Engine runs rough after hour+ drives

[timnosenzo]

Hello all! Probably my first post here, but been doing plenty of reading and searching. I’m hoping to get some thoughts on an issue I’m having from the Samba experts.

A little background, I recently acquired a 1964 Bug from my father that he owned since 1979 and restored and built himself over the years. The car has a 1641 engine in it, with dual Solex carbs (old Gene Berg kit) and a some other mild hop-up parts (counter-weighted crank, I believe a cam, exhaust, etc). The car does still have a points-based ignition system. I grew up with this car and am certainly familiar with air cooled VW’s, but by no means an expert trouble-shooter.

The car generally runs great, except when I drive the car for extended periods - typically an hour or more. Then, it starts stuttering and loses power, and if I keep going it gets progressively worse to the point where it’s undriveable (but still runs). If I park the car overnight, by the next day it will run fine again (or so has been the case in the few times it’s happened).

Some observations - my father had installed in inline fuel filter in the engine compartment (which I have already removed). Normally the bulb would be full of fuel, but at the times it was acting up it would be nearly empty - and when I would check it the next day it would be mostly full again (with the car just sitting). The car had this behavior both before and after I removed the inline filter. I also replaced all the fuel lines from the pump to the carbs.

When it’s acting up, it doesn’t seem to matter if I let it sit for a while. It did this yesterday, and I let it sit and cool down for over an hour. When I got back on the road it was marginally improved for the first couple minutes, but got to be really bad again after that. Time seems to be the only thing that helps. Highway driving vs mixed driving doesn’t seem to matter. Ambient air temp doesn’t seem to matter.

The fuel pump has been replaced somewhat recently (within probably 2k miles), but it is an aftermarket pump of unknown manufacturer.

My feeling is that it’s being starved of fuel, but I may be being duped by the fuel filter observation (I’ve read some people say it doesn’t matter if there’s fuel in there or not). I had thought that possibly the gas tank wasn’t allowing air to vent in, so the system would eventually the system wouldn’t be able to pull full through, but I don’t hear any airlock when I take the cap off and it doesn’t seem to change anything.

Please let me know your thoughts or any possible things I could check.

Many thanks in advance for your help!!

[Eric&Barb]

Fuel filter full or empty means nothing. Would help next time you have this problem to remove the top of the carb and see if it is low on fuel. Also check for spark with a spare plug and note what color, this last part easier seen in the shade or night.

Could be:

1. The fuel pump push rod is sticking in the fuel pump stand/base. Might need to carefully ream it out with a slightly larger drill bit.

2. Coil failing, replace with known good one.

3. Condenser failing...
_________________
In Stereo, Where Available!

[Max Welton]

If the valve lash is (or are) too tight one or more valves may not be closing all the way when the engine gets hot.

Assuming aluminum pushrods of course.

Max
_________________
1967 Type-3 Fastback
Under the Knife https://shoptalkforums.com/viewtopic.php?f=24&t=151582
Home Stretch https://www.thesamba.com/vw/forum/viewtopic.php?t=767836

[Cusser]

VW used vented engine lids for beetles starting with their first 1600cc engine for 1970 year. Your 1964 likely has a solid lid. I'd try lid standoffs, or at least try the tennis ball trick.

Does your engine have ALL the tins and rubber seals?

Re-adjust the valves when cold.

Show us some good engine pictures !!!
_________________
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

[Pruneman99]

Gas tank vacuum. Remove the gas cap to check.

[timnosenzo]

Thanks everyone for the replies! Some good leads here and will look try some of these out.

@Eric& Barb - I like your suggestions - I had thought about trying to evaluate fuel delivery/supply while it was acting up. The coil/condenser is an interesting option as well.

@Max Welton - Still alu push rods as far as I know - I will check this out.

@Cusser - Yes, still a solid hood. It does have all the tin & rubber seals, my father was pretty adamant about that stuff. I will get an engine photo!

@Pruneman99 - This was one of my immediate thoughts, though when I remove the gas cap it didn't change anything and I didn't hear any airlock noises. I was also wondering if the fuel line could be obstructed in the tunnel or something and restricting flow. That's on the list to check as well

Just to add more info - as I had mentioned, this issue popped up while out on Sunday. I was quite a ways away from home, so I had made a few stops to try and give it a break and see if it would improve - including about an hour stop for lunch. The car has an oil temp gauge, and after the lunch stop the engine was cooled enough that the oil temp didn't register on the gauge and the engine was coolish to the touch (though the dist was still quite hot). But after a minute or two of driving, it was still struggling.

