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68 Deville Carb question

Started by Doug Sprinthall, August 24, 2005, 09:44:42 PM

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Doug Sprinthall

I have a 68 Deville convert with a starting problem that seems to be getting worse.  If the car has sat for longer than a day, it takes a lot of cranking to start.  It seems as if there is no fuel in the carb and the fuel pump has to re-fill the carb before it will start.  After that, it starts and runs fine.

Anyone else experience this?  The carb dosent seem to be leaking externally so I suspect the bowl is somehow draining.  The last time I took a carb apart, Jimmy Carter had black hair so any suggestions would be welcome.

Doug

Fourcoms@msn.com

I would venture to say you have a tired fuel pump and/or a clogged fuel filter.

John

Doug, Ill answer this the best I can not having a way to draw a picture. I assume on a 68 with a 472 you have a Rochester Quadrajet.You need to remove the carb and in between the throttle plate and the center section in the middle of the two plates you will find an indentation or cut out about 3/8 deep and triangular shaped. In this recess you will see two tubes which are capped with the tube crimped over the cap. Mix a small amount of epoxy and place it in the cavity covering the crimped ends. This will stop the fuel from draining out of the bowl. Be careful not to ruin the gaskets when taking the unit off the car or apart. If you do, any good parts house will have a rebuild kit for it, though if Carter had black hair when it was last removed I believe it is due for a good internal cleaning and resealing.

If you have a shop manual for the car look at the exploded view of the carb to get an idea what Im trying to explain.
Ill check back after to work this afternoon to see if you need a better explanation. Good Luck!
John

steve

jonh is right about your leak.but if you decide to rebuld it make sure the metering rods attached to the top oof your carb are clean. even aftera soaking i have found these still plugged. you can you a very fine piece of wire to run through them.and if they are loose or fall out gently tap/swedge them back in place. also main meter rods are held in w/#6screw between secondary air valve butterflys.carfully remove and lift straight up/replace the same.and last dont over tighten your carb to the manifold you will disstort the body.i cant tell you how many i have had to straighten.my illistration to this fact is if you set a carburator on a motor that is running well.you cant lift it off the manifold with the engine running with a good seal.goodluck and dont rush.

Lynn 10923

Leaking well plugs are common in Q-jets.  But Im voting for a leaky fuel pump in this case.  Even if the plugs leak and the carb drains out, if the fuel pump is any good it will fill the thing right back up when the engine is cranked and it wouldnt take long to start.  A leaky fuel pump will have trouble filling the carb back up at cranking speed.  Once the thing is running it will outpump the leak and seem okay.  I had a 68 once that had this hard start problem, even after the carb had been rebuilt.  The well plugs didnt look like they had been leaking beforehand, and they definitely werent leaking afterwards.

Lynn

John

Well Lynn,
   If you read all the answers to the problem, all of COULD be right. So if you were the owner of the car where would you start......at the cheapest item. The filter. Me, I would install a larger capacity filter before the factory unit in the carb. That thing is no bigger than a thimble. A new pump is about $35-$40. The carb is the expensive part.

   I gotta go before this hurricane here in Ft. Lauderdale takes out my Internet connection.

Good Luck Doug, I hope things work out right for you. Let us Know either way!!!
                       John, in the midst of the storm.
   

Andrew 10642

If none of the above is correct, maybe the eccentric that pumps the fuel pump is worn down?  Would have to be a pretty high mileage engine, though

Doug Sprinthall

Thanks for the helpful advice.  I think Ill start with the carb and if that doesnt help Ill replace the fuel pump.  The carb was rebuilt about 7 years ago (Ive owned it for 5) so I dont think it will be all that hard to take apart.  Ill let you know how it turns out although it maybe a little while before I tackle it.  Being in Minnesota its hard to waste a Sunny Sunday  afternoon working on a car.
Thanks again,
Doug

Porter 21919

Doug,

Ive been following this thread, seems to me if you pull the carb apart and it is dry then it is leaking.

I have a 66 429 with a Carter I rebuilt and a 67 429 with a Rochester: the latest project, it runs great, no fuel leakage from sitting.

Porter

Lynn 10923

If I were the owner of the car, I would not spend money on things I could eliminate as being the problem, like fuel filter and carb rebuild.  Let me break the sentence down a little bit, maybe make it easier to understand.  Even if the plugs leak... if the fuel pump is any good... it wouldnt take long to start.  Leaking fuel plugs do not make the car hard to start.  But thats just me I guess.  Anyone else is certainly welcome to spend money on anything they want.

Lynn

John

Lynn, Dont get me wrong. I dont want to get in a pissin thread with anybody here. I just using 35 years of experience in G.M. products. Mainly Cadillac. Read Porters answer and it will explain my solutions. If the bowl is dry then there is no fuel for the accelerator pump to pump. Therefore it is going to take quite a bit of cranking to replenish the supply in the bowl for the accelerator to pick up and that wont happen without excessive pedal pumping to squirt the fuel through the main jets to fire the engine.
Have a good evening. Im through with this one!!!

Andrew 10642

Porter makes a good point. I have a 68 DVC, and it can sit for over 2-3 weeks, and it will start right up.  Its obviously a Q-jet.  Never rebuilt the carb.

Porter 21919

John,

This happens all the time, good experienced advice and many people weighing in with W.A.G.s to many problems and symptoms with engine problems. All just people trying to help out.

Lynn has rebuilt many 472s and Rochester carbs, I havent, he has owned two 68s for many years.

I have read about the leakage problem with Rochester carbs, so I offered that advice. I am only familiar with 429s, although my ragged 67 CDV runs great I will get to rebuild a Rochester carb for the first time, just like everything else that needs to be rebuilt on this project Rat Rod car, the bodywork is the lions share of the labor required.

http://www.modifiedcadillac.org/ TARGET=_blank>http://www.modifiedcadillac.org/

Porter








Mike #19861


Im with John on this one. These leaking plugs are common on Q-Jets, and give just the symptoms described when they leak.

 A good cleaning of the carb and sealing of the plugs will make the car run like new again. And, while you are in there, replace the float and set the float level to spec. Float level is an important adjustment in these carbs and can really affect driveability and fuel economy.

  Mike