Hi everyone! I joined today as I am having problems with my 78 Olds Delta 88 with a 350 4 barrel Rochester Quadrajet. I have googled this question for 3 days with no luck, so I am hoping someone here can help. I bought the car from my GF who passed away from cancer in July, so I want to keep this car going in her memory. I purchased a carb rebuild kit for my carb model (# 17051853). The accelerator pump was shot (likely due to ethanol-blend gas). Replaced the float, check ball, gaskets, and everything else that was in the kit. When I start the car, it idles really high (1500 RPM), but as soon as I put it in drive, the RPM's go down to 350 and the car stalls. The other question I have is: Is the front choke pull-off vented/air bleeded? I can suck on the vacuum line and the lever moves, but after 1/4 of a second, vacuum is lost and the lever goes back. The rear pull off can hold a vacuum forever. I have googled to see if the front pull off is supposed have an air bleed, but can't find an answer. I have looked closely at it and can't see any air bleed hole. I am on disability and cannot afford to run out and buy a bunch of parts hoping I will stumble across the one with the problem. The distributor has a new coil and module installed 4 months ago. The car ran great (23 MPG) until last week when it suddenly started stalling, idling badly, etc., and gas mileage went down to 9 MPG. When I try to drive it now, I have to keep my foot on the gas and the other on the brake at red lights to keep it from stalling. I have replaced all the vacuum lines, but I still think there is a vacuum leak somewhere. When I am at a red light and pushing the gas and brake at the same time (to keep it from stalling), the brake pedal goes all the way to the floor and the brakes barely hold (Brake pads are almost new). I could not replace one vacuum line because it is connected to a small round thing that is behind the water pump. I think this vacuum line goes to the tranny modulator. When I got the car, the lines going to the charcoal EVAP canister were off/broken, and I have replaced them. I can't understand why the car ran great, the suddenly developed this stalling problem. I try to adjust the idle, but it jumps around and won't keep at an even speed. I have adjusted the float level to .420 inches (specs from the rebuild kit). There is ONE gas station here in town that sells pure, non-ethanol gas and I have been filling up there since I rebuilt the carb. I have adjusted the choke, idle mixture screws, fast idle screw, and front choke pull-off until I am blue in the face and I still can't get this thing running properly. The other confusing thing is there is a spring clip that goes on the end of the float to lift the inlet valve. The rebuild kit says NOT to put the end of the spring through the holes in the float, just to hang it from the rear edge or it won't center properly in the hole. So why do they have holes at the end of the float if you are not supposed to clip anything in them? The new brass float has no holes. I just don't like the idea of installing a spring with no hole for it to go into and make sure it stays in place. I did mine according to the sheet that came with the rebuild kit (says DO NOT mount spring through holes). I know this is a long question, but at the same time the stalling started, the car now "diesels" after shut-off. Any tips, tricks, or info would be greatly appreciated!

Dave

 

Sounds to me like you on top of other things have a vacuum leak. I'd start at the brake booster, remove the hose, and plug it off. That will tell you if the diaphram is shot.
To the choke issue, is it hot air or electric, I'm thinking electric. What position is the choke plate in on a cold start? If it is FULL closed does it open when warm? You probably have a linkage on the pull off binding or not correct.

Rochester Quadrajet Tech Info - The Carburetor Doctor

 

Thinking, since you had the carb off, what type mounting gasket did you use? Is it the thin black one?

 

Thanks for the reply Kevin. I have the choke plate set so it is almost closed, maybe 1/16 inch gap when the engine is cold first thing in the morning. The gasket where the carb mounts to the manifold is about 5/16 thick. Choke is hot air operated. Thanks for the tip about the brake booster! I am thinking it is a vacuum leak somewhere, and the power brake booster has a big vacuum line to it. I will plug the hose to it to see if that helps. I'm thinking about the evap canister as a vacuum leak too. Since it wasn't hooked up for years and I have hooked it up again, the diaphragm might have dried out and sprung a leak. The car ran like a top. Got excellent gas mileage, then I was pulling into the driveway and it stalled. It's 9 PM here, so I will have to wait till morning to check the booster. Thanks again for your advice, and I will let you know how it works out. Cheers!

