Fuel issue, won't start for 1-2 hours after it dies...

[grittycereal]

Before I parked my 1971 vw the summer before last as it was starting to run like crap, I had this reoccurring issue and I was tired of dealing with it.

Scenario: Hot summer day, cruising down the highway, drive for 20 or so miles then it sputters out like it's out of gas. Go around to the back, and the fuel filter between the pump and carburetor (which I know shouldn't be in the engine bay, that's just the way the mechanic hooked it up) is only 1/4 to half full, with air bubbles flowing up through the bottom. I have to wait at least 1 1/2 hours sometimes 2 before it starts again. I assumed that this was due to the hot summer day over heating and vaporlocking as I didn't seem to have any problems if I left the back hatch open when driving. Did this to me 4 or 5 times before I gave up on it.

Well I got it back up and running last month, got new points and adjusted the distributor and is running good again. Well a week ago I took the first longer trip that I've taken it on in a while, figuring that since the weather is cooler now in October, didn't think I'd have any issues. Drove 15 miles out of town then it parked it for about 30 minutes before heading back, then 15 miles back, right as I got back into town it died on me the same way it was doing it 2 years ago. Then the other day I hadn't even driven it 10 miles and it did it again. Then it happened AGAIN yesterday. 3 times in a week. Frustrating. I'm starting to think that it was never an overheating issue to begin with. I'm getting real tired of getting stranded for hours at a time until I can start it up again.

A mechanic told me that he believes there might be a crack in the fuel line between the gas tank and the pump. I would think that would leak gas out, not let air in but I'm no mechanic. Wanted to get some other opinions. I understand to get to the gas tank you have to drop the motor so I'm hoping it doesn't have to come to that! Thank you for your thoughts, ideas and help!

(Edit, I replaced all fuel lines from the tank to the pump and still no change)

[aeromech]

Let’s start with what year bus you have and maybe some pictures of your engine

Edit: oops, 1971

Well since I have roughly 30 years as a 1971 bus owner I may be able to help
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[grittycereal]

Any help would be great! I understand the 71 has a unique dual port motor that was made only for this year as a transitional motor between the '70 and '72 models. Sitting around for 2 hours waiting for it to be able to start again is no fun!

[[email protected]]

Maybe check the simple things first. There should be a metal tube portion to your fuel line in the engine compartment. It goes through a small rubber grommet in the front tin, then gets secured by the plug wires in the little black plastic clip on the edge of the fanshroud. If it’s not secured out of contact from heat of the cylinder tin, intake heat riser, or heat exchanger, it could cause vapor lock. You should be able to access the tank outlet above the transaxle without too much difficulty. Try draining out as much fuel as you can, then unscrew the hex nut to remove the little pipe outlet of the tank. You could take a couple sections of hose, and slip them over some needle nose vise grip jaws to clamp the fuel hose while disconnecting it. There’s a brass screen that goes over the top of the pipe. You could check it for any rust/debris that might be limiting fuel flow. I worked on a “restored” 70 about a year ago, and had the tank out to replace the sender. Once I pulled the sender, I found the entire inner surface of the tank was horribly rusty, and would have caused nightmares for the new owners.

[Wildthings]

[aeromech]

This isn’t going to come across well but here goes...

Since you are the first to admit that you aren’t a mechanic, let’s get those pictures. We can tell way more about your engine by seeing than you’d be able to tell us. Things like improper parts or missing air seals. We are here to help but right now it could be dozens of reasons and each one is going to cost you money and time until we hit gold so pics are a real value
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[mikedjames]

I would suggest you have both a blockage at the tank and a small leak in the fuel hose.
A stock fuel pump can suck hard and if there is a pinhole in the fuel pipe it can suck air.


I know this because it used to suck a fuel shutoff solenoid valve down so hard that it wouldnt let go when I turned on the ignition...
(I ended up boosting the drive to the solenoid to 24 volts for a short while to pull it open..)
_________________
Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy

[SGKent]

I can think of 20 things that can cause this. You need someone who is a mechanic and who can rule out items one by one. Start by putting you location in your Avatar so we can figure out whom to send to you, or whom to send you to. IMHO you haven't the patience to deal with this systematically. That is an observation and not a slam. With so many things being possibly wrong you could spend 2 weeks here on the forum reading replies. Really. A good mechanic could find it probably in about an hour.

