Stumped in New Mexico

[robox]

Hi folks-

This is my first post here.

By way of introduction, I am not new to forums and I'm also not new to working on cars. Although I will say that working on gasoline engines is not really my strong suit; I'm a bit more familiar with diesels.

I owned a 1971 240Z in my 20's, and I bought another one about a year and a half ago. I bought this Z in southern California and drove it home to northern New Mexico. The car is in decent condition, although it took a lot of tinkering to get it back here.... new plugs and a few filters along the way... but it did make it.

It's been basically sitting for the last year and a half. I drive it every once in a while just to keep it alive.

Well, about a week ago I decided to give it some attention and get it to run better. I drove it into my workshop (yes it was drivable a week ago) and installed a Pertronix Flamethrower coil and replaced the points with a Pertronix Ignitor. After that, the engine fired right up. At that point I decided to do the timing, and I observed that the pointer on the crank pulley was showing at about 35º on the little scale (which only goes to 30º). My old Chilton manual said it should be about 5º, and I'd read online that it should be around 10º, so it was way off. I moved the distributor and got it to be about 15º, which caused the idle to go way down, but the car was still running. At that point I shut the car off, and pulled the tops of both SU carbs to clean them up a little (I could see some oily residue on the round slides which I wanted to clean.) After cleaning up both slides and reinstalling them, the car would not start. Almost a week later, after doing lots of work, I still cannot get the engine to start again.

Things I've done:

• Adjusted valves (twice)

• Put timing back to 35º, and every other setting you can imagine

• installed new plug wires

• Cleaned and gapped all plugs

• Checked fuel levels in the float bowls with the 23mm clear tubing method

• Verified good fuel pressure out of pump (visual verification only; watched fuel squirt out of float bowl tops into plastic container while float bowls were disassembled)

I also checked compression, which came in between 122 and 132 for all 6 cylinders. I understand these are fairly low numbers, although I have a mechanic friend who assures me they are not TOO low. In any case I'd have a hard time believing that compression was my problem, as the car ran OK before I (minimally) messed around with the carbs and the timing.

What I can get the car to do occasionally is run VERY poorly for a minute or less. It typically dies on its own. Also it does not respond to throttle, throttle usually kills it. From feeling the headers after the engine dies I can tell it's usually only running on 2 cylinders, typically 1 and 6. Sometimes I will hear what sounds like detonations in the exhaust pipe. Also when it does run, it frequently coughs big spurts of air-fuel mixture BACK out of the carbs.

Other info: I am at 7000 feet elevation. It frequently seems to me that the carbs are too rich. I currently have the mixture nuts turned down about 1 turn, although I have played with settings between one-half turn, and two turns. Also, it got quite cold here right around the time the engine stopped starting, probably averaging in the 20's in the last few days. I did put some work lamps on the engine for a few hours this evening in an attempt to warm things up, but the car still would not start. Also, the engine seems to want to run on starting fluid, although at the moment I am out of it. Also, right around the time the engine decided NOT to start again, I filled the fuel tank (but I can't see how that could be significant).

It's a mystery to me.... as well as to my mechanic friend.

Any insights would of course be appreciated.

I am going to post this in both the HELP ME! section as well as the general engine section, because, not being too familiar with this site, I'm not sure which is really the right place.

Thanks again,

Christian

[Dr. 240Z]

I'll step up and make the first guess/suggestion: Revisit the fuel system with a thorough cleaning from the carbs to the tank. After that, compliment the cleansing with a new fuel filter.

[gogriz91]

I had a 260 with an electric and a mechanical fuel pump on it. Went to Yellowstone (7500 ft), vapor lock, fuel starvation, bought an electric fuel pump to replace the one by the tank which apparently hadn't been working and that seemed to fix things. It seems heat from the exhaust manifold and elevation were preventing enough fuel from getting to the carbs even though I could see fuel getting pumped in to them, it apparently wasn't enough.

I'm presuming you only have a mechanical fuel pump?

Edited November 28, 2013 by gogriz91

[robox]

Thanks guys for the replies.

In retrospect, it seems like a dumb idea to post this same post in two different places on this site, so I am going to end this thread and move the discussion over to the other place I posted it, which can be found HERE.

I will reply to you guys over there.

Thanks again!