Vapor Lock 1956 Cadillac Series 62

[fishnjim]

I believe there was a well written "starter" article on this a few years back.
I couldn't find my info, right away, but ethanol shifts the boiling point curve of the gasoline away from that of the period gas specification, quite a bit.   (If I find it, I'll post.)  Vapor pressure(determines boiling point) is a "molar" property, one would have to add substantial amounts of MMO or similar to affect the boiling point.  Those amounts likely to cause smoking, fouling, carbonization.
All good thoughts, the problem comes more in the inlet side of the fuel pump where the pressure is negative (sucking).   Once vapor occurs and expands, the pump can't function so starves fuel.   The discharge side feeding the carb is supposed to be at higher pressure(~6 psig) and less likely to boil.   There was recent reporting of pump failure issues with certain designs also, the check valves would detach.   That's why supplemental pumps seem to solve this, pressurizes the feed.   But I'm not a proponent for safety reasons, needs quite a bit of engineering as in modern vehicles.
Also, if you drive/live at high elevation, likely worse.
This is just one of the many issues associated with owning a "correct classic" these days.   The good old days, weren't as good as people would like to think as the technology was from the war period and took many decades to improve.  Styling was ahead of reliability and safety.   {Vacuum wipers - what a fiasco de jour.}
There's been quite a bit of effort to eliminate ethanol, including going around the law.  But it still has major Congressional support, because of the corn and environmental lobbies.   Non-attainment areas, can't get the non-ethanol.  Anyone that remembers CA in the '70s with the smog, will understand.   Write your congress persons.

[leedlast]

Thanks, James.  I will replace the pump, but now my dilemma is that the NOS fuel pump should be rebuilt with modern ethanol resistant materials. I'm tempted to rebuild it myself, but prefer that a pro do it.  Michael at Cadillac Parts has temporarily suspended rebuilding pumps, so can anyone recommend another rebuilder?
Thanks.

[Omarine]

Hello Ed, et al,

I just had my rebuilt pump rebuilt again with ethanol resistant Kit. The pump i bought from a well known vendor failed in less than a day of operation.

Dave at Yesteryear Antique auto in Fl, did the job for me this time as i didn't want to keep dealing with the other vendor. The pump has yet to be installed in the car.

I have a 52 cdv all stock and i live in FL and the vapor lock left me stranded more than once. While the mech pump was off the car, i bolted a delete plate i made and ran a 6 volt electric pump near the tank.

I also got a spring and wired the heat riser valve open as it had been closed since i had gotten the car.

I routed the fuel line away from the filler neck and didn't use any vapor lock sleeve on the steel line to the carb, but the rubber line near the block is wrapped.

The real test came when i drove it 250 mi from Orlando to Miami for upholstery two weeks ago. Ran like a dream to include the 2 pm arrival in the heat of the day.

My plan is to reinstall the mech pump as my electric pump runs on a toggle (plan to put oil pressure switch on one day).

There is also a 3/32” sheet of phenolic material i ordered to duplicate the shape of the carb base gasket, but i haven't gotten around to blocking off the manifold with it yet.

If the mech pump gives me any more issues, i will install it for looks and rely on the electric 

It was very nice driving that whole distance without missing a beat in that heat. Upholstery should be done tmrw or Thursday.

Cheers
Oscar

[Lexi]

This place on the East coast sells kits and I believe also offers a rebuild service. Seen them once at a GN and bought a kit from them. Clay/lexi

http://www.then-now-auto.com/fuel-pump-repair-kits/

[leedlast]

Thanks Clay and Oscar.  It seems that there are not many fuel pump rebuilders, so your recommendations are appreciated. 

[Saturnin15]

Does adding a phenolic spacer modify the tv rod adjustment?  Where can I source a phenolic spacer for a 56?

[Omarine]

if the phenolic spacer is tall enough, then it will probably mean the TV rod will have to be adjusted to compensate.  Mine is thin, i only intended it to block off exhaust - 3/32".  Got mine at McMaster Carr for $4 but it needs to be shaped as it's only a sheet....

[Omarine]

Good evening gentlemen,

I was the last one to post and since then ive re installed the re built mechanical fuel pump. It produces vacuum and meets psi and volume requirements. Does everything it should until the slightest traffic where the fuel boils super easily. Flip on the electric pump and you can actually see the bubbles coming through the glass dome.

So has anyone successfully used one of the gas vapor separators with a return line back to the gas tank?

Im thinking of drilling a hole in the filler neck to accept the return line. My gas cap a small hole drilled into it.

Any feedback out there?

