Vapor lock 1 and 2

[Vic Piano]

Everyone knows that Vapor Lock doesn't exist... that is until they experience it! Ford knew VL existed, if you read their tech manuals you'll see where Ford engineers were trying to figure out how to solve the problem, well up into the '60's... As we have read here, there appear to be myriad fixes for the problem. From my own experiences with VL, in various vehicles, I have found that different remedies apply to particular vehicles. For example, when our '39 LZ gets a case of VL, I open the locking gas cap, pull the choke and nine times out of ten, she fires up... the '39 CS does not respond to that "easy fix"... The one "fix" I have found, is to install an electric fuel pump as the primary pump. That has worked on our '47 Convertible and our '51 F-1. I'm about to install an electric fuel pump in our '39 CS and hope that the results are the same as in the '47 & '51.

[G.M.]

Vic put in a simple return line, that's the real fix.
Just came back from a 30 mile each way ride to Arcadia for lunch 85 here in Punta Gorda and just about 90 in Arcadia.
Only had an 1/8th tank of fuel when I left so the fuel was warm and some more heat added to the fuel in the tank from the returned fuel which accounts for the cooler pump and carb temps after filling the tank.
On the trip over traveled at about 65 except for about a 2 minute spurt at 90. Ran good at 90 with no notice of any fuel starvation. Water temperature was 180, slowed down to 45 for 3 or 4 miles and the temperature dropped to about 178. Stopped for lunch water temp 178, carb temp 110, fuel pump temp 112. closed hood went in for lunch. Came out in 25 minutes water temp was 184, carb 125, fuel pump 128 and carb fuel bowl right on the sight glass line 1/2" from the top.
Stated up on the first turn, drove 1/4 mile and stopped at a store, came out in 10 minutes and it started on the first turn. Went 1 mile stopped and filled the tank with 10% ethanol and it started on the first turn. Drove 25 miles and stopped at a friends, got out and checked temps. Carb was 115, fuel pump 112. Let it running about 8 or 10 minutes and temp went to 190. In 3 miles the temp came back down to 182. Went about 8 more mile through town and arrived at where I am now. Carb temp 107 and fuel pump temp 105., water 182. It cooled down slightly out here by the water. So with those results I have no doubt this is the best cure for VL along with the 1/2" vented carb space from Bob Shewman.
I have some idea's for better installation. Drill a 3/16" in the pump to carb line a few inches from the pump aiming towards the flex hose. Clean and silver solder a 2" piece of the 3/16 OD steel brake tube in the hole. Put the Airtex CI-8000 fuel valve back at the fitting installed in the filler neck with the arrow towards the filler neck. Use a brake tube fitting for 3/16" flared brake line into the input or fuel pump side if the check valve. They make all lengths of brake tube all ready flared with fittings on them. Use them from the filler neck up the frame and up the firewall along with the 1/4" fuel line that supplies fuel to the pump. Get a 3/16" ID thin fuel hose and slip over the cut off end of the return line run with the flex hose and plug it on the tube silver soldered in the carb line. There is only a lb or so of pressure in the return hose so the small band ring clamps you sqeeze will be good. I don't need to do any more testing but would like to see a few others try it so they can verify my results. You could run a plastic tube back and with and an old gas cap drilled for the tube return the fuel that way to test it. Don't forget if you use tube with an Id larger than .130 you need a .130 restrictor in the return. G.M.

[Bolts]

I personally like the idea of a return line to solve the problem of VL because it does not require moving parts.
Way to go George.
Thanks for all the hard work and for sharing your results.

[Vic Piano]

That sounds good George. I may give that a try, but I know the electric pumps have prevented VL in my '47 & '51... With the OEM style FP that Marv modified, to make it a "pass through", everything will look stock on the intake manifold, no block off plates on the FP stand. I'll keep a (known to be good) mechanical FP in the trunk, just in case the electric pump has a problem...

[G.M.]

