1981 M-Block Fuel pump issues
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From: Marysville, WA
1981 M-Block Fuel pump issues
Alrighty, From what you guys have told me before the motor in the truck is an m block if i recall correctly, I sent the truck to get some work done at a friends shop, they got all there work done but just today the fuel pump gave up and from what they've told me is its not the pump it self but the shalf/cam whatever you call it is simply not spinning which drives the pump. Any ideas of the cause? and should i just pay them for work done and fix this myself or just foot the bill.
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Look it up on the web or get yourself a book that has a exploded view of the pump so you can see how it works.
Basically it's a metal cup bolted onto the front of the cam gear. The key is the cup is not bolted in the center, it's bolted off-center so it wobbles as the cam turns. If you go to Autozone's site and look at the picture of a fuel pump for your truck, you will see it has a long arm. This arm rides against the cup, and as the cup wobbles, it pushes up and down on the pump arm.
You need to ask how the mechanics know there is something wrong up inside the cup area. Was the pump arm tore up? Or if you just want to take a look, you will have to tear down the front of the engine to get to it. This might not be a bad idea if the engine has a lot of miles on it, since the factory most of the time used a plastic coated top cam gear, and the plastic likes to chip off after it gets old, and the timing chain gets loose also.
One thing you need to really look out for if you get in there, is the cup is two pieces. The fuel pump arm does not rub directly on the wobbling cup. The cup has a thin hardened piece around the outside that slips like a bearing. This thin piece gets a oil film on it's id, and it is what slips on the cup, and it stays stationary on the pump arm so the arm does not wear out.
Basically it's a metal cup bolted onto the front of the cam gear. The key is the cup is not bolted in the center, it's bolted off-center so it wobbles as the cam turns. If you go to Autozone's site and look at the picture of a fuel pump for your truck, you will see it has a long arm. This arm rides against the cup, and as the cup wobbles, it pushes up and down on the pump arm.
You need to ask how the mechanics know there is something wrong up inside the cup area. Was the pump arm tore up? Or if you just want to take a look, you will have to tear down the front of the engine to get to it. This might not be a bad idea if the engine has a lot of miles on it, since the factory most of the time used a plastic coated top cam gear, and the plastic likes to chip off after it gets old, and the timing chain gets loose also.
One thing you need to really look out for if you get in there, is the cup is two pieces. The fuel pump arm does not rub directly on the wobbling cup. The cup has a thin hardened piece around the outside that slips like a bearing. This thin piece gets a oil film on it's id, and it is what slips on the cup, and it stays stationary on the pump arm so the arm does not wear out.
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From: Northeast, OK
X2 on what Dave said. Plus, this isn't peculiar to the M-block. It is the way the Ford engines, and many others, worked.
If your friend is correct and the cup isn't spinning then there is nothing else to do but pull the water pump and front cover off of the engine. That exposes the timing chain and gears as well as the fuel pump eccentric. It will be very obvious what the problem is at that point in time.
If your friend is correct and the cup isn't spinning then there is nothing else to do but pull the water pump and front cover off of the engine. That exposes the timing chain and gears as well as the fuel pump eccentric. It will be very obvious what the problem is at that point in time.
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From: Denver Metro Area, CO
Does this help?
Yes, Demeron, I agree, that thing looks GOOD!!!!
Well, to begin with, I agree with Gary in that you're probably OK with the pump installation if you got everything lined up and installed smoothly. There is an eccentric mounted on the cam that spins around and pushes the arm down:
In real life:
Anyhow, two things in your video jumped out at me...
1) You showed us your in-tank pump & sending unit.... an aside here, but can you PLEASE find any numbers or insignias on it and post them here? Pretty please?
OK, back to my point... you explained about how you routed your hoses. My point is, if that was a factory installation, it would have been steel tubing with short pieces of rubber hoses at the ends to connect to the mating devices.
2) I'm not entirely positive, maybe it was just my perception, but it looked to me like you had that plastic filter installed backwards? Isn't there an arrow on them that indicates FLOW THISAWAY -> ?
Once again, that things looks good! And, thank you for *talking* in your video! We see too many out here that are just of an engine, or an exhaust, or some such - without any sort of editorial comment. Speech helps greatly IMHO.
Well, to begin with, I agree with Gary in that you're probably OK with the pump installation if you got everything lined up and installed smoothly. There is an eccentric mounted on the cam that spins around and pushes the arm down:
In real life:
Anyhow, two things in your video jumped out at me...
1) You showed us your in-tank pump & sending unit.... an aside here, but can you PLEASE find any numbers or insignias on it and post them here? Pretty please?
OK, back to my point... you explained about how you routed your hoses. My point is, if that was a factory installation, it would have been steel tubing with short pieces of rubber hoses at the ends to connect to the mating devices.
2) I'm not entirely positive, maybe it was just my perception, but it looked to me like you had that plastic filter installed backwards? Isn't there an arrow on them that indicates FLOW THISAWAY -> ?
Once again, that things looks good! And, thank you for *talking* in your video! We see too many out here that are just of an engine, or an exhaust, or some such - without any sort of editorial comment. Speech helps greatly IMHO.
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