Ok so here it goes.....again!

Since chasing gremlins and ultimately getting the Bronco to fire and run, I took it out over the weekend and drove from NE Denver out to Wheatridge with no problems. On the way back, I started to sputter on the highway and it died (thought I was out of gas-- gas guage does not work.) I got out, pulled the cap, there was quite a bit of fumes that came with it and put about a gallon of gas in. Fired right up and made it home the 3-5 miles left. This weekend, I pulled the drain plug on my 23 gallon tank because it had a leak (was fixing it with seam seeler)-- and it poured probably a good 8-10 gallons of gas out. Clearly I had not run out of gas the day before.

So this evening, I took it out for a drive- city streets, about 3 miles to dinner, never getting it over 40mph. It started stalling again. It sputters like its gonna die and then dies. I rev it up and it fires right back up. After I parked and had dinner, I put another gallon of gas in it to make sure it wasn't just extremely low-- fired it up no problem.. started driving it home and it started to do the same thing.. I did notice a couple of backfires this time and looked back to some smoke ting out. I pulled over, fired it up again and kept the RPM's reasonably low and never got it over about 30 mph-- seemed to be running smooth... as soon as I punched the gas... backfires, sputtering, stalled out.

What is going on? I was really hoping to have it running for the Platte River meeting this weekend but there is no way that I can take this thing out like this. It is entirely too unpredictable. I am at the point of taking it to a mechanic to check it out but I was really hoping not to.

Thanks for reading-
Eck

I'm definitely not an expert, but if it's carburetored , I wonder if the float is sticking.

Had mine quit in tunnel number 5 in clear creek canyon once...right in the middle of it! That was a bad (brand new) fuel pump. I've also had it do exactly what you described twice and it seemed to be the fuel filter. Hope to see you there. Peter

If I remember correctly you've replaced pretty much the entire fuel system, right? Pump, lines etc.? Do you have a fuel pressure gauge? Have you checked voltage at the fuel pump (vaguely recalling that you went electric)? Have you checked spark again? How about timing?

Look at all the fuel connections from the tank forward. A loose connection before the pump could suck air and not necessarily leak fuel out.

Checked all fuel connections this morning and they all seem to be tight. Fired it up this morning, and am getting 5psi on the fuel pressure guage. Should I fill the tank to see if that helps? Right now there is probably only a couple of gallons in it. Although it would really piss me off if everytime the tank gets below 5 gallons or so, it acts like this. Like I said-- I don't know what to do and I have been chasing this damn thing for months now and I just can't imagine it is vapor lock or something like that. It happens when I drive under 40mph for 15 minutes when the outside temperature is less than 80*.

It doesn't sound like vapor lock to me either.

I also doubt that the tank being low would cause it either unless you are on a hill or something and fuel isn't staying at the pick up tobe.

Here's a thought. Any chance that the pickup tube has been dislodged inside the tank or is leaking air into the system?

I suppose it could be possible, but I doubt it. The Bronco is getting enough fuel to start. I started it this morning and was getting steady pressure. If the pick up tube were dislodged, I'd think I would have problems starting it, not just stalling and backfiring.

I agree, it seems unlikely. You said that it's dying when it's under load? Can you floor it and really go?

So after it stalled last night, I was able to start it right back up and cruise in 2nd gear going about 30mph for a mile with no issue. As soon as I floored it, it missed, backfired, and then felt like it lost power before crawling to a slow and stall. Does that make sense?

With the fuel level being low in the tank and the pump not mounted below the tank the carter may not have enough power to pull the gas out of the tank when the level is below the pump. Thats why all instructions say to mount the pump lower than the pickup tube. How is your mounted?

or, heres another possibility............your new tank has welding and grinding crap that didn't get totally cleaned out of it.

under light conditions the fuel flow in the tank isn't sufficient to pick up the debris but under load it does ?