Thanks
Cheers
Oscar

[James Landi]

Suggestion :  perhaps the bubbles you're seeing in the glass filter bowl are from a tiny air leak in the fuel supply line from the tank.   I'm thinking that the leak may even be right at the  fuel pump input where the engine heat causes the connection to react to the heat and allows a slight flow of air. Having owned 2 '56 sedan de villes, I vividly recall how hot the engines get, and you may recall that I mentioned in this thread the issue with a failing fuel pump that developed too much wear on the pump's fulgham pivot shaft--- (for lack of grease lubrication in the pump's internal cavity).  Having said all of this, I never experience stalling due to vapor lock, in either '56, and I drove one of the '56's five days a week, for 90  miles per day, and in heat, with that big a/c unit cranking.  SO i respectfully suggest that you have an air leak.   Hope this helps  Jamess

[Caddy Wizard]

Good evening gentlemen,

I was the last one to post and since then ive re installed the re built mechanical fuel pump. It produces vacuum and meets psi and volume requirements. Does everything it should until the slightest traffic where the fuel boils super easily. Flip on the electric pump and you can actually see the bubbles coming through the glass dome.


Cheers
Oscar

I have mentioned this on the Forum before, but in my experience, of all the years of the OHV V8 Cadillac engine, the 56 is the most prone to vapor lock.  This is so because the same radiator was used from 49 to 56, even though the horsepower in those years doubled from 49 to 56.  More power equates to more heat produced that has to be shed.  The 56 cooling system just isn't up to the task.  In 57, Cadillac completely redesigned the radiator and things got a lot better.

Having driven a 56 FW with AC here in the hot South (in Atlanta), I suffered with plenty of vapor lock and heat soak.  My solution was three-fold.  One, take the rod out from under the mechanical pump and use a very robust electric pusher pump situated back by the tank.  I used an Edelbroc pump that cost about $200 as I recall.  I pushed the fuel through the mechanical pump that was there just for looks (having removed the rod).  That change makes a huge difference.  Secondly, I got a superior original style radiator from Walker Radiator that has a lot more cooling capacity.  That helped too.  Third, use ethanol-free fuel exclusively.

If you want to stay with the mechanical pump only, good luck!  In that case, make sure that there are NO LEAKS prior to the pump.  Try to minimize the use of rubber hoses and clamps and stick with the stock steel lines as much as possible.  You may have to replace the pump periodically.  Because if everything is perfect, and I mean PERFECT, in the stock set up, it will minimize vapor lock.  But you are still at risk for vapor lock.

Only a robust pusher electric pump just in front of and below the fuel tank can really eliminate the risk of vapor lock.

[Lexi]

Also, make sure you have an original water pump installed. Other years may fit and basically the casting looks near identical, (different cast numbers on them though), but I recall that at least one of the port fittings on the '56 had a larger diameter. Perhaps Cadillac's way of addressing what Art pointed out by increasing flow? If your pump was swapped out with a lower efficiency one that won't help the cause. Can't miss the '56 fitting as it is huge. Stand to be corrected but I think this was another '56 one off. As Art pointed out the cooling system components on the '56 have to be in top shape. Remember that phone call we had Art where you said the heat generated by the '56 would melt your face off? That is correct.     Clay/Lexi

[Caddy Wizard]

Also, make sure you have an original water pump installed. Other years may fit and basically the casting looks near identical, (different cast numbers on them though), but I recall that at least one of the port fittings on the '56 had a larger diameter. Perhaps Cadillac's way of addressing what Art pointed out by increasing flow? If your pump was swapped out with a lower efficiency one that won't help the cause. Can't miss the '56 fitting as it is huge. Stand to be corrected but I think this was another '56 one off. As Art pointed out the cooling system components on the '56 have to be in top shape. Remember that phone call we had Art where you said the heat generated by the '56 would melt your face off? That is correct.     Clay/Lexi

That pipe on the lower right with the arrow pointing to it is part of the heater system and shouldn't affect the overheating and vapor lock in the summer.

[Lexi]

I always wondered if it would affect overall volume (rad) flow, hence cooling efficiency. Good to know that it should not. Clay/Lexi

[Omarine]

Thank you gentlemen for the replies. Just to clarify mine is a '52' which shouldnt matter much and i already have been running an electric 6 v pump mounted on the frame in front of rear tire.

The electric has done great but it did get questionable once in traffic with my small kids in the back. So i thought it would be nice to make the mechanical do most of the work and rely on the electric in a jam. 

I will check mech pump for leaks but it does everything perfectly until it gets hot which is driving then any idling like traffic, etc.

Which is why i wondered if running that gas vapor separator cannister with a return line to the tank might be my last ditch effort to see if the mechanical pump could be made reliable enough for florida driving. So far, the electric has carried the day. The mech pump came to me rebuilt by Fusick.

Cheers
Oscar