Originally Posted by Vic Piano

That sounds good George. I may give that a try, but I know the electric pumps have prevented VL in my '47 & '51... With the OEM style FP that Marv modified, to make it a "pass through", everything will look stock on the intake manifold, no block off plates on the FP stand. I'll keep a (known to be good) mechanical FP in the trunk, just in case the electric pump has a problem...

Vic you have to try the bypass, 39 runs better with the cool gas than it ever ran on a 90 degree day. G.M.

[Old Henry]

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Congratulations G.M. Looks like you got it figured out, at least for the low lying coastal areas. Hope it keeps working for you as the temperature there rises.

[G.M.]

Try it I believe will work in higher altitudes as well. G.M.

[FlatheadTed]

Yes Sounds like you got it figured GM .Didn't really want to get into this debate .I will start a new thread later when I do the fuel level tests as you suggest. Re: Vapor lock 1 and 2
I don't believe that VP is purely a vaporisation of fuel I think its a fault with the fuel system ,Pump or flex line or sucking air ,then again I might be proven wrong here . There is a myriad of things that can go wrong on mechanical pumps .sucking air at the top ,joints, leaking diaphragms, worn arm mechanism's, push rods .If electric pumps solve VL then a mechanical one should also ,the last two cars that came in from CA I pulled the aertex pumps off and did up the mechanicals ones ,the pumps were fitted in such a way that on a low tank they wouldn't get fuel . Most tank out lets are hallway up or on the top so you don't really get gravity feed if the out let was on the very bottom then a different story will result it could depend on how full the tank is .Drain back or siphoning back has been mention here .About 10 years ago I pulled a modern pump to pieces to see what valves they had in them the Ford escort had a series of laminated rubber wafers most likely Neoprene ,I fitted these in side the pump on top of the mica pictured (P4) to see how the pumping action went ,seemed to work well .I now notice that the pump kits you get now are Neoprene (P1) as apposed to the old Mica Formica type product (P4) ,so I think drain back should be near eliminated this has a much better sealing action .This topic was discussed a while back and at the time a buddy of mine was here who was a car dealer in LA for 30 years , he regularly brought cars through HI way 40 through the hot Arizona desert .I asked him if had experienced VL he said they changed the mechanical pumps more than once and the problem went away . I don't really have time for this I am a one finger typist but more to add later .

[gary635g]

Volume could be my problem 16 OZ. in 45 sec or less the best I get is 12 oz. I wanted to pull and clean the strainer but did not have a new gasket. Pressure 4.5 # on starter and Idle.

[G.M.]

Originally Posted by gary635g

Volume could be my problem 16 OZ. in 45 sec or less the best I get is 12 oz. I wanted to pull and clean the strainer but did not have a new gasket. Pressure 4.5 # on starter and Idle.

I went back and saw your other post where you had VL and poured water over the pump to get running. With 4.5 lbs pressure your VL heat range is a little higher. Since you have a pressure gauge installed let the engine get hot watching the carb line fuel pressure. I have found the hotter the pump gets the lower the fuel pressure. When the pump temperature gets about 130 the fuel pressure drops to down about 1 lb . This is right at VL range. Next the fuel pressure will start to bounce up and down, this is VL starting, next is a full blown VL. You need a laser pointed thermometer which costs about $30.00 to see the temperature on the top of the pump. G.M.

[Shadetree]

I have owned and driven several flathead Fords in my lifetime and have never experienced a vapor lock. I have driven the `35 on 90° days without an issue. On the other hand as a kid working in a service station I saw lots of clothes pins on fuel lines...

[jimTN]

VP exists! GM, when you have would up your experiments and have a successful go, would you please post a diagram, pics and bill of materials. I truly appreciate your efforts.

[Cecil/WV]

I just returned home late eve. from a near 2700 mile trip through the southern states with Fla being the destination state in my '50 Ford. The first day, Apr. 13, it was a moderately hot day in Va as I headed south. I filled my tank at the northern end of Va on I-81 at the Flying J around 9:00am. By noon time, I was using my electric pump to aid the gas flow on any long grade. Later in the afternoon, I filled again and for the rest of the trip, even in slow traffic in Orlando, it never ever missed a beat. ????

