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Fuel pump?

7K views 30 replies 11 participants last post by  speedyweasel 
#1 ·
The old Bronco has been sitting for about three years due to deployments, anyway, I dropped the tank and cleaned it all out blew out all the lines, rebuilt the carb and refueled it. Now I am getting fuel to the pump and about 10 inches from the carb (installed a clear hose to see if it was pumping), but then it stops. Does anyone have a clue as to why? Do I need a new fuel pump, or more patience?
 
#2 ·
Look to see if you have fuel dripping from the weep hole on the fuel pump, might have a blown diaphragm in the fuel pump.
 
#4 ·
I rebuilt my engine recently and tried to reuse the fuel pump from the previous engine, which was a few years old but low-mileage. It had worked fine prior to the rebuild. When I put it on the rebuilt engine, it didn't work at all. I never noticed any fuel leaking from it, but replacing it with a new pump solved my problem.

Edit:
Also, my first go on the trail this weekend I started having apparent fuel issues with nothing getting into the carb after a mild obstacle (this is with the above-mentioned new fuel pump). Pouring a little bit of gas directly into the carburetor allowed me to get the engine started and it had no problem staying running. I think my clunkly carb was/is having priming issues. Might try starting it this way to see if you can keep it running, and if so likely rule out the fuel pump as the problem.
 
#6 ·
Bad pump, or sucking air, as said above.

I think my clunkly carb was/is having priming issues.
Priming issues? How's that? You should have about half a cup of fuel in the carb bowl, even when it's not running.
 
#9 ·
I'm having what started out as a similar problem to Big Mikes. On way home from work I filled up the tank (33gal) and got back on road. About 5min/5miles down road truck started to run like pooh. Slowed for a light and it bogged down like going to cut off and then cut of. Tried restarting and no go, pulled in lot and check filter before carb and it was dry. Originally thought it was pump so I replaced it. I had fuel, not much at pump where it connects to soft line. I tried starting it and nothing. Started to think a more difficult problem based on that. Had it towed home, tried again and it started. Surprised so I popped hood and filter had fuel in it, halfway usually 3/4 any other time. Moved Bronco let run for 10 and it did then ran dry again and cut off. So I checked lines thinking one had a hole in it and pump was pulling air. Started at tank because it is most dif to get to. Pulled soft line off hard line and I took a gas shower. Put line back on and moved to soft line at pump. No fuel there so I assumed line was bad (felt soft and brittle) replaced it and had fuel to carb in no time. Let it run for 10+ so I'm like problem solved. Drove it up street for test drive and got about 7 miles up street and cut off on me. Still had fuel in filter and getting fuel in carb. Would start but after a second it cut out. Waited and tried for 10 min and finally started, halled ass home. Got home and was like :scratchhe, Bronco sat overnight while I pondered what was going on. Thinking maybe bad sending unit or clogged sock at sending unit. Go out next day to see what I get and Bronco just turns over no fire up/start. Work my way to a bad coil replace that and now no fuel again. Same process, but this time no fuel at soft line for tank. Take air hose blow air in tank to clear sock and line, move up front and blow out hard line on frame then soft to hard line and then prime pump. Have fuel to pump which sends it to filter. Start Bronco and let run for 20 mins, fine. Start next day same thing runs fine, start today and try luck drive to pick kids up and gets me there and back (surprised). Pop hood and damn filter is dry agian. My thoughts now are sending unit is clogged or sucking sock in line and preventing fuel or I have a hole somewhere on fuel line. Your thoughts?
 
#10 ·
My thoughts? Weird shit.

Clogged wouldn't explain it being intermittent like that, IMO. Dropping the tank sucks, but at least the screen on the fuel pickup is cheap... I got mine from Dennis Carpenter. It was like $5.00 + $600 shipping. Fit just like factory and took ten minutes to install once the tank was down.

I don't know that a clogged screen like that would be the problem, but it's an easy (albeit time consuming) task to replace it. I don't suppose you've tried seeing if there's a pressure leak between tank and pump, have you? Pressurize the line and see if it leaks down?
 
