MEL engine in my 59 vapor locks

The 383 in my 59 Mercury vapor locks anytime that it is shut off and restarted at normal operating temperature. It'll cruise on the highway just fine but if you stop and shut it off it will not deliver fuel and once the fuel in the carb is burned off that's it.

The line is clear and all connections are tight.

The pushrod travel is correct (1/4 inch per factory service manual) so that tells me the eccentric on the cam is good.

The manual also says that suction should be 4 in/Hg which it is IF the output is free-flowing into a container but if it is pushing into a full carb it only pulls about 1 in/Hg. That makes sense but is it correct?

Flow test should be 1 pint in about 20 seconds and it delivers that easily unless it is in the vapor lock state. (I have confirmed this on the side of the road)

The engine is not too hot because the gauge reads good and there is no coolant boil.

I have checked the pump and it is clean inside.

What am I missing?

I have thought about running a return line but they didn't do that at the factory so I'd rather correct the problem than re-engineer.

All advice appreciated

 

Only a couple of suggestions? Does your gas tank have a breather in the cap could that be blocked causing problems getting air into tank as fuel is removed by pump, also could carb be getting hot, is there some kind of heat shield or insulating block missing?, I'm no expert but just a couple of things that crossed my mind.


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Look at the gas cap. Sounds like it is not vented. Vapor lock does not exist with todays gas, with a properly designed fuel system.

 

If it is actually vapour lock, a return line or an electric pump at the tank will fix it.

 

Thanks for the replies-

The cap is not a breather but the tank has a vent line to let air in as fuel is pumped. I checked that line and it is clear.

The carb has no heat shield but gas isn't getting there when vapor locked.

A return line will probably be the final fix.

 

Just a thought: is the line from the tank possibly pinholed?? I had a Studebaker that would act like that, and it was a pinhole over the axle that caused the line to lose prime.

Didn't happen all the time, had to pressurize the line to find it.

Cosmo

 

my thought is that fuel is boiling out of carb
most carbs need insulator plates now with our current fuels
JMHO

still rember being at a station last year and fuel boiled and would not start , was getting late for show, and battery went down cranking and some one give me a jump
got to buy 3 insulator plates for the tri power and that is at least $90

 

Some of the crap in gas now- days can mess up the plastic in older fuel pump check valves.

 

I suggest you temporarily install one of the little square universal electric fuel pumps to confirm if the problem is the mechanical FP. If the problem goes away, replace the mechanical FP or eliminate it. Easier than running a return line.

 

I have had many 383-430 mercs and lincolns, that fuel problem is present in all of them. the 383 mounts the pump on top of the timing cover, and makes it difficult to suck fuel that high. if there is ANYTHING even close to being wrong with the lines, hoses, dirt in the tank, it will show up right away. I got tires of fighting it and just mount a cheap Napa electric pump near the tank. make sure you install a god filter BEFORE the pump. I wrap the pump in foam rubber so it is not so noisey. but it works. the fuel and brake systems are the first I do on my restorations, learned the hard way not to skimp, put in new tank, lines, hoses, pump,etc. this god-darn gas we have now is not carburetor friendly, so makes it all harder to handle, but that 383 Merc was a hell of a good engine. I used to beat the hell out of my Dad's 58 Merc. had a fast top end.Merry Xmas!!

 

Alcohol vaporizes much easier than gasoline.

 

The answers you've gotten should fix the problem. To that, I'd add:

1. Start at the tank. Pull it, clean it, pressurize it to confirm no problems waiting to happen.
2. Clean the pickup inside the tank.
3. Pressurize the line from the pickup to the fuel pump. As mentioned, sometimes pinholes will leak the vacuum the fuel pump is trying to develop and prevent it building pressure at the carb.
4. Add a small electric booster pump inside the tank or as near as possible. Always use an impact/roll-over switch. The wrecking yards are full of them. I look in the older Fords with EFI. As another mentioned, use a filter before the pump.
5. Add a return line with a small orifice to circulate fuel.

jack vines

 

The factory did provide a return line from pump on the 462s 66 and 67 Pumps for these engines had the provision for a 3/16 line.back to the tank. On my 48 Pickup with a 462 I was always fighting vapor lock. The return line cured it.. Actually even if you have an electic pump you might need a return line to make sure cooler fuel gets into the carb after shutting the engine off and heat soaking

 

Today I inspected everything closely and found something interesting:
The pushrod does not contact the pump lever for over half of the rotation. There is a 1/8 inch gap. Is this normal? Maybe the wrong pump or pushrod?

Regardless, I am going to run a return line. Is there a pressure regulator I should use or should I simply use a line smaller than the 3/8 supply to provide the pressure?

