[rockdoc]

The short version:
67 with 2BBL starts and idles fine for 20-30 sec, then won’t idle, stumbles, and dies. Timing, dwell OK, all plugs almost new, new wires. Carb rebuilt, fuel lines replaced a year or two ago.

The long version: All of a sudden I can’t get my engine to idle or run after about the first 20-30 seconds. The car is a bone-stock ‘67 GTO with a 2BBL carb, running on no-alcohol regular gas (always used this).

History: Car had been running rich at idle, and I discovered that my vacuum advance was shot. After replacing it, I checked dwell, timing, and vacuum, all good, it idled well, ran better than ever. Of course to do the replacement, I had the distributor cap off, all inside looked good. Timing was right on so I didn’t loosen the distributor. I did remove and reinstall the (same) condenser.
Recently the car began to run very roughly at idle. It would start just fine, idle great for 10-30 seconds, then begin bucking and stumbling. If I gave it some gas, it would try to run but it finally died. I could see two good shots of gas in the carb whenever I manually hit the accelerator, even after a few days of sitting, so there’s gas in the bowl and the acc. pump is good. I thought this may be due to crud in the carb, so I rebuilt it with a kit from Cliff. When I loosened the gas line, gas spurted out under pressure (float must be good and needle valve must be working). Intake manifold was wet when I removed the carb. Everything inside looked good, but I found that the power piston was stuck (THIS may have been the source of my original running rich problem). I worked this loose and buttoned it all back up. It fired right up and almost immediately began to buck, run very roughly. I tried to keep it running but it finally died with a big POOF out the carb (lots of vapor and some liquid).
Have checked everything I could think of, although I did consider that I could have a bad batch of gas. But the gas is reasonably fresh, was running fine on this tank earlier.

Anyone have any ideas? Could I have screwed up something inside the distributor? Nothing else changed. Right after starting it runs just fine for about half a minute, almost making me think that it’s all good, then it goes to pot. This makes me think it’s something related to fuel/carb. I do have an inline fuel filter just before the carb, with a return line (i.e., three ports on the filter). I have not replaced the filter yet.

Thanks for any ideas!

[hgiv]

So you got a lot going on here because you messed with two major systems. You have a carb that has been "messed with" a bunch. Basically anything is game there. Maybe you messed up the rebuild? Who knows.
Of course you also messed with the distributor so something could be off there too. You got it close enough to start but things are way off.

Start from the basics. Do you have spark at all cylinders? Check the wires. Cap on correctly.
Are your points ok? If you have points.
If everything looks good try pulling the carb. Go through it fully.

Then try again. I know that is really obvious advice but check all the obvious boxes... again.

[rockdoc]

Thanks. The carb has been "messed with", but I am confident that it's good. If I did screw up the rebuild, I screwed it up so it's the same as it was before (not my first rebuild). Float adjustments are right on, needle valve is closing. It doesn't leak down, there's gas in the bowl after a week, good squirts from the acc pump. I did NOT remove and replace the power piston after freeing it up. Did install a new power valve (on the bottom of the bowl). There really isn't a lot of stuff to do inside the Rochester 2 BBL, but maybe I missed something.

I didn't really mess too much with the distributor, I just removed the cap and replaced the vacuum advance. Admittedly I could have done something, but I don't know what. I did remove and reinstall the condenser, will replace it with a new one today, as another guy said he had exactly the same problem and that's what it was.

The strange thing is that it runs beautifully for the first 30 seconds, idles smoothly, dwell right on (yes, I have points). I did recheck the dist cap, all plug wires, etc. I'll go over it once again, check all the obvious and simple things again.

[Geoff]

If the carb has a choke, make sure it comes off as the engine warms up.

[rockdoc]

Yep, carb has an automatic choke. As it's warm right now, the choke is almost completely off.

Thanks for the suggestion.

[PontiacJim1959]

Wrong gas cap? Make sure you have the correct one for your year, vented/non-vented, and check your tank venting lines/hoses if so equipped.

The "sock" on the end of the fuel pick-up/sender in the tank has collapsed or is plugging the end of the tube so it cannot suck the gas down the line. Could also be something floating around in the tank, like a rag, and it has caught & covered the pick-up tube - which happened to me with a car I purchased as someone must have used the rag in place of the gas cap they lost and it went down into the tank.