In general there are 3 things that are involved

Spark and spark timing
Fuel to Air ratio (too lean or too rich)
Compression (like tight valves could make it not start)

find out which is missing and that will solve it.

Also - be very careful how you describe things. If you say it won't start we assume you mean it will turn over and crank but not fire. BUT you could mean you turn the key and nothing happens.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[grittycereal]

You guys are great thank you for the ideas and suggestions! I will go over the replies one by one for you guys,

aeromech here are a couple of pictures of the engine bay for you https://bit.ly/2ObXZxD

Gkeeton thank you for the ideas! I crawled under and found the tank outlet, the gas line is clear of the heat exchanger going into the tin, I do have some foil heat tape around the gas line going from the tin to the pump, I did notice the line was indeed resting on the header which I have just remedied, however I have noticed that it is still pretty cool to the touch when I'm broke down. I disconnected the line from the tank to the pump and the gas flows out beautifully.

Wildthings, as previously mentioned, when I disconnect the line from the pump the gas flows out perfectly. I have not thought to try this when it's broke down and there is no gas from the pump to the filter/carburetor, but I will next time. I did try driving it without the gas cap by your recommendation yesterday but it did it to me again, dang it!

Mikedjames, I will try to see if the gas flows from the tank to the pump by disconnecting it the next time it breaks down. A leak in the fuel hose could explain the bubbling that I am seeing. I don't see any bubbles at startup, just until I'm broke down on the side of the road, but I will periodically check as I'm driving and study the habits on when I start seeing any air coming through the fuel filter if that is of any help.

SGKent thank you very much for your reply. My location is in my avatar now, there is a vw mechanic here in town, but my vw friends tell me to steer clear of him. There is a great shop that is 130 miles away from me but that's the problem, it's 130 miles away and their turnaround time is usually 2-3 weeks before I can get it back. I had a mechanic put in new points and set the timing and adjust the valves because it was running like crap but she runs so much better now. Fuel to air ratio could be an issue I suppose as I don't think he did anything carburetor-wise. She runs great... right up until the second it doesn't. And yes I can crank crank crank it all day long but it won't start up until I let it sit for a couple of hours, I apologize for the confusion on that.

Another thing I have noticed, is that from my experience with old trucks over the years is that usually when you pour some gas into the carburetor, it will start up and run for a few seconds, then if you pour a little more gas into it you can keep it running. With this bus, when I pour a little gas in, it starts up but only short of a second before it dies. I can't get it to stay running by shooting a bit of ether or pouring a little gas in like I was normally able to do with other vehicles. I doubt this information is of any help but I thought I'd throw it out there as I attempted to do this yesterday hoping it would give me any sort of clue.

Thank you again you guys for all your help, I will see about installing a new fuel line from the tank to the tin (all other fuel line in the engine bay is newer and in good shape) and I will check to see when if any air bubbles are going through the filter before she dies on me, and also double check if there's still good fuel flow to the pump the next time it craps out.

[Wildthings]

You may have more than one problem. Have you checked that your points are actually opening. If the wear block breaks off it can leave the points so they barely open cold, but once the current starts to flow and they warm just a bit they don't open any more.

[grittycereal]

[aeromech]

Thanks for the pictures.

Two comments

1). Your brake booster hose looks like it could be original. Disconnect it at the intake manifold and plug the hole in the manifold. Drive it and see if that helps. You can live without power brakes for a while.

2). You carburetor also looks like it could be original. That’s a great thing. You have the throttle damper and the throttle positioner. I suggest you send it to Volzbitz and have Tim make it like new. Then hook up the altitude corrector to the throttle positioner and you’ll be back pretty close to how VW built it. Then all you need is a DVDA 205q to be complete.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[Wildthings]

[grittycereal]

If that's been the culprit this whole time, then in theory I can drive it until it dies on me, and THEN disconnect the brake booster hose, and the problem should go away and it should be able to start back up?

