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Hi guys. I have a Canadian 52 with the 251 cube engine. My problem is, the fuel pump works great on the bench but doesn't do squat on the truck. When you manually push the rocker arm, there is at least 3/8" loose play befor it comes up hard and pushes the rods. Any thoughts on this? Is this too much play and can it be fixed? I've had it apart and can't see where the play comes from. Or do I have a worn cam
Thanks

Many will tell you your best option is to replace the mechanical pump with an electric pump and block off the hole in the block, prevents the diaphragm from ever failing and flooding the crank case with gasoline.

I have a new electric fuel pump i am going to install. I still want to get the original functioning and have it on standby.

Maybe someone else will respond here, but the only issue I could think of without having the pump in hand would be wear on the end of the lever that contacts the cam. I had a V8 engine that had the same issue, the end was worn so the plunger running off the cam didn't move it enough. We're assuming its still the military pump? I have had another truck running the civy pump and it worked finem just now vaacum for wipers but hat one didn't have wipers anyway.

Anyone else help out here?

I don't think it is wear on the rocker arm pad. I know an old x RCEME mechanic in my area and will take it to him and see what he thinks. He may have another pump handy that I can compare it to.

Hi Point,

How about a few more details......when you say it pumps fuel fine on the bench what is the fuel supply you're using......are you hooking it up to the truck fuel system or a small gas can? I guess I'm asking if you're sure the fuel system in the truck upstream of the pump is free and clear. Did this pump work before you removed it? In regards to free play I just checked the used pump I have and a rebuilt one.....neither has any play in the arm......so it sounds like you have some play in yours, but I don't know what the full travel distance (stroke) of the arm is to know if this is relevant. I guess you could measure the cam lobe lift with a ruler or stick as the engine rotates, but I can't do that currently.

bob

When I clamp the pump on the bench and manually stroke the push rod it's full length, you can feel it pumping. It is putting out at least 4 lb if you hold your finger over the outflow valve. On the truck, there is not a hint of suction. So I assume there is too much play in the stroke.

my grandpa and uncle run 2cycle oil in their gas and they claim that it preserves the fuel pump diaphragms
they are still running their original fuel pumps on their m38a1 s,
they have never even had them apart and they have never had a problem either

I occasionally run 2stroke oil in my M37. Mostly because it is the most primitive engine I have, with no MAS, computers, injectors or catalytic converters. My M37 eats my stale dirt bike gas and doesn't miss a beat. I have an electric pump though, so no benefits there

My mechanical pump failed this afternoon on the way home from the show. When the rain stops later in the week, I'll pull it and see what the cause was. It was running fine and then died from running out of fuel. testing showed no discharge at all. DX'd the line at the tank, (10 gals in tank) blew the line out. Was clear. Pressuring the tank and fuel ran out at the line to the pump. DX'ing line from discharge side and no fuel at all. Got a ride home and grabbed an outboard motor tank and strapped it to the hood to get to the garage.

Almost makes you want to carry a spare electric pump in the tool kit.

Actually, I made a wire harness and put a pump and mount hardware in the toolbag this afternoon.

Took my pump off last night. (Carter 2090 civilian pump)The issue was simple, just couldn't see it when the pump was mounted. The pivot pin had worked loose from the weak bit of staking they did and was about to fall off the pump.
Therefore, the lever wasn't doing anything but flopping about. Pushed the pin back in and it is working fine. Will make a small c shaped keeper and JB weld it in position. I will also at this time get the rebuild kit for the original AC pump and go back to vacuum wipers.