Testing of Fuel Pump

[Drbrown]

On my '47 59AB, I separately tested fuel pressure at the carb inlet coming from (1) my back-up electric Airtex pump used for starting, and (2) my mechanical pump - newer version with glass bowl. Pumping individually, I got maximum/constant/steady readings of about 3.0 to 3.2 psi. Based on other posted threads it sounds like these are good readings.

I'm curious about the fact that once each of the readings built-up to their maximum, and I stopped the pumps, the reading would remain as long as I waited and until I disconnected the meter. Is this appributable to the valve in the mechanical pump or is that the way pressure meters work ?

[Kurt in NJ]

it means the valve in the pump is very good

[ford38v8]

There are two identical one-way valves in a mechanical pump, installed opposite each other:
The rocker pulls the diaphragm down, creating a vacuum behind the outlet valve, which closes, enabling the vacuum to pull in fuel as the inlet valve opens due to that same vacuum.
The rocker arm then pushes the diaphragm up, pressurizing the chamber, reversing the function of the valves, the fuel being pushed out the then open outlet and closed inlet.

I hope I made that easy to understand, as I managed to confuse myself a few times in the writing of it!

[Drbrown]

Thanks Kurt and ford38 ! Never done any pump work but after reading other threads I was guessing that the valves in the mechanical pump were sustaining the fuel pressure. Its good to discover something in this car that actually works like it should !!

An experienced forum member PM'd me and expressed that the pressure readings are on the high side of being acceptable. The two pumps have been on the car since I bought it 5 years ago.

I did the testing to verify the two pumps are working properly. Been having engine problems .... darn 12 volt neg grd Pentronix distributor modules burn out after idling for short time. Had distributors rebuilt (my user and spare) and coils tested, crawled all thru car checking with my elec meter, considered possible heat build-up, replaced a good tested/working alternator, removed other electronic devices (elec radiator fan, tach) .... no gremlins found; voltages and R's test proper. Wiring and carb were replaced some time ago. Disgusted and now abandoning the module for points. We'll see ....

[koates]

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Drbrown, you say your coil has tested OK, but what were the tests ? The killer of the PERTRONIX modules is excessive coil primary current going through the pertronix unit. When the engine is idling the coil primary current is higher than if the engine is revving higher. So have you fitted an accurate test ammeter in the coil primary circuit to read the current draw ? Pertronix recommends certain coils to match the module with primary windings at defined ohms resistance. You cant just use any old 12 volt coil. I have used PERTRONIX units in several Fords for years with not one problem. Tell me the coil primary current readings at idle and at revs. Don't leave the ignition on for to long without the engine running. Regards, Kevin.