Last sunday I drove my car to church/work it was about 100 degrees as I was driving on the fwy it started to lose power , I pulled over and sure enough it would not start. It felt like vapor lock...
Could this happen while I'm driving????
after a bit it fired right up.
Click to view attachment

Sounds like the classic hot-start problem. I suffered with it until I replaced my starter with a high-torque.

Could be tight valves.

Could Definitely happen while driving. Happen to me several times until I move fuel pump to the fire wall.

Not sure how a high torque starter solves the loss of power on a hot day? "No start" doesn't always mean won't turn over. We need a little more detail. For OP, yes, vapor lock could explain what happened, but so could a few other things....

Ok Jamie ..... the air temp may have been 100+, but what do you think the temp was coming out of the heater flappers and blowing on the fuel pump? Yes, it will "vapor lock" while driving, especially at low speeds .... in other words, the fuel boils and fuel pumps don't pump air/bubbles very well. After things cool down the fuel returns to it's liquid state and it works again.

I have vapor locked so many times I just expect it in hot weather. Yeah, I'm to lazy to move the pump up front.

I thought that was your summer project after the last trip...

I declare a work Party at Rons!
I'm paying for the pizza!

That's the last I heard. Sounds good to me.

Hey Jaime,

Save yourself the greif & just move the fuel pump up under the fuel tank behind the steering rack cover as the Porsche Tech Bulletin advised since about 74-ish. AA sells a kit with the parts, or you can collect the parts yourself, or have a shop who knows 914s near you do it.

I did mine back in `77 after having to wait a couple of ours at the Blythe Denney's in 115 heat on the way to the River to water ski. Got back, told my guy Hans what happened, & he knew right away what it was & what to do (he was factory trained on 914's when the first came out & he was still at Circle Porsche in Long Beach).

Good Luck!
Tom
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This is what the Cap'n had to say about vapor lock.

This is what the Cap'n had to say about vapor lock.


Wait a second on the fuel lines; didn't the factory use the same nylon lines AFTER moving the pump up front.
Agree to make sure the tank is clean and all that stuff.
Of course the situation is much worse for a carbed car not using a return line, as the return equipped cars keep cool fuel circulating.
Barefoot

One of the very few things that he wrote that I disagree with. Vapor lock is real. It happened on a regular basis on my 1955 Chevy. A wooden clothes pin on the fuel line solved the problem. It's real on the 914 too. My 1.7 would just die till it cooled down a bit. I was afraid to drive when it was over 95°, and that's a lot around here. Carried a water gun to squirt the pump and cool it down. I moved the pump to the front trunk and it never happened again in 30 years.

"Wait a second on the fuel lines; didn't the factory use the same nylon lines AFTER moving the pump up front."


No. The late cars used a different type of fuel lines rated for the pressure. Early cars had a white pvc type tubing. 75/76 had the black vinyl.

Yeah, vapor lock. In July of '73 I took my brand new 1.7 on a road trip from SoCal to Colorado, after the recommended 600 mi. break-in and oil change. Had the same symptoms: loss of power, non-start, wait for cool down then starts and runs normal. Happened about four times. When I took it back to the dealer they just nodded their heads and said, "we'll take care of it." Moved the pump up front and never had the problem again.

I don't disagree. Just thought I'd give Jaime another option to look at. From the Cap's experience.

Good to know, thanks much.
Barefoot

I've done quite a bit of driving in hot weather, stop and go traffic, and so on. I have experienced vapor lock exactly once. In the Nevada desert, in late June, with ambient temps well into triple digits, grinding up a long hill.

SLOP (Sudden Loss Of Power), the tach was reading the correct RPM, taking it out of gear killed the engine, putting it back into gear spun the engine back up again. Pulled over and checked the fuel pressure gauge in my engine bay--ZERO pressure. That is either vapor lock or a bum fuel pump... I dumped some water up in the front corner of the engine bay, and then jumped the fuel pump relay to run the pump. For about 30 seconds at a time, until the fuel pressure built up.

And I got on my way again. The behavior did not repeat.

--DD

IMHO One of the contributing factors is the hot air from the heater system.

When ever the engine is running air is always being blown through the heat exchangers. It flows from the engine fan housing through the heat exchangers and out through the flapper valves (heat control valves). When you pull up on the heat lever you open the flapper valve and route some of that air into the passenger compartment. When you are not using the heater all the hot air is dumped out of the flapper valve through the bell shaped cover. The passenger flapper valve is very close to the fuel pump and all that hot air (on a hot day when you are not using the heater) dumps into the lower right front corner of the engine compartment where the fuel pump is. This has to add to adds to the heat soak of the fuel pump.

So getting the hot air discharged from the heat exchanger away from the fuel pump is helpful, especially considering it hot ambient air coming into the engine fan and then into the heat exchanger where it is heated even more.

On several car I have removed the bell from the passenger flapper valve and added a short piece of corrugated aluminum flex tubing and bent it to route the heated air away from the fuel pump. The flex tubing is the type used on some VW defrosters or some heated air cleaners on domestic cars, about 1 1/2 inch diameter. Use a hose clamp to hold it on and point it down and back away from the pump.

Works well and is cheap and quick.
I like cheap and easy
Jim

You've been saying that since God was a little boy.


I was born about 200 miles south of you and will vouch for vapor lock. And, I used to do the the same clothes pin trick on my 283, '56. As far as the Cap'n, may he rest in peace, I believe he never saw a vapor lock issue; ever! But then again he probably never saw a water pipe freeze. We are in California after all. Besides, Porsche knew vapor lock was real enough to address the matter. Yet every year, just about now, the debate emerges from it's hibernation.


Curt, mine were clear. Well, brown, tan and opaque.

With all due respect to the Cap'n (God rest his soul), I also know that vapor lock is real. A nagging problem in my 65 mustang until I added a phenolic carb spacer.

Anyone else ever notice that the good Cap'n's posts often contain the words "...in x years, I've never seen it" as his basis for dismissing the problem? And how, exactly did he become Krusty?

Jaime,

Just move it to the fire wall.

Less work.

Mine is there and never a problem.


+2 on work party at Ron's.

I agree! Firewall is much easier. Moved mine there 20 years ago.

How about a party at my shop in upland....and this is in the same lot...check this out !
and I'll let you print your own 914 world t-shirt...

Thanks for the posting you guy's rock...