Thread: Fuel Delivery Problem... Any help appreciated!!

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Im new to this site so I appreciate anyone that can help me. I have recently taken on a project for my father. He has a 1982 Chevy Caprice. I have done an engine swap on it and I cant get it to stay running. Its a late 70's 350 that has flat top pistons and 194 heads with an Edelbrock preformer intake and Edelbrock Q-Jet 1901. Other than that we got rid of the exhaust manifolds and put a set of hedman ceramic headers on it. The cam and crank and everything else as far as we know is stock.

Now onto the problem. If I prime the carb with gas the car will start. The first time I did this the car ran for about 5 minutes and then died. After running the car would not start back up unless the carb was primed again. Pumping the throttle does not work. All it will do i crank over but will not fire unless I put gas in the carb. So I primed it again. It started and it ran for a a minute or so. Throttle response is good at first. Then it starts to die and then the throttle does no good at this point. Its like it loses its fuel supply.

What I have done:

I have put fresh gas in it ( as the car has been sitting a while)
I check for flow of fuel at the line that goes to the carb. Its seems to be getting plenty of gas.
I have checked the fuel filter and it appears fine.
We heard the engine run before we bought it. as far as i know none of the carb settings have been changed. The guy we bought it from pulled the engine for us so im not 100% sure nothing has been changed but i assume not since he wouldnt need to change any of that to pull the motor.. Im just kind of at a loss why all of a sudden it seems to not be getting the fuel it needs to stay running. What am I forgetting??? Carbs are not my strong suit as i dont know a whole lot about them.... Thanks in advance

fuel pump . gass tank lines ?that car had many lines off the tank vent . charcoal can . return ot tank . fuel filter in the gas tank off the fuel pick up full of junk . the carb full of junk . many other things but i start here first

Sounds like it's time to go back to basics. Don't trust anything until you've verified it. Remove the line at the carb and put it in a can or jar, spin the motor over. Any gas coming out? If not, verify that the line is open and not plugged, maybe use compressed air to verify it's clean.

While the line is disconnected from the pump, spin the motor and see if fuel comes out, if not, remove the other line and verify fuel is available to be pumped. Remove the pump and check the ports for blockage or just replace the pump for the cost of it.. also, check each line for cracks , kinks or any damage. Especially the rubber lines, a crack in the line can let air in and stop the fuel flow.

You need to figure out where you're losing the flow, just don't trust any component until you personally verify it can operate as designed. Take it step by step and get back to us and let us know what you found... 8-)

That 1982 Caprice had fuel injection originally, right? I think the delivery pressure would have been 8-9psig at the engine, but not 100% sure. That's too high for your carb. Have you put a regulator on it to drop the pressure to the 5-6psig range and verified fuel pressure? You might add that to the list Mike gave you.

i do not think so in 82 still was carb

Originally Posted by pat mccarthy

i do not think so in 82 still was carb

Yep, later in the '80's - sorry.

First thing you will want to do is to order this book written by Cliff Ruggles. He's the Quadrajet guru. The Q-Jet is in my opinion, the best air/fuel mixing device on the planet, short of EFI and Cliff knows his business.....
How to Rebuild and Modify Rochester Quadrajet Carburetors (S-a Design): Cliff Ruggles: 9781932494181: Amazon.com: Books

The floats may not be set high enough to allow enough fuel into the bowls, regardless of the output of the pump. First things first. Follow this tutorial and set the float levels properly. While you're in there, carefully remove any foreign material in the bowls that may be clogging the passageways or jets.
How to Set a Quadrajet Float Level | eHow.com
If the motor continues to quit after this operation, then I would suspect the fuel pump for weak or intermittent operation.
In that event, you will want to tee off at the carb inlet (not at the fuel pump) and run a line back to the firewall and up past the lip of the hood to the cowl in front of the windshield. I've been trying with no luck so far, to find a tee that will screw into the Q-Jet inlet fitting and have two inlet or outlet holes.....something like this, although this one does not have the correct threads to thread into your Q-Jet fitting.....What we need here is capability to run the motor while we read the fuel pressure through the windshield.....
Dual Banjo Style Fuel Fitting, 5/16 Inch Hose - Speedway Motors, America's Oldest Speed Shop
What we want is to allow you to hook up one line from the fuel pump and run the other line up to the cowl (the grillework in front of the windshield).
Here's another example if it had the proper threads......
Right Stuff Detailing Intake Manifold Fittings IMF68RS - SummitRacing.com
You don't want to read the fuel pressure right out of the pump. It might have sufficient pressure at the pump, but might not have enough poop to raise the fuel in the line up to the level of the carburetor, so you want to always take pressure readings at the fuel inlet on the carb.
Use a liquid-filled, analog gauge with 0-15 psi resolution such as this one from Summit....
Summit Racing® Analog Mechanical Gauges SUM-800115 - SummitRacing.com
Mount it on the cowl with tie wraps or duct tape or whatever. It'll only be on there temporarily so that you can get the fuel pressure dialed in and monitor it while you drive a few miles down the road. With a Q-Jet, you want to shoot for maximum 6 psi and 5 would be better. Any more pressure than that can overpower the needle and seat and allow the pump to blow raw fuel into the intake manifold, creating untold tuning nightmares for you.

i appreciate everyones promp responses.. I woulda got back to yall sooner but the keyboard on my computer took a crap. Ok so yes the 82 is came factory with the infamous Q-Jet that all the SMCs came with. I know they didnt start TBi till late 80's. I have checked all the fuel lines all the way to the tank and they all apear to be in good condition. I have checked for fuel flow and i am getting it to the pump. Brand new pump we bought when we put the motor in. The guy that we bought the motor from claimed that he had been having problems with the fuel pump so we figured for all they cost may as well buy a new one. So the pump is good. It IS pumping fuel the carb. if i disconnect the line at the carb i get fuel when the motor is cranked. I checked the fuel filter.. Looks good.. I was talking to a guy at work today he said the float may be sticking and shutting off the fuel flow to the carb?? Im an kind of unsure exactly as carbs are before my time. I have a little expierence with them but not much. as far as a filter in the tank... I was unaware that there was one IN the tank. I have not actually checked the fuel pressure as i am unsure how to do this on a carb.. the days of fuel injection have seemed to make that easier. so i will check out the links that are posted.. and ill see about this float situation maybe tomorrow and i will get back to yall.. thanks again for all the info.