Vapor Lock condition?????

[RedBarchetta]

ohekk, FYI. I'm running a mixture of Sunoco 110 racing fuel with 91 pump gas. Roughly 5 gallons of 110 to 12 gallons of 91. I realize that fuels have different boiling temperatures, but the Sunoco has a decent temperature and stability rating.

Since yesterday was the first really warm day I've ever had the car out (I acquired it January 2), I'm narrowing down the culprit to either some form of vapor lock condition or a gremlin within the ignition (as many have pointed out).

I can't thank everyone enough for their inputs and support. This is what a forum is all about!

-Deano

[Goober]

Deano, I just hope you find the problem and get it fixed. Too nice of a car to leave in the garage.
Mark

[ohekk]

next time it happens, squirt a little fuel down the carb.

at least you'll know for sure whether it's elec vs fuel problem and you can go from there.

[RedBarchetta]

ohekk, I wanted to but the air cleaner had an allen wrench holddown and I was tool-less! I now have one in my "kit" in the trunk....I'm not even going around the block without tools anymore.

[Hal Copple]

on my SPF, some years ago, had some subtle corrosion on the horseshoe connector at the coil, i would lose power and spark, would clean it, finally, put on a new coil with clean terminals, cut off the horseshoe, put on a coil with ring terminals, never had a problem with lost spark ever again. Also, check your ground strap for a good connection to the frame.

By the way, when it is warm, my Holley will boil over and percolate the gas, despite my prevention measures (four hole phenolic spacer, carb heat shield, etc), and if SC is still selling "winter gas", my car will stall, stumble, and flood. I can tell in the fall when winter gas comes out, and tell precisely when it goes away in the spring. I have an in-cockpit VDO fuel pressure gage, and can tell and then watch my fuel pressure drop when my carb is boiling over. You can't overpressure a Holley fuel bowl, as it is vented, but you can boil the gas out and down the intake.

Sometimes, on warm winter days, i have to put a foam block under the rear of the hood, to prop it up an inch or so, to allow hot air out, reducing my carb boiling. Or manually run my fans to keep the motor a bit cooler. If it floods out, which it will do even at "speed", like last week, i just try to keep speed up until i can see my carb getting cooler fuel, then my pressure will come up.

If i stall, then i hold the throttle all the way down, to "air out the motor", and spin it until it reluctantly fires with black smoke out the exhaust. Pressing the throttle down does of course put a "squirt" down the carb, so don't pump it, just hold it down. By the way, one way to slightly reduce this is to drop your float level a tad. But too much, and under full throttle, you will run your bowls dry, creating a lean condition.

check out the simple things, and try propping your hood open the next warm day, and see if you have the problem.

Remember, you are driving a race car on the street, and you will learn to live with the compromises.

[RedBarchetta]

Hal, once again you step up with awesome experience and advice! Personally, I'll install a cool can for the fuel before I start driving around with the hood propped up!

[RedBarchetta]

***UPDATE***

Pulled the distributor cap and rotor today. Both the cap contacts and the rotor needed a clean-up. Took a dremel tool with wire brush to the contacts, and some emery paper to the rotor.

Checked the resistance of the magnetic pickup on the distributor....610 ohms, so that is within tolerance.

Ran out of time, but the fuel levels in the bowls look a tad high. Other than that, I need to buy a fuel pressure gauge and check the pressure when the temp gets warm.

Hmmmmm.....still looks like a vapor lock condition so far. Stay tuned.

[Rick Parker]

And.................................

[RedBarchetta]

Rick......

Okay, ordered the fuel pressure gauge from Jeg's on Monday, so hopefully that will get here soon. Once I install, then I'll adjust the floats down a tad and go from there. Right now she's on four jack stands as I fabricate some brackets for the driver's seat (I'm removing the adjustable rack and bolting it to the floor for some extra clearance). I completed the brackets last night and hit Home Cheapo this morning to get the correct Grade 8 hardware.....now I just need to paint them and button everything back together.

Brackets today....pounding out my own aluminum bodies tomorrow.

[RedBarchetta]

*** FINAL UPDATE ***

Pressure gauge installed....7 psi upon start-up and maintained that after fully warmed over. So I'm still leaning toward a vapor lock condition on the one warm day I drove her. Still bugs me that it may repeat itself....I'll have to take on extra measures.

[Cobra20646]

Red,

Was that a liquid filled gauge? If so, don't be surprised if it starts to show bogus readings....... I tried two of them and both did the same thing after a good heat soak, i.e. hot summer day and hot under hood temps. Sometimes would read zero with the engine running fine.

[RedBarchetta]

Rut roh....thanks for the heads-up, Jim. Yes, it's liquid filled. Should I just go to a standard?

[Cobra20646]

Red,

Try it out first..... maybe just a bad run of them a couple years ago. Like I said, I went through two of them before going to a non-liquid type, and since then, have had no issues with it.

- Jim -

[TerribleTed13]

I have a mechanical,liquid filled gauge from jegs, and when things get warm under the hood the gauge is not accurate. The gauge is mounted on the carb fuel line. Car problems have diminished since I now have a trunk mounted tool tray/box. Its a b!tch getting stuck on the side of the road. Also have both electric and mechanical fuel pumps,a 1 inch carb spacer and still have boil over/vapor lock after a warm restart.Dam winter gas!!!!

[Al Bockman]

Last weekend I had a terrible time when the club went to Boulder, CO. Temps in the 60s, boiled fuel after almost every stoplight. I was able to avoid big trouble by toggling the fuel pump switch. When I got home I finally gave in to some scientific testing.

Using an infrared thermometer, I discovered that when the fuel was boiling, the temperature at the primary inlet was 99.7 degrees, secondary inlet was 117.7! I finally gave in and completely insulated the fuel lines all the way to the carburetor. It was in the 70s Sunday. Went on a long drive with a lot of stop and go driving. It didn't boil at all. When I got home to check the temperatures, the primary was 93.8 and the secondary was 92.8.

The wife doesn't like the way the fuel lines look, but at least we didn't have problems Sunday. Tomorrow, however, is another day!

Al

[sp1410]

Hey guys, I had a problem last week that I suspected was boiling fuel. Since I'm new to the Cobra experience, don't laugh at me for asking this: does the rotton Winter blend fuel have a lower boiling point? And, does anyone recommend any additives to correct this? Lastly, when does this "witches brew" fuel go away...? (I'm in Oregon)

[Morris]

A return line to the Fuel cell or tank prevents this vapor lock condition....

Morris