Vapor Lock

[Logan]

My 53K seams to vapor lock AFTER I have driven it until it's hot and let it sit a few minutes to 1/2 hour.  It never does it on me when I'm actually driving, but under the conditions named above, it's farely common for me to come out, start it up, and have it die as soon as the gas in the carb bowl runs out.  Then I have to wait another 1/2 hour or more before it will start.  Is this common and are there fixes you know of?  Also, I am right in diagnosing this as vapor lock, aren't I?

[Gordie]

Vapor lock has always been a problem for Kaiser's and Frazer's in fact in early 1947 they moved the fuel pump to try to solve the problem.  Do what many of us have done and install an electric fuel pump in the back and your troubles should disappear.

[84RabbitGTI]

Mine does that exact thing, Logan.  I stopped in at McDonald's for a quick drink while we were driving back from the McMinnville Airplane Museum in Oregon during the National in Salem.  We started her back up, and it died just as we got out on the Main road in a bad place.  We had all the experts from the club there trying to help us get going again.  It just took time, pretty much.  We just got some chairs out and waited.

[Fid]

The thing I always did is if I had to stop somewhere on a hot day, I'd shut the car off and pull the Overdrive cable out so the car would not freewheel when I started up again. If you got up to speed, and it vapor-locks, the wheels moving at that speed would keep the pump pumping till it got past the vapor pocket.  Of course if your car is a Hydramatic or does not have overdrive, that won't help. An electric fuel pump is a good cure.

[Logan]

Mine is a hydramatic.  I hate to put an electric fuel pump on it because I'm stubborn (a purist?), but I might have to break down and do it.  Fid, if I were able to get up to speed, wouldn't it be the same thing with the hydramatic?  I mean, I think that as long as it's engaged, it would be be turning the engine if it's rolling.  After all, you can start a hydramatic car with a dead battery by getting it rolling and popping it in gear.

[kaiserfrazerlibrary]

I am afraid that all different makes of older car and truck will need electric pumps already and more will need them as time goes by.  The real problem today is the gasoline itself.  In order to compensate for the octane loss that resulted when lead and other additives were banned by the EPA, the formula for gas itself changed and evaporates at a lower temperature than it did back when our cars were new.  If you check K-F shop manuals you will notice that the fuel system runs at a relatively low pressure (less than 7 psi) which means that when gas bubbles build up in the line (especially the run from pump to carb) there is not enough push to keep fuel moving, and a chain reaction takes place.  Electric pumps not only run constantly (the regular pumps start loosing presssure when the engine begins to sputter) they run around 9-14 psi giving a bit more force.  The added pressure does not affecting fittings and seals but does make a difference.

To illustrate how critical the situation is on newer vehicles, when GM was developing the first Saturn SUV platform in the late 1990's, desert testing showed vapor lock with the prototypes equipped with the L850 engine.   The engineers had to add a shim between the fuel rail and the block so air could move UNDER and up the back side of the part as well as over and down the back.  It lowered the temperature 40 degrees on the part, which was enough to get reliable performance.  By the way, this rail is designed to hold the injectors and stay sealed at fuel pressure of 60 psi. 

[Fid]

What I recall about Hydramatics is you need to be going pretty fast to engage them to start. I could be wrong but that's what I recall.  When the '51 I used to drive vapor locked, it seemed it always happened right when I was shifting from first to second. Pulling it out of OD really helped in that regard because the wheels would keep the engine moving at close to the same RPM, hence keeping the pump going which a stalled engine won't do.  Of course, not all other things remain the same necessarily.  We also made an aluminum baffle / sheild and mounted it on one of the front engine plate bolts. It fit between the manifold and the pump and deflected a lot of heat away.

[kaiserfrazerlibrary]

Back in the old days, the Hydra-Matic manual suggested around 35 mph for engagement speed based on gearing of the box and rear axle, but I do not know which gear you dropped it into (low, regular drive, etc).

Various ideas work to varying degrees, but the electric pump seems to work best as even with the latest and greatest seals, the alcohol in gasolines (another octane substitute) will attach the rubber parts in the pump.

[Logan]

I may have to break down and get an electric pump.  Where do I get one for a 6-volt system and where do I install it?  Will it work in tandem with the mechanical pump?

[boatingbill]

I used to carry a cola bottle and have it full with water for vapor lock on hot days. Just pour water on the fuel pump and you'll be on your way. This is what I did until I found out that the AC pumps hardly ever had vapor lock problems. I put on a AC and never had the trouble again.

[84RabbitGTI]

Part number on the AC Pump?  and does it have a dual diaphragm to operate the windshield wipers?  I think I'll also try the soda bottle full of water trick.  Thanks!

[Gordie]

I may have to break down and get an electric pump.  Where do I get one for a 6-volt system and where do I install it?  Will it work in tandem with the mechanical pump?

Most full line auto parts stores carry 6 volt fuel pumps.  Mount it in the back so that it pushes rather than pulls.  It will work in tandem with the factory pump but I use a small toggle switch under the dash so that I can select when I want to use it.  When I put one on a '48 Frazer it had way too much pressure so I put a regulator on the top end.  After installation be safe and check your fuel pump pressure so that you do not have too much.  It will end your hard starting and vapor lock problems caused by your mechanical fuel pump.

[joefrazer]

The 6V fuel pump will solve the problem...but in the interim, carry a bottke of water in the car with you. My 53 usually doesn't vapor lock, but will if it's hot enough and I've run it harder than usual. I give it 5 minutes then slowly pour the water over the pump and line up to the carb and it starts right up. Not the most technical fix, but it does work!

[Logan]

Hey, that waterbottle sounds like a really great idea.  I'll try that for sure.  About the AC pump, I don't know what mine is, but I recently bought a rebuilt one from Rudy's.  It is a single action, as I have the electric wipers.

On a side note, as I've been looking down the carb a lot lately, I notice that even when the engine's cold and I depress the the accelerator, the accelerator pump squirts a little unsteady, i.e. the stream is not constant, but cuts out a little.  Is this normal?

[boatingbill]

Logan: If your pump is an AC, it will have AC stamped in 1/2" high letters on the top. Sorry, I don't know the part number. Your accelerator pump should put out a strong steady squirt as you quickly depress the throttle rod. Do you notice a hesitation when you are driving and give it the gas? There is a single gasket around the pump rod that may be leaking. It is a simple fix.