Fuel Pump Bad - Repair or Replace?

[stevedar]

I have a '97 Maxxum which we have been spending a lot of time maintaining/improving over the past few weeks. We added a water/fuel separator and everything seemed fine. Tested the engine out of the water, then put it in the water and ran it at low speed through the no wake zone. Went to open it up a little bit and it died. We bypassed the water/fuel separator and it still would not stay running, but when we took a little bit of the gas from the line and dumped it into the carb, the boat started and ran fine for about 5 seconds. It appears that there is a small amount of fluid in that tube going back up to the carburetor (it's nowhere near full though) so we suspect the diaphram gave out.

The question is should we just try to replace the diaphram or should we replace the whole pump? When we were going through and fixing things we also changed out the fuel filter. I was quite surprised to find that it had what's known as a "stone filter" and we read that it was ok to replace that with a traditional paper based filter.

We're just wondering - with all these changes-in-design would it be better to just replace the entire fuel pump?

TIA - this forum has been tremendously helpful!

 

[Lyle29464]

Re: Fuel Pump Bad - Repair or Replace?

My last diaphram kit was delivered by pony express. I would get a new pump. Be sure to check for gas in your oil.

 

[Todd157k]

Re: Fuel Pump Bad - Repair or Replace?

I would bet you have a blockage somewhere and it's not the fuel pump. You can check by disconnecting the fuel line (dry dock.. NOT ON THE WATER) and putting a hose on it. Run that hose into a gas can. Crank it over a couple times and see if gas spits heavily into the gas can. (clean out that vacuum line too)
When mechanical pumps go bad, they usually pump better at speed than at idle.
Once you've checked the flow, then look for: 1) check the anti-siphon fitting (usually on the gas tank). Looks just like a hose NPT to barb fitting but there's a check valve in there. Pull it off and (after you kinda clean it) suck/blow air through it and see if it's somewhat free. There is a little resistance. 2) take off any other fuel filters besides your new one. There's no need for multiples. 3) check for a filter screen either on the tank fitting or on the carb fitting (not the fuel line, but the fitting that attaches to the line) if you have something like that. 4) If you've found nothing, take the feed line out of your tank and make sure the hose is not blocked.. or even broke.
You may/may not have some of the above pieces. The anti-siphon is USCG reg. so you do have one.. somewhere in that line on the tank.

 

[John_S]

Re: Fuel Pump Bad - Repair or Replace?

It appears that there is a small amount of fluid in that tube going back up to the carburetor (it's nowhere near full though) so we suspect the diaphram gave out.

Yes, pump is bad, replace it.

 

[ziggy]

Re: Fuel Pump Bad - Repair or Replace?

The question is should we just try to replace the diaphram or should we replace the whole pump?

to me it depends on if my trusty service manual says my pump is serviceable (diaphragm replacement) or not. some fuel pumps aren't serviceable, some are. the s/m will let you know which kind you have. imho, the minor changes you talk of are irrelevant.

mine in my old boat was serviceable, so i did R&R the diaphragm on my fuel pump successfully.

 

[John_S]

Re: Fuel Pump Bad - Repair or Replace?

to me it depends on if my trusty service manual says my pump is serviceable (diaphragm replacement) or not. some fuel pumps aren't serviceable, some are. the s/m will let you know which kind you have. imho, the minor changes you talk of are irrelevant.

Outside of possibly a 3.0L, I believe the 4.3, SB, and BB, had non-repairable pumps by that year. Even if the SM shows a procedure for repair, remove the existing and make sure you have the right one. The SM covers multiple years. As another poster pointed out, finding diaphrams in stock can also be an issue.

 

[gdombroski]

Re: Fuel Pump Bad - Repair or Replace?

I would vote on Todd re anti-siphon valve. Check it first look cheaper then fuel pump[.

 

[Fishermark]

Re: Fuel Pump Bad - Repair or Replace?

Whether or not anything else is wrong, you know the pump is bad since there is fuel in the overflow line. Like the others have said, I do not think you realy have the opton of rebuilding your pump as I doubt you will be able to find a kit or diaphram by itself.