I have a 455 in my 1976 jet boat. It appears the mechanical fuel pump may have gone bad. It start ok and ran for bit and then died. I had a similar situation last year where it looked like it was starving for fuel. Looking at the fuel filter on the carb. side of the pump there appears to be no fuel whatsoever in the filter bowl. I checked and I do have spark coming from the coil and at the plugs. So I'm going to start with the fuel pump, being that it is 30 years old. Is there anything to be aware of when replacing the fuel pump to insure it's in correctly?

Thanks, Mark

 

Why not check the pump first? Disconnect the fuel line from the filter on the pump side. If you are able to divert the line enough to place an empty coffee can in a safe spot and put the line into it then do so, if not you may need to use a longer section of fuel line. Stuff a clean rag into the can to secure the fuel line and prevent the fuel from splashing. It is best to have an assistant. Disconnect the coil wire from the coil to the top of the distributor to prevent the engine from starting. Turn over the engine for about ten seconds, while your assistant watches the coffee can. If the coffee can begins to fill with fuel then you have a good fuel pump and the filter is probably clogged. If the coffee can does not begin to fill with fuel then the pump is bad. Of course you could use a pressure gauge if you have one but this is the cheap way. A mechanical pump should provide at least 5-6 pounds of pressure.
If it is the fuel pump then the only thing you need to be careful for is to make sure the acuator arm is resting on the camshaft eccentric when you insert the new pump. The arm rests on the top of the eccentric so inserting the arm into the block opening with the arm a little higher than the pump body is a good idea and then tighten the lower bolt a little bit and as you begin to tighten the upper bolt the arm will begin to move and you will notice some resistance as the pump draws closer to the block surface. I don't remember which hole is englogated but I think it is the top hole of the pump body which makes it possible to do what I described. It would be a good idea to use something like permagasket on the gasket surface and stick the gasket to the pump, not the block, but, whatever works best for you, just be careful not to tear the gasket. Of course, you mount the pump and then attach the fuel lines later. Good luck.
A last minute idea, your carburetor may also have a filter on the inlet. It may be either a paper filter or a bronze filter. this could cause trouble if clogged and I would replace it while doing the other maintenance. Don't loose the tensioning spring when you disconnect the fuel inlet on the carb.... the filter will go flying out and the spring right after it.

 

Thanks. I did change both the filter from the pump and the filter in the carb and nothing. I then did as you suggested by running a hose from the output line of the pump, turned the engine over and there was no fuel from the pump. I'm going to try replacing the pump first to see if that works.

The only other variable I have is that I had a new fuel tank installed in this boat back in Oct. I just recently filled the tank and yesterday was the first real day I started the boat and let it run for more that a min. or so. The boat was running yesterday for about 10 min or so prior to it dying and no fuel being pumped.

After changing the pump if I still don't get any fuel I'm going to think there may be something related to the tank - perhaps the new vent line is clogged or something like that so I'll try running fuel from another fuel source. If that works then I guess it's back to the shop that put the tank in.

Mark

 

Two thoughts...try with the gas cap off (eliminates any venting problem) and try disconnecting the line that goes into the fuel pump to see if it freely runs from the tank. Even though it's a new tank, there could be crud in there clogging the tank sock.

C.J.