Torn, cut, ripped, collapsed rubber fuel line. Looks good on the outside, but..... Ethanol gas will eat and/or deteriorate rubber gas line. Check front & rear lines and simply replace them for good measures. But, before putting on the hoses, blow air through to make sure something is not lodged in the steel line - this has happened.

[Tony_D]

I recently resolved a 'stalling' problem on a 1987 El Camino that I traced to a collapsed fuel hose at the gas tank as PontiacJim stated.

Does the car stumble and die after coming off the choke? Could be a vacuum leak; can you check your new vacuum advance unit? If automatic trans, did the vacuum line to the modulator come off at the trans? Had that happen before also...

Does it restart immediately? If so, that would rule out fuel starvation but I would check the fuel filter just to be sure.

Could it be due to a rich condition after initial cold start? Not sure what could cause that and usually associated with black smoke, but just throwing it out there.

[rockdoc]

Good suggestions, thanks for all them!

I have the original gas cap that I've been using for over ten years, haven't messed with it. I'm pretty sure I don't have a plug/restriction in the fuel supply, as I have loads of gas (too much at this point). When I loosened the inlet line at the carb, gas spurted out. I've checked the acc. pump several times, often days after I last started it, and I get two good spurts of gas. I also have two good spurts AFTER it dies. All lines have been replaced, including the hard line from the rear (that was fun with body on frame!), perhaps a year or two ago.

I did check the new vacuum advance after installing, and it holds vacuum and I have good engine vacuum, although I haven't checked it lately as I can't get it to run more than about 30 seconds. I did check timing with and without vac advance hooked up, and it looked good.

Another guy suggested that I replace my condenser, will do that and report back.

[66sprint6]

If you want to eliminate the gas tank and fuel lines as an issue, Simply run the line from a small gas can to the fuel pump and see if that makes a difference.

[GT182]

Rocdoc, is the coil ok? That could cause it to not idle and quit running after 20 to 30 seconds.

As for the points distributor, the best cure for it "if" it's acting up is replace it with a HEI distributor. I replaced mine with HEI and I've never looked back. And I've never had a problem with this HEI distributor either.... knock on wood.

Yeah it's not correct, but the engine always starts.

[gtospieg]

Rockdoc....Had your car been sitting for any length of time before these problems started? The reason I ask...a friend of mine had what sounds like a very similar problem. The car would start and run fine and then start to stumble and die. He could wait a while and try again with the same results. The problem ended up being a plugged exhaust...those damn critters. I don't know if that's your problem but it's worth a look. Maybe disconnect the exhaust and see what happens. Good luck...

[rockdoc]

Thanks for all the tips!

I was convinced this was a carb/fuel problem, so I went through the carb again. Verified that I had fuel, float and needle were working. I had removed the condenser when I installed the new vacuum advance, so on the advice of BLK69JUDGE I installed a new Blue Streak condenser, something easy to try. When I installed it, I noticed that the connection on the wire to the coil was very loose and tried to tighten it (breaking one of the tabs off in the process). I was able to solder the wire onto the connector and button it back up.

It fired right up and stayed running well!!

I don't know if the condenser was bad, but I think the problem was probably a very poor connection on the wire to the coil. I have since replaced it with a new one (including grommet), and it literally runs better than it ever has.

In the process I've solved the problems of poor idle (inoperable vac advance), rich idle (stuck power piston).

Time for a drive!

[gto19]

Awesome!

When you say condenser . Do you mean the condenser by the voltage regulator?

[Geoff]

I think he is referring to the RF suppression condenser that connects to the coil [+] terminal.

[rockdoc]

Sorry not to be clearer. The condenser I was referring to is the one mounted on/in the distributor, under the cap and centrifugal advance weights. I have points ignition still. The condenser connects to the same post as the wire from the coil (negative post), so in removing the condenser I likely disturbed the coil wire connector which was frayed and loose (I later discovered).

As an aside, I was going to simply put a new spade-type connector on the end of the wire, but I could not find the "flag-type" spade, the type that goes in from the side rather than the end (I could find them online but I didn't need 20). So I bought a new wire with connectors.

[DANTIP]

Thank you for sharing the root-cause and remedy!! I find it very helpful when people take the time to document the fix!