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Wed Jul 11, 2012 9:52 pm

OK today I was driving down the interstate and it has been warm around here lately and I had about half a tank of fuel or just a tad more. I started up an incline and the engine started sputtering so I limped off the exit and got to the light and the engine shut off but restarted right away. I made it to the closest gas station and filled the tank but seen nothing out of the ordinary but i did not look at the fuel filter. I then restarted and continued down the highway but a little slower pace for about ten miles and started up another hill and the same thing only once reaching the top and starting down the other side it shut off and when checking the engine the gas in the glass filter was only half full and boiling. I sat for a while and after cooling down a bit I could pump the gas and it would almost restart but did not do so untill sitting for some time and I had it towed home just to be safe but once home and getting it off the rollback it started and I was able to get it into the garage and the fuel filter was ful again. Need to keep this from happing again. I have made this same trip twice in in the same day in the same heat before and have had no issues till today. I know I need to move the filter down by the trans and am planing to do this. However in doing this will this cure the vapor locking or am I going to experience the same issues in the hose from the pump to the carb but now just not be able to see it and is this really occuring in the pump itself and just going up the line. Also what fuel line should I use and if the answer is what is on there now where do I get it. I used the search feature and read thur several threads but none really answered all my questions. Any guidance would be great. I am not completely lost working on cars but am in no way a VW expert but am trying to learn from everyone here. Also I have added some pic's to see if it helps in answering my questions. Everything you see was as I got it from the PO. Thanks

Thu Jul 12, 2012 2:00 am

I don't think moving the filter will help with the vapor lock problem. Your engine compartment seems pretty well sealed up, so that looks good. I think all of us will be seeing much more of this going on with today's ethanol mixed fuels and warm ambient temperatures. I hear this on AACA's forum all the time these days and so it's not just VW's, but all makes when it comes to engines with carburetors. The FI cars don't have this problem because their fuel is high pressure and is constantly recirculated back to the tank keeping it much cooler. Lets face it our cars are getting older and the type of fuel's that are being used have passed us by. Are older cars are not really designed to run on this stuff. I can't wait for the EPA's mandated 15% ethanol to begin. Those guy's just don't understand (maybe they do) ethanol not only increases the incidence of vapor lock, but attacks some metals, fuel hoses, some plastic's like neoprene and cork. I pulled up this little tip for ac VW's you might want to read;

Vapor Lock

~~~
Have you ever had this problem? You are driving home from work late in the afternoon. It's 90oF (32oC) outside and there's lots of traffic, so accelerating and decelerating a lot. The engine is working, and you know it's getting hot.

Then, about 4-5 miles from home, the engine suddenly starts surging and then decides to take a rest altogether. As you pull off the road you think to yourself, "This couldn't be an electrical problem - the engine wasn't actually cutting out, just surging."

Alternately, you drive to the store on a hot day (far enough so that the engine gets thoroughly hot); when you return from the store to the car, it won't start! What's up with that!?

So you lift the engine lid and notice right off that there is no fuel in that small fuel filter in the line between the fuel pump and the carburetor (if you have such a filter -- we actually recommend that you don't have a filter here). So right away you know the problem (right?) - vapor lock! Every VW we have had has done this when it got hot. They seem to be especially touchy both when they're hot and when it's getting close to "Tender Loving Care" time, when timing or valves may be a bit off the numbers.

The usual problem is that the whole engine gets thoroughly hot, and when you switch off, there is a 'heat soak' period when the temperature in the tinware and engine compartment rises because the residual heat in the cylinder/heats isn't getting blown away by the fan. The heads run at about 265-285oF (130-140oC) and can run up to about 355oF (180oC) on a really hard run which is pretty hot.

This causes the metal fuel line around the tinware, the fuel pump, and the carburetor to all heat up somewhat, causing either excess vaporization of the fuel in the carburetor, or and actual vapor lock in the fuel line or fuel pump.

As a result, starting is sometimes hard. With hot fuel in the carburetor, the least reduction in pressure (through the carburetor throat) causes instant vaporization, perhaps of fuel in the float bowl too (which breathes into the top of the carburetor throat), and of course a vapor lock in the fuel line or pump is even worse, because it will result in an empty fuel bowl in the carburetor - the car uses that fuel and stalls because it can't get any more. Then it takes a lot of cranking to fill the fuel bowl, once the vapor lock itself is cleared.

In summary, following is the cause and the cure for vapor lock -

Cause: The engine overheats, causing the fuel line, fuel pump and carburetor to heat up.

Result: Excess vaporization of fuel in the carburetor and/or actual vapor lock in the fuel line or fuel pump.

Cure:

Wrap the fuel lines on both sides of the pump with aluminum foil.
Note: This is a precaution if your car is prone to vapor lock. It won't help much once the problem has
already occurred.

Pour a little water over the fuel pump to cool and re-condense the fuel, being careful not to splash the distributor. If no water is readily available, hopefully there is some in the windshield washer bottle. It doesn't take much.
Hold the throttle open just a bit with the accelerator pedal while you crank. Don't move the throttle at all while cranking, or the accelerator pump with flood the carburetor. The reason for cracking the throttle open it to avoid using the idle jet alone, as this runs the car richer than the main jet, and a rich-hot mixture makes the car flood easily.
When the engine catches, hold the throttle still until it clears the excess fuel (revs up smoothly).
Away you go!

