Fuel system problem

[lminor]

Ihave a Mercruiser 4.3l. The engine was just replaced with a new block, carb, & many used parts. The mechanic finds no problems, but when I get it on the water, it won't start until I either prime the fuel pump by filling filter & line with gas or trickle gas into the carb until the fuel line pressures up. It will run fine all weekend, will run fine on monday for the mechanic, but come Friday it won't start unless I do the above. He has replaced the original fuel pump with a square box looking thing which sounds like a machine gun until it pressures up. HELP?

 

[180shabah]

Re: Fuel system problem

Replace/install the antisiphon valve. it is located on the fuel tank, the fuel line running to the engine will be attatched to it.

Fuel Pump - is it a marine pump??

 

[Bondo]

Re: Fuel system problem

Do you have the Merc/ Weber 4bbl. Carb,..??

Cause it sounds like your Carb is leaking off internally........

 

[lminor]

Re: Fuel system problem

4bbl, assume merc or aftermarket, thx.

 

[lminor]

Re: Fuel system problem

Thanks, I have been reading a lot of posts concerning similar probs, but wanted any ideas. It doesn't look like a fuel pump I have seen before, I questioned it as soon as I saw & heard it. Are the antisiphon valves generic or boat, motor specific? Are they readily available? The original pump looked like the ones I have seen on diagrams I have viewed on the web. Also, should the pump be on the tank side or the carb side of the filter?
I won't be returning to the shop that fixed it after the headaches I have had.

 

[180shabah]

Re: Fuel system problem

Antisiphon valve is generic. It should have a 1/4NPT on one side that threads into the fitting on the top of the fuel tank, The other end is barbed, just calmp the fuel hose to it. They are cheap also, +/- $10 at just about any marine store/dealer.

As for filter location, your system should be in this order. Tank, antisiphon, water seperator/filter, pump, carb.

Again, you NEED to verify that your fuel pump is marine rated(it will be stamped ON the pump). An automotive pump is a huge explosion hazzard.