Fuel pump question
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New User
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Fuel pump question
Guys-
I'm a complete beginner and new to the forum, so bear with me. My truck went out on me yesterday and I noticed that a secondary fuel pump that had been mounted underneath was no longer working. My question is, will the main fuel pump work in conjunction with the secondary, and if the secondary goes out and quits working, will it revert to the main fuel pump?
I bought a new one today to put in, and I'm hoping that's all the problem is. I'm just not sure why the previous owner installed the secondary one, and why? It seems pointless based on the price of a new primary pump. Any input appreciated.
As far as the truck goes, it totally crapped out on me to a complete power loss, and it was obvious that no fuel was getting in. I was able to get it started again, but it broke down on me two more times before I limped it home.
BTW, 78 F150 with a 302.
I'm a complete beginner and new to the forum, so bear with me. My truck went out on me yesterday and I noticed that a secondary fuel pump that had been mounted underneath was no longer working. My question is, will the main fuel pump work in conjunction with the secondary, and if the secondary goes out and quits working, will it revert to the main fuel pump?
I bought a new one today to put in, and I'm hoping that's all the problem is. I'm just not sure why the previous owner installed the secondary one, and why? It seems pointless based on the price of a new primary pump. Any input appreciated.
As far as the truck goes, it totally crapped out on me to a complete power loss, and it was obvious that no fuel was getting in. I was able to get it started again, but it broke down on me two more times before I limped it home.
BTW, 78 F150 with a 302.
Elder User
Joined: Sep 2014
Posts: 862
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From: like subarctic, brrr man!
If there are any holes in the line, it will suck air instead of fuel. I had serious problems with my lines and tried various things and fixes, but couldn't get it right. Eventually went with a Facet Electric Fuel Pump, like this: NAPA AUTO PARTS except mine was 60104. Seemed to work well, but I still had problems which I think was the small rubber line I used.
Edit: Oh yeah, if you do go with an electric pump, don't wire it to the ignition coil circuit or you'll wreck the ballast resistor...
Edit: Oh yeah, if you do go with an electric pump, don't wire it to the ignition coil circuit or you'll wreck the ballast resistor...
Last edited by ZarK-eh; Sep 19, 2015 at 08:17 PM. Reason: warning about wiring to ignition coil
Moderator & parts slinger
Joined: Feb 2007
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From: S/W Missouri, Polk county
Sounds like the pervious owner added the secondary (electric?) one because the mechanical one on the side of the engine quit? And or he could not figure it out.
As far as the mechanical one, usually they either work or they don't. Sounds like maybe a FUEL FILTER problem, since you could get it running again.
Do you have any in line clear or metal canister filters up in the eng bay or down on the frame?
Also could be a clogged fuel tank mounted, sending unit, pick up tube, filter sock....it all that makes sense?
As far as the mechanical one, usually they either work or they don't. Sounds like maybe a FUEL FILTER problem, since you could get it running again.
Do you have any in line clear or metal canister filters up in the eng bay or down on the frame?
Also could be a clogged fuel tank mounted, sending unit, pick up tube, filter sock....it all that makes sense?
Postmaster
Joined: Nov 2011
Posts: 2,553
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When an electric pump is combined with mechanical pump, the electric pump will often block the flow if it is not running.
The electric could have been added to prevent vapor lock or as mentioned because the mechanical failed. Today's gas is made for pressurized EFI systems and boils eaisly which can create vapor lock, especially in hot weather. I run a Mr Gasket mini electric pump (parts store) mounted on the frame rail along with the mechanical pump to deal with vapor lock.
In general, getting the fuel system sorted out is a key step in getting these trucks reliable. As a start, suggest you inspect steel lines for serious corrosion or damage and blow them out with air. Replace all rubber sections... old rubber line can dry out and crack or get soft and sucked shut by the pump. Also replace fuel filters. The OE filter screws into the carb plus any added filters.
The electric could have been added to prevent vapor lock or as mentioned because the mechanical failed. Today's gas is made for pressurized EFI systems and boils eaisly which can create vapor lock, especially in hot weather. I run a Mr Gasket mini electric pump (parts store) mounted on the frame rail along with the mechanical pump to deal with vapor lock.
In general, getting the fuel system sorted out is a key step in getting these trucks reliable. As a start, suggest you inspect steel lines for serious corrosion or damage and blow them out with air. Replace all rubber sections... old rubber line can dry out and crack or get soft and sucked shut by the pump. Also replace fuel filters. The OE filter screws into the carb plus any added filters.
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