~~~
Other things to check if vapor lock has become a regular problem:

Is the heat riser under the inlet manifold getting too hot? It should be hot enough to keep the manifold above it warm, but if the heat riser is providing excessive manifold heat, it can also be overheating the fuel line which runs close to it on the way to the fuel pump. There are "small hole" heat riser gaskets available (you'll have to look for them though) which can reduce the heat flow through the heat riser if it's running finger sizzling hot.
Is the carburetor running lean? Many new H30/31 and 34PICT/3 carburetors are supplied with lean jetting as an emissions thing, which makes the engine harder to tune, and causes higher engine temperatures. There is information elsewhere in these articles about suggested jetting for various distributor, engine size and carburetor size options.
Is the carburetor pre-warmer working properly? The paper tube up to the carburetor inlet is supposed to draw air from near one cylinder head to speed up the engine warm-up process, but if it's stuck full on (breathing hot air) the engine will run hotter than it needs to, which will worsen any potential vaporization problem. There are two actuating mechanisms - the earlier engines (up to about '71-'72) have a pull-wire operated by the right hand cooling flap assembly, and later engines have a vacuum line from the manifold directly under the carburetor, up to a temperature switch in the air cleaner and another vacuum line from that switch to the vacuum canister on the side of the air cleaner inlet. The early type is just on-off, depending on whether the flaps mechanism (controlled by the thermostat) is open or shut, but the later type may hold a partial position, depending on the temperature inside the air cleaner. Of course if your engine has no cooling flaps (tsk tsk) or if it has no vacuum lines connected, or an aftermarket air cleaner, then the carburetor inlet will be breathing full cold all the time - a potential icing problem, but not an excess-heat problem.
Is any of the tinware missing?. If the engine is missing any of the tinware which controls the flow of cooling air around the heads and cylinders, it WILL run hot, and this will worsen any vapor lock problems.
Is the engine tuned properly?. If the car is out of tune it has to work harder to provide the power to drive the car, so it may run hotter. Keeping the car well tuned keeps the engine temperatures in the normal range, minimizing any vapor lock problems.

Thu Jul 12, 2012 9:16 am

My first bug had a 3 piece glass fuel filter. Wasn't on there very long. I replaced it after it fell apart. Left me stranded on the side of the road. Til I bypassed it with washer hose. Drove home at half throttle. I'm just glad it didnt start a fire.

You should get a better one.

Thu Jul 12, 2012 9:21 am

First i would move the move the filter from the engine compartment. Regardless of all the arguments about having it in there or not, the less connections you have to leak the better.

A much better place for your filter is under the fuel tank or alongside the transmission.

Next, it is normal for there to be air in the filter. It is also normal to see bubbles in there.

Many of those filters fill from the inside of the filter element. So fuel and crap flows from the inside of the filter to the outside. So the crap gets stuck inside where you can't see it.

Vapor lock is normally caused by too much heat at the fuel pump. Once the fuel boils it gets air in it and the pump can't move the air out to allow fuel in.

Many years ago I had this problem on a 63 that was my daily driver. I carried around a gallon jug of water and anytime it happened I simply poured about a quart of water on the pump and it would restart every time.

But you need to really check and make sure your issue isn't simply crap in the system.

