Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Fuel pressure issue? Comes and Go's
429bbf:
just reread the post. i don't know why a rebuilder would tell you not to run the filter in the carb. this is the fastest way to have to rebuild the carb again. it take very little garbage to mess a good carb.some of the holes in the carb are as small as .025 thats not a very big piece of dirt to cause problems. fwiw
BARRACUDA1968:
My builder wants me to run a fuel filter just not the one on the front of the carb. I'm going to install an inline filter.
Since the tank and all parts are new I wasn't real worried about starting the car without a filter just to get it lined out. I will install a good filter before I do any real driving.
I still have the electric pump I took off the car so I may try that.
Now that you mention the adjustable part throttle I remember him saying that.
Can the vapor line from the tank cause an issue? And just so I know my lines are hooked up correctly, (I just hooked them up like they were when I installed the new tank) Is the return line on the sender or the metal line welded on the tank?
429bbf:
i can't answer that I've never owned one I'm sure somebody on here will know . sorry i can't help.
blazer74:
I feel your frustration, sorry I cant help you due to I'm dealing with the same issue with the fuel pressure and mine also falls on its face @WOT most of the time when it warm outside but not always.
I Think its solved then comes back.
Went thru all with new rubber everywhere, rerouted away from heat.
Blew out lines feed and evap vent to tank. Left gas cap off.
Replaced fuel pump with edelbrock high volume 6 psi, no help.
I get the steady 6psi then drops like yours and can watch the fuel go down in the glass filter just before the carb, then it will recover after some time and repeat. I'm lucky to hold 3 psi when this happens at idle. I dont know what my fuel pressure is as it falls on its face but am going to install an electric fuel pressure gauge for that.
Mine will also surge a little after shutting off hot for a short time and then restarting and going under light or hard throttle momentarily then its ok.
Im also going to upgrade the tank and install a new sender with the extra return line port, currently I dont have the 1/4 inch return line to the tank, just the vapor line to the canister.
Im going to install an early GM fuel filter with the extra 1/4 vapor port and connect it to the return on the new sender and see maybe its vapor lock because the hotter out the worse it gets.
I've also tried different Q-Jet and distributor to rule that out but I may throw on a Holly 600 I have just to try.
This has been going on for quite some time but didnt have this problem years ago, Ive had the turck since 1988. Modern fuel is probably not helping.
Now thats is no longer winter I want (need) to get to the bottom of this already. Good Luck
1974 K5 Blazer 355
von:
May be a long shot but it could be possible that the pump pushrod or cam lobe is worn and not giving the pump a long enough stroke.
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