Ford V8 flathead vapor lock

Tim Berry · #1 22-01-06, 05:38

Any ideas on how to combat this problem without an electric pump. My F15A was never fitted with an electric pump.

Jordan Baker · #2 22-01-06, 05:50

I think I overhead Alex Blair saying he used Ice Cream cones before on the fuel pump. Since they might not always be handy just keep a few bottles of water nearby. Simply splash it on everyonce in awhile and that will keep the pump cooled down a bit.

I watched Alex work his magic last June at CC4 in the back of Stewarts T16. Lots of hissing and steam all over the place but it got us home. Come to think of it I think Geoff was back there too.

I hope this helps.

Keith Webb · #3 22-01-06, 09:25

These vehicles must have been designed to run under these conditions when new, so what has changed?

I think one of the main problems I have come across is the fuel pump, and in particular wear in the actuating rod which transmits the energy from the camshaft to the pump... Old "bushies" here talk about the threepenny solution where a thruppence coin was put under the pushrod to restore clearance to make the pump effective. This rod can wear quite a lot in service. Another solution is to add some length to the rod with a bit of weld added to the bottom of the rod.

Alex Blair (RIP) · #4 22-01-06, 14:42

Quote:

Originally posted by Keith Webb
These vehicles must have been designed to run under these conditions when new, so what has changed?

I think one of the main problems I have come across is the fuel pump, and in particular wear in the actuating rod which transmits the energy from the camshaft to the pump... Old "bushies" here talk about the threepenny solution where a thruppence coin was put under the pushrod to restore clearance to make the pump effective. This rod can wear quite a lot in service. Another solution is to add some length to the rod with a bit of weld added to the bottom of the rod.

Hi Keith
That is the usual answer and the fix...
Should take away most of the problems..
And the Articicized Ford Flatheads were fitted with electric fuel pumps..

Phil Waterman · #5 22-01-06, 22:35

Vapor lock or flooding take your choice, but electric fuel pump with a isolation switch is the answer. Rod Lincolns and Fords have run in my family as long as I can remember. I suspect that at times what is blamed as vapor lock is actually a combination of boiling the fuel in the fuel line and flooding the engine because the fuel boiling pushes excess fuel from the carburetor into the engine as soon as you shut of the engine. My first car was a 49 Lincoln which had been extensively modified, it had been by dad’s, it didn’t like the hot southern weather the fix had been to replace the mechanical fuel pump with a electric fuel pump mounted back at the tank. It also had a under dash switch to turn off the fuel pump (early antitheft device). I leaner early on that to start that 350 cubic inch high compression flathead V8 on a 6 volt battery you did want to crank it over for long. So starting procedure was to turn on the fuel switch and ignition wait for the pump to stop clicking, meaning fuel line and carburetor were full of fuel, then hit the starter button. Usually the reward was the nice rumble of the dual exhaust. If however it didn’t start and it was hot out then you turned the fuel pump switch off pushed the gas peddle to the floor held it there and hit the starter button again usually this resulted in the engine catching after a couple of turns.

When my brother started playing with flat head Ford V8 he found that they really did like to vapor lock or boil the fuel line he tried the same fix but didn’t completely cure the problem so he added a return line to fuel tank using small tubing. In this way the electric fuel pump back at the tank could purge the line of any vaporized gas in the fuel line.

Tim Berry · #6 23-01-06, 04:30

It is certainly an interesting subject and I suspect my CMP is doing it.
I have used aviation fire sleeving on the fuel line from pump to carby. Is this line the one that boils the fuel.

Surely this problem must have shown up in North Africa and PNG.

My wife's grandfather drove CMP's in New Guinea during WW2. They used to carry a bag of oranges. Simply cut an orange in half, Squeeze it onto the top of the fuel pump like using a juicer and leave it there.
The juice apparently evaporated,cooling the pump and the orange wouldnt catch fire.

Fruit for thought?

Lang · #7 25-01-06, 06:56

While Keith's comment that "these were designed to operate in these conditions" might be a reasonable assumption, I do not believe it is so.

CMP's of both types and Dodges were designed and tested in areas far removed from 100+ degree temperatures. The stories of Fords, in particular, but Chevs and Dodges also, boiling and vapour locking in hot climates come from almost every driver who sat behind the wheel in the Middle East, Pacific Islands and Northern Australia.

Without the simple, cheap and obvious solution of putting an electric pump on the truck you are left with getting everything in the fuel system running perfectly as Keith suggests.

The first thing to look at is the fuel line and filters. If the pump has got so hot that it is "wheel spinning" on fuel starting to vapourise it is not going to lift as well. Check all lines are fully free and filter perfectly clean. Filter might be OK but blow back into tank to see pick-up is clear. Tighten and check all lines and unions for leaks - these may not show as fuel weeping but may let air in when pump sucking starts.

Are all fuel lines well away from the engine, particularly exhaust manifolds and pipes? Are any heat shields in place and properly positioned? Some vehicles have a tin plate fixed to the fuel pump bent to catch air from the fan and blow it over the pump.

