Rochester carbs really getting under my skin...

[martyscarr]

Well.... I found the problem, but this really confuses me.

Something caused the fuel in the float bowls to gel. The fuel in the lines is good, no gel upstream of the sintered brass filters. but in the float bowls, and throughout the passages, there were globs of gelled fuel.

This isn't contamination from the tank or lines, and it's not left over varnish. I chem dipped and scrubbed the carbs and blew the lines out before rebuilding them initially. I also drained the tank and lines, changed the filters, and refilled with new gas at the beginning of this whole process. The only thing I can think of is some kind of chemical or microbial action that caused the gel... I've seen this with diesel, but never with gas. At least it explains the crazy shifting symptoms as passages blocked and cleared.

Anyway the carbs are all cleaned up and back on. Hopefully whatever caused the problem is out of the system. Time will tell.

Glad you found the problem. I had a similar issue a few years ago, did your gel look like this?

I never did figure out what caused it, only happened once but was a mess.

Marty Scarr

PS What brand of gas are you using?

[scottydont]

Similar looking Marty, but mine was a little more brown colored. Also no globs that big (BTW isn't that on the fuel line side of the filter? Mine was all in the float bowl, the lines were clean.)

Anyway, I have the carbs pretty well tuned. It's a little choppy at idle, (dunno if that's normal or not) but considering the NEW problem I had this morning that might pass....

Apparently I'm getting fuel running down the carbs and into the engine. Enough that yesterday before I removed the carbs, the engine was hydraulically locked. I assumed at the time that goo had caused a float needle to stick open or something. It was locked up again this morning though and there was at least a quart of fuel in the crankcase. So I pulled the plug and let it drain while I went to the parts store to get more oil. 45 min later it was sill dripping oil/gas at the drail plug at about a drop every two seconds, so I MAY still have a fuel leak at the carbs.
This is one very reluctant engine.....

[scottydont]

I heard a guy in my club say if you rebuild a carb, run the engine, and let it sit for three months, you will need to tear the carb down and rebuild again. The problem is the gas we get these days, particularly the alcohol gas. For mine, I use gas with no alcohol, very expensive, but seems to help. Not sure if this is what is happening, but maybe some Stabil would help?

I definitely haven't left this engine to sit for three months, and the carbs seemed ok except for the sterno that formed inside them. Along a similar line though, I have heard that the oxygenated fuels that they use in emissions areas will eat the rubber carb parts on some older cars that used natural rubber. My dad had this problem on the stock carbs in his old MG. But I expect that the carbs and kits on the corvairs probably don't use natural rubber parts. Besides, I live in a non-emissions area and we don't have oxygenated fuels. As far as alcohol goes, most of the carb cleaners and water removers contain alcohol (suggesting that it is unlikely to damage the carbs).

[martyscarr]

Similar looking Marty, but mine was a little more brown colored. Also no globs that big (BTW isn't that on the fuel line side of the filter? Mine was all in the float bowl, the lines were clean.)

Anyway, I have the carbs pretty well tuned. It's a little choppy at idle, (dunno if that's normal or not) but considering the NEW problem I had this morning that might pass....

Apparently I'm getting fuel running down the carbs and into the engine. Enough that yesterday before I removed the carbs, the engine was hydraulically locked. I assumed at the time that goo had caused a float needle to stick open or something. It was locked up again this morning though and there was at least a quart of fuel in the crankcase. So I pulled the plug and let it drain while I went to the parts store to get more oil. 45 min later it was sill dripping oil/gas at the drail plug at about a drop every two seconds, so I MAY still have a fuel leak at the carbs.
This is one very reluctant engine.....

Yes, that picture is of the bronze inlet filter. I also had a canister filter in the fuel line before the pump. It was full of that crap. Cleaned it all out, never happened again. Very strange.

You have an electric pump on your engine, do you know the pressure output? Ideal pressure is 2.5 - 4 psi.

Are you parked on a slope, with the nose of the van uphill? A bad float can fill the crankcase when parked like that.

[davemotohead]

Gee wizz Marty,,looks like jelly beans in your filter? that is weird? I have not had any problems with weird stuff like that with the new gas,I have cars that sit for months and they fire up with no problems,That is just strange.

[scottydont]

In my case Marty, the lines and in line filter were clear. All the "grunk" was in the carbs. So far it hasn't come back, but it's only been a few days.

I was parked on a slight slope (nose up by maybe 4" vs tail), but with the tank above the carbs I could be getting leakage even when parked on the level. The floats are both fine (I checked when I had the carbs apart on friday). So far I haven't seen any additional signs of leakage. Fingers crossed that the gunk in the carbs caused the leakage... I think it's a safe bet since several other metering valves were stuck.

In terms of the fuel pump output, It's rated for 2-3.5 psi. I don't have much faith in the accuracy of the rating, but I doubt the pressure is over 5 psi.

[davemotohead]

Do you have the helper springs on the carb floats and did you see if the floats "Float" when you had the carbs apart? they sometimes spring leaks and sink to the bottom because they are full of gas.

[scottydont]

I do have the helper springs. Didn't float the floats, but I did feel them for the weight of gas inside, visually inspect for cracks, and shake to listen for fuel in the floats. They're fine.

BTW, When I first fired the engine up after all the leakage, it smoked like a mother since the gas filled oil was seeping past the rings. That's dissipated somewhat, but it's still smoking. I'm really hoping that the incident didn't cause some catastrophic damage.

[Jerry Whitt]

An idea has come to mind, that one of the carburetors is a secondary carb, without an accelerator pump and idle mixture screw.

Do both carbs have working accelerator pumps?