 

OK, the car sat all night. Before I started it this morning I took the hose off the brake booster and I could hear hissing air being sucked in, so it held a vacuum overnight. Started the engine and plugged the booster line and there was no difference in the idle (there was a lot of vacuum in that line) Then I took the 2 vacuum lines that go from the evap canister to the carb and plugged them. Now it idles right and does not stall when I put it in gear. I left 2 lines connected to the canister (there are 4 lines in all). One is the tank vent line and the other one is the purge valve line that goes to the carb. Can I rebuild the canister? A new one is almost $200, and I'm sure a 34 year old junkyard one would not be in great shape. We don't have smog testing here, so can I just run the car without the canister?
I really appreciate your help. I was looking for a fuel problem, but you suggested a vacuum leak, and I think that's what it is. One thing I forgot to say in my first post is when the car was idling badly, I tried adjusting the mixture screws. I could turn one all the way in with no change in idle. Then if I turned the other one all the way in, it would die (of course). It did not matter what side idle screw was turned all the way in. I could turn the left or right one (one at a time) all the way in with no change in idle. Also, the carb base gasket is blue and it is not paper, it's some kind of neoprene or something. It is pretty thick. I hear of guys putting 2 gaskets under the carb because of heat issues, but the one that came with the rebuild kit was a lot thicker than the original one. I know a way to check for vacuum leaks is by holding an unlit propane torch around all the vacuum fittings. We live in a condo unit that does not allow car repairs (stupid rule). They have put up with me taking the carb off and fiddling with the carb, but the strata board will freak out if they see me with a propane torch. They are really afraid of fires here (the next condo unit over burned down last year from a propane BBQ). When my buddy gets back from holidays, I will go to his place and do the propane leak check there. It's running a TON better with the 2 evap lines plugged, so I can at least drive it without fear of stalling. I want that 23 MPG back! We are paying over $6/gallon for gas here! Funny though because I used to have a 1987 Mercury Topaz with a 2.3 liter fuel injected engine, an it also got 23 MPG. Thanks again for the help! I will let you know how the leak test goes. I also thing investing in a good vacuum gauge would be well worth it!

 

Dave, the evap canister is your tank vent, as you know. I have a 70 Delta 88 with an evap canister 3 line, vent tank, tank return or whatever. You might try either replacing the filter, however I think (it is charcoal) canister is at fault. Only thing I can say IF you don't have to worry about emissions, try a vented gas cap, and do away with the evap canister.

 

Thanks Kevin! No smog testing here, so I don't have to worry. I found out the hard way that one line from the canister was a vent for the tank. When I bought the car, the line was broken so I plugged it. Drove about 10 miles, went to the gas station to fill up and when I unscrewed the gas cap, a huge rush of air got sucked in. Glad I didn't collapse the gas tank. You have a 70 Olds? Nice cars. My granddad always bought Oldsmobile's and had great luck with them. He bought a 73 Cutlass Supreme new in Dec. 1973 with a 350. He put 768,000 miles on it and it never burned oil and ran like a champ. My dad bought a 78 Delta Royale exactly like mine, same color even, but he had it converted to run propane. He got 300,000 miles from it and then gave it to his 16 year old grandson. It only lasted a year after that! I've owned 2 other Olds, a 75 Cutlass and a 1976 Anniversary edition Cutlass. They all had quadrajets, and I found how touchy and finicky they are. Lots of people call them Quadrajunk or Quadrabogs, but when they are tuned properly, they are great carbs (hence my 23 MPG Hwy). Thanks again for pointing me to the vacuum leak....I was about to buy a carb from the auto-wreckers! Saved me a ton of $$$ and work!

 

Sorry, it was Dec 1972 when my grandad bought his Olds!