Very Low Fuel Flow

[Shayne]

I posted a previous issue with gas not being pulled from the aux tank, and it is now affecting the main tank. If the bronco has been sitting the fule filter immediately fills with fuel as normal but after 1-2 minutes the engine drains that gas and from then on I can only see small amounts of fuel entering the filter or sporadically shooting into the filter.

The bronco has two tanks and I was switching the selector valve between the two tanks... any ideas as to what could be causing the low fuel flow? I am thinking the valve may be clogged, any advice on how to correct this? It also has a fuel flow when the switch is in the off position....

[tortuga]

Re: Very Low Fuel Flow

Starting to sound like your fuel pump might be an issue, Something similar happened with mine and an electric pump fixed it right up. I was too lazy to bypass the mechanical pump, the electric just pushes fuel to it.

[earlybronco72]

Re: Very Low Fuel Flow

I would start by bypassing the filter(mint be plugged), and then the selector and see if that helps out or not. Third thing I would do is make sure the pump is still pumping. They make a hose clamp pair of vice-grips that if you have rubber hoses you can clamp off the line and limit the amount of spilt gas. If you have the hard plastic lines mine came stock with than you don't want to pinch them.
If you are close to Roseville, I have a spare electric you could borrow to do some troubleshooting.

[TBS-POPS]

Re: Very Low Fuel Flow

Does your engine die like its running out of fuel???

[Shayne]

Re: Very Low Fuel Flow

Is there only one filfter, the one near the carb? I looked all over underneath and could not see another... I have a clear filter near the carb and can witness the fuel flow, before I started switching between the tanks the flow from the main tank was perfect.

It runs fine while sitting at idle, but the dies when I drive it since it is not getting enough fuel. I purchased it about 3 weeks ago and before that it was sitting in a garage for five years. I have replaced the master cylinder, plugs/wires/distributor cap etc.. and have been driving it around with no issues, other than a few leaking seals... Both Tanks were near empty when I picked it up and the main has always been fine, I have never had much luck getting gas from the auxillary tank--other than what I descibed above. Since it has been sitting so long I am assuming the fuel line is clogged somewhere. Not sure how to check it though and clear the line.

Will mechanical pump burnout if there is a clog somewhere in the line? I have been wanting to check the selector valve, is the access to it above the aux tank? Both tanks are full and I have been unable to siphon any gas out. Was the electric pump easy to install? That may not be a bad option.... are there issues with it pushing gas to the bad mechanical pump?

[kwspony]

Re: Very Low Fuel Flow

the diaphram in the fuel pump may be cracked. Have you tried with the fuel filler caps off? What are your fuel lines made out of?

[Shayne]

Re: Very Low Fuel Flow

I got a new pump but am also going to clean out the fuel lines and selector valve.

[tim]

Re: Very Low Fuel Flow

Try bypassing the selector valve run the main tank line directly to the line that goes straight to the carb. Try this before replacing the pump. Mine did what your describing and I went through replacing the lines, fuel pump, and a few other thing before bypassing the valve (the one at the drivers floor board). It was the valve that was mis-labeled (by the previous owner) and once bypassed, everything worked fine.

[Shayne]

Re: Very Low Fuel Flow

I am going to try that tomorrow night, it should be easy so it will be the first thing I try. Does anyone know what size the stock fuel lines are?

I had someone bring up the idea of having both tanks hook into a T line and pull gas from both tanks at the same time. Has anyone actually done this? I guess that it would work providing that one does not get dry.... I don't think I will do that, just thought I would pose the question.

[Sierra Backwoods]

Re: Very Low Fuel Flow

If it sat with gas in it, everywhere the gas sat will need to be replaced, or flushed and cleaned.

I had the same problem, fuel starvation under heavy load. I had to go to a high volume mechanical pump to solve it.

[Shayne]

Re: Very Low Fuel Flow

I replaced the pump and bypassed the switch. When I took the line from the main tank off the selector valve gas was free flowing with no end in sight, however, the same thing is happening. I took it for a drive and would stop once in a while and check the clear filterand sometimes there is gas in there and sometimes it was dry. I am new to working on cars, is this normal or should there always be gas in there? The filter after the pump and just before the carb... when I was driving it ran fine, but I did nothing more than go around the block a few times--no faster than 40.

Also, I thought fuel lines were made of metal with rubber connections, but these lines are a plastic type material....

[kwspony]

Re: Very Low Fuel Flow

sounds like the stock fuel lines. What about vapor locking? Also, how tight do your filler caps fit? Maybe they are so tight that a vacuum is being created in the tanks not allowing fuel flow.

[TBS-POPS]

Re: Very Low Fuel Flow

Fuel will not fill the Clear type fuel filters. The float valves in the carb will not allow enough fuel flow between cycles of open and close to fill the filter. Mine does not fill and is never fully full. Yours, if the engine stays running and does not run out of fuel at any point, is perfectly normal... RUN IT!!

[Shayne]

Re: Very Low Fuel Flow

Thanks! I am going to start driving it again and see how it goes, have more to do to it. I guess worst case it dies for a little while... So far it has been easy to work on, but I have had people over that work on cars and they thought that filter should remain at least half full.

I have not been able to get fuel out of the auxillary tank and when I pulled then line off where goes into the tank no fuel came out and when I tried blowing air in there nothing happened. The tank is full and has a screen in the filler tube so I cannot siphon any gas out, is there another way to drain the gas? Like I said, I am new to this so working on the fuel system has me a little nervous beacuase of the danger and possible mess... However, I am willing to give it a shot, I really want to learn how to do it all...