Jump to content

Recommended Posts

I have recently purchased a 1986 Caterham with a Kent 1700 CC crossflow engine with Weber 40 DCOE's. I had put about 200 miles on the car with no problems.


The heat has now hit southwest Idaho with daily highs in the 103 to 110 degree F range. I took the car out for a drive and was running it fairly hard in 105 degree temps when it acted like it ran out of gas. The gauge was low, but not on empty. Since the car is new to me I thought the gauge might be off.


I called my wife and she brought me the gas can with 5 gallons. After adding the fuel, I still couldn't get the car to run. It would try to start, but would not run for more than a second.


After sitting for about 40 minutes I finally got the car started and headed for home. It was running fine, but after about 10 minutes it again acted like it ran out of gas. I left the car and came back at night when it was cooler and it started right up and I drove it home.


I'm thinking the car was vapor locking. Has anyone else had this problem? Is vapor locking a common problem with this engine setup? And finally, any suggested fixes other than don't drive when it's hot out.




Paul Mascuch

Link to post
Share on other sites

Metal or metal shielded fuel lines help. Avoid vertical loops in the fuel line that can accumulate vapors.Low float levels in your carbs can make you sensitive to fluctuations in fuel supply.

Link to post
Share on other sites

I'm not an expert, but here are some problems I've had:


-Could you have a bad coil? Perhaps your coil over heated or is not in good condition.


-check for a loose coil wire

Link to post
Share on other sites

Twobone -


I also thought about an overheating coil, but the car was firing and trying to run. Adding choke seemed to help. This is why I thought it was fuel starvation.


I'll check for loose wires.





Link to post
Share on other sites

A friend of mine has a Datsun 240Z that suffers from vapor lock in the summer time. He found that by wrapping some aluminum foil around the fuel lines running from the fuel pump to the carbs, the problem is virtually eliminated. It looks a little crappy but it seems to work. This apparently is only valid with steel fuel lines, and it would seem that those who have vapor lock have steel fuel lines. I have never heard of anyone with rubber hose fuel lines having an issue but not really sure if that's a golden rule.

Link to post
Share on other sites

Check the fuel lines, make sure you don't have any touching the exhaust system or engine it self.

If you don't have any touching try running without the hood on a real hot day, if it runs fine then it is probably heat buildup and you need some compartment air flow.

If the fuel line is not touching and it still wont run with the hood off, maybe look at some other simple things like the fuel filter, fuel pump getting hot etc.



Link to post
Share on other sites

Not sure if this will help. I have Webcon fuel injection instead of carbs. So I am running much higher fuel pressure. For the last 4

years my car was exhibiting similar problems to what you describe. I have a Superformance S1 and the engine compartment is fully

enclosed so heat is a problem I am still dealing with. I found a couple notes that talked about the fuel pick up when using a Bosche

fuel pump. Both highly recommended only picking the fuel up from the bottom of the fuel tank and NOT putting an in-line fuel filter

before the fuel pump. Mine was picking up the fuel from the top of the tank and it had an in-line filter before the fuel pump (I bought

the car used this way). At times my fuel pump would buzz louder than normal. This was the loudest when the car would stop running. It

would act like the fuel pressure was dropping. I eventually figured out that air was getting into the fuel line before the fuel pump

and was causing the buzzing. This past year I finally used a bulkhead fitting and started drawing my fuel from the bottom of the tank

and I removed the in-line filter prior to the fuel pump. Since doing this I no longer get the loud buzzing and the car has not stopped

running. In retrospect I think my problem was 2 fold. One being when the air bubbles were going through the fuel pump the buzzing was

indication that my pump was no longer supplying full pressure. And two, on very hot days when the pressure dropped I believe I ended up

with vapor lock in the fuel line. The car could not be restarted right away, but by taking the hood off and allowing it to cool for 15

minutes or so it would then start and run again. In the last 4 years there were a couple of times where I had to pull the hood multiple

times to cool it down before I could get it back home.


I don't know what kind of fuel pressure is required to prevent vapor lock. But what I would recommend is to try and make sure your fuel pressure is always there. From my experience as long as my fuel pressure does not drop I don't get a problem. I would think that there are a lot of other cars out there similar in setup to yours and I doubt yours is the only one experiencing hot temps. It sounds to me like you may possibly be lossing fuel pressure which then allows the fuel to boil and cause vapor lock.


Good Luck,


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...