Dale Von Krosigk

I have a 1971 442 with a 455 engine, it has a new gas tank, new fuel pump, new gas cap, I know the fuel pump is working, but I seem to be getting air in the line to the pump and my car stops running, then after awhile it starts back up, I need help, the tank has 3 vapor lines could they be sucking air into the tank?

redoldsman

I think you have found the most logical place to start. If the lines are old, just go ahead and replace them. I am betting that will fix your problem. Good luck.

Dale Von Krosigk

Are you talking about replacing the main supply line to the fuel pump, and have replaced all of the rubber lines.

redoldsman

I am talking about the lines (hoses) back by the tank. If you haven't replaced the lines at the pump I would do that also.

Tedd Thompson

Does this happen in cold (cool) weather? If not you are probably having a vapor lock issue. As a test you can try and insulate your intake line with foam pipe insulating used to protect water pipes from freezing and see if that doesn't help. At least it would be a cheap test to isolate the problem....Tedd

oldcutlass

Make sure all the rubber lines are serviceable and not cracked and tight from the tank to the pump.

droldsmorland

All good advice here.
Are the metal lines good?
How are you seeing the air?
Replace all the soft lines from the tank to the pump, especially if of unknown age and they are brittle.
One of the 3 lines is a vent at the tank, so no way for it to pull air into the suction side of the pump. The other smaller line off the pump is a return back to the tank. So its on the pressure side of the pump, not likely the source of the air. That leaves the main line to the pump from the tank. Could you have a lose or over tightened clamp from the sending/pick-up unit when the tank was installed? Look for wet spots on the line. Could have a pin hole in the metal line.That will show as a wet spot. Try to twist all clamped soft lines, it should be very difficult if not impossible to spin the hose on the nipples.

Dale Von Krosigk

I have replaced all the rubber lines from the tank forward. Whoever owned the car before me had one of the fuel tank vent line plugged off. Any reason for that ? It seems to vapor lock in all types of weather. I guess my next step is to replace the steel line?

Tedd Thompson

Doubtful if it is a true vapor lock in cool weather unless a fuel line is setting on the exhaust or something, gotta have a abundance heat for that to happen...Tedd

droldsmorland

Wait, before you go through that trouble lets dig a little further....As to why that line is capped off Im not exactly sure what its proper application is on a 72, 442, 455. Look in your assembly manual for the proper hose routing, location and application. It will show the options for how it all came from the factory. Didn't all 72s have the charcoal vapor canister? Again the manual will show it.

How did you "see" the air?

There are several possible reasons your experiencing a lean condition...if that's what it is.
Read the plugs and exhaust pipes. Are they white. Thats lean.
Have you taken a pressure reading on the new pump to see thats its putting out 5.5-6.5 psi?
Maybe somethings wrong with the pick-up and sock in the tank? Obstructed...kinked...who knows what was done. You have to do some trouble shooting...the right way.
Check the float level and drop settings. Set the level slightly lower than the spec. by maybe a 32nd to compensate for today's gas.

Are you sure you're not experiencing ignition failure vs fuel system? Do you have points or have you converted to HEI? If HEI how did you hook it up and was it used from a 70s engine or new?

Vapor lock usually only rears its ugly head under extreme heat where the liquid gas is being converted(boiled) to a vapor prematurely where it should still be in the liquid state. Air is another story. Thats fuel starvation. That will show up as lean.

More info before you try to replace the metal line. Its a PITA to do with the body on the frame.

oldcutlass

When it stops running have you looked down into the throat of the carb while moving the throttle to wot and see if its spraying 2 solid streams of fuel?

Tedd Thompson

Or have you tried taking the gas cap off and see if it will now run. If it's a un vented cap and the capped off line you mentioned may be the reason no air is getting to the tank..... Just a thought....Tedd

CutlassDad

Are the tank vents, fuel pump, and tank made to work with each other?
When the car has stopped running, is there a "woosh" when the cap is removed?
Is the fuel cap correct for the application?

nsnarsk65cutlass

Steel line in back have any rust?May have pin holes in it.

D. Yaros

I second the gas cap investigation. What you are experiencing sounds exactly like what occurs when one installs a non-vented gas cap in place of the correct/required vented gas cap.

New caps, in order to comply with EPA regs are non-vented.

Vented caps have "VENTED" stamped in the metal.

Doc350s

I've heard of vapor lock being an issue on the big block cars. Reason why they went to a return line to the tank to provide recirculation flow to prevent it. Gas cap is definitely a good start. Curious about the plugged line though.

CutlassDad

From when I started driving in the early '60 vapor lock was the fuel boiling in the carb bowl(s) causing a very rich condition on the next hot start.

Dale Von Krosigk

Thanks for all of the help, I've got a lot of places to start looking. I did look at the gas cap all ready and it is a vented one. I took the cap off and it did start and idle in the garage ok.