'67 starts fine, runs fine...for about 20 minutes, then...

[Jim Bear]

1967 Beetle

OK, first the scenario:
I start up the beetle and drive to a friends house about 15 minutes away. Runs fine. Cruise at 60 the whole way. Takes the one hill fine. Get to friends. Chat for 5 minutes. Get back in beetle and fire it up. Hit the road, friend wants to drive for a few, the bug is clearly getting unhappy. Slight loss of power. Slight stutter/buck. This gets worse over the course of the 5 minute test drive. Drop friend off and start for home. The bug is running like crap. Hard to get it up to speed to shift. If I push it there is a slight backfire. I can cruise in third as long as I do not give it too much gas or hit a hill. Hit a hill, barely make it up. Have to downshift to 2nd. Stuttering and slightly bucking. Barely make it home.

Back story: I have had this car since last year and have not really driven it. Prior to the summer the bug was running fine. I took the engine out to fix an oil cooler gasket leak. Cleaned everything up, reassembled, tuned on an engine stand, all good. Put it back in and the above issue manifests.

This weekend: Check fuel filter, it's clean. Pull carb. Shoot it with air, squirt it with carb cleaner, inspect the choke, shoot with more compressed air, put on new gasket, reassemble, start car, drive, same damn problem.

Have checked: cut-off solenoid, choke element, fuel filter.

Any assistance would be appreciated.
_________________
"You're either on the bus, or you're off the bus." ~kk
'85 Vanagon Westy - George In the Stable 2020-?/'74 Weekender - Ophelia In the Stable 2007- ?/'69 Beetle Convertible - SOLD 2017-2020/'67 Beetle - September SOLD 2013-2016 /'67 SO42 Westy - Sage SOLD 1996-2001 /'69 Transporter - Baby Blue SOLD 1995-1995/'72 Westy - Nelly - SOLD 1990-1995--STOP FRACKING

[clubtreb]

Check your points gap is .016.

[Bret2094]

[djshutup]

check for kink or gas clog right under the tank?
had similar experience and I had a nice kink under the tank.
Also if you go that far blow out the gas link with air for grins and inspect the filter in the bottom of the gas tank (the sock filter).
_________________
1967 Volkswagen Bug (stock). 1980 Yamaha XS400 Special II (stock). Ya I like stock classics

[61SNRF]

This is one of those issues that can go either way, spark or fuel.

Easy enough to first check to make sure the fuel tank vent is not clogged or restricted. If it's not vented properly, after 20 minutes or so it could go into a vacuum and stop the fuel from flowing. When the problem occurs, loosen the gas cap and see if it's back to normal.

As said above, a bad coil can also do the same thing. When heated up they can only produce a weak spark and the car will act exactly like it's not getting enough fuel. Easiest to just swap out a known good one and give it a try.

Condenser is near the bottom of the list, but again can cause weak spark, so replace it if it still acts up

Don't think your temps are high enough this time of year to induce vapor lock, but you never know. Report back if the above has no effect.
_________________
-Bruce

An ounce of prevention is worth a pound of cure.

[Eric&Barb]

Full tune up first.

If that does not do the trick, it could be the coil or dist condenser is going bad.
_________________
In Stereo, Where Available!

[Aussiebug]

As vwkind says, check the in-tank filter. For the standard bugs, it comes out when you unscrew the tank outlet (careful - you'll loose any fuel still left in the tank). The metal gauze filter does corrode and collapse and allows rust flakes to partly block the outlet and that produces exactly the symptoms you describe. Non-corroding plastic replacements are available.

Of course checking simple things like the points gap is good too.

Re Brett's "Bosch blue coil" comment above. Not all "blue coils" are the same.

The stock ignition system works best with a coil with 3.5-4 ohms between the + and - terminals (all other wires disconnected). Pointless ignition systems work best with a coil having about 2 ohms resistance in that primary winding (but will usually work with the 3.5-4ohm version).

Bosch blue coils come in both varieties (not usually marked on the can or the box). So you need to take your digital mulitmeter with you when you buy a coil.

Using a low-ohm coil in a stock ignition system increases points-burn so you need to check the gap more frequently and replace the points more often.
_________________
Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com

[2bugtony]

Hello
How cold was it when this happened? I had a car do this and what was happening is the intakes was frosting up. The gas was not getting to the engine. They had ice on them like the top of a freezer. I went out the next day after they warmed and the car ran fine. I don't know the proper term for it but im sure someone on here does. I bet that is your problem. if it happens again check the intakes. This will happen in temp above freezing too.

[Cusser]

Next time this happens, unscrew the gas cap. If it goes to normal, then you have a fuel tank venting issue.

Don't laugh, it happened to my 1970 VW in 1984:
...in mid-summer
...in middle of the day
...in the southern California desert
...at 112F temperature
...50 miles away from either Blythe or Indio
...driving at 30 mph on the Interstate 10 shoulder was not fun
...I didn't figure out what was wrong until I stopped in Indio
...and still had the Arizona desert to cross
_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Jim Bear]

Weather was not a factor, this happens in hot and cold.

The gas cap trick had no affect.

Next, I am going to pull the coil from the bus and try it in the bug. Same coil - Blue 00 012.

Then I'll keep checking the other stuff...
_________________
"You're either on the bus, or you're off the bus." ~kk
'85 Vanagon Westy - George In the Stable 2020-?/'74 Weekender - Ophelia In the Stable 2007- ?/'69 Beetle Convertible - SOLD 2017-2020/'67 Beetle - September SOLD 2013-2016 /'67 SO42 Westy - Sage SOLD 1996-2001 /'69 Transporter - Baby Blue SOLD 1995-1995/'72 Westy - Nelly - SOLD 1990-1995--STOP FRACKING

[fla2smoker]

Also check to make sure nothing is blocking airflow to the fan (tarboard, rag, etc.)... Had a rag get sucked up into the fan many moons ago and it ran just like that before melting and warping everything....
_________________
View my 66 build thread here: http://www.thesamba.com/vw/forum/viewtopic.php?t=507996

[jzjames]

[Jim Bear]

OK. I think the coil swap worked. I started it last night and let it run for 15 minutes. Then I drove it for about 15 minutes to a local strip mall. Then I drove around the parking lot to emulate city driving. Then I shut the car off for 5 minutes. Then I started it up and drove it home. The issue seems to have cleared. Now I can tune it proper. Thanks guys!
_________________
"You're either on the bus, or you're off the bus." ~kk
'85 Vanagon Westy - George In the Stable 2020-?/'74 Weekender - Ophelia In the Stable 2007- ?/'69 Beetle Convertible - SOLD 2017-2020/'67 Beetle - September SOLD 2013-2016 /'67 SO42 Westy - Sage SOLD 1996-2001 /'69 Transporter - Baby Blue SOLD 1995-1995/'72 Westy - Nelly - SOLD 1990-1995--STOP FRACKING

[Cusser]

Great !!!
_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Jim Bear]

It's back. The next drive I took the issue manifested again. The new coil was an anomaly. Have not dug deeper. Hopefully I'll have a chance this weekend.
_________________
"You're either on the bus, or you're off the bus." ~kk
'85 Vanagon Westy - George In the Stable 2020-?/'74 Weekender - Ophelia In the Stable 2007- ?/'69 Beetle Convertible - SOLD 2017-2020/'67 Beetle - September SOLD 2013-2016 /'67 SO42 Westy - Sage SOLD 1996-2001 /'69 Transporter - Baby Blue SOLD 1995-1995/'72 Westy - Nelly - SOLD 1990-1995--STOP FRACKING

[highroller]

Do you have an electronic ignition?