I made it to a friends house and kept the car there overnight. Last night I went to pick it up, it started right up and made the 20+ minute drive home flawlessly (including a run on the highway and some goos size hills up to my house). So frustrating!

Very helpful, thanks again!!

[Max Welton]

Well it doesn't really seem to correlate to heat from your description. So I would not think poorly adjusted valve lash to be the cause.

Max
_________________
1967 Type-3 Fastback
Under the Knife https://shoptalkforums.com/viewtopic.php?f=24&t=151582
Home Stretch https://www.thesamba.com/vw/forum/viewtopic.php?t=767836

[Cusser]

I have a lawn mower that would crap out when it ran a while and got hot. It turned out that its choke was stuck in the "rich" position, never opened up correctly, fixing that solved that issue.
_________________
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

[timnosenzo]

[Eric&Barb]

Do get:

1. Plug in the side of the distributor to keep out junk.

2. Flexible plastic conduit for all the uncovered wires there. Left as they are the insulation will get worn thru and short out.

3. Rid of all those cheap wiring connectors, and either get factory ones that use a factory style crimper for a gas tight connection, and/or solder and heat shrink. What you have now will get loose and have voltage drops from corrosion.

https://www.thesamba.com/vw/forum/viewtopic.php?t=338938

4. Lower fresh air tubes seals.

http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=113119571B

or

http://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=113119571
_________________
In Stereo, Where Available!

[andk5591]

Clogged fuel vent, obstructed fuel outlet in tank, pump issues as mentioned. Without measuring the fuel pressure when it happens means you are flying blind.
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[pb_foots]

Might be crud in the tank. Clogs the 'sock' and stops fuel flow, overnight crud falls off and everything is fine.

My Mom's squareback had that happen once on a roadtrip. Every hour or so the car would idle OK but wouldn't run at freeway speeds. Pull over and wait an hour, everything is fine for a a while.

Smart AAA kid figured it out and got us going again.

Easy enough to check anyway. Bit of a pain to drain the tank, but if you see a lot of rust or gunk in the drained gas you may have found your culprit.

https://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=111209147A
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[Pruneman99]

Maybe the fuel pump rod is hanging up. If the fit is tight through the spacer block, once it gets hot it can start sticking? IDK, a fuel pressure gauge would help narrow down fuel delivery issues, whether it's the pump, line, or tank.

I can't tell if you're running points/condenser. By the coiled green wire I'd assume so. I've have had a bunch of problems like you describe with new condensers. Now I'm running a really old one I stole off a core distributor. Works great. No more random crappy running especially when hot or under load. Avoid the small polished looking ones. Try to find one with the Bosch numbers stamped on the outside.

On a unrelated note, where did you get the air filters to fit those pods? I've been looking for some and haven't had much luck.

[timnosenzo]

Thanks again for all of the replies, I really appreciate it! Yesterday I had some time to go through a few things. I took the tank out, blew air through the fuel line to the engine (seems unobstructed). Inside gas tank is clean. So those seem good.

I also took the fuel pump off to check the rod. The rod movement seemed fine (though the engine was cold), but I did fine a big wad of what would only be described as a sticky/waxy substance in where the rod actuates the lever under the fuel pump. Possibly some old lubricant? I cleaned it out a bit, but wasn't sure what kind of lubricant should be in there, if any. Any thoughts on that? The stuff I took out of there definitely seems like it could obstruct the lever from a full range of motion.

[Q-Dog]

The bottom of the fuel pump, around the actuating arm, should be packed with grease. That information should be in your shop manual.
_________________
Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[andk5591]

Blowing through the lines is not adequate. Allthough its messy, hook up the gas tank and check the flow near the rear axle. Should be a nice steady stream. Had a 66 I restored a couple years ago. Would idle all day. When I had the RPMs up for any length of time, it ran out of gas. Snaked the main line and cleaned out a lot of crap.
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[timnosenzo]

[Pruneman99]