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Bad fuel pump?

Moderator: Mod Squad

Krussell
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Posts: 27
Joined: Sat Sep 30, 2017 11:47 am

Bad fuel pump?

Post #1 by Krussell » Fri Aug 02, 2019 2:43 pm

Completely inconsistent. Yesterday it ran fine, today it runs like crap. It's been having problems starting when it's facing up hill, vapor locks constantly, hesitates when accelerating, etc.

Then I took the fuel line off to redirect it because I thought the gas may be getting boiled, and fuel dumped all over the ground. Now I was on a fairly steep hill, so I thought that could be the cause of. But I changed the fuel pump a couple of years ago and I don't think it dumped the fuel like that.

So best guess, do you think it's the pump? Bad diaphragm? I mean this pump isn't very old, but it's maybe not the best.
68 Ford F-100
300cc I6
Manual choke

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MechRick
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Posts: 975
Joined: Wed Jan 04, 2012 7:43 pm
Location: Las Vegas, NV

Re: Bad fuel pump?

Post #2 by MechRick » Fri Aug 02, 2019 3:01 pm

What;s the year-make-model of the vehicle?
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam, aluminum cam gear
Hedman header, full mandrel bent duals, crossover, super turbos
http://fordsix.com/forum/viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap http://fordsix.com/forum/viewtopic.php?f=13&t=72863
1988 F250 2x4, 460 ZF 5 speed.

Krussell
Registered User
Posts: 27
Joined: Sat Sep 30, 2017 11:47 am

Re: Bad fuel pump?

Post #3 by Krussell » Fri Aug 02, 2019 4:31 pm

'68 Ford F100
68 Ford F-100
300cc I6
Manual choke

Soldmy66
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Posts: 394
Joined: Fri Jan 09, 2004 11:09 pm

Re: Bad fuel pump?

Post #4 by Soldmy66 » Fri Aug 02, 2019 5:07 pm

When did you last replace the fuel filter?

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Shorty
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Location: southern Ontario, Canada

Re: Bad fuel pump?

Post #5 by Shorty » Fri Aug 02, 2019 6:57 pm

could there be an issuue with fuel tank vent? could build pressure or vacuum depending on temp changes or run time. Run it with the gas cap loose for a bit and see if there is improvement. I used to have a tractor like that,it would run rough after extended run time if the fuel cap was tight, but would run all day with the lid loose.
85 F150 on 78 bronco frame C6 np205 welded dana44 front, trussed posi nine inch rear. EFI exhaust manifolds into one 2 1/2" rolls on 35x12.5x15 Maxxis Trepador.

Wesman07
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Re: Bad fuel pump?

Post #6 by Wesman07 » Fri Aug 02, 2019 8:54 pm

I’d start with fuel pressure and work back. Test one thing at a time and watch the gauge. All of what is mentioned is possible.
In-lines we trust

86 f150 300 efi with advanced stock cam. Np435, Dana 60/ 10.25, 35" BFG's, four link front suspension with 12" travel fox coil overs, custom deaver leaf pack in the rear.

Krussell
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Posts: 27
Joined: Sat Sep 30, 2017 11:47 am

Re: Bad fuel pump?

Post #7 by Krussell » Fri Aug 02, 2019 10:05 pm

So I changed basically every fuel component out from the fuel cap to the float last year since I bought a new carb and didn't find out that the float was leaking until about two months ago.

I changed that fuel filter out about two months ago. I changed that gas cap out last year. That was one of the first things I did after changing out that carb and it kept flooding over.

I would think that fuel pump would be fine since it's not very old and I haven't used it since the truck hasn't run since I put it on, but I tend to find really bad new parts somehow.... Like a brand new carb with a leaky float.

Thanks for all the suggestions. And I did buy a pressure regulator, but haven't put it on yet
68 Ford F-100
300cc I6
Manual choke

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bubba22349
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Location: Flagstaff, Az. 86005 near the old Route 66

Re: Bad fuel pump?

Post #8 by bubba22349 » Fri Aug 02, 2019 10:56 pm

Did you get the float level set correctly? If it’s still flooding out after changing the float out, it’s not likely to be a bad fuel pump. Next check the needle and seat for damage or if a piece of trash holding it open. Testing the fuel pressure is a good move. Good luck :thumbup: :nod:
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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