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It’s been a long time since I changed my pump but tightening those stud nuts to final torque should give you resistance as it actually is pulling the arm taught against the cam. If it just mounts flush against the block without a little effort it’s the wrong pump....IMHO
JB
And where the cam lobe is at the time of pump install, determines just how much resistance you feel fitting the pump into position. Try my witness mark suggestion.
Well I took off the pump to carb line and pumped it manually, sprayed fuel all over the garage so the pump is solid. Lined it up and bolted it back on, using a breaker bar I turned the motor over a few times but no fuel came out. I’m going to 3d print a few shims and attach them to the arm to see if that helps.
It’s been a long time since I changed my pump but tightening those stud nuts to final torque should give you resistance as it actually is pulling the arm taught against the cam. If it just mounts flush against the block without a little effort it’s the wrong pump....IMHO
JB
And if you can work the pump by hand, that is unlike any mech fuel pump I've installed. Very hard to operate by hand, even when the body is held in a vise.
Going to ask a very basic question here that will elaborate on what Ross said above. Does that pump have a very heavy spring that returns the arm to the 'home' position? Spring should be visible. And yes, the pump should be hard to operate by hand and you should feel resistance in positioning it to the engine.
And if you can work the pump by hand, that is unlike any mech fuel pump I've installed. Very hard to operate by hand, even when the body is held in a vise.
Seems to me that the travel is very short when operated by hand. Maybe .25" of travel at the end, almost a click that ejects fuel out the end. With a two hand grip and both thumbs pressing on the arm I can fairly easily depress the arm.
Originally Posted by raytasch
Going to ask a very basic question here that will elaborate on what Ross said above. Does that pump have a very heavy spring that returns the arm to the 'home' position? Spring should be visible. And yes, the pump should be hard to operate by hand and you should feel resistance in positioning it to the engine.
It does, yes. I'll post some more pictures shortly. I wouldn't say the pump is EASY to operate but it's definitely not that difficult. I feel no real resistance when mounting it.
The eccentric on the flat V8 cams only provides 0.200" of movement. I'd expect the 6's to be similar.
That seems much closer to what I'm seeing. I felt the eccentric and couldn't really tell it wasn't round. I'm thinking either the arm is too short/wrong shape or the gasket is too thick? Something is preventing that arm from getting its full stroke. Stand by for measurements.
There was roughly 0.75" between the mounting face and then outside of the arm when fully depressed. As the picture shows I was able to full depress the arm with one thumb but decent effort.
I think you may just be taking up the slack in the linkages. I'd estimate it takes 30 - 40 pounds force to cycle the diaphragm on most pumps. If that's all it's got, it's DOA.
I think you may just be taking up the slack in the linkages. I'd estimate it takes 30 - 40 pounds force to cycle the diaphragm on most pumps. If that's all it's got, it's DOA.
Really? When I move the arm that last 1/4" it sprays fuel like 4'.
The way the pump works, when the arm is squeezed like in your pic, the pump is sucking in fuel. When released, the springs in the pump force fuel out to the carb. So at the least, it sounds like your pump's check valves are not closing.
Ray had a good idea! I checked the pump I will use on my engine and confirmed it is identical to the one on the engine before the rebuild. After the arm reaches resistance it moves a good 5/8" by hand, very tight. Pictures attached.
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