[riesman20]

I have a 1984 GMC Truck with a 305. I am not getting fuel at the carb. I took off the fuel pump and compressed it and it sucks good. Is my cam NFG and if it is how could I tell. It ran great before this problem. ps I ran out of gas after I rebuilt the carb and it has not pumped since.?????????

[johnsongrass1]

Have you checked the pump push rod?

[Jmark]

Do you have dual tanks? Is it possibly switched to one that is empty? The switching valve could be bad too, just sucking air.

Try putting some low pressure in the tank and remove the rubber hose from the pump and see if any gas comes out. Could be a bad hose collapsed or sucking air too.

Is the pushrod stuck in the block? Although rare, it does happen.

[riesman20]

I had to push the pushrod back up into the block, when I re'installed the pump, and I thought it maybe went to easily, But their was a definitive end when I pushed it. The hoses seem fine but what do I know, I have a single tank. I loaded the gas line with gas and hooked up the influent line and pushed it once and she shot out. How hard should the fuel pump be too compress? as I had to give it a good squeeze. How exactly does the fuel pump work? I always thought the cam turned and each revolution it compressed the fuel pump?

[Jmark]

the pump push rod is about 4" long and "floats" inside the block between the cam and the pump. The rod is pushed by a seperate cam lobe once every other revolution of the engine.

The spring in the pump is STRONG, as it has to keep the heavy steel rod against the cam lobe.

When the pump lever is pushed, it pumps gas TO the carb, when its released, it sucks fuel from the tank. There are 2 check valves inside the pump that keep the gas going the right direction. If one valve is bad, it won't work. You can remove the metal line at the pump and have someone "bump" the starter some and see if it pumps any gas. If it does, ck the filter in the carb to make sure its clear.

Mark

[riesman20]

I'm sure the fuel pump is fine. I had the line off right at the fuel pump and nothing comes outr when I turn the engine over.

[Jmark]

Well, at this point, i'd pull the pump off and take off the plate on the pump mounting pad. Remove the pushrod and look at the other end. If its all buggered up, i'd say the cam lobe is gone. You can also push it up into the block while the plate is off and hold it agains the cam and have some one crank the engine. The rod should push about 3/8 of an inch with you keeping pressure against it. If it doesn't move, its cam time.

Mark

[slvrbllt]

You said you run it out of gas ? If so you might have a high spot in the fuel line and sometimes just cranking the motor does not run the pump fast enough to overcome the air lock. You either need to blow air into the tank till the fuel comes out in a good steady stream or dribble gas into the carb to keep it runnung till it picks it up.

[troy-curt]

Sounds like you missed the push rod with the pump arm, they can be hard to get right.

Troy

__________________
If you don't make mistakes. your not doing anything.

69 ss rs full custom camaro 98 ISCA grandchampion
69 ss rs bb camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 ss chevelle bb conv.fresh frame off
26 T sedan street rod

[riesman20]

I took off the fuel pump and held the pushrod up as far as I could, I estimate that it was about 3"4 -1" from bottoming out(when I let go it bottoms out). I turned the engine over and I felt absolutely nothing on the arm. How long do you have two crank for two revs of the camshaft? I held for 5 sec. So where does this leave me? Engine tear down? What are the bolts on the directly in front of the pushrod?

[troy-curt]

If you are holding the rod against the cam and turn the engine over, you should feel the rod move. If it don't move then the cam is shot. But just running out of gas would not do that.

Troy

__________________
If you don't make mistakes. your not doing anything.

69 ss rs full custom camaro 98 ISCA grandchampion
69 ss rs bb camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 ss chevelle bb conv.fresh frame off
26 T sedan street rod

[Jmark]

You need to push the rod up inside the block hard, then crank it over. It runs off the camshaft. You can remove the 2, 7/16" head bolts and remove the plate that is inbetween the pump and block. At that point, the rod will slide all the way out and you can look at the other end of it.

If the cam is infact bad, you can get a blockoff plate for the fuel pump and cover it up, and install an electric pump on the fender well to get you by.

Mark

[troy-curt]

Where did all the ground up metal go?

Troy

__________________
If you don't make mistakes. your not doing anything.

69 ss rs full custom camaro 98 ISCA grandchampion
69 ss rs bb camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 ss chevelle bb conv.fresh frame off
26 T sedan street rod

[riesman20]

Will the remnants of the lobe be carried through into the oil filter or do I have to worry about a bigger problem??

Thanks for the help so far guys!!!!!!!!!!!

[troy-curt]

If you have determined that is what is wrong, then you need to change the oil and filter. The metal off of the cam lobe will go through the pump and the crank bearings. causing failure.

Troy__________________
If you don't make mistakes. your not doing anything.

69 ss rs full custom camaro 98 ISCA grandchampion
69 ss rs bb camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 ss chevelle bb conv.fresh frame off
26 T sedan street rod