Blowing bubbles Options

[emerygt350]

I know it's click bait but whatever. So gradually working through the starting issues on my 73 djet 2.0. is anyone aware of a bubble blowing condition that doesn't require vapor lock? Is there something that can go wrong with a stock 73 fuel pump that would cause it to blow audible bubbles into the tank? This only happens after I have driven it, but doesn't require it to be hot n hot. If I turn the key to the on position and the fuel pump starts I can hear bubbles coming into the tank (even when the tank is full). This is at 40 degrees ambient. This is the real kicker, this will continue after the point at which the fuel pump cuts because the engine is not running. However , when I turn the key off, even after the pump has stopped , the bubbles will stop. ????? When this happens I have a difficult time starting, but it really smells and feels like a rich condition, not what I know from vapor lock. Under true valor lock I can't hear the pump at all.

After I get the engine to catch, normally only a few tries, it stumbles a little then immediately runs great
I think there are two separate problems here, but perhaps not. It's the bubbles that have me stumped. How could I get bubbles without vapor lock?

[BillC]

Are you sure they are bubbles?

What is the fuel level in the tank? If it's really low, maybe you are hearing splashing from the fuel being returned to the tank.

Maybe you can have someone try cranking the engine while you look down the filler with a flashlight?

[76-914]

Sounds to me like cavitation. See if your intake line is kinked or has an obstruction.

[emerygt350]

Are you sure they are bubbles?

What is the fuel level in the tank? If it's really low, maybe you are hearing splashing from the fuel being returned to the tank.

Maybe you can have someone try cranking the engine while you look down the filler with a flashlight?

Yeah, bubbles, full tank. No mistaking it.

Nothing has changed in the system but I am going to look through everything as soon as it stops raining.

I should mention as well that I had no such problem last year before its long winter sleep but I was noticing what I thought was some pretty poor gas mileage but that turned out to be.a broken thermostat cable. Wrong side of the engine for messing with the fuel lines.

[emerygt350]

Dbl post

[Literati914]

I've heard of the internal sock getting clogged and causing similar noises when the fuel is run low, just a thought.

[emerygt350]

That's the thing, it does it with a full tank. Not saying that couldn't be it though.

[porschetub]

I know it's click bait but whatever. So gradually working through the starting issues on my 73 djet 2.0. is anyone aware of a bubble blowing condition that doesn't require vapor lock? Is there something that can go wrong with a stock 73 fuel pump that would cause it to blow audible bubbles into the tank? This only happens after I have driven it, but doesn't require it to be hot n hot. If I turn the key to the on position and the fuel pump starts I can hear bubbles coming into the tank (even when the tank is full). This is at 40 degrees ambient. This is the real kicker, this will continue after the point at which the fuel pump cuts because the engine is not running. However , when I turn the key off, even after the pump has stopped , the bubbles will stop. ????? When this happens I have a difficult time starting, but it really smells and feels like a rich condition, not what I know from vapor lock. Under true valor lock I can't hear the pump at all.

After I get the engine to catch, normally only a few tries, it stumbles a little then immediately runs great
I think there are two separate problems here, but perhaps not. It's the bubbles that gave me stumped. How could I get bubbles without vapor lock?

Where is your pump located ? ,not 100% sure but appears you are drawing air from the suction side of the pump only answer for what you are experiencing ...could be wrong however ?,cheers.

[bkrantz]

Are you sure they are bubbles?

What is the fuel level in the tank? If it's really low, maybe you are hearing splashing from the fuel being returned to the tank.

Maybe you can have someone try cranking the engine while you look down the filler with a flashlight?

Just don't use a candle! (IMG:style_emoticons/default/happy11.gif)

[emerygt350]

I know it's click bait but whatever. So gradually working through the starting issues on my 73 djet 2.0. is anyone aware of a bubble blowing condition that doesn't require vapor lock? Is there something that can go wrong with a stock 73 fuel pump that would cause it to blow audible bubbles into the tank? This only happens after I have driven it, but doesn't require it to be hot n hot. If I turn the key to the on position and the fuel pump starts I can hear bubbles coming into the tank (even when the tank is full). This is at 40 degrees ambient. This is the real kicker, this will continue after the point at which the fuel pump cuts because the engine is not running. However , when I turn the key off, even after the pump has stopped , the bubbles will stop. ????? When this happens I have a difficult time starting, but it really smells and feels like a rich condition, not what I know from vapor lock. Under true valor lock I can't hear the pump at all.

After I get the engine to catch, normally only a few tries, it stumbles a little then immediately runs great
I think there are two separate problems here, but perhaps not. It's the bubbles that gave me stumped. How could I get bubbles without vapor lock?

Where is your pump located ? ,not 100% sure but appears you are drawing air from the suction side of the pump only answer for what you are experiencing ...could be wrong however ?,cheers.

Pump is in the stock location, in the back.

[Superhawk996]

See post 26 - pay attention to the cutaway diagram and path to purge air bubbles

www.914world.com/bbs2/index.php?showtopic=350416&st=20

Also keep in mind you don’t need high ambient temps to get vapor lock (or partial) especially if pump is in rear and even more so if winter blend fuel is still in the tank.

[emerygt350]

See post 26 - pay attention to the cutaway diagram and path to purge air bubbles

www.914world.com/bbs2/index.php?showtopic=350416&st=20

Also keep in mind you don’t need high ambient temps to get vapor lock (or partial) especially if pump is in rear and even more so if winter blend fuel is still in the tank.

Interesting. One thought I had is if it isn't holding pressure after shutdown the gas will 'boil' more easily making it even more prone to this.

I just did a quick test, ran it nice n hot out on the interstate for 30 minutes. Parked it and let it sit for 10 minutes. Maybe 50 this morning. Went out to see if it would burble, nope, and it started right up without issue. Sigh.