 

I use to maintain a fleet of trucks for a local municipality and I happened on a really cool ford truck fuel return system. I believe they were on the 1986 F-350s with a 460 engine. It was a fuel filter that screwed into the carb and it had it's own return line port. Just takes a 1/4 inch [I think] fuel hose and a hose clamp. I'm thinking of using 2 of 'em on my dual-quad pontiac engine.

 

engine man, it is my understanding that E85 is reduced to E70 or so for cold weather. so it vaporizes better at cold temps??? I could be wrong, just ask my wife!!

 

There is also a hard line version that came on E 350 vans with the 460. About $80 from Ford, I replaced the one on my motorhome thinking it was bad, turned out to be a weak electric fuel pump.

 

I seem to recall Pontiac using a 3 line filter. Some searching found a Wix 33041 which is a NAPA 3041. It has a return to tank to prevent vapor lock. It was used on air conditioned vehicles.

http://www.amazon.com/Wix-33041-Complete-In-Line-Filter/dp/images/B000C9UJAU

 

There are plenty of additives in today's fuel that wasn't present many years ago. Vapor lock is highly unlikely today.

A issue with the tank vent being blocked, or bad rubber lines allowing air to be introduced into the fuel lines is most likely the culprit.

 

Just wondering if you have checked the fuel line to make sure it is not to close to the exhaust.

 

Most of the additives in modern fuels are used to meet emission laws and work with modern vehicles with fuel injection systems. Have you ever run alcohol in anything with a carburetor? Vapor lock is a constant concern. Vapor lock is not a problem in modern vehicles with fuel injection that run higher fuel pressures and have a regulator that returns fuel to the tank to keep it cool and vapor free.

 

Yes as a matter of fact I have. 410" and a 430" Gaerte engines in a street car. Never had an issue using straight methanol, or a methanol mix.

Obviously, vapor lock is not an issue with modern fuel injection. The original fuelie Vettes I know currently run pump gas non E85, with no issues these days. Those same cars 10 years ago had to run AV gas. The only thing changed on those cars between then and now, the fuel. No issues anymore on 90+* days.

I still think he has another issue going on.

 

Everything checks out, no leaks in the line, not near any heat.

I found that the pushrod does not contact the pump lever for over half of the rotation, there is about 1/8 gap. I don't think this is normal. Either the pushrod is too short or the the pump is for a different application.

Since the supply is 3/8 I'm going to try a 1/4 return line and see how that works.

 

Run octane of 87 or higher. I found that in warm temps that 85,86 octane would cause vapor lock on my 53 Merc with flathead.

 

Just alked to and old Merc-Edsel guy. He said it is common to have that kind of wear on pushrod . His recommendation was to shim the lower end of mounting gasket on fuel pump, He said about a matchbook thickness or else get another pump. MEL site does have more info on vapor lock trouble shooting.

 

I am pretty sure if you install a 427 side-oiler, your problem will be solved. Well, maybe not, but go ahead and see!

 

Why do you think a return line is going to solve fuel delivery if
no fuel is present at the carb?
Next time it won't re-start, crack open the fuel line on the suction side of the
pump. If fuel is present, the pump needs replaced or rebuilt. If their is no fuel
at the pump, problem is at the tank.

 

I have a 60 Thunderbird with a fresh 390, new fuel pump, heat spacer under the carb, fuel line from the pump to the carb insulated, checked tank venting and the same problem. The car is fine until you park it for a few minutes when the weather is hot, then it will run for a couple of blocks and die, no gas, second fuel pump, no change. Haven't tried an electric fuel pump but the Squarebird site has a lot on this problem, common to the MEL and FE motors.

 

The HAMB troubleshooting quality has gone over the top.
...not one mention of wooden clothespins on the steel lines!

In my experience, the position of that fuel pump is causing the gravitational pull (and return) of fuel to the tank, losing the 'prime'.
1976 Porsche 911 had such a problem, and addressed it with a hard plastic line, 1.5 meters long; Inside the sealed line was a ball check valve.
Solution? Yes, and no. We were constantly replacing factory lines with defunct check valves! (on cars with fewer than 500 miles! Often as many as 3 times...)

Porsche finally introduced a stage-ll line, which was said to fix it. I had opened my own shop by then, so dropped 'out of the loop' in Factory Campaigns and 'Pink Slips'.
Funny thing about that: Electric pump, high PSI, and return line; Still needed a check valve. Defied all the laws of fluid dynamics.

 

You stumbled onto something with your discovery. There can be issues with mismatched push rods/fuel pumps on MELs. Do a search in the MEL Forum as well as in The Lincoln Forum and on Squarebirds.com in their 430 section on this. We had a tech article on this topic in Vintage Thunderbird Club International's "Thunderbird Scoop" magazine a few years ago, and it pointed out that push rod length changed in '61 or so with the Lincoln 430s/'66-7 462s.