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fuel pump wont pump


scott83
03-12-2008, 02:52 PM
i have an old 76 chevy p/u with a 350. thought the fuel pump was bad. Put in a new pump and it wont pump. all the lines are good and i made sure that the push rod was in the correct position. Could the cam be worn down and not pushing the rod down for it to pump? I even put some gas in a pop bottle and put a rubber line down in it and it wouldnt even pump the gas out of it. The old pump was still good.

J-Ri
03-12-2008, 03:50 PM
It could be worn down, but I doubt it. How many miles are on it? I would pull the cover off the block and take a look just to be sure. My '86 has 169,5xxx miles on it and when I replaced the pump a few thousand miles ago the cam still looked good.

If it is worn down, I would just install a blockoff plate (available from Sumitt and probably other places) and use an inline electric pump.

scott83
03-12-2008, 04:08 PM
well its actually a mini pumper fire truck. it has 129xxx on it but several hours on top of that. when we took the old fuel pump out the push rod was slightly bent. we put a new push rod in it. yeah i have a electric line pump, we are gonna try to put that on.

rockwood84
03-12-2008, 05:13 PM
does the new pump croak when you move the pump lever? if not the the new pump is bad.

scott83
03-12-2008, 08:37 PM
i didnt check the new one to see if it did

jasom
03-12-2008, 08:51 PM
i have an old 76 chevy p/u with a 350. thought the fuel pump was bad. Put in a new pump and it wont pump. all the lines are good and i made sure that the push rod was in the correct position. Could the cam be worn down and not pushing the rod down for it to pump? I even put some gas in a pop bottle and put a rubber line down in it and it wouldnt even pump the gas out of it. The old pump was still good.

Was it atleast running before you changed the fuel pump? If not and the fuel pump is fine I would be pulling the distibuter cap and see if the rotor is turning.

scott83
03-12-2008, 09:53 PM
well no cause it wouldnt pump gas but if you put a little bit of gas in the carb it will run and run fine til you burn up the gas

jonnik
03-13-2008, 04:02 AM
Check to see that the push rod is the correct length.

j cAT
03-13-2008, 04:51 PM
i have an old 76 chevy p/u with a 350. thought the fuel pump was bad. Put in a new pump and it wont pump. all the lines are good and i made sure that the push rod was in the correct position. Could the cam be worn down and not pushing the rod down for it to pump? I even put some gas in a pop bottle and put a rubber line down in it and it wouldnt even pump the gas out of it. The old pump was still good.

if the fuel pump arm was bent then you have a problem in the engine normally the spring breaks or diaphram ruptures..

scott83
03-14-2008, 05:01 PM
it wasnt the arm that was bent. it was the push rod that operates the fuel pump.

scott83
03-14-2008, 05:02 PM
also the push rod was the same length and diameter

j cAT
03-14-2008, 05:13 PM
also the push rod was the same length and diameter

i would remove pump and manually see if the pump will pump... but i would see if gas line is not rusted out....the line that feeds pump... if this line has a hole in it it will only suck air!!!!
i would try to pull gas from tank threw the line that feeds pump use a siphon etc... see if you can pull out gas from tank......

777stickman
03-14-2008, 08:51 PM
So, you say the fuel lines are good. You say the pump push rod was bent. You say the old fuel pump was good??

So what would cause the push rod to bend?? The only thing I can come up with is a frozen fuel pump, but you say it was ok.

Here's what I would do to check check the cam lobe for the pump.

1. Disable the engine ignition system.
2. Pull the pump mounting bracket off the block.
3. Here's the tricky part. Put the push rod in and have someone crank the motor while you feel the push rod end for movement. I don't know the exact lobe deflection but I would think somewhere around 1/2 inch of rod movement would be sufficient.
4. Good luck and be careful.

j cAT
03-15-2008, 11:57 AM
So, you say the fuel lines are good. You say the pump push rod was bent. You say the old fuel pump was good??

3. Here's the tricky part. Put the push rod in and have someone crank the motor while you feel the push rod end for movement. I don't know the exact lobe deflection but I would think somewhere around 1/2 inch of rod movement would be sufficient.
4. Good luck and be careful.

i believe that the 1/2in movement is correct on the arm... if the pump is mounted with the bolts loose he should see the pump movement upon cranking engine.....

scott83
03-17-2008, 11:30 PM
ok ill remove the pump and see if the push rod has movement

j cAT
03-18-2008, 07:07 PM
ok ill remove the pump and see if the push rod has movement

make sure you can suck gas out of tank at fuel pump supply line.....

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