I assume your main problem comes after stopping for a short while and heat soak from the engine heating the fuel pump or if you are grinding up steep hills on hot days. Have you taken the thermostat out of the engine - if so put back a new one! Does the engine run at 180 degrees in normal service? If it runs at 190-200 on a slightly warm day or with only a moderate amount of load or hills you should look at that - clean water system and check the thermostat. Maybe those rotten Ford water pumps are faulty.

You might try using AVGAS 100LL from your local airfield. With the price of normal fuel today, it wont be much dearer than service station fuel. Much better for the engine also for, despite its Low Lead name, it has heaps more lead than modern car fuel and is great for old valves. Main point is its vapour pressure (the point where it goes from liquid to gas) is much higher than car fuel and might solve you problem without doing anything else.

Lang

Hanno Spoelstra · #8 25-01-06, 11:03

Quote:

Originally posted by Lang
Without the simple, cheap and obvious solution of putting an electric pump on the truck

Correct; all Fords built under Indian Army contracts were fitted with the Autopulse electric fuel pump.

Regards,
Hanno

Lang · #9 26-01-06, 07:27

Just thought of another suspect.

Modern fuel attacks the "rubber" tips on the old fuel needles. This can cause the tip to deteriorate.

When it gets warm (from carb heat soak after stopping) the tip gets soft and can either cause bad seating and flooding as described above or it can stick in its seat giving the impression of vapour lock.

I know many jeeps have suffered from these problems. Cure is to get a replacement all-metal needle and seat from any tune-up shop.

Lang

Phil Waterman · #10 26-01-06, 13:54

Quote:

Originally posted by Lang
Just thought of another suspect.

Modern fuel attacks the "rubber" tips on the old fuel needles. This can cause the tip to deteriorate.

When it gets warm (from carb heat soak after stopping) the tip gets soft and can either cause bad seating and flooding as described above or it can stick in its seat giving the impression of vapour lock.

I know many jeeps have suffered from these problems. Cure is to get a replacement all-metal needle and seat from any tune-up shop.

Lang

Lang – You raise a very good point about the modern gas attacking rubber parts. The changes in the last couple of years have been sudden (here in the US) gaskets, fuel pump diaphragms, fuel lines that had been fine all of a sudden designate. I’ve attached what happened last summer with a gas can that I’d been using for years with no problem (didn’t leak around the cap) then all of a sudden after buying gas for the generator at a different gas station the bloody gasket disintegrated in a matter of a half an hour. Your point of care with rubber tipped valves should also be taken for NOS fuel pumps.

cletrac (RIP) · #11 26-01-06, 17:10

One thing most people never think about regarding this problem is make sure the fuel line goes uphill all the way from the pump to the carb. If you get like an inverted p-trap the vapour bubble gets up there and won't push out. If there's no place to trap the bubbles they just go through the needle valve and escape to the atmosphere. The same applies from the tank to the pump.

Jordan Baker · #12 27-01-06, 03:55

Hi everyone

This thread has become really good from my original comments. Ok this is the setup I have installed in my UC. Ive used steel brake line tubing for the fuel lines. From pump to Carb is a 10" 5/16 line. Would this shape cause me any problems with traping air bubles?

Is there any suggestions for improving it. The tank to pump line is the same kind of tubbing but I have also installed an outboard motor primer bulb (thanks Charlie). What kind of fuel filter should I put in or is it needed if I have my original tank cleaned out and resealed/relined.

Lang · #13 27-01-06, 07:46

Jordan,

Apart from it looking pretty agricultural I think the set-up should work fine.

You will ALWAYS need a fuel filter. The absolute best system is a modern in-line plastic filter. They are cheap, you can look at them to see dirt or water and take 2 minutes to replace. They can be put anywhere in the line without having to fit unions etc - just cut the metal line, slide on the rubber tubes supplied with the filter with their clips and you are finished. Every gas station carries them.

They filter down to a size to cater for modern day fuel injection. The old military filters (both oil and fuel) only stop logs and dead sheep passing through.

The outboard fuel squeezer is a great idea but you should keep an eye on it as they were never made to suffer the heat of an engine bay.

Tony Smith · #14 18-05-06, 18:46

Should anyone be interested, there is a 12V Autopulse pump on e-bay. Exactly the same style as the original C29Q-9350 Autopulse, but in 12 volt!

Lang · #15 18-05-06, 22:24

Just one more comment as Tony has brought the thread back up. Most of the vapour lock problems are suffered by Fords. It does happen to Dodges but mainly when people remove the heat shield on top of the fuel pump and allow radiated heat from the exhaust manifold to roast the pump when stopped. I think most Dodges seem to have had this shield removed for convenience or during a fuel pump change.

My Carryall suffered badly from vapour lock after stopping on hot days. Replacement of the shield fixed the problem.

Fords on the other hand are behind the eight ball from the start. The fuel pump position on Chevs and Dodges is at the bottom of the engine but the Ford is on top requiring an additional lift capacity of about 18 inches. This does not seem much but when you are talking about only 3 or 4 psi to start with and it requires roughly half a pound a foot to lift fuel the Ford pump has to work much harder.

