Fuel delivery issue

[xtremjeepn]

Okay. I am a bit stumped today and need a little help figuring out what I am missing here.


I am having a fuel delivery problem.

-I looked in both tanks and found about 1/2 of old fuel but tanks are clean and clear of junk.

-I put a bottle of "heat" in each tank and some fuel. 4 gallons in the drivers tank and 2 in the passenger tank.

-We wired up the missing switch to be permanently on the drivers tank. The fuel gauge moves and all.

-There is a brank new mecanical fuel pump and pushrod on the truck AND a brand new electric fuel pump on the truck. (both are working fine)

-I can dump fuel straight into the carb and the truck fires right up. (but won't keep running)

-I pulled the fuel line off at the carb and stuck an air nozzle in it and you can feel air coming out of the drivers side tank. No other leaks in the system.

-I have tried running just the electric pump for a few minutes and it will never pick up any fuel.


What am I missing? Lines seem clear and tight, all the pumps work, tanks have fuel in them but I just can't get fuel to the carb!!!

[xtremjeepn]

Okay. I am a bit stumped today and need a little help figuring out what I am missing here. (this is on the "trail clean up truck I am building.. 74ish crewcab 454, carb, dual tanks)


I am having a fuel delivery problem.

-I looked in both tanks and found about 1/2 of old fuel but tanks are clean and clear of junk.

-I put a bottle of "heat" in each tank and some fuel. 4 gallons in the drivers tank and 2 in the passenger tank.

-We wired up the missing switch to be permanently on the drivers tank. The fuel gauge moves and all.

-There is a brank new mecanical fuel pump and pushrod on the truck AND a brand new electric fuel pump on the truck. (both are working fine)

-I can dump fuel straight into the carb and the truck fires right up. (but won't keep running)

-I pulled the fuel line off at the carb and stuck an air nozzle in it and you can feel air coming out of the drivers side tank. No other leaks in the system.

-I have tried running just the electric pump for a few minutes and it will never pick up any fuel.


What am I missing? Lines seem clear and tight, all the pumps work, tanks have fuel in them but I just can't get fuel to the carb!!!

[red4wd]

Is your pump connected to the supply line or the vent line?  The vent line only goes into the vapor space on the tank. 

Is the pump plumbed into the line correctly i.e. the suction end on the tank side?
 

[xtremjeepn]

I did nothing with the hoses other than hook up the fuel pumps.

The one at the engine can only go on one way. (large hose and small hose).

The inline pump could only fit on one hose also.

So I have no idea what could be wrong there.

[xtremjeepn]

I have been beaten by the truck today!!!

-Tried swapping the lines around to make sure I was using the right ones. (using the electric pump to try to draw fuel)

-Bypassed the switching unit totally so I am drawing straight from one tank.

-took the mechanical pump off, checked, changed line arrangements. (since there is no indicator as to which is in and out)

-when to blow out the lines to make sure they were all clear. When I pressurized the first (small) line it flooded fuel out the other line. So the pressure in the tank pushed fuel through. I hooked everything back up and pressurized that line again to fill/prime the system.

NOTHING I DO WORKS!!!! I CAN'T GET FUEL TO THE CARB AND EVERYTHING SEEMS TO BE WORKING???!!!!


I am totally out of ideas. So unless someone has some this thing will be in my garage forever.

[TexasRed]

Where is the electric fuel pump, before the mechanical or after coming from the tank? Fuel filters? Can you see fuel coming down the pipe from the electrical fuel pump hook up? I mean, keep going back until you can find fuel, if that makes any sense.

[Stewart G Griffin]

First, let me state that my mechanical knowledge and expertise dealing with cars is, at this point, very limited.

Despite all that, and also due to curiosity reasons,  i have a question for you.

If the truck is going to be used for "just"  "trail cleanup,"  then why do you need a mechanical and electric pump?

Based on my complete non-knowledge of 4x4ing, i would ASSume that "trail cleanup" and 4x4ing in general is basically low-rpm operations.  Which further begs the reasoning behind using an electric pump in conjunction with the mechanical.

