z11375ss

So my buddy has a GTO that starts hard when it sits for a few days. It seems the fuel drains back into the gas tank and he has to crank the daylights out of it to get fuel up and fill the carb to get it to start. Does someone sell a product that works like a checkball keeping the fuel above the fuel pump in between using the car?

Lady72nRob71

Some fuel filters have check valves (rubber flaps) in them for this purpose. See if he is using the right filter and that the flap is any good.

z11375ss

I was also thinking of bending a new line with an elbow in it to keep the fuel in the carb. We'll see tonight hopefully. We may get to it.

TripDeuces

My guess it's not the fuel draining back but rather leaking past the primary fuel well plugs. This would also contribute to hard starting. The needle and seat fuel inlet is above the level of the fuel when the car is level. Unless it's not screwed in tight it's not leaking back from there.

jcdynamic88

i have seen this a number of times and it was the fuel pump.i believe if the pump doesnt maintain pressure it acts as a syphon.jc

jcdynamic88

i have also seen the checkball for the accelerato pump stuck or missing if the carb was recently rebuilt cause this problem.jc

TripDeuces

You can't have a siphon effect if the two sides aren't physically attached somehow and they aren't in this case. Even if the needle and seat were stuck open the level would go down only to the windows on the needle and seat and drain back would stop. It's not a closed system to allow any kind of siphoning. The check ball in the accelerator pump is to stop drain back to the bowl so you consistently have a pump shot. Once again there is no attachment to the inlet side of the carb. The only drain back you could have would be between the fuel inlet and pump or pump to tank. The bowl would still be full unless it leaked out or evaporated away. Check the well plugs

I'm not trying to be a jerk but these things are mutually exclusive.

z11375ss

So, are you saying the fuel is draining into the motor while it sits? It starts hard only after sitting for days. It will start correctly if sitting for minutes or hours.

TripDeuces

Yes that's exactly what I'm saying. Well plugs are notorious for leaking and it can take days to drain the bowl

z11375ss

I talked to him earlier and he said he had no issues with gas in the oil. Your expertise is very much beyond what mine is. I think with a little education though I may catch up. Thanks for the info. Jim

Ozzie

Since there seems to be some doubt about the source of the problem, why not do more investigation. Let the vehicle sit for a few days, then remove the fuel line to the carburetor. If there is fuel in it, the problem will probably be the carburetor. If not, then look for how it left. While you're there, a volume & pressure test for the fuel pump might also be worthwhile. If it's draining back both of those one way valves would probably be leaking.

jcdynamic88

i have to agree with your explanation ,my memory must have transposed symptoms and solutions.different ideas and opinions are a good way to solve problems and learn and in my case relearn something i probaly knew and forgot.sometimes i forget i have a lousy memory.jc

brown7373

Another thing to check is the proper adjustment of the choke. A carb that is without sufficient fuel at start-up, for whatever reason, becomes even harder to start if the choke is not right.

Most of the fuel that leaks through the well plugs would evaporate in the intake, so it's doubtful it would contaminate the oil. Drilling out the well pluds and treading in metal plugs sealed with Maine-Tex makes a MAJOR difference in Q-jet operation and is something I do to every Q-jet I have regardless of whether I think it is leaking or not. Most do to some degree, or they will some time down the road.

MDchanic

In addition to the above, this problem can be caused by leaky lines between the tank and the pump, whether rubber or steel - the lines leak down a bit, and the pump has a hard time sucking gas back up, because it keeps getting air through the pinholes.

If this really bothers him, he should drop the tank.

- Eric

z11375ss

Holy Cow! Now we're dropping the tank! I think he'll live with the hard starting issues as he drives it about 1000 miles a year. Cool car though. Turquoise/Turquoise with a 400/400, Dual Gate, heater delete. Thanks for all the info and I bet those lines have never been changed as the car is as it left the factory.

MDchanic

Yeah, mine has done this for the past couple of years, in spite of a check valve in the filter and a new fuel pump installed by the PO just before I bought it. It also will leak if I fill the tank all the way up.

I ignored it, and just poured gas into the carb if it wouldn't start, but I had a moment this fall where it took over ten minutes, and probably a quart of gas before it would stay running, so I've accepted the fact that the tank's got to come out.

Should have done it a long time ago.

- Eric

ELY442

My 70 Cutlass Convt has the same problem. I start my car every weekend and i have to pump and crank 3x before she starts. I did install a new fuel pump but that didnt work. So i got under the car and the fuel rubber hoses was crack and peeling. These hoses and clamps from the gas tank to the fuel pump was replaced. Inline Tube sells these hoses/clamps kit for 1/4" and 3/8". Now my car starts with 1 pump. But TripDeuces is right about the well plugs. Qjet is notorious about fuel leaking thru the well plugs. If you get your carb rebuild, they can apply an special epoxy on them.

J-(Chicago)

The epoxy only lasts so long, although it is a suitable bandage for a while. The best way, is to pry out the old plugs, tap it, and screw in permanent plugs.

ah64pilot

Someone mentioned a little more testing above...I think that is mandatory if you're going to isolate this problem. I also don't see how the gas tank has anything to do with it.

Run the car, shut it down and wait. After a couple of days check the fuel line between the carb and the pump...if it's dry it could be a pump problem. If it's full, then suspect the carburetor itself. But really, I don't see any need to go into the tank. Besides, a pump costs $22...I just did one on my convertible for the same problem and guess what? My $22 shot in the dark solved my problem It also had a new-ish pump from the silver car...they go bad, sometimes quickly.