Move that filter and since it is a glass one you should be able to take it apart and clean it. If not, replace it.

Next jack up the side of the car so the filler neck is on the down side and look in the tank with a flash light. Crud looks like crud. Water will look like little geletin globs on the bottom of the tank.

There is a sock screen on the pick up and it can get clogged. If you don't know how long it's been in there, you may want to think about replacing it.

Fri Jul 13, 2012 8:28 pm

Thanks everyone for the replies this helps very much. :D

Sat Jul 14, 2012 7:10 am

I haven't actually tried this, but I'll throw it out there into the mix of this discussion:
Instead of pouring water on the fuel pump, how about a couple of squirts from a can of Dust Off (generic for pressurized air) like you use to clean computer keyboards and the like? The air coming out is quite cold and could do a good job on fuel lines, heat risers, etc.
I wouldn't recommend long blasts of super cold air on an overheated fuel pump, but maybe some blasts from a distance could do the trick?
Just asking.

Sat Jul 14, 2012 8:17 am

Listen to drscope. Diagnose for vapor lock before you decide it is the problem.

Sat Jul 14, 2012 8:56 am

Throw that damn death trap filter away. :wink:

Sat Jul 14, 2012 8:57 am

doc hopper wrote: I haven't actually tried this, but I'll throw it out there into the mix of this discussion:
Instead of pouring water on the fuel pump, how about a couple of squirts from a can of Dust Off (generic for pressurized air) like you use to clean computer keyboards and the like? The air coming out is quite cold and could do a good job on fuel lines, heat risers, etc.
I wouldn't recommend long blasts of super cold air on an overheated fuel pump, but maybe some blasts from a distance could do the trick?
Just asking.

Those cans are expensive.

Water is free.

Sat Jul 14, 2012 7:32 pm

Make sure to hose clamp both ends of both fresh air tubes. Otherwise when one of those hoses pops off you can fry a head or engine.

Sun Jul 15, 2012 8:55 am

The boiling gas isn't fixed by moving the filter because gas can boil inside the fuel line or pump. My '67 continued to have vapor lock after removing the filter. The only thing that worked was offset hinges on the engine lid. I don't like the look but until I can find a slotted lid for better air circulation I'm stuck with it. Everything else about the engine is good so I can't blame the problem on timing or rich gas or whatever. My probem is it's a '74 bus engine trapped inside a tightly sealed '66 engine compartment.

crvc

Sun Jul 15, 2012 9:22 am

Next time you have the problem, pull off the air cleaner and see if fuel is coming out of the larger brass tube that comes out into the throat of the carb. Could be your real problem is too much fuel going to the engine and flooding it.

If you see fuel coming out of that tube, it could be caused by bad/cracked float, or just too heavy or you need a second gasket between shut off valve and the top of the carb.

Fri Aug 10, 2012 3:16 am

I was at the local VW Garage and was getting some fuel line and ran into an old gentelman probably in his 80's and we got to talking about my 58 and I was explaining what had happened and that I thought it to be vapor lock and he smiled and shook his head and said I know what your problem is and here is how to fix it. He went on to tell me that with his he would start out to work in the summer months and almost daily about the same distance from his house his would quit just like it was vapor lock and leave him on the side of the road till it cooled off. What he found his to be was the phenolic block under the fuel pump was swelling just enough to squeeze off the rod and keep it from pushing against the diaphragm and pumping gas. once it cooled it would work again. He said he took his rod out and put it in his drill and polished it with some emory cloth and never had anymore issues. I also asked the mechanic/owner at the garage if he had ever heard of this and he said yes he had because some of the blocks came from China and they would have to remove them and even drill out the hole for the rod a bit to keep this from happing. I have not removed mine yet but I am going to give it a try when I move the fuel filter down by the trans. Anyone else ever heard of this?

