1967 Eldorado rough starting and running issue

[67_Eldo]

A week ago, I hopped into the ol’ Eldo on a sunny morning and turned the key. Instead of immediately springing to life, I heard the depressing (slow) rawr … rawr … rawr … click, click, click, <silence> that we’ve all heard when a battery is almost dead.

I hooked up jumper cables and turned the Eldo’s key again. Click, <metallic stutter>, click, <silence>. That made me realize I had battery-terminal corrosion instead of a dead battery.

I cleaned off the battery terminals and clamps with a wire brush and some baking soda, coated the connecting surfaces with a bit of petroleum jelly, hooked everything together, and turned the key once more.

Varooom! The engine immediately started and, equally immediately began to slow down, stutter, cough, and, within five seconds, die. Subsequent turns of the key resulted in vigorous starter action, but no actual start. It sounded as though there was no spark. (The carb was new three weeks ago.) By the time I gave up cranking, there was gas all over the place: It was coming out of the top of the carb. But I figured that under the circumstances, it was flooding as cars without spark tend to do.

Checking the ignition system, I found I was getting spark out of the coil but not out of the distributor.  I replaced the distributor cap and rotor, as well as the plug wires. The spark plugs were new three weeks ago. I quadruple checked the plug-wire order â€" 1-8-7-2-6-5-4-3 â€" so I know that isn’t wrong.

I turned the key again and after a long period of cranking, the engine came to life in a very shaky fashion. By holding the throttle down at least 1/3rd of the way, I could keep it alive, but there was no way it could idle normally. I kept it running until the engine began to warm up, thinking it might smooth out. By the time the temp gauge hit 160 degrees, for example, you’d think that any of the plugs that had been fouled by too much gas the day before would have dried out? But the roughness never went away. I tried to drop it down to idle speed, and it stumbled and died.

I made a short video of its behavior (which has remained the same) two days later. In this case, the engine is starting cold.

https://youtu.be/dJzK5rdjUzk

I don’t want to believe that my timing chain has slipped a notch. All of the timing pieces â€" cogs and chain â€" are pure steel (no Nylon in sight) and were installed a mere 3.5 years ago.

Does anyone have a suggestion that doesn’t involve removing the nasty 1967 timing cover?

Thanks!

P.S. I’ll clean up the plug-wire organization once the engine is running properly. :-)

[fishnjim]

Just a thought, but I suspect your choke wasn't open.   Sometimes, when they flood, the gas flashes off and cools the carb, so the choke stays shut.   We used to stick a screwdriver down it, to hold open until it ran OK.   
I'd inspect everything that has been changed, because our old friend NASA troubleshooting asks, "what has changed in or around the object that might cause the problem?"

[wrench]

Or, since it was a cold start, maybe the choke was not closed.

Does sound like a choke issue.

[67_Eldo]

I gave the choke idea a quick shot (as it started to rain), but with the choke open, it won't even begin to start.

Thanks for the idea, though!

[35-709]

"(The carb was new three weeks ago.) By the time I gave up cranking, there was gas all over the place: It was coming out of the top of the carb."

Sounds like a stuck float to me if it floods that badly and the fact that it is a new (new or rebuilt?) carb just makes me more suspicious.   
I ask new or rebuilt because in a '67 that should be a Q-Jet and a correct "new" one would normally be hard to come by these days.

[67_Eldo]

It's a rebuilt carb. I matched the number on the carb I had with the rebuilt carb I bought.

The QJ that was originally on my car (when I got it) was a 1969-vintage model (according to the carb number). But if you look in the Cadillac parts book, it lists the same carb part number from 1967 to 1969: the carb numbers for the (1967) 429 and the early 472 are the same!

However, the QJ experts claim that there were internal improvements to the QJ between 1967 and 1969. So if you have a '67 or '68 QJ, it is best to move up to a '69 QJ anyway.

I've been running that new carb for almost a month and it has been perfect. My O2 sensor stays between 13.5 and 14.4 under practically all conditions.

I'll pop the top of the carb to see if the float is sticking. We'll see.

Thanks!

[cadman56]

granted your engine may be flooded now, but, check the choke pull off diaphragm.  It may have failed.  An immediate start and run good then quickly start running rough, slow , then die  is a classic sign of a failed pull off diaphragm.

[35-709]

Yes, another good possibility.

[Daryl Chesterman]

It appears that the choke butterfly is wide open in the video that you posted.  Was the engine cold when you did the start for the video?  If so, the choke system might need to be checked to be sure that all of the adjustments for it are correct.  Is it an electric choke, or is it a hot air choke?  If you have a helper, you can manually play with the choke butterfly, once the engine starts, to see if closing the butterfly a little, or a lot, improves the smoothness.  If it does, the choke adjustments may be the problem.  The choke butterfly should not be wide open on a cold engine start-up.  If the carburetor has a vacuum choke pull off, once the engine starts (when cold), the pull-off will open up the butterfly a certain amount (whatever the specs call for), and from there, the bimetal coil in the choke housing will open the choke the rest of the way as the engine warms up.

Daryl Chesterman

[klinebau]

You might also try changing points and condenser.  I have sometimes had weird symptoms when the points failed.  After I overhauled the fuel system on my car, it was hard to start and sputtered.  I thought for sure I messed something up with the fuel system, but it turned out to be failed points.

[67_Eldo]

Given the carb comments, I think I'll put my old carb back on and see what happens. If it works, then I'll send the new one back to be checked.

As far as points go, I've got the Pertronix Ignitor I system. Given that the mechanic who replaced my transmission's vacuum modulator last year (under warranty) fried my Flamethrower coil by leaving the key in the ACC position for a while, I thought the Ignitor finally died too. So I replaced the no-name coil that the mechanic installed plus the Ignitor I Hall-effect sensor. When I pull a plug wire and crank the engine, the spark seems quite strong now.

Pertronix Hall-effect Ignitor I advice: The gap between the Hall-effect sensor and the magnet-encrusted ring you install above it has to be held to a very small distance (e.g. a millimeter or two). Given that precision requirement, you'd think that all Pertronix Ignitor I sensors come out of the box adjusted to a precise height. That is a bad assumption.

When I installed the replacement Ignitor I sensor, it just barely made contact with the Hall-effect ring. In other words, the sensor height was 1 mm greater than the old Ignitor I sensor I had just removed. If you swap Ignitor Hall-effect sensors, get out your calipers and measure the sensor height before screwing it into your distributor.

The Pertronix lobe-sensing (LS) versions of their products do not suffer from this problem since they don't require a Hall-effect halo.

Thanks!

[67_Eldo]

You carb guys were right!

I bolted on the old carb (with an extra gasket between the base of the carb and the stainless-steel shim), turned the key, and it started immediately. It didn't even need to crank to get gas to the carb.

Of course, given the leaky nature of the old carb, it doesn't idle perfectly smoothly. But it idles, which is a lot more than I could say before.

Thanks for pushing the carb-based solution! It's a hell of a lot easier to deal with than the timing chain. :-)

[klinebau]

You will be better off getting your old carburetor rebuilt than using a "generic" rebuilt carburetor.