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ok, sounds dumb, but here goes...

tasker

Contributor
all knowing of nothing
Joined
Jun 2, 2006
Messages
20,729
Loc.
NH
the new edition, 68 1/2 cab 289. Seems to be running out of fuel. Put a clear filter on, will run for a good 1-2 minutes before boggin down like it's running out of gas. Filter still a little more than half full. pump it starts back up and does it again. Could it be just crappy gas? It does have an old electric fuel pump to replace the vaccum mechanical pump. I do see the clear filter getting lower wnd lower after repeated tries. Maybe just a weak pump? doesn't seem to have any vacuum leaks. any ideas? (also, which way on the manual selector valve is for main tank? i'm thinking towards driver's side) Thanks guys and gals!
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,833
Have you tried removing the fuel line from the carb and running the pump and see what it flows? I remember some old mechanic telling me an engine should fill an empty soda bottle in under 30 seconds. This is a mechanical pump at idle. The electric mupm would have to move at least that at idle as it doesn't get any extra speed that a mechanical pump would as the engine speeds up.

It sounds like you are sucking the fuel bowl dry then after the pump runs a little it fills the bowls back up again for another couple minutes of running. Not knowing what carb you are running are you sure you don't have a filter at or in the carb that is clogged?

If the suction side of the fuel line has a pinhole in it then air will get sucked in with the fuel through the pump severly decreasing it's volume. But I don't think that is what is happening as you should see bubbles in the clear fuel filter.

If I remember right, there is a plate on the floor that is marked main and aux that the arrow points to. Indicating which tank you are drawing from, providing no one switched hoses sometime in the past.
 

SteveR77

Full Member
Joined
Jan 16, 2004
Messages
185
Loc.
Greenbrier,Arkansas
I had one do this same thing once and it ended up being the switch under the drivers seat was clogged up. You might try bypassing it temp. to see. Steve
 

jsander

Full Member
Joined
Feb 28, 2006
Messages
165
Loc.
Under your Bronco
SteveR72 said:
I had one do this same thing once and it ended up being the switch under the drivers seat was clogged up. You might try bypassing it temp. to see. Steve

I just went throught the same scenario a couple of months ago, and to my suprise when I bypassed the fuel selector switch under the seat, I had a steady flow of fuel to the carb. Of course this wasn't the first thing I tried, I actually went through three carbs before checking my fuel pressure. I would definitely recomend bypassing the fuel switch first, second thing would be to check your fuel pump.
 
Last edited:

JeepGuy

Contributor
Bronco Guru
Joined
Aug 24, 2006
Messages
1,210
I think you said this was a new addition. Do you know what the inside of the fuel tank looks like. I had a similar situation with my CJ-5 and it ended up being a clogged pick up from inside the tank. Just a thought.
 

eb66to77

Bronc'Ownly
Joined
Mar 26, 2005
Messages
2,558
Loc.
NOVA
I would go get a small fuel pressure gauge ~$15 and nipple that will thread to it and also fit your fuel line. My fuel system is still routed for efi. It consists of a mallory adjustable fuel regulator with return and I have the fuel pressure gauge permanently mounted to. When I have a fuel problem I can eliminate so many factors by just looking at that.
 
OP
OP
tasker

tasker

Contributor
all knowing of nothing
Joined
Jun 2, 2006
Messages
20,729
Loc.
NH
The fuel is not bubbling, it does look kind of nasty though. As for the electric pump, i'm thinking thats suspect. I don't feel it pulsing when runing. I'll look into the switch thing, never thought of that, but i'm going with a new electric pump too. Put more gas in both tanks, we'll see if that cures it.
 

SeaBiscuit68

Bronco Guru
Joined
May 26, 2003
Messages
1,404
Loc.
Tacoma Wa
Is there a filter before the pump? When you mention the fuel looking nasty, I'm wondering if the pump is full of crud.
 

Skiddy

Bronco Guru
Joined
Oct 8, 2003
Messages
11,557
SeaBiscuit68 said:
Is there a filter before the pump? When you mention the fuel looking nasty, I'm wondering if the pump is full of crud.
Could very well be. Also x3 on the selector switch. I went though this on my brothers p/u and that is what it was doing.
 

fireman1749

Sr. Member
Joined
Nov 27, 2005
Messages
970
Loc.
Clarksville, TN
Check and see if there is an air leak between the carb and egr plate and intake, i had the same problem and after a new fuel pump, carb, fuel lines, fuel pickup, plugs, wires, dist cap and rotor, cam eccentric, coil, and ignition box, i realized that the egr plate was leaking and making it run bad. It would idle perfect, but as soon as i would give it a little gas it would choke up. All it needed was 2 new gaskets......
 
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