Fri Aug 10, 2012 6:10 am

crvc wrote: The boiling gas isn't fixed by moving the filter because gas can boil inside the fuel line or pump. My '67 continued to have vapor lock after removing the filter. The only thing that worked was offset hinges on the engine lid. I don't like the look but until I can find a slotted lid for better air circulation I'm stuck with it. Everything else about the engine is good so I can't blame the problem on timing or rich gas or whatever. My probem is it's a '74 bus engine trapped inside a tightly sealed '66 engine compartment.

crvc
same here.... look what I did
when driving up hill, full throttle, 3rd gear, 80degreesC-176f......engine dies.
no gas, period. (but still idles)
Pour some water to the fuel pump(with the engine running)
solved!
after 8 days trying to find the error, came out to be that the pump has to have a preload in the diaphragm before tightening the screws (1.4mm as I remember)
and the other probable cause is that the rod that pushes the diaphragm up and down is rubbuing against the black base which will give same diagnose...check this short video for rod size and ...http://www.youtube.com/watch?v=L-QDI74acLY

Fri Aug 10, 2012 9:21 am

that video explained a lot, thank you for posting that link!

i'm going to look into this. my car has been giving the same symptoms as stated by others.

Fri Aug 10, 2012 10:31 am

thedudeabides13 wrote: that video explained a lot, thank you for posting that link!

i'm going to look into this. my car has been giving the same symptoms as stated by others.

There are two things that bother me about the video. 1. It's just great that the guy explained the differences of the pumps-we all need to know the differences, but the second most important thing we need to know is the MEASUREMENT of the two different rods! Second,that plastic fit in the case ( he calls a block) is there for a reason. The reason it's there is to keep the rod at the proper angle alignment to the distributor drive's rod to the eccentric on the distributor drive gear. It's supposed to be a slight interference fit to get the alignment angle correct.

D.

Fri Aug 10, 2012 10:34 am

Helfen wrote: thedudeabides13 wrote: that video explained a lot, thank you for posting that link!

i'm going to look into this. my car has been giving the same symptoms as stated by others.

There are two things that bother me about the video. 1. It's just great that the guy explained the differences of the pumps-we all need to know the differences, but the second most important thing we need to know is the MEASUREMENT of the two different rods! Second,that plastic fit in the case ( he calls a block) is there for a reason. The reason it's there is to keep the rod at the proper angle alignment to the distributor drive's rod to the eccentric on the distributor drive gear. It's supposed to be a slight interference fit to get the alignment angle correct. If that angle is sloppy you will wear out the tip of the drive and the drive cam.

D.

Fri Aug 10, 2012 3:53 pm

Just to throw another possibility out there. Is it possible you have another fuel filter in line? I had two (one by tranny and one in the engine compartment). This caused a vaccuum and would leave the one in the engine dry and cause the car to die. After it sat a while the filter in the engine would refill. I pulled the one on the engine and left the tranny location filter. Haven't had a problem since.

Sun Aug 12, 2012 12:10 pm

I don't know why this works as a quick fix but my 68 would vapor lock in the summer. An old timer suggested putting a wooden clothesline pin on the fuel line between the pump and the carb. I was able to drive for the rest of the night no problem. In fact, being the brainless teenager I was, I left that clothes pin on the fuel line for the whole summer without another vapor lock incident.
When I took it off in the fall, it was soaked with gas and no evidence of the cloth braided line leaking....weird.

Anybody ever hear of this type of fix or why it works?

Sun Aug 12, 2012 9:50 pm

gusss wrote: crvc wrote: The boiling gas isn't fixed by moving the filter because gas can boil inside the fuel line or pump. My '67 continued to have vapor lock after removing the filter. The only thing that worked was offset hinges on the engine lid. I don't like the look but until I can find a slotted lid for better air circulation I'm stuck with it. Everything else about the engine is good so I can't blame the problem on timing or rich gas or whatever. My probem is it's a '74 bus engine trapped inside a tightly sealed '66 engine compartment.

crvc
same here.... look what I did
when driving up hill, full throttle, 3rd gear, 80degreesC-176f......engine dies.
no gas, period. (but still idles)
Pour some water to the fuel pump(with the engine running)
solved!
after 8 days trying to find the error, came out to be that the pump has to have a preload in the diaphragm before tightening the screws (1.4mm as I remember)
and the other probable cause is that the rod that pushes the diaphragm up and down is rubbuing against the black base which will give same diagnose...check this short video for rod size and ...http://www.youtube.com/watch?v=L-QDI74acLY

So if I remove the pump to try this trick with sanding the block am I going to have to reset the pump with a preload or should it be ready to go right back in as long as I did not move anything on it. And if it dose how is this acomplished. Thanks for the vid it was a big help as well.