7 Mechanical Fuel Pump Failures?!?
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7 Mechanical Fuel Pump Failures?!?
Hey guys, I have a 1980 f150 with a carbureted 302. I’ve owned it about 6 months and have been through 6-7 mechanical fuel pump. It keeps blowing gas out of the weep hole in the side (straight onto the EXHAUST MANIFOLD) or just failing to pump fuel. I’ve tried spectra from auto-zone, Car-quest brand and Delphi. Does anyone know what could be causing them to fail?!?!? Any help would be appreciated, thanks.
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From: Virginia
Clogged line should not affect the pump. When the needle valve closes in the carb, that is the same as a clogged line, the flow just stops. The pump is designed for this. I would suspect lousy quality pumps from overseas. I am not sure where you could get a better quality pump. I would keep a close check on your oil level, sometimes when the pump goes bad it will pump some fuel into the crankcase.
Post Fiend
Joined: Feb 2008
Posts: 5,831
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From: St Albert, Alberta
Clogged line should not affect the pump. When the needle valve closes in the carb, that is the same as a clogged line, the flow just stops. The pump is designed for this. I would suspect lousy quality pumps from overseas. I am not sure where you could get a better quality pump. I would keep a close check on your oil level, sometimes when the pump goes bad it will pump some fuel into the crankcase.
Nope not the same at all.
When the needle closes in the carb the pump diaphragm just does not move as the diaphragm return spring can't overcome the outlet pressure as the lever arm can move independently of the diaphragm during the pressure stroke. The pressure stroke is as the arm comes off the fuel pump lobe.
If the flow is restricted the pump diaphragm is working against that extra vacuum/suction. On the suction stroke, the diaphragm is fixed to the lever arm and MUST move with the arm it the suction stroke is as it rides up the pump lobe.
High suction on the inlet will lead to fuel pump diaphragm failures.
So they are not the same at all.
He is experiencing repeated diaphragm failures and this really can only be attributed to high vacuum on the inlet. One or 2 pump failures ya bad pumps but 7 from 2 different manufacturers this is not just bad fuel pumps.
The OP should probably drop the tank and check the inlet screen on the inlet on the sending unit. And back blow the feed line out with shop air.
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Nope not the same at all.
When the needle closes in the carb the pump diaphragm just does not move as the diaphragm return spring can't overcome the outlet pressure as the lever arm can move independently of the diaphragm during the pressure stroke. The pressure stroke is as the arm comes off the fuel pump lobe.
If the flow is restricted the pump diaphragm is working against that extra vacuum/suction. On the suction stroke, the diaphragm is fixed to the lever arm and MUST move with the arm it the suction stroke is as it rides up the pump lobe.
High suction on the inlet will lead to fuel pump diaphragm failures.
So they are not the same at all.
He is experiencing repeated diaphragm failures and this really can only be attributed to high vacuum on the inlet. One or 2 pump failures ya bad pumps but 7 from 2 different manufacturers this is not just bad fuel pumps.
The OP should probably drop the tank and check the inlet screen on the inlet on the sending unit. And back blow the feed line out with shop air.
When the needle closes in the carb the pump diaphragm just does not move as the diaphragm return spring can't overcome the outlet pressure as the lever arm can move independently of the diaphragm during the pressure stroke. The pressure stroke is as the arm comes off the fuel pump lobe.
If the flow is restricted the pump diaphragm is working against that extra vacuum/suction. On the suction stroke, the diaphragm is fixed to the lever arm and MUST move with the arm it the suction stroke is as it rides up the pump lobe.
High suction on the inlet will lead to fuel pump diaphragm failures.
So they are not the same at all.
He is experiencing repeated diaphragm failures and this really can only be attributed to high vacuum on the inlet. One or 2 pump failures ya bad pumps but 7 from 2 different manufacturers this is not just bad fuel pumps.
The OP should probably drop the tank and check the inlet screen on the inlet on the sending unit. And back blow the feed line out with shop air.
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One tank, I’ve already changed the tank and sending unit, haven’t touched the lines though.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Have you replaced all the rubber fuel lines?
Tank to hardline, hard line to pump, and might have some from pump to carb.
The rubber can break down on the inside but look good on the outside.
Dave ----
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From: Virginia
Sorry, I missed the "before the pump" description.
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Tuned
Joined: Apr 2008
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well you may very well need a new line, but I would blow it out with an air compressor first for testing purposes. There will probably be a few different comments on "how to do this". I'm lazy. I'd remove the gas cap, remove the line going IN to the fuel pump and blow in from there. It will probably blow the sock off in the tank, so when you're all said and done you'll want to put an inline fuel filter before the pump.
Post Fiend
Joined: Feb 2008
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From: St Albert, Alberta
Nylon was used if you had an in tank pump otherwise it would be rubber and steel..
nice I thought they switched them all that way
Junior User
Joined: Aug 2012
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My 1986 f150 I6 has nylon lines with metal at the end could it be the pushrod or lobe or the way it's being installed. ? Just for thought. Had a friend once had issue with his on third one he realized it was him by mistake . When the engine pushed it out and it was hanging on 1 bolt
Cargo Master
Joined: Oct 2016
Posts: 2,738
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From: Northern VA
I've never had a problem with various cheap off the shelf pumps.
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