And thank you for the suggestion on volzbitz I would love to have the carburetor redone to make it like new again. I believe I had the DVDA before I got it replaced, the diaphragm went out on it, but I couldn't find a new one and didn't want to take my chances with a different older one, that's why I went with this one that isn't DVDA, would like to have it back to the stock distributor again, I've been told that it will help it run with more power..

And yes, they have been lubricated! Good looking out!

[aeromech]

I’d just plug it now and see if there is any change.

The theory is that when your engine is cold, the choke closes to make it run richer. When the choke opens and leans the mixture, it may be too lean with a leak.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[grittycereal]

Alright guys, sorry for the delay, hard to find enough time to run around and risk being stranded for a while but I did it today, problem just keeps getting worse and worse. Made a few stops about town, drove less than 10 miles altogether, and it pooped out. Luckily just a few blocks from my house so I could walk home and hang out for a couple hours. Here's what I have replaced, and the things I have tried, to no avail.

Replaced the hose from the tank to the steel line (old line appeared to be in good condition but I replaced it anyways), removed the steel line from the firewall- tested- no leaks

Adjusted fuel lines to make sure there were no hot spots, and all lines were cool to the touch.

Plugged the brake booster hole in the manifold

Removed the gas cap

Despite these things it still died on me, this is what I checked as I was on the side of the road.

Removed incoming fuel line from tank at the pump after it died on me, and gas flows freely, and no air bubbles appeared when I submerged the line in gas.

Removed outgoing fuel line from the pump to the carburetor and cranked it for a few seconds a couple of times to see if any gas would start filling the filter, no luck. (so it appears that the carburetor has anything to do with it.)

After parking it for a couple, again tried the test mentioned above and gas was starting to come out again, seems to be weak (but I've never tried with a known good pump to compare it with so I don't know) but still starts pumping again nonetheless, enough to start it back up again and let me drive it around for a while again.

What has been puzzling me all this time is why the hell there's air bubbles going through my fuel filter! So with all this information, I'm coming to the conclusion that there's something wonky going on with my fuel pump as gas is flowing freely to it, but the pump isn't pumping when I'm cranking until it sits for a few hours. Here is a video of what the filter between the pump and the carburetor is looking like right before it starts being starved of gas and dies and won't start back up again for a few hours.

https://www.youtube.com/watch?v=KWThxFjO9Jc

There is no bubbling at first, then the more I drive it the more it starts bubbling a little bit, then the more I drive it it gets to what you see in this video right before the fuel level gets lower than half and there is no more gas getting to the carburetor. As I said before, after it dies, when I disconnect the fuel line going TO the pump, the gas flows out perfectly fine!

Let me know what you think... Replace or somehow repair the fuel pump? Could it be crudded up and need a good cleaning? Where is the air coming from? Why won't it pump anymore after it dies until I wait a couple hours? I hear the pump push rod can wear down over time creating a weak flow, would a new one of these work? https://www.mamotorworks.com/VW/product/fuel-pump-push-rod-61-73-generator-40hp1200cc-1600cc_378951

Any other tests I can try?

Edited to add:

Basically to recap: through all of my diagnostics this is what I'm getting out of this.

When the bus dies I observe 4 things quite plainly.
1: As I'm driving through town the fuel filter is bubbling progressively worse until air is getting sucked into the carburetor instead of gas and that's why it dies on me.
2: Gas is flowing TO the pump freely with no bubbles. (No blockage or suction from gas tank or cap)
3: When cranking, gas isn't pumping FROM the pump even when the line to the carburetor is unhooked.
4: Pump starts pumping again after sitting for a couple of hours and the bus happily starts right back up.

Thanks again for all your help guys!

[aeromech]

Don't know why it has bubbles but that sure looks like a problem. Don't think a pushrod would cause that. How about a picture of your pump?
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[grittycereal]

Removed fuel clamp on upper hose when testing after it died, just fyi.

[aeromech]

no worky
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[grittycereal]

Hmm, try these links then..

https://i976.photobucket.com/albums/ae249/moneyequ...1840_n.jpg

http://i976.photobucket.com/albums/ae249/moneyequa...4976_n.jpg