Lately, when my 1974 Delta 88 w/350 motor, Q-Jet has been sitting for a few days, it will not start. You can grind it for 20 seconds and nothing. If you prime it of spray starting fluid, it immediately starts and runs fine. Will start all day after getting it going. Do I have a bad fuel pump, maybe a small tear in the pumps diaphram?

 

Could be one or a combination of the issues you mentioned plus a few I will add. Gas leaking out of carb bowl plugs, gas just evaporating out of carb into the air, bad check valve in fuel pump, accelerator pump not working (probably not this if car runs without stumbling after start up).

You should address each part one at a time and eliminate each one separately, and this is a common problem with older cars and today's gas.,,, Tedd

 

x2

Tedd hit the nail on the head.

 

X3 with Ted. Today's shtt gas can evaporate quickly. I run ethanol free in all my carbureted machinery for this and other reasons. Check the fuel lines as well. Any pinholes can cause problems. It may not drip but it will show up as a weep or as a wet spot on the line or the frame. Pay attention to all of the soft fuel lines from tank to pump. If they are 43 year old originals consider replacing all with high qual ethanol tolerant lines and new clamps.
How to trouble shoot: Let the car sit the required amount of time which typically produces the problem. Pull the air cleaner lid off, hold the choke open and pump the accelerator while looking down the carb, You should get 2,3,4 strong shots of fuel. If not you likely have a leaking carb float bowl. Secondly, your start procedure could be wrong. Try this... Get in car, Push accelerator down to the floor twice. This sets the choke and gives it a shot of gas. Turn the key without touching the accelerator. It should start. If not repeat this process 1-2 more times. If it still doesn't start then check the choke settings and the float bowl for the above mentioned leakage. You do not mention additional drive-ability problems so I wont go into more detail. Oh and it cant hurt to pick up a good vacuum/pressure gauge to verify the fuel pump pressure, 5-7lbs. A vac/psi gauge is a crucial tool to have. Its a tuning tool and will show you if you have vacuum leaks. Check all vacuum lines too.
Circle back when you find and fix the problem.

 

After trouble shooting it appears to be a bad accelerator pump, thanks for the suggestions guys. I did a search but can't find a thread on replacing the pump, is it difficult to do? It looks like it is easy to get to, how do you remove the old one? The carb was rebuilt 2 years ago so I do not want to do anything more than replace the pump.

 

The hardest part is getting the fuel line nuts to break lose. Do yourself a big favor and get a set of high-quality line wrenches and a can of PB blaster. Soak the fuel lines with PB a few days in advance, Remove the old pump. Clean the gasket surfaces on the new pump and the block using brake cleaner. Spray (3M or other high qual spray) gasket contact glue to one side of the gasket and stick the gasket to the pump. Put a very light coat of black RTV on the block side and torque to spec. Dont over torque the pump or the lines. Start car and look for leaks retighten as needed. Oh and be sure the pump lever engauges the eccentric properly. Google that for an exploded view of what that looks like.

 

I thought she wrote 'accelerator pump'...

 

Actually, she wrote accelerator pump. I think DrOlds may have misread my post. I decided to take it to the shop in any case, seems best as I am not too versed in carbs. Thanks for the help guys.

 

Brenda, you should be able to get one of the locals to help with that as it's a fairly simple job to remove the air horn and install a new accelerator pump. Just need the accelerator pump and a new air horn gasket, which should be available from NAPA or many online sources.

What area of town are you in? I'm down south near I-10 / Chandler Boulevard so if you are somewhere near I may be able to help ya.

 

Thanks for the offer Ken! I just spoke with a friend of mine and he will do it and I will trade him the Holley Carb that was on the car when I got it. Not a bad deal. Do you ever make it to the Pavilions on Saturday night in Scottsdale? I am there often. Would love to meet in real time!

 

Yep I had a fuel pump on the brain....its a very simple brain with about 3 and a half cells left for vital functions so cut it some slack, lol!
Make sure you can find a high-quality carb service kit, do not cheap out here...OR send it out for a quality rebuild/tune up. There are many settings and things that can be updated within a QuadraJet. Some parts that wear over time and need readjusting or rebuilding etc...You will have a like "new" car with a properly rebuilt Q-Jet. You will think you've installed another 50 horsepower with a properly tuned Q-Jet and distributor. Several good rebuilders out there. A rebuilt carb and fine tuned ignition timing are the two best things you can do to a stock engine to extract the best and most efficient performance out of the car. The carb place can likely tune the distributor for you as well.
Cliff Ruggle, The Carb shop, and others are the higher end Q-Jet people. Google all of this and ask questions. Be extra careful removing the fuel line from the carb. Be real careful removing the large filter nut where the filter lives. Those fine threads are easily damaged. Be real careful when reinstalling the carb. Do not over torque it to the intake. You will distort the carb. Retorque it after a few hundred miles then about a year after that.

 

I get there now and again for the OCAZ meetings. I used to be a regular but nowdays not as much.