Vapor Lock condition?????

[RedBarchetta]

I was out for a cruise late this afternoon. Car was running well and maintaining 190, despite the warm day here in So Cal. I'm cruising down a main throughfare, maintaining a steady 60mph (55 mph zone). I start approaching a light/street signal toward the end, so I lift and depress the clutch to prepare for braking.

Well, the car just flat plain SHUT OFF! So I immediately coast to the side. It didn't want to turn over with the starter without a little coaxing, but then it would spin without nary a sputter from the pipes. Hmmmmmm.....I check under the hood and don't see anything obvious (leaking fuel, spun distributor, loose electrical connections, etc.). Of course, since I was cruising close to home I neglected to bring one tool with me!

I wait ten minutes and still no sputter. So I grab the cell phone, call AAA, and they flat bed tow me back home (an ordeal in itself and no damage to report....what a hassle!).

Not one minute after we finally get it in the garage (it's thoroughly cooled down by now), I pull the air filter housing with an allen wrench and check the squirters for juice. Yup, she's getting fuel....must be in the ignition. I sit inside and try to spin her up for grins and WHAM!!!!, she roars to life!!!

What the hell happened? I've never experienced vapor lock on any hot rod I've owned. It was warm under the hood, but it wasn't THAT warm! Or was it?

-Deano

[Hotfingrs]

Well 2 things come to mind, clogged fuel filter and weak diaphram in the fuel pump, if you're running a mechanical one.

[Rick Parker]

If you are running electronic ignition with a magnetically triggered distributor you may be experiencing an open circuit in the electronic module inside the distributor. When this happens you will have nothing to initiate the voltage spike to trigger the ignition. When Ford first brought electronic ignition to the market place in 1975 they had many complaints for this very thing. Heat was the enemy of the first versions. It is not difficult nor expensive to repair. If this happens the tachometer will immediatly drop to "0" while the car coast to a stop. This is indicating a failure in the primary side of the ignition system.


Rick

[Bill Wells]

Good thoughts posted already, but IF it is / was vapor lock, do you have a heat spacer between the carb and intake manifold ? if not, something ya might want to add...1/4" spacer and/ or the Holley (or other brands) heat shield . also, if electric fuel pump, make sure you (or someone else) does not accidentally bump the toggle thus turning it off, which happens more times than folks want to admit (including me . LOL). B

[auto10x]

Rick is right!
auto10x
Bill

[trularin]

Do some tests. Connect a fuel pressure gauge to the car and drive it with it connected. If the pump is running, you should be getting about 3 to 5 pounds for a carb and as much as 39 PSI for EFI.

If the car stalls and you have pressure, it is most likely Ignition.

Personally, I know guys who have a points distributor in their trunk just in case.

Just a thought.

[Ron61]

All above replies are correct, but I might add one thing to Rick's. I had this happen three times before I traced it down. The trigger lead from the distributor to the Jacobs went to a connector and during the years that connector had worked loose enough that it would open once in a while and then after a little bit everything was ok. Replaced the connector and have never had another problem.

Ron

[Cracker]

CHECK YOUT STATOR?

[blykins]

heheheheheheheehheheh....I had forgotten about that...thanks Cracker...

[RedBarchetta]

Thanks to all for the replies. Here's some more info:

Car does run a mechanical fuel pump. Ignition is an MSD billet distributor running all MSD gear (wires, coil and 6A "booster"). The carb (BG Mighty Demon) has a one inch spacer sandwiched above the intake.

Checking fuel pressure is probably a good place to start. Changing the fuel filter is a cheap process, too. I just don't want to get to a point where I'm just throwing parts at the solution (i.e. electronic module, fuel pump, etc.). And I definitely want to find the culprit...getting towed was no fun....good thing I was less than 3 miles from home.

[RedBarchetta]

Originally posted by Cracker


CHECK YOUT STATOR?

Haha. Very funny. Hey, I've got a dwell meter I'll sell you for cheap! I'll even throw in a .030 feeler gauge.

[Cobra20646]

Deano,

Have to lean towards the ignition system for your problem.

A year or two ago, I had a vapor lock problem. Car ran fine, but then was shut off and parked for about a half hour. Wouldn't restart at all....... checked for fire at plugs... OK. Check for fuel at accelerator pump.... dry to the bone. Took top of carb off and the fuel bowls are dry. Turn over engine with fuel line stuck in a coffee can to catch fuel, and after a few seconds fuel starts squirting out. Put things together and she ran just fine..... and never another hick-up from that day. I was told this was classic vapor lock...... and I could have just ran some cold water over the mechanical pump and fuel line and things would have corrected themselves..... well next time I'll know

[Morris]

FYI

Gas vaporizes at 70 degree's.....

[trularin]

Vapor lock is caused by boiling the gas out of the furl system. Morris is correct, except I heard was a littel lower.

Once boiled out, the pump has to deliver gas to a system that is locked by the pressure built by the boiling.

Hence the pump can not deliver gas as it thinks the system is at full pressure.

You can install a bleeder fitting which allows you to monitor the fuel pressure . This would be the first thing to do.

Once you have determined you have this condition, you can install an assortment of things to help with the problem.

Fuel coolers are a favorite solution.
Pressure regulator with return line works as well.

Hope this helps.

[Goober]

Same thing happened to me. The coil is mounted on the passenger side on the inner wheelwell. The coil wire was arcing next to the frame. I noticed it one night when the lights were off in my garage. Easy fix. If your wire is like mine, it didn't have much stretch to the distributor and was trying to pull away from the coil causing the spark to leak from under the rubber boot.
Try it and see.

[RedBarchetta]

Goober, my coil is mounted high on the driver's side fender, but I'll check that out, too.

trularin, thanks for the explanation on fuel pressures. I definitely will install a gauge at the carb to monitor this during cold and hot conditions.

[Rick Parker]

http://www.msdignition.com/1troub1.htm

400-1300 ohms resistance in the ignition module itself, if you have more or NONE you have a bad module.

Stuff happens!

Rick

[RedBarchetta]

Rick, much appreciated!

[Rick Parker]

A few years ago I had a OEM Ford distributor that I removed the vacuum advance from and modified the centrifical advance mechanism. I had used this for some time and it worked and looked great. I had seen the MSD distributors and they used what appeared to be the same module but instead of riveting the magnet they used machine screws and mechanical lock nuts. This allowed for adjustment of the air gap between the reluctor and the magnet itself. I thought this was a good idea so I decided to do the same, however while reassembling it I unknowingly got the magnet in upside down and effectively reversed the polarity of the connecting wires. The engine would idle ok but at about 2800 it backfired and ran poorly. Not until I replaced it temporarily with a point type distributor did I realize that the distributor was at fault. DUMB DUMB DUMB.

Rick

[ohekk]

We have to run gas with 10% ethynol because of some air quality regulations.

If I get gas ( what we call "Good gas ) from outside the county, no problem!


good luck as you try all the other remedies!