: 472 starting/ smoking problem



Dav68Caddy
05-15-04, 02:19 PM
My Deville convertible ('68) has been "in storage" for 2 years; started it once a month during that time. Always had to 'prime' it with a little gas down the carb, even though I had installed an electric fuel pump, and it wouldn't run well until warmup - black smoke. I had it towed from Phoenix to Tucson (120 miles) as I had the dash and instrument cluster taken apart and no place to work on it and this somehow affected how it ran??
Anyway, since I have a garage now, I rebuilt the Rochester Quadrajet hoping this would get her running okay again. Replaced it in the yard where she was being kept and she fired right up (no priming) and ran fairly well at idle. I was amazed (great carb rebuilder that I am).
Now the question part - I had her towed across Tucson (30 miles) to her new home and when started, she ran like s***. Wouldn't idle without using the gas pedal and thick black smoke out the pipes.
Been tinkering with the carb, but doesn't seem to help. Checked firing - didn't seem to spark at plug-wire end - checked with timing light on wire and it didn't light. Sooo I changed the points (slightly pitted). Now the timing light worked, but didn't improve the performance. Started thinking I imagined it not sparking before.
List of possibilities (check the one(s) you think it is)
1. Ignition - I'm not very good at point gap, but didn't mess with the original set. Gapped the new set correctly?
1a. Would a bad coil do this? Would towing a car somehow affect this?
2. Carburetor - thinking about changing to an Edelbrock anyway.
3. Vacuum - think all the hoses are hooked up where they should be.
4. Anything else - I haven't worked on cars since moving to Tucson, so don't remember a lot.

I rebuilt the 472 a year prior to moving. Ran great then.
I know this is a lot to read, but hopefully i can get some input; hopefully I'm not rambling so much that you don't know what I'm asking.

Thanks Dave

Dav68Caddy
05-20-04, 01:27 AM
Hopefully, I found my own trouble - it helped to look thru past posts here. I tore the carb apart again; everything looked fine, but I filled the 'sore spots' with a JB Weld type stuff (can't remember the right name, but where the little freeze-plug type things were (4) when they cast the carb.) Apparently (hopefully still), the bowl(s) was leaking and mimmicking a rich mixture to the cylinders. I originally had a thin metal plate/ gasket along with the 'asbestos' gasket under the carb, but my brother-in-law talked me into leaving it off. It's back on now and I don't have the 'steam' (fuel vapor) problem now.
She's running pretty well now (Wednesday - 9 o'clock). If she runs like this tomorrow (and the next day...) I'll be very happy and KNOW that this was the trouble/ solution.
Also, I've installed the Pertronix electronic ignition (no help, but no more points either) Have a Flame-thrower coil enroute (40,000 volts won't hurt either)
I LOVE this forum - thanks all.

Dav68Caddy
06-08-04, 12:19 AM
I'm pretty sure I have the problem licked now. Started having trouble again after the last carb rebuild. No response and intermittent backfiring when throttling (punching it). Got to the oint where it seemed like the throttle was stuck - wouldn't stop revving.
I was all prepared to get a new carb, but found out the linkage on Edelbrock's Q-jet replacement was made for GMC and Chevy only - buttheads.
Took the top off the carb and noticed some spill-over into a cavity that shouldn't have any. Voila - float was set too high. I knew the float setting was important - now I know it's actually crucial. She's running great now, better than I remember she ever ran. Passed the start-and-run test the last 3 days; almost ready to uncross my fingers.

limousine rider
06-09-04, 08:51 AM
i have a quick question to ask, why did you put an electric fuel pump in? :tisk:

Dav68Caddy
06-09-04, 10:26 PM
Electric fuel pump - hmmm. Seemed like a good idea at the time. I didn't drive the car much (every coupla weeks or so) and it wouldn't start after sitting that long. Changed the carb twice (first to see if this was the problem and then 'cause I had a warranty on the first one - I never do anything simple) Changed the fuel pump also. If I primed the carb, she'd start. After reading about the problem(s) inherent to ALL Quadrajets, I'm thinking it was a leaky float bowl, which I've repaired on the existing carb (I hope). In short (too late??), I'm considering going back to the old pump. I'm all gung-ho again (new garage to work in), so she may not sit for any longer than a day or so and the problem(?) won't return anyway.

