Vapor lock or failing fuel pump?

[TheRetroBug66]

Spring has finally arrived so I’ve been able to daily drive my 66 again. Had it out all day Sunday with no issues. Yesterday however it left me stranded after about 8 miles of driving on a 60F day. Got out and checked the fuel filter only to see it bone dry and the carb wouldn’t squirt. Clearly a fuel delivery issue. Waited over an hour and still wouldn’t pump or squirt fuel. Got it towed back and as soon as it got back it fired up and ran fine. I’ve driven the car a couple times this year when we had some good weather and had no issues and drove the car daily from September until we got snow and salt here in northeast Ohio. Only thing that changed recently was a few weeks ago I changed the fuel pump spacer since the old one was cracked and leaking oil. I’ve driven it since then with no issues and have verified it is free and not seizing up. The pushrod length seems to be about 0.350” out at the top of the stroke. This morning with it cooled down I manually pushed the pump and it indeed shoots a healthy stream of gas out. This has me completely stumped and puzzled. Gas tank also appears to be free of any debris that could plug the outlet and the vent tube isn’t plugged either. Again there’s been no change from driving it all day Sunday to failing after 8 miles Monday afternoon. I did notice it seemed to be low on power yesterday like it was foot to the floor and taking a while to accelerate up to 45mph. It was smooth acceleration just slow and sluggish. Engine is a 1600dp with a 34pict3 carb.

[Cusser]

1. Could the new spacer be grabbing the steel pushrod when hot?

2. Bad venting from fuel tank, so tank gets under vacuum? Try running with gas cap loose to check.
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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

[TheRetroBug66]

I’ve verified the pushrod isn’t getting stuck plus having driven it a few times since changing the spacer I don’t feel like that’s the issue. I’ll double check and make sure the vent is truly clear of debris.

[TheRetroBug66]

So I think I found the issue? The new pump spacer seemed to be too thick. When I measured with no gaskets the pushrod at its highest point was only 9mm. I sanded the heck out of the block and now with gaskets it’s at 12mm. Hooked up my pressure gauge and it’s showing a constant 4psi at idle and around 3000rpm. I’m thinking it just wasn’t making enough fuel pressure for the 60mph trip I did yesterday compared to the several short 40mph trips on Sunday. I will update after test driving.

[TheRetroBug66]

Test drove it about 25 miles with no issues. Still unsure of the exact cause for yesterday’s problem but it seems to be fine now.

[petrol punk]

Sounds like you figured it out. I definitely don't think it was vapor lock. I have NEVER had vapor lock on a 1600 style motor with the cheap stamped steel fuel pump, and I have driven my bugs in 118* weather. I have only ever had vapor lock on my 36hp, and I think the coolest day I ever had vapor lock was probably 95-100*. The 36hp style pump seems worse about this, maybe because it's near the muffler and it's made from a more thermally conductive material than steel that can soak up any heat radiating from the tin below it.
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36hp '56 European DeLuxe oval
'70 bug 1835cc

[Cusser]