[gary635g]

No gage installed, when I get a new gasket I will remove the screen ands clean it, I suspect it has not been out for many years after cleaning screen if volume still less than 16 oz. in 45 secounds I will replace the pump with an Mechanical Fuel Pump AIRTEX 578 they are about $35.

[G.M.]

Originally Posted by gary635g

No gage installed, when I get a new gasket I will remove the screen ands clean it, I suspect it has not been out for many years after cleaning screen if volume still less than 16 oz. in 45 secounds I will replace the pump with an Mechanical Fuel Pump AIRTEX 578 they are about $35.

How do you know you have 4.5 lbs of fuel pressure at Idle and higher RPMs with out a gauge?? G.M.

[G.M.]

Originally Posted by jimTN

VP exists! GM, when you have would up your experiments and have a successful go, would you please post a diagram, pics and bill of materials. I truly appreciate your efforts.

Thank you Jim, The only thing I have to refine is the ID of the return or a drilled orfice in the return line. I think the fuel pressure is just a little low with the .130 ID of the return line controlling the fuel pressure. I had a little incident Friday when it was a little over 90 and driving for an hour or so I stopped with the black car sitting in the sun with the hood closed for 1/2 hour. Came out and started it and it took about 4 turns of the engine, went about 100 yards and it stopped running. I kept it rolling in gear, flicked the switch off and on with no change. Pumped on the pedal and it came back to life. I guess the whole thing lasted about 50 feet. Ran fairly good about 3 miles back to the shop where I pulled it in the garage and checked the fuel pressure which was down to 1 lb. Engine was about 190. I want to look at it Monday and see what the fuel pressure is cold and boost it up some with an orfice in the return. I'll completely block the return first to see how the pump is. I have pictures and will provide a list
of parts after I test it. I put a NEW LR wheel cylinder Thursday morning and Friday it started leaking, this is the second foreign one to leak. G.M.

[Old Henry]

Originally Posted by gary635g

Volume could be my problem 16 OZ. in 45 sec or less the best I get is 12 oz. I wanted to pull and clean the strainer but did not have a new gasket. Pressure 4.5 # on starter and Idle.

Originally Posted by gary635g

No gage installed, when I get a new gasket I will remove the screen ands clean it, I suspect it has not been out for many years after cleaning screen if volume still less than 16 oz. in 45 secounds I will replace the pump with an Mechanical Fuel Pump AIRTEX 578 they are about $35.

As I explained earlier (Post # 76), at 75 mph and 15 mpg (typical) the engine only burns 10.66 oz of gas per minute. So, even if you're only getting 12 oz in 45 seconds you've still got plenty of flow for a stock engine and carburetor going 75 mph. Also, you don't need to worry too much about pressure. At just 1 psi 25 oz. per minute will flow through the valve into your carburetor bowl. That's over two times the amount necessary to sustain 75 mph and 15 mpg. No need to be replacing any pumps yet if the engine is still running fine.

[ford38v8]

Originally Posted by Old Henry

As I explained earlier (Post # 76), at 75 mph and 15 mpg (typical) the engine only burns 10.66 oz of gas per minute. ...

Just a little optimistic there with your math, aren't you? 15 mpg at 75mph?

[Old Henry]

Originally Posted by ford38v8

Just a little optimistic there with your math, aren't you? 15 mpg at 75mph?

I get 15 mpg @ 65 mph without overdrive. That's why I used that number.

If it was 12 mpg that would be 13.33 oz per minute. At his 12 oz in 45 seconds that's still 16 oz per minute - plenty to go 75 mph at 12 mpg.

If his mpg was as low as 10 mpg @ 75 mph he'd be right at the 16 oz per minute he'd be burning.

[ford38v8]

With all due respect Henry, even at 65 mph, 15 mph is optimistic. Perhaps if your engine is down tuned, your tires are at 36 lbs, your foot is light, you cruise at 45 mph and never hit the brakes, but realistically, who does that anyway? I start the engine, goose the pedal to hear the rap, wind out the gears, compression brake to rap it again, hey, this is fun! Who cares about mpg unless your gas gage is broke?