#11 ·
I'll try the pressure trick Charlie and see what happens. I've played with this thing so much I get 10' out and I swear I smell fuel. If I do the sending unit I'm cutting a hole in the floor to access it. I have another unit already because Shamrock has a hole in the tank that needs replacing.

Thanks
 
#12 ·
I believe your 79 had the charcoal evap system OE. IF you have a non-vented cap and the charcoal evap system becomes clogged, you will in essence pull a vaccuum in the fuel tank. Try driving with a vented gas cap, to check for a clogged vent. I'm lucky. My 78 was the last year for non cat leaded fuel. NO evap system, and big hole in the filler neck!!
 
#17 ·
I THINK that is the correct location. Yes, leaving the gas cap off will prevent a clogged evap line from pulling a vacuum. If the OE system is still in place, there will be 2 lines, approx the same size going forward from the gas tank. One will be the fuel supply line, and the other will be for the evap emission control. You can find out which is which, and try blowing air back thru the evap line, from where it attaches to the charcoal canister. I don't think there is a check valve, so you should be able to hear air/bubbles in the gas tank. I hope you find the issue soon. Its not much fun having "toys" you cannot depend on.:beer
 
#18 ·
Sorry I cannot be more specific about the canister location, its prob been 25 years since I have seen one. Seems like they were black, and shaped kinda like the washer fluid res. There should be a rubber line coming off the canister that connects to engine vacuum, to draw the fumes out and burn them. I remember people plugging THAT line and causing problems, also,
 
#21 ·
Rick,
I had to drill a tiny hole in my gas cap after getting rid of all the evaporative stuff on my (long gone) 79. Easiest way to figure out if this is your problem is to drive around with the gas cap off or loose and check the fuel filter.
Tyler
 
#22 · (Edited)
Ok I'll look into that. This is turning into an indepth little event. Never tested that before going to have to seek a little experience to help. I appreciate your help with this problem. That pump is on it's way out as it is to a sag/hydro setup.

Thanks Tyler, the locking cap is new about 2 months old. I'll keep you guys in the know. It might be a while before I can get to this.
 
#25 ·
Update

Well I hate to say it but I'm still having that issue. I pulled the cap off and put a rag in the down pipe. It held up for two trips to mom & dads which is about 4 miles each way. Each time I arrived and before I left I checked the fuel filter in front of the carb. Each time it had a full filter. Except for the final stop at home. I checked it and the filter was 1/4 full.

What I'm thinking of doing now is pull the tank and put in a new sending unit and clean the tank while out. Put it back with new fuel lines from tank to hard line on frame and then one from the frame to the pump and another from hard line on top of engine to carb. I'll also replace the breather line while the tank it out. What ya think?
 
#28 ·
I'm pretty sure man, that's what I thought it was in first place & changed.

Mine did this and the accelerator pump was broken and leaking fuel just enough that I couldn't smell it but always had the empty filter and it would die at idle after warmup .
The two flat head screws directly below the pump were also loose.
Look there while it's running to see any moisture (fuel).

I'll take a look see what I got thanks.
 
#27 ·
Mine did this and the accelerator pump was broken and leaking fuel just enough that I couldn't smell it but always had the empty filter and it would die at idle after warmup .
The two flat head screws directly below the pump were also loose.
Look there while it's running to see any moisture (fuel).
 
#29 ·
This BIOFUEL is causeing alot of engine problems. Some of the rubber in some fuel pumps and carbs will get messed up big time time the biofuel. Their has been alot of complaints and it should be done away with. Run some of your fuel out into a clear container and check your fuel for dirt or water. I did and found it looked liked coke . I had to drain 33 gallon and do away with it. It will turn into water in a short time period. I was told buy a weigt and measuer guy--he saw it in a quick as 2 days.
 
#30 · (Edited)
I'm happy to report that the fuel delivery issue is gone. The soft fuel line that connects the two steel lines was the culprit. It was cracked and as stiff as a piece of steel. I replaced it and the other soft line for the breather line. I drove the ol girl, filled her up and put the gas cap back on. After 70+ miles runs like a top. Thanks for all your help guys!
 
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