole trip 1 mile, great fishing that night though! On the way back if I throttled up the rpms wouldnt even go up at all.
I thought it could be a spark issue, but they both fire fine tested with spark tester.
One thing I noticed now, is that when I pump bulb, there is a dripping of gas comin from bottom of fuel pump diaphragm. Should I inspect the diaphragm first? Just would like to know which direction to go first.
thanks!

 

[Jiggz]

Re: fuel pump bad?

The dripping fuel is a sign of a broken fuel hose or it could be the fuel pump diaphragm is already torn. It's not that hard to take the fuel pump off and inspect it. At the same time, you might want to install an in-line see through fuel fuel filter between the fuel pump and the carb so you can have a visual if you are getting enough fuel from the pump to feed the carb.

 

[acalabro]

Re: fuel pump bad?

Thanks for your reply Jiggz,
If I take it off for inspection, what should I be looking for? Will it be obvious?
this is my fuel pump http://www.**********/parts/search/Merc/Force/1990/H0507F90B/FUEL PUMP/parts.html
And where can I buy an in-line clear fuel filter for that test and what should I look for in that? Is there a size fitting?

 

[Georgesalmon]

Re: fuel pump bad?

Get clear filter from any auto parts store. I wouldn't do it, just two more places to leak. Look for a crack or hole in a diaphram. Rebuild kits are cheap just get one and put it in.

 

[Jiggz]

Re: fuel pump bad?

Thanks for your reply Jiggz,
If I take it off for inspection, what should I be looking for? Will it be obvious?
this is my fuel pump http://www.**********/parts/search/Merc/Force/1990/H0507F90B/FUEL PUMP/parts.html
And where can I buy an in-line clear fuel filter for that test and what should I look for in that? Is there a size fitting?

They actually sell them here at iBoats for cheap. The main purpose of the see-through filter is for troubleshooting rather than filtering. There is already a fine filter at the fuel pump so there is no need for an additional one except in the case of rupture fuel pump diaphragm then it can serve as a back up filter to prevent messing or clogging the carbs. Yes, with a exploded picture diagram of the fuel pump, it is very easy to spot a crack in the rubber diapgragm. If you have doubts, replace it.

 

[acalabro]

Re: fuel pump bad?

There is no hole in the diaphragm, it seems kind of worn. The hoses also look fine. I had to search for the right kit but I found it. It's # GLM 40870 . Amazon has it for $15 . One thing I noticed when I went to remove the pump is that my hose on my fuel tank was loose enough to let air in, the fitting is virtually stripped. I remember that time it idled fine and was smooth until 20% forward throttle. After that it started hesitating rpms went up and down. I would'nt think that the air getting in that far back could cause this problem but maybe I'm wrong. Wouldn't that be caused by something from fuel pump-carb? A gasket in the back of the fuel pump that looks like it is in between the pump and block looks completely flattenedand almost melted to the head. That could let air in too I guess.
After I recieve the kit and install it I will test it and get back.

 

[Frank Acampora]

Re: fuel pump bad?

Air leaking ANYWHERE in the fuel supply will cause loss of power. Fix the air leak at the tank.

If you choose to install a filter--highly recommended-- install it AFTER the fuel pump and before the carb. Fuel pump diaphragms and check valves do fail and pieces will be swept into the carb causing all sorts of headaches. A filter between the pump and carb will avoid this. And as far as leaking----If you use the correct size fuel line and tighten it correctly, the line will fail before the joints ever leak.

 

[acalabro]

Re: fuel pump bad?

Air leaking ANYWHERE in the fuel supply will cause loss of power. Fix the air leak at the tank.

If you choose to install a filter--highly recommended-- install it AFTER the fuel pump and before the carb. Fuel pump diaphragms and check valves do fail and pieces will be swept into the carb causing all sorts of headaches. A filter between the pump and carb will avoid this. And as far as leaking----If you use the correct size fuel line and tighten it correctly, the line will fail before the joints ever leak.

Yes I noticed after I cut the fuel line going into the pump and re tightened, there was no more fuel dripping, it was apparently coming out of the fuel line at the joint when I pumped the primer. I think it's a cheapo line and ball that the previous owner threw on it and maybe it wasn't tightened properly either..

Would a simple in-line fuel filter between the pump and carb restrict fuel flow if my motor didn't come stock with one? (like the ones sold here on iboats.com... http://www.iboats.com/Force-Fuel-Filters/dm/*******.624012788--session_id.487691647--view_id.271712 )

Just ordered my pump kit to replace all the old parts anyways, even if it ends up being a simple fix of eliminating air leak at tank! Test run tomorrow with different tank.

 

[Jiggz]

Re: fuel pump bad?

Yup, that fuel filter will do. I re-did all my fuel lines buying fuel hoses from Ace Hardware and costs me less than $20 for all the hoses. For another $10, I also got stainless hose clamps and everything works perfectly. The fuel filter will not restrict fuel flow between the pump and the carb unless it is blocked with debris which you would readily see (see through) since the filter will be full of fuel while the carb bowls are empty.

 

[acalabro]

Re: fuel pump bad?

She ran like a champ with the different fuel tank. Gues I'll stick with the 6gal until I replace the fitting on the 12gal tank.
Thanks all for helping me get this resolved. Thankfully it was something so simple that an infant baby could have spotted it had they looked where I finally did.