Ok I rebuilt the fuel pumps and having same problem

[dsrtuck]

1964 merc 650 4cyl. Would run good in water but the primer bulb would go soft causing it to sputter and die. So someone reccomended rebuilding pumps, so I did, 99.9 % they are rebuilt correctly. I go to start it today and same problem, runs until the bulb goes soft, if you squeeze it while its bout clunk out it will pick back up, but if you squeeze it too much a little fuel spits out the mouth of carbs and it sputters for a sec. any ideas, I'm desperate?

 

[mmf]

Re: Ok I rebuilt the fuel pumps and having same problem

How about the check valve in your primer bulb? In good shape? Also, check for cracks in tank to engine supply fuel line for sucking air. Surely the tube that runs from the top of your fuel tank to the strainer is not cracked or broken is it? Check for a good vent on your cap too or just remove it while testing.

 

[dsrtuck]

Re: Ok I rebuilt the fuel pumps and having same problem

How about the check valve in your primer bulb? In good shape? Also, check for cracks in tank to engine supply fuel line for sucking air. Surely the tube that runs from the top of your fuel tank to the strainer is not cracked or broken is it? Check for a good vent on your cap too or just remove it while testing.

check valve? is that the white plastic piece on one side of the bulb? what should I check on it? No cracks or air leaks to my knowledge. Im using auxilary tanks so they have vents. and are you talking about the hose inside the tank being cracked? Thanks man..

 

[mmf]

Re: Ok I rebuilt the fuel pumps and having same problem

yea, your primer bulb has a check valve built in to it on one end. You can check it by taking the hose loose from the fitting that hooks to the motor, now take a 2 1/2-3" bolt and insert it in the hose and use a clamp and tighten make sure it does not leak, then pump up the bulb. It should get hard. Walk away from it and check it again in about an hour, it should still be hard, if it is soft then the bulb check valve is leaking back or you have air entering the hose somewhere on the tank side. Those vents screws on the portable tanks sometimes clog with rust or trash, even if it is loosened it still might not be venting, a quick check for that is to just take loose the whole cap.

 

[dsrtuck]

Re: Ok I rebuilt the fuel pumps and having same problem

yea, your primer bulb has a check valve built in to it on one end. You can check it by taking the hose loose from the fitting that hooks to the motor, now take a 2 1/2-3" bolt and insert it in the hose and use a clamp and tighten make sure it does not leak, then pump up the bulb. It should get hard. Walk away from it and check it again in about an hour, it should still be hard, if it is soft then the bulb check valve is leaking back or you have air entering the hose somewhere on the tank side. Those vents screws on the portable tanks sometimes clog with rust or trash, even if it is loosened it still might not be venting, a quick check for that is to just take loose the whole cap.

I bought a new bulb, all of the lines look fine, the vent is clear, pumps have been rebuilt. the bulb stays firm now but the motor is still sputtering bad and then conking out. I guess I could put some fresh gas in but it was doing this before i rebuilt the pumps on fresh gas weeks ago, but now i think it's doing it worse to be honest. Also I had to replace the fuel hose from the bottom pump to the quick disconnect because it cracked, well i couldnt' find the part so I got 1/2 in fuel line to go around the fittings i found at the store and clamped the hose down on the brass fittings on both sides, its air tight so it should be fine. I can hear the fuel rushing in around the bottom pump when I prime it. surely it's not because i used 1/2 in fuel line, because it was starting to do this before i even replaced the line or rebuilt the pumps.

 

[dsrtuck]

Re: Ok I rebuilt the fuel pumps and having same problem

Oh btw, before it started sputtering a bit, i had it on the water and it was cruising fantasticly, a couple times the motor would start to lose power so i would check the bulb and it would be a little soft. friend pumps it while we head back and that keeps it alive. this is what lead to me rebuilding the fuel pumps.

 

[speedrik]

Re: Ok I rebuilt the fuel pumps and having same problem

How old is the fuel line. The gas today eats the inner linings and when at an idle may work fine, but once you give gas and more pressure, it can collapse the inner linings. I have had to change a couple and was told by a mechanic to replace yearly. Not sure about that as no one else in my club has had fuel pick up problems like I have, but just a thought. It did resolve the problem. May also want to try some carb cleaner for a quick low dollar try

 

[j_martin]

Re: Ok I rebuilt the fuel pumps and having same problem

The problem is between the bulb and the tank. Fuel line, filter, pickup tube, screen on the tube, anti-siphon valve on the tank. It could be either plugged or leaking air.

hope it helps
John