Spitfire 1978 Spitfire possible Vapor Lock?

[Kiko16]

I purchased a '78 spitfire last year and am having what sounds like a familiar issue. It has happened a few times while driving in the summer. I am cruising normally and then the engine just shuts down. No warning, no puttering, just shuts off. After a while, she will start back up as if nothing happened. I've checked sparks, ignition, etc. to no avail. Could it be vapor lock? Right before it got cold I filled it with higher octane gas and it seems to have worked. Any help would be greatly appreciated.

 

[sp53]

My first experience with a bad coil was in a spitfire. Mine would do what yours is doing and then one night it happened on the freeway and when I did get it started again I could see a spark arcing off because it was night and going to ground from the coil. I believe the coil was on the passenger side and the arching was coming from one of the studs mine was a 1971. Hope it helps.

steve

 

[Kiko16]

I am not a mechanic but can google with the best of them. I replaced the ignition coil already which is why I am thinking it's something else. Have you had any issues with vapor lock? Apparently the Spitfires don't like ethanol in their gas.

 

[Gliderman8]

Check/change your fuel filter as a possible cause.

 

[Kiko16]

Thank you sir. I should clarify, it's had a full tuneup, oil filter, fuel filter, battery, etc changed.

 

[poolboy]

When it happens next, if it does, pull off the fuel line to the carbs, if gas squirts out from either the carb nipple or the fuel line it's not 'vapor lock'.

 

[Kiko16]

Awesome, thank you very much! That helps.

 

[Sarastro]

Doesn't sound like vapor lock to me. When the engine cuts off suddenly, I usually start thinking "electrics." Might be the coil (having a new one does not necessarily rule it out), might be an electrical connection that is loose and overlooked. One way to find such a problem is to get the car idling and start jiggling wires and connections, and see if you can reproduce the problem.

 

[Kiko16]

Thank you, will try that as well.

 

[Jayplum]

While I tend to look at electrical issues (Coil, points/condenser etc) easiest check on vapor lock is put your ear next to gas cap and slowly open. Vapor lock at that end will give you a whistle.

 

[Kiko16]

Thank you. The way I understood it (and I am not a mechanic) the issue is that the ethanol in lower octane gas boils at a lower temp. As the gas is going into the car the ethanol is heating up and boils. The resulting vapor logs the line and prevents gas from getting to the carb. After I let the car sit for a bit it starts up like nothing ever happened...until it happens again. With the help of google I opted to use a higher octane gas and some non-ethanol gas...so far I have not had the issue again but winter has prevented me from taking her out to truly test it.

 

[Jayplum]

I m glad it’s working got you. Yeah even the more talented mechanics admit much of it is a trial and error method in diagnostics.

 

[welove3]

I would suspect the ignition module in the distributor is the culprit. It gets hot and stops working, generally quite suddenly, then works normally once it cools. You are not experiencing the same issue in the winter because it doesn't get hot enough to fail.

 

[Sarastro]

Glad it's working for you, for now. I still think it isn't vapor lock--with vapor lock, fuel flow is reduced or eliminated, and the car runs for a while on what's left in the float bowls, then starts sputtering and dies. If the engine is running fine and then dies suddenly, that's almost always electrical.

The fact that the problem is temperature-related makes me think it might be the coil or, if you have one, electronic igntion.

Once, while sorting out an apparent vapor-lock problem in my Bugeye Sprite, I replaced the fuel lines with clear tubing ad watched what was happening in the lines. Pretty impressive--the fuel looked like ginger ale, a large bubble formed in an upward arch in the line, and the plastic fuel filter looked empty. Yet, fuel was still getting through! I think that the fuel has enough pressure to get past large bubbles in the lines, but if a bubble gets trapped in a small area, like the carb float valve or fuel pump valves, the force on the bubble, at ~3 psi pressure, just isn't enough to dislodge it, so it blocks the flow.

It's not just ethanol. Fuel these days has a lot of high-volatility components to provide anti-knock properties and to minimize air pollution. We have to learn to live with foaming fuel. In the Bugeye, I reoriented the fuel lines so they were continually upward, and bubbles could then flow to the carbs and be vented through the carb vents. No more problems.

 

[Kiko16]

Doesn't sound like vapor lock to me. When the engine cuts off suddenly, I usually start thinking "electrics." Might be the coil (having a new one does not necessarily rule it out), might be an electrical connection that is loose and overlooked. One way to find such a problem is to get the car idling and start jiggling wires and connections, and see if you can reproduce the problem.

I idled and jiggled all electric cables, unable to reproduce.

 

[LarryK]

This happened to me once. Heading to work and all of a sudden I see black smoke out the back and the car died. Pulled over and it started, drove on to work. On the way home the same. Next morning black smoke died, got out checked ignition. Coil was hot, wires loose. Tightened wires went to work. Came home no problem, ordered new coil. You may want to put fuel guage in line and watch. Wrap the fiel line near engine with a heat wrap to keep line cooler.

 

[UltimateQuestion]

I had vapor lock issues on my GT6, stopped on a hot day on the freeway. I re-routed the fuel line from the pump to the carbs across the bulkhead away from wrapping around the head.