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#1
10-02-2019, 04:25 PM
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fuel pump '70 GTO 400
Hi guys, I'm not an engine builder but can do minor engine work. My '70 gto 400 lost the fuel pump, I replaced it with another mechanical pump which was a disaster! No fuel and pulling the pump it had the pump all the way up and would not release. Don't have a clue to what the problem is! Replaced with an electric pump but would prefer to use the mechanical style. Anyone got an idea what ids wrong? I would appreciate the help. jciwolf
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#2
10-02-2019, 05:04 PM
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I may not understand your problem. But the fuel pump lever movement is caused by the fuel pump eccentric, which is bolted to the end of the camshaft. I suppose you could compare it to the lobe of a camshaft. As the cam turns, the eccentric will push the fuel pump lever down, then let it come back up, and continue this up & down motion as long as the cam is turning. If the engine stops, with the lever in the down position, you'll have to rotate the engine/cam, in order for the lever to come back up.
So, it's best to have the eccentric in the position where it is not exerting down force on the lever, when pulling or installing a pump. The lever returns to the up position because it has a spring in the pump which performs this function. So, when the eccentric is exerting down pressure on the lever, this spring pressure will make the pump harder to install. Last edited by ponyakr; 10-02-2019 at 05:19 PM. |
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#3
10-02-2019, 05:55 PM
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Yep, ponyakr has it right as always
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#4
10-03-2019, 05:30 PM
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Hi Ponyakr, My explanation may be a little rough. I was not aware of this setup so the pump was put in and bolted up. My BAD!! When I noticed no fuel and pulled the pump out the lever was all the way up and would not come back down no matter what I did. Tried to force it back down with vice grips, and finally resorted to hammer with no luck! Still have electric but I probably need to buy new mechanical, would this happen to fuel pump if put in incorrectly? Thank jciwolf
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#5
10-04-2019, 10:47 AM
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You probably installed the pump with the lever above the cam eccentric. So it wasnt doing anything. Not sure if its even possible to install it over the eccentric? The lever is always in the up position. It gets pressed down by the eccentric. Ponyakr has it right, there is a spring inside the pump that keeps the lever up. Its pretty stiff, but it can be pushed down by hand.
If yours has the lever up and wont go down, maybe it got pushed up or bent up by the eccentric. Picture's worth a thousand words. Its not a Pontiac, but eccentric-driven mechanical fuel pumps all work the same. 
Last edited by MescaBug; 10-04-2019 at 10:52 AM. |
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