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914World.com _ 914World Garage _ Vapor lock on '75 1.8?

Posted by: 57lincolnman Jul 12 2015, 07:30 PM

I was driving my '75 1.8L on a very hot afternoon (+94 degrees) in combination highway and city driving for about an hour. While waiting at a stoplight, the idle became very weak. I gave it some gas, it backfired (twice) and then died. I got it to fire-up again but the car barely had any power - just enough to barely get through the intersection. Then it died completely. After sitting for a few hours, it started right up again. Prior to that the engine would hesitate when getting out of first and then go.

I was at PCA event today and some 914 gurus suggested it could be vapor lock. Is this rare in 914s with the fuel up front? Is it still possible even with the engine running to get vapor lock? Or could this be a fuel pump starting to fail, or perhaps a relay? I have stock L-jet fuel injection. Up until now the car has been running very well. Checked for vacuum leaks and found none. Fuel lines replaced a few years ago with stainless steel. Thanks for insight.

Posted by: PBC914 Jul 12 2015, 09:04 PM

Check the points and dwell. I had the same exact year and engine size and had no Robles in hot weather. However I did have the same exact issue when my dwell and or points were off. Good luck!

Posted by: 57lincolnman Jul 12 2015, 09:13 PM

QUOTE(PBC914 @ Jul 12 2015, 07:04 PM)

Check the points and dwell. I had the same exact year and engine size and had no Robles in hot weather. However I did have the same exact issue when my dwell and or points were off. Good luck!

Should have mentioned that I have a Mallory unit. No points.

Posted by: timothy_nd28 Jul 13 2015, 08:29 AM

If you are certain of zero vacuum leaks, I would guess the valves are adjusted to tightly

Posted by: aircooledtechguy Jul 13 2015, 09:21 AM

You can eliminate vapor lock by simply loosening your gas cap and ensuring that no fuel lines are near a heat source.

If you do this and the issue continues, I would suspect a failing coil. Idling a car will cause the coil to heat-up and if it's on its way out, the car will often times stall and kind of act like vapor lock. After it cools down it'll start right-up and run normally until it gets hot again. I had this problem running a Mallory with a Promaster coil. Changed the coil to a standard Bosch Blue and all was well.

Just something to consider.