Running great, then running terrible

[wegngis]

I'm going to throw this one out there to get everyone's take on it. My EB has gone from running great, to running bad, back to running great, to running terribly in a very short time period. Yesterday it was running bad so I thought I'd check the timing. It was advanced too far, so reset it back to where it needs to be and it was running very smooth. Took it for a test drive and everything was great. I took it out about 15 minutes later and as soon as I got out of sight of my house it started backfiring and stalling, and running really rough. It was so rough it was almost as if every-other cylinder was firing.

Now I can't get it to even idle without pumping the gas. It runs strong, then starts to gag then tries to die, no matter what the rpm's happen to be. The only thing that keeps it running is by pumping the gas a little. Then it pops back to life, only to try dying again in another 10 seconds. All this while continuing to run rough.

The following parts are 15 months old:
Dist. cap, rotor, plugs, points (oh how I hate points) and condenser. Plug wires are about 3 years old.

Help!

 

[70_Steve]

Carb? Floats may be stuck and holding the needle valve closed.

 

[MattW]

Carb is my guess too.

 

[wegngis]

I just replaced the float and needle 15 months ago, too. I've thought about pulling the carb and just rebuilding the whole darn thing. I've got the rebuild kit.

 

[1970mule]

could it be maybe you picked up some trash from one of the tanks? did you take the tank all the way to empty, that maybe i, and when is the last time it was cleaned?

 

[73azbronco]

water in tank resulting in gas in float bowl?

 

[Viperwolf1]

Forget to tighten the distributor back down?

 

[wegngis]

Forget to tighten the distributor back down?

You mean the cap?

 

[wegngis]

water in tank resulting in gas in float bowl?

You mean getting water in the float bowl? Forgive me, I'm slow sometimes.%)

 

[Viperwolf1]

You mean the cap?

No I mean the hold down bolt and clamp.

 

[wegngis]

No I mean the hold down bolt and clamp.

You're just referring to the one bolt that holds it in place after you adjust the timing, right? Yes, I did tighten that. There's nothing else there that I'm missing, is there? Just the one bolt?

 

[gearida]

I would have to agree that you have a fuel problem. Check for a dirty tank or bad gas. rebuild the carb and replace the filter. Look at your rubber line or replace it, sometimes it will come apart on the inside and pieces of rubber will lodge in the carb. How about vapor lock? Or maybe a bad fuel pump... just ideas to check.

 

[wegngis]

The fuel hose is only 15 months old too, so that's covered. The mechanical fuel pump was replaced with an electrical, but that was about 5 years ago. I suppose I could pressure test it!

I'll pull the carb, rebuild, and go from there.

 

[Viperwolf1]

You're just referring to the one bolt that holds it in place after you adjust the timing, right? Yes, I did tighten that. There's nothing else there that I'm missing, is there? Just the one bolt?

One bolt with a clamp under it.

 

[mcdobson]

Is the timing jumping all over the place?
You may be in need of a new timing chain and gears.

 

[wegngis]

Is the timing jumping all over the place?
You may be in need of a new timing chain and gears.

No, it was just out of whack, I think. I reset it and then it stayed.

 

[Broncotj0]

I ran into a problem kind of like this on a '77 Scout. It would run fine for about 20 min or so and then it would try and backfire through the carb and spit and sputter. You could be driving it and at one stop sign you would have to double foot the peddles to keep it running and the next it would be running at 2000 rpm's. It had a rebuilt 2V motorcraft carb on it that I just rebuilt and all new fuel lines and filters. It ended up being that the distributor weights were sticking so it was technicaly advancing and retarding itself. You say you have replaced the distributor but that is what I found to be wrong with this truck.

 

[wegngis]

I only replaced the distributor cap, not the distributor itself. I'll keep this one in mind. How were you able to diagnose that problem with the distributor weights?

 

[ugly74]

that sure sounds like a teeny tiny goober floating around in the carb to me.
if it's some where in the float bowl, it's not necessarily always gonna get in the way of a metering orifice...so it may run great, then like shit, then great, etc etc.
take it apart, blow out the idle circuit at the very least, and then put it back together.
I recommend putting an additional filter as close to the carb as possible.
my problem always seems to be from removing the fuel line, and then reinstalling it, and accidentally shaving a sliverof rubber off the line, which leads to a PIA. a filter right at the carb eliminates that

 

[Broncotj0]

I pulled the distributor out(marking where the rotor and everything was) and started to take it apart. In the bottom of the distirbutor there are two weights that open and close. They are spring loaded and run on say guide pins. On this distributor the pins had small bushings on them and they were all torn up on the one side and the other side didn't even have one. The weights were all gummed up and did not move freely. You could spread them apart and being spring loaded they are supposed to come back together. These would not. They would stick spread apart. It's worth a try. I have a friend with a '78 ford truck that this same problem happened to.