Steve

z11375ss

The pump works and has worked fine for the last 14 years he has owned the car. I'm guessing it's the carb. Enough guessing though. We need to do some tests! Probably have to do at least one full throttle run to make sure everything is in working order. Time is running out though. Old Man Winter won't stay away for ever.

Tedd Thompson

If the car smells of raw gas in a confined area my guess is carburetor leak down as stated by Trip Duces. Very common these days. So is cheep ethanol gas evaporating out of the carb in hot weather, same sympoms....Tedd

MaxDog

I had this exact same problem. As suggested on this forum, a cheap and easy possible solution was to replace the fuel pump. So I started with that, and it fixed the problem!!!!!! Now it starts like its a new car.

Looks like the worn fuel pump (diaphram maybe?) was no longer holding the gas in the fuel lines after a day or two and it would take 30 to 45 seconds of cranking until the gas would be pumped back up to the carb.

Good luck!!!!

Olds64

As others have said, Qjets are notorious for leaking fuel from the primary well plugs. If a Qjet is rebuilt this is one thing that should definitely be repaired.

BILL DEMMER

quadrajet secondary well plugs are notorious for leaking prior to the '68 model year, when they changed to spun-in plugs. the primary plugs can leak, but it's fairly rare. even more rare are the secondary well plugs leaking '68 and newer. if your carb. was sitting on the bottom of a lake for 10 years-then all bets are off.


bill

CaptOharry

I just finished rebuilding my Q-jet,it had the same problem,once the Engine is off the Fuel kept leaking into the Intake,the Metering rods were worn out
also the Needle and Seat were Toast.

BILL DEMMER

your needle and seat were the problem, no fuel flows past the metering rods when the engine is off. worn out metering rods? i'd like to see this.


bill

ah64pilot

Z, if he has a 14 year old (or older) fuel pump that would be the first place I look. Still, tests are in order to really pin it down.

4rims

X2 on check your choke to see if closed before starting. I had the same problem

CaptOharry

Hello Bill,your right about the Needle and Seat,what happened was the Fuel filter failed ruptured inside the Carb.Sunday AM going to Church the car would not run at idle,got some dirty looks from the other Church goers as i had to keep reving the car to keep it running,once back at home i removed the top of the Carb and found a pulp like garbage inside,it appeared that the Pulp came from the Filter which somehow this bent the Metering Rods just the tips.This AM the Carb is back on adjusted and running again,In all my time of working and tinkering on Cars I've never seen this happen.

z11375ss

Fuel injection would be nice. Damn expensive though.

brown7373

The only way the metering rods get bent is if the assembly doesn't stay seated when the air horn is pt back on. That would pull the rods out of the jets and they would bend on the fuel bowl when the air horn is tightened.

MDchanic

+1

- Eric

W30post

I haven't looked at the Cliff R. book closely enough for this very detail but I question if some fuel will bleed past the metering rods and through the air idle mixture screws. I have never looked for this before but it would be a path, maybe a difficult path, but a path for fuel to enter the motor. Power piston is up so the path through the main jet is at its max. The bowl is open to the air cleaner so there would not be a vacuum on that fuel sitting in the carb. Is this a possible path for fuel loss?

Another easy way to check for well plug leakage is to inspect the base plate to intake gasket. It will be swelled in that area if it is fuel soaked from a well plug leak.

I too had a fuel pump leak just a couple months ago. Replaced the 9 year old 4500 mile pump and now it starts easier. I had visible staining where at high RPM the fuel would push out between the cast pump body and the crimped on top.

BILL DEMMER

bill

MDchanic

Never mind Cliff Ruggles's book - any cutaway view from the Chassis Service Manual would be fine.

Picture this:
Fuel enters through the needle and seat in the air horn and falls DOWN into the float bowl.
Air flowing through the venturis, when the engine is running, creates a vacuum, which pulls fuel from the float bowl, DOWN through the primary and / or secondary jets (past the primary and secondary needles), into the wells, then UP through passages in the body of the carb., then DOWN into and through the nozzles.

When the car is not running, there is no air flow through the venturis, so no suction through the nozzles, so the gas stays in the float bowl, because it CANNOT climb uphill on its own (at least not until the laws of physics are repealed).

- Eric

BILL DEMMER

md,

the needle and seat are in the bowl. the fuel actually comes up into the bowl, then through the seat, then flows down slightly into the bowl. the jets are below the bottom of the float bowl. fuel is pulled up the passages, mixed with air, then the mixture(emulsion) is pulled back down to the idle discharge ports/transition ports.

(not trying to be a dick)

bill

W30post

Thanks Bill, I just never researched the idea of how the fuel makes it from the actual jet to the idle circuit.
The other topic of the gasket covers if the primary well plugs are leaking. When I removed my carb the last time the base plate gasket was swelled between the primary bores. I had not seen this previously and thought it an interesting indicator.

MDchanic

Duh. Brain fart.

I've removed the air horn without removing the fuel line enough times to know this.

Semantics, but you are correct - I was trying to keep it simple:
Down through the jets in the floor of the float bowl into the wells,
Up through the passages (with aeration), then
Down (just a bit) to the nozzles.

Point being, the fuel can't flow downhill through the nozzles or idle jets, because it first has to flow Up, and past the air bleeds (as you point out), which would break any siphon effect that the next wise guy will postulate.

As they say: "You can't get there from here."

- Eric