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Old 03-03-2013, 06:12 PM
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SBC mechanical fuel pumps keep going out

I keep having fuel pump issus on my 350 SBC (stock as far as I know since I dont know what cam it has). I have replaced 3 pumps over the past 300 miles or so on the engine. I am hesitant to buy another but dont know if this is common or not. I have ran Napa brand pumps for the most part. Im sure its the pump since I have tested with the inlet line in a gas can to test suction side, while observing the disconnected outline line. I let it crank for 30 seconds each time I test with no gas. So I am certain this is a bad pump. The pump rod is not getting bound up or stuck on anything that I can tell. The only thing that I think may be causing these pumps to fail early is possibly running a filter on the suction side? Thanks for any suggestions or things I might check. I also would prefer not to go electric but might have to if I cant find a mechnical solution.

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Old 03-03-2013, 06:27 PM
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Suction side okay.

Are you pumping arm by hand and its not pullin fuel through? What you describe by cranking could be the pushrod is not make contact. I place a 6" pice of pipe on the arm and prime it in a vice with a fuel can.

Mechanical pumps for me last a very long time.
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Old 03-03-2013, 06:27 PM
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How much travel does the pump rod have? Lately I have seen a few flat tappet cams with the fuel pump lobe worn badly. Anoher victim of the junk oils sold now..
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Old 03-03-2013, 06:38 PM
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I have not tried priming in a vice but that would have been useful last time I had it off the block. I will test it with my other pump though to see what it does. Thanks!
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Old 03-03-2013, 06:40 PM
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I have heard of the cam lobs being flattened, but I think rod is ok on cam since it seems to run fine and then go out after awhile. I would think if it was a flattend lob, it would never run at all. Thanks
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Old 03-03-2013, 06:46 PM
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Did you place the pump cam lobe on base circle? That way it will be easy to hold that rod up and more room to slide the pump in.

If it all of sudden quit , im guessing the pump cam lobe has enough meat to run the engine.
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Old 03-03-2013, 06:51 PM
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Well, I use the "grease on the rod method" each time to hold the rod in place while I put the pump in. Do you mean rotating the crankshaft to a certain point (Base circle??) to give the max. room to put the rod in?

Thanks
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Old 03-03-2013, 06:54 PM
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Yes, it will be harder to install if the lobe is trying to press down on the pump.

The pushrod resting on the finger tip is better. Have someone bump the engine, with your finger on it. Find the highest point.
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Old 03-03-2013, 07:03 PM
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All good advice here. Also as suggested the possibility the sock filter in the gas tank could be plugged and not allowing fuel to get sucked through by the pump.
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Old 03-03-2013, 08:28 PM
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Quote:
Originally Posted by LATECH View Post
All good advice here. Also as suggested the possibility the sock filter in the gas tank could be plugged and not allowing fuel to get sucked through by the pump.
I bought an old Suburban that would run fine untill the ambient air temp would reach 82 degrees. Which in Michigan isn't all that often. Then it would only go only 40 mph. Drove me crazy,,

It also ate fuel pumps. After the third one in six months. I took the last failed pump apart and the suction side valve had been pulled (sucked) out of it's staked hole. I then pulled the tank and the sock was melted!! to the tube. Replaced the unit and pump, drove the thing 140,000 with no more problems.
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