Engine Woes

[Dr Doogenstein]

I've been working on this Beetle for over a year. Right now I'm having a problem and i'm not sure where it is stemming from. 1971 Super, stock carb, oil bath air filter.

So, it starts up fine, even after sitting for a few days, and while it is idling, it runs perfectly. After about 15 minutes of driving (sometimes sooner) it sputters and dies out and then will not start up for a few minutes. When it sputters out, the in line fuel filter is almost empty. The same fuel filter never fills completely up, but when it is running it's best, it is a little over halfway full. Sometimes, in order to get the fuel back up into the filter, I have to take off the air filter, cover the intake up with my hand and create a vacuum then let go to get it to burp up into it.

I have replaced vacuum lines, fuel lines, repaired the wiring issues, taken apart the fuel pump and filter.

The possible issues I have come down to are:
Coil getting too hot - After it sits for a while, it will fire back up. The coil looks super old and maybe even stock.

Fuel pump - I took it apart and it looked good inside, but the diaphragm was showing some wear.

vacuum lines - there is one coming off the carburetor that is just plugged. Creating a vacuum makes the fuel come back up into the filter and allows it to start.

Carb - Not sure it it is choking correctly.

Any thoughts, ideas, solutions, would be helpful! Thanks!

[alykat]

Way out in left field, but... as soon as it quits go to your gas filler cap open it with your ear close to it and see if you can hear air being sucked in. If you do,something is wrong, so check to make sure that your tank is being vented properly.

[purplemyth]

My bay does this but it's debris in the tank.
Hubby's old baja used to do this, bad on hot days.

But it sounds more like Alykat's idea, non venting. More a fuel issue than firing if the filter is not staying filled.

[Double D]

yep, sounds like it could be debris in the tank or main supply line or a venting issue.

[Dr Doogenstein]

I disconnected and blew out the main gas line today, but I disconnected it at the tank. So, it could still be crud in the tank, or the venting issue (I also had to replace a rubber section of fuel line because it was cracked). How would one repair a venting issue? I'm guessing that the plastic filter looking thing over the top of the tank is a vent or filter of some sort. I see that all of those lines connect up to the filler neck. Do I need to leave the filler cap a little loose? I have been screwing it all the way in. It doesn't seem to have a venting system on the cap.

[metalmaster1766]

Ya know I just had a similar problem, but it was right after I put the engine back in, I started it after hooking everything back up, only let it run to make sure it had oil pressure & that the alternator was working

Next morning I got in, started it up, after it warmed & pulled down the driveway, hit the throttle and it stalled

To make a long story short (I so wanna drag it out ) I traced it down to a pin hole in the fuel line that comes out the rear of the frame horn, luckely I had enough rubber fuel line to slide it all the way down & into the pan, then put 2 clamps as close to where it enters the pan & went on my way

I just have the feeling that the metal fuel line that goes thru the tunnel is gonna need replacing in the near future, it's a PINTA replacing it, unless you reroute it, much easir butt can look like shit

Hope ya track it down

Ron

[alykat]

To test vent issue, just leave the gas cap off/loose and run the engine long enough to see if that makes a difference/cures the problem. Then you can go from there.

[Dr Doogenstein]

Thanks for all the replies guys. I'll run it without the cap and check Saturday!

[alykat]

Wait !!! Don't drive around without the cap ! Just run it sitting in your driveway. If you drive it, you will have gas sloshing around and the whole car will be full of gas fumes. Oh yeah, did anyone mention that it a REALLY GOOD idea to have a fire extinguisher in your VW at all times ?

[Alpenretter]

I don´t know what u call it in the US,
but it sounds as what we here call "steam lock" in your gasoline pump

I had the same problem on my Corvair with a Vw-motor,
a external electric fuelpump solwed my problems

I just "looped" the original fuelpump on the motor (disengaged)

[purplemyth]

It's called 'vapor lock' here Al, but he said he replaced all his lines.
Unless he has a line too close to an exhaust, doubt that's it.

[Alpenretter]

Originally Posted by purplemyth

It's called 'vapor lock' here Al, but he said he replaced all his lines.
Unless he has a line too close to an exhaust, doubt that's it.

The engine block heats up the pump enough to create "locks", my lines were new and far away from all form of heat sources.
I had my doubts about "the steam lock theory" too,
but it worked !

[purplemyth]

Hmm, That is true too.