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Posted by: jims914 Mar 30 2023, 02:30 PM

Anyone have a problem with vaporing with a three port pump ?
Any solutions ?

Thanks Jim

Posted by: Rrrockhound Mar 30 2023, 06:13 PM

I cut out a piece of aluminum-backed heat shielding and tuck it between the pump and the heater valve and never have a problem anymore.

Similar to this:

https://www.menards.com/main/building-materials/insulation/radiant-barrier/reflectix-reg-r-3-7-reflective-insulation-24-x-25-50-sf/bp24025/p-1444452049106-c-5778.htm

Posted by: emerygt350 Mar 30 2023, 07:35 PM

As the original slime insulation falls off the fuel line from the firewall you may want to replace it with dei insulation. That and the shield does wonders. Instead of a shield I put an extension on the heat valve as described in the service bulletin. No problems since the dei and extension.

Posted by: wonkipop Mar 31 2023, 01:39 AM

where is it.
in the original spot?

if it is in original spot its not the pumps problem.
the pump is a fabulous design with no faults.
its that cast magnesium fan shroud.
its a heat sink.
all the heat in the engine just conducts to the magnesium.
........and radiates. after you shut down.
as deborah harry would say!

and boils the fuel in the line feeding the pump.
and maybe even the pump itself.

you either put up with it for the sake of originality like i do.
or move it up front.

Posted by: brant Mar 31 2023, 07:26 AM

It’s not the pumps fault
Just the location

Move it

Posted by: PCH Mar 31 2023, 05:10 PM

The vapor lock problem disappeared after I went to carbs.

When I had the FI, it would vapor lock fairly regularly, especially after a short stop. I started to carry cans of cold (off hand I don't remember what they were called) and cool the fuel lines and pump when it vapor locked. That worked every time to get me back on the road.

Posted by: emerygt350 Mar 31 2023, 06:27 PM

You don't have to redesign the car and send high pressure fuel 6 feet through the tunnel to fix this.

Posted by: brubou Mar 31 2023, 06:46 PM

Pressurized fuel is going through the tunnel either way, pump in front or pump in back, the system is 29psi.

Posted by: wonkipop Mar 31 2023, 07:25 PM

not strictly correct.

the fuel circuit from the pump to the fuel pressure regulator is pressurized in the pre 75 stock pump scenario. that is restricted to the ring from the pump near the engine to the fpr in the engine bay. the rest of the lines are at lower pressure.
the feed line is more or less just weaker suction/gravity feed. flow rather than pressure. the return line is the bleed out of the relief valve in the pump and the fpr. thats why they are two different diameters. the feed line is larger diam by 2mm.

different matter in the 75 cars. the feed line from the pump up front to the fpr is at full pressure right through the car. it was also made of an entirely different material. a high pressure nylon plastic.



in the case of a healthy 1.8 L jet the fuel pressure is at 35 lbs. drops to 28 at idle and off throttle. slightly higher than the D jets.

Posted by: jims914 Mar 31 2023, 07:28 PM

Thanks everyone for your input.

Posted by: brubou Mar 31 2023, 08:09 PM

No kidding. TIL

As far as two port pumps go; if in the engine bay the supply line thru the tunnel is gravity (lower pressure) to the pump, and the return line is pressurized?

However, if the two port pump is up front, both the supply and return are pressurized?

Posted by: JeffBowlsby Mar 31 2023, 09:52 PM

Factory fix: https://bowlsby.net/914/Classic/zSB_1973-10-06_P213.pdf

Posted by: wonkipop Apr 1 2023, 12:55 AM

ok mate

what would i know?
you must have a pressurised fuel tank as well.
you probably do. mine isn't.
think about it and get back to me.
who knows. american mind set. no better than average aussie mind set?
the chinese will do you if you don't up the game?
they are most certainly doing us!

flow yes.
pressure no.
there is a difference.
you build pressure with a "dam".
thats what the fuel pressure regulator does.
the fuel pump doesn't actually do pressure. it does flow. primarily.
and it supplies the flow against the dam wall to build pressure.
and once the resistance builds against the dam wall it blows it out the side via the check valve - should the fuel pressure regulator fail to do its job and jamb up.



thats why there is 2 tests for a fuel pump?
there is a flow test - volume in prescribed time.
and a pressure test, where you apply resistance and see if it can build pressure before it blows the relief valve.
not trying to pick a dumbo internet fight.
just trying to be helpful.
but then again just a dumb aussie so what would i know?

think about it. its fluid mechanics. there is flow, and there is pressure.
i can assure you there is very little pressure in the return line. but maybe quite a bit of flow.
same in the supply line. with a pre 75 set up.

post 74 there is a longer pressure line between the fuel pump up front and the fuel pressure regulator in the engine bay. thats the pressurized section of line.

but believe what you want to believe and do what you want to do to your car.
its your car.


the point is @http://www.914world.com/bbs2/index.php?showuser=25740 is correct. i'll put a 1000 aussie pesos on his opinion as a mere wager.
after all he is a ford man. he thinks like henry. the great american engineer.
maybe even superior to ferdinand porsche?
gives him real cred in my book. go ford.

and......two port fuel pumps relieve pressure by blowing it back through the supply line.
thats where the pressure relief valve is.
they do not need a third port.
its a very smart simplification.
i think mercedes in league with bosch worked that one out around about 1975.
its a long time ago.
and everyone in the USA making fuel pumps has benefited from their thinking since.
because lets face it, the US car manufactures were not even doing fuel injection in mass market cars back then, with high pressure fuel circuits, they were still frigging about with vacuum choked carbies.

i've rebuilt 3 original 3 port fuel pumps.
and a slightly later 2 port bosch pump off a merc.
i've seen what is in the guts of these things and got my tiny antipodean mind around it.
they are brilliant pieces of german engineering.
and they arrived at it long before the rest of the automotive world.

one word. physics. understand it and move ahead.