Why don't you try running the engine with just the mechanical pump for now and bypass the electrical?
(this is sort of like gary coleman giving basketball advice to michael jordan)

So, i apologize that i could not give specific help, but maybe my question may spark some thinking towards the solution?

[HAULIN IT]

Cole, When you say "I can't seem to get fuel to the carb" Do you mean if you take the line off at the carb, no fuel comes out? Or are you just assuming that there is no fuel there because it won't run without you pouring gas in the top? If you look down the carb & work the throttle, do you see any "squirter action"? If so I bet it's full of water,holding the float up & no gas comes in. Just a thought, Good Luck, Lorne

[Bubba13]

You may have to drop the tanks to see if the fuel pickup tube is intact. There are tubelike screens around the fuel pickups, check to see if they are not clogged. Next, the valve may be stuck between the two tanks. I had to replace one once for this. Also, I had to run an electric pump just on the downstream side of the valve to help out the mechanical pump to keep the truck from vaporlocking when going up long steep grades.

[xtremjeepn]

Okay. I will try to answer all the questions.


If I take the fuel line off the carb it is bone dry.

I started with the mechanical pump only........BUT when I bought the original donor truck it ran with ONLY an electric pump.  So in the effort to fix the problem I bought an electric pump today thinking that maybe there was a reason (like a flat fuel pump lobe) that the motor only had an electric pump originally.

The electric pump is located about 8 inches in front of the swtiching valve. Which I took out of the loop earlier today. So the drivers side tank runs straight to the electric pump now and then into the mechanical to the carb. (Which is the only fuel filter).

I took out the mechanical pump and left the lines off. I could not get the electric pump to get any fuel out. I stuck an air fitting down the little hose and as soon as the tank presurized it blew fuel out the large line. So I know the lines are clear and picking up.


I then hooked everything back up, tried presurizing though the small line to prime it and I still get NOTHING. can't even get fuel to the pump.


Just flat out lost and frustrated at this point.

[VileZambonie]

You need to prime the fuel line. Use one pump or the other but you can't have both.  If the lines are primed and you still aren't getting fuel out of the fuel pump replace it.

[autorepr]

Howdy,  First at this point resist (I repeat) Resist the erge to set the truck on fire, shoot it, or push it off a cliff! That's where I'd be at this point.

It could be that there is a pin hole in the steel or rubber hose part of the large line preventing adaquate suction between the tank and pump. Or possibly the strainer sock on the pickup in the tank is clogged with varnish, bodywork dust, or some other type of debris. When you pressurise the tank it can forcefully push fuel thru but when the pump(s) have to suck it thru they can't.

U can try unhooking the rubber line from the top of the tank and adding a rubber hose from the steel fuel line going from the tank to the pump and drop it in a gas can and see if it picks fuel up thru there on it's own. ( don't prime the hose just let it suck it up) Then you'll know if there's any holes in the fuel lineto the pump. Check all that and let us know.

[xtremjeepn]

Use one pump or the other but you can't have both. 

(not really true, many people use electric pumps as "helper" pumps for the mechanical.)


Thanks for the ideas guys. If I get ambitious I may work on it again.......otherwise it may sit here for a few weeks before I feel like dealing with it again.

[Captkaos]

If you are running a carb setup there is no need for 2 pumps, expecially on a normally aspirated motor that is stock using a carb.  All a carb needs is 7lbs max.  You would have to regulate that down before the mechanical, and that defeats the purpose of having the electrical pump.

What kind of tanks are they and what kind of sender (EFI or non)?  the mechanical pump should be more than sufficient to supply a carb motor.
Has this never ran?  fill the float bowl up with gas and see if it will prime the pump up.

[Captkaos]

Suggestion, but with the mech pump (by itself) hooked up, does it pull fuel out?
what about the electrical pump by itself?  Is the selector valve still on the truck?  The ports are marked on there..

Sounds like you need a couple hours break from it.  Which is why I am on here now....