MMNineInchNails
06-11-04, 03:46 AM
What kind of fuel pump did you put on and what kinda psi is it running?

Dav68Caddy
06-12-04, 12:26 AM
Honestly, it's been so long ago (about 11 years) that I put the electric pump on that I don't even remember where I bought it. It's just some sorta generic brand (no label anymore) and i don't remember the psi rating. Still have the original type fuel pump attached to the block (needed it to plug the hole) . Need a fitting for the outlet and I'll try it to see if it still works - running it dry like that may have damaged the diaphragm.

jk1000
06-12-04, 01:52 PM
just my 2 cents worth.

1.) I would check fuel pressure (as mentioned in a previous post), if memory serves the fuel pressure should be in the 5 to 6 psi range, anything higher could cause the needle valve to be lifted off its seat.
2.) Thick black smoke is generally caused by a very rich fuel mixture.
3.) Float adjustment is critical (I don't remember the exact numbers, it has been quite a few years). Also, replace float when rebuilding carb, the solid floats tend to absorb fuel with age making it slightly heavy and causing a rich mixture.
4.) Add a fuel filter just before carb inlet. Some will argue this is not necessary (but I strongly believe it is). On many occasions I have seen a very tiny particle of dirt make its way to the needle valve and lodge between the valve and seat. In mild cases it would cause a super rich mixture and very rough running. In other cases, the engine will die and fuel will flow out the top of carb while cranking. I have always added a glass filter (the type with a replaceable element) with a carb rebuild for piece of mind.

Good luck

Dav68Caddy
06-13-04, 12:51 PM
Everything you've said is so true; figured the float level to be the problem (after three tries I got it adjusted correctly). I thought it may have been the float itself, but didn't know where I could get a new one. Gonna go back to the mechanical fuel pump because I found out the electric has a 5.5 to 9 psi range (I thought it may be unseating the needle also). I have noticed that the pump doesn't want to shut off when I know the bowl is full, if it should.
Right now, all is well. Idles just a little rough, but haven't really spent much time adjusting the idle mixture screws - don't have a really accurate tach. I installed the inline fuel filter soon after I bought the car (10 years ago) when I changed to an electric pump. There is also one just before the pump, although I no longer have the in-bowl ceramic one installed.
Thanks for the advice - now it's on to my faulty climate control.

Angela Desmond
06-13-04, 07:45 PM
4.) Add a fuel filter just before carb inlet. Some will argue this is not necessary (but I strongly believe it is). On many occasions I have seen a very tiny particle of dirt make its way to the needle valve and lodge between the valve and seat. In mild cases it would cause a super rich mixture and very rough running. In other cases, the engine will die and fuel will flow out the top of carb while cranking. I have always added a glass filter (the type with a replaceable element) with a carb rebuild for piece of mind.

I agree entirely about using the extra filtering, but remember to keep an eye on them. Edelbrock uses tiny (almost microscopic) screens inside their carbs and many people don't put them in during a re-build, but the extra fitering never hurts, as long as you remember they're in there and could be clogged if you're having carb problems. I replace them when rebuilding one.

limousine rider
06-14-04, 02:34 PM
your:welcome:

Dav68Caddy
06-21-04, 09:05 PM
Thanks all for the input - it has helped me and hopefully will continue to help others thru the archive. I'm finally convinced that I shouldn't have any more problems (engine-wise anyway) as my 'honey' runs great again. I still have the electric fuel pump on; don't wanna fix it if it ain't broke. If/when it does need it though, I intend to go back to the manual pump. Can't find an outlet fitting for the pump locally (it goes straight out towards the fan belt) and forgot to look when I was at the salvage yard today for the original line assembly.
Anyway, anybody with a working climate control on a 67 or 68 deVille, please see my post on 85 and older re: climate control. Thanks again.