The pump is very convenient to work on but the position is extremely poor. If I was a freezing doormouse this is exactly the place I would choose to warm up if I found myself in a Ford CMP.

Lang

horsa · #16 18-05-06, 23:08

Another thing that will simulate a vapor lock is having an in-line fuel filter between the fuel tank and the electric fuel pump. Same type of air bubble problem can occur and the pump will not be able to maintain a prime for suction at anything other than an idle.

If you use these modern parts, put the filter between the carb and the pump.

Jon Skagfeld · #17 18-05-06, 23:38

He he he...

Any Fords wanna be pulled by Chevs?

Alex Blair (RIP) · #18 19-05-06, 00:03

Quote:

Originally posted by Jon Skagfeld
He he he...

Any Fords wanna be pulled by Chevs?

Jon..
Don't start throwing stones..Last time I saw your Chevvy ,you couldn't keep oil in it long enough to drive it ..What was the fix for that..??Other than a tow rope...
And will we see it under its own power at CC5???

jim sewell · #19 19-05-06, 01:36

Just to add a few points to what has been mentioned before about vapour locks , fuel boiling and starvation .

Mechanical fuel pumps should produce about 3 to 5 PSI pressure idling and have about 10inches of vacuum suction . the pressure is determined by the amout the diaphram spring is compressed so worn links and arms will cause the pressure to be lower and the volume pumped to be less .

Placing the plastic inline filter between pump and carby has several advantages , it acts as a serge chamber of the pump pulsations and may prevent needle and seat problems and also acts a expansion area ( usually these filters are part filled with air ) when the vehicle stops after a hot run and the heat from the stopped engine raises the temp in the fuel line thus expanding the fuel and compressing the trapped air and not forcing the needle open at the carby ( flooding ) .

In some cases vapour lock can occur on the suction side of the pump when the suction fuel line and fuel pump reach higher temperatures , the reason being that pressure increases the boiling point ( vapour ) whereas vacuum or suction will decrease it so we can have vapour lock occurring in the suction line if the vehicle has some sort of restriction in the pick up line ie partially blocked filter or pick up screen .

Fitting an inline electrical pump on a remote switch as close to the tank as possible is a good safe guard and still use the mechanical for every day use . the electrical can be turned on when the vehicle has not been used for a while or when the vehicle runs out of fuel to save those long cranking spells and if there is a suspected fuel supply problem as stated above .

An electric pump makes it quick and easy to check if there is a fuel supply problem by using the remote switch and disconnecting a fuel line near the carby and safely observing the fuel flow with engine stopped .

Regards
Jim S.

Jon Skagfeld · #20 19-05-06, 04:11

Quote:

Originally posted by Alex Blair
Jon..
Don't start throwing stones..Last time I saw your Chevvy ,you couldn't keep oil in it long enough to drive it ..What was the fix for that..??Other than a tow rope...
And will we see it under its own power at CC5???

Fix was dropping in a "new" 216.

Yes, it will be roaring around at CC5...(ready to tow Fords!)

Lynn Eades · #21 19-05-06, 08:21

I would like to very simply clarify some things that Keith and Jim have talked about.
The ONLY thing that dictates delivery pressure in these pumps is THE SPRING.
Wear in the linkages, push rod etc. causes a drop in the delivery Volume. This problem will cause the engine to die under load, having idled well, and initially seeming O.K. (Because it runs out of fuel)

Now to the separate subject of vapour lock.

Some things that might help to prevent vapour lock;
Use steel tube instead of copper (less heat tranfer)
Try to minimise the volume of fuel exposed to the heat by keeping the fuel line between the pump and carb to a minimum length, (at the same time it must be clear of heat sources.
Have I not seen these (original) pipes lagged with asbestos?
Dont take any short cuts with any part of the cooling system. Make sure all the shrouding is in place
Use a MONO grade oil in these engines (more efficient heat transfer)
Use a quality gasket material at the fuel pump mount face (do the same with the carb)( to reduce the heat transfer)

Paul Singleton · #22 19-05-06, 08:31

I was at a cruise night last Friday and there was a Ford there with a flathead. There were wooden clothes pins clipped to the fuel line between the carb and fuel pump. The owner claimed it prevented vapour lock because the clothes pins would dissipate the heat. It would be interesting if it really worked!

Tim Berry · #23 21-05-06, 08:33

Here are the problems I found:

1. A minor air leak at the top of the fuel pump. A new gasket fixed this.

2. I has a cheap plastic fuel filter between the tanks and the pump located just over the bellhousing. During operation the plastic became very very hot and not much fuel going through it. After removing it I went for a drive of 80 miles in Queensland 38 degrees c heat. I could have cooked an egg on the engine cover. After shutdown and letting it heatsoak, she started easily and then a further 80 miles home.

Not a sign of fuel starvation or vapor lock. I hink horsas post is right. The nasty cheap modern fuel filter the biggest cause as she still kicked up a fuss after repair to the fuel filter gasket.

Tim Berry