Fuel filter

Typically when I floor it and it starts to stumble-- once I back off, its too late and stalls out. I have read that the backfiring could be a timing issue, so I am wondering if the distributor might by bad. I am also wondering if the new tank could have a multitude of debris that is clogging the fuel filter. I suppose I could put a cheaper, clear filter in and see if that helps.

How much stuff would have to be in the fuel/tank to clog a fuel filter enough to cause this?

I think it's the fuel filter and here's why. When I put in my new tank I was having some similar issues (not as bad as you describe, but hesitation under load). I took off the filter, which had been new, and when it dried I pounded it in the work bench and a varnish type crap came out in little pieces. I think it was like a clogging artery and under the stress it doesn't let enough fuel to pass through. Since they are so cheap, give it a try! Peter

I doesn't take much to clog a filter so that it won't allow high volume, yet it will allow the vehicle to idle.

I agree, sounds filter related however I will add that when mine had a carb I tried to add a fuel pressure regulator and found it did the exact same thing you are describing. I pulled the regulator and it ran fine. May be worth a try since this stalling sounds different than your last round of stalling.

Yah-- I am gonna give a new fuel filter a shot. What sucks is I bought a more expensive filter from JEGS when I put the new fuel pump on. I can see that as the fuel level gets lower, their is less volume for the sludge and debris to be in so it could pull more of it out.

Crawler-- I do not have a pressure regulator, just a guage. The Carter regulates it's own pressure.

ZOSO-- the pump is installed about 12" away from the tank and actually sits below the fuel line. So it sits below the pick up tube and above the bottom of the tank. From what I can tell, I have it installed in a pretty optimal spot.

Hopefully a new fuel filter will do the trick...

Good luck! Hope to see you on Sunday.

Ok so I obviosuly did not make the event today. Put a new fuel filter on, and that did not fix my problem. I am seriously getting frustrated with this thing. I warmed the engine up for about 15 minutes before I started driving. Drove it for about 2 miles and really tested it-- got it going into some high RPM's and all was working until all of a sudden, it started to stall out again and die. I can get it started back up, but it starts to stall out again-- especially when I push the clutch in to come to a stop. I did test the battery with the engine on and I am getting between 13-14 volts.

What the heck is going on? I was not having this problem initially when I put the new tank on, and it seems to be happening sooner into my drives now than when I first had it going on.

do you have a catalytic converter?

have you tried a different coil? IIRC booger had a similar issue once with his 83 bronco. Turned out to be a bad coil. I also had a similar issue with my 79 when it plugged the cat.

No cat. I have not tried a new coil because when testing the current one, it shows it's good. Not sure if it could test good but still be a bad coil?

Very interesting, mine is doing somewhat the same thing but I have efi so it seems that it might be the same issue.

Things to consider-- check the carb float level when it starts to stall out to see if it is sticking and not getting enough fuel.

I am also sort of wondering if it is still somehow creating a vacuum. I am not sure how the vented cap is suppose to work, but I noticed that when this starts to happen, I pop the cap off and there is a lot of fumes that come out (I would have thought that the vented cap would release a good portion of this on its own?) Also, when I was pulling the fuel filter yesterday to swap it out, there was less than 3 gallons or so of gas in the tank and as soon as I pulled the filter, gas started a steady poor until I scrambled out from under the truck and pulled the gas cap. As soon as I released the pressure, the gas immediately stopped flowing. I will say I had not driven the Bronco for about a week at that point, so that pressure had been in the entire time.

Is there an easy way to check that vacuum pressure?

The last thing I can think of is that their is still a large amount of sludge in the tank itself and it is somehow getting sucked into the tube randomly when driving and then it clogs up the line. This would mean dropping the tank-- which I would prefer to not have to do-- so this is my last resort.

I don't know how you'd assess the issue of vacuum in the tank, so I'll leave that to others. Given that you've exhausted most of the other options, I'd drop the tank, especially in light of how many problems others in the club have had.