Electric fuel pump

[rondahart]

Last season, I had an electronic fuel pump installed on my A4. The mechanic did not install a fuel filter, did not connect the hot lead to the oil safety switch (goes direct to coil), and connected the outgoing fuel line directly into the the mechanical fuel pump, which in turn feeds to the carb. This season, I have since installed a fuel filter (between the electric fuel pump and the fuel manual shutoff valve). I will be re-wiring the fuel pump to the oil safety switch. Should I by-pass the mechanical fuel pump completely, and connect straight to the carb?

Ron

[Don Moyer]

Ron,

It would definitely be best to bypass your original mechanical fuel pump. The most important reason is to eliminate the possibility of fuel ever entering into your crankcase in the event that there is now (or would ever be) a leak in the diaphragm of your mechanical fuel pump.

Don

[rondahart]

Don,
Thank you!

Ron

[rondahart]

Don, continuation from previous fuel pump question. I intend to remove the mech fuel pump. I can not determine what the device is at the input end of the mechanical fuel pump (with elec lead connected to coil and grounded). It is bolted inline with the pump, with the fuel line going directly to it. What is it and it's function? It is maybe 1 1/2 in diameter and 2 in. in length.

[Don Moyer]

Rondahart,

Very interesting! You seem to be describing an electrical solenoid valve that is probably intended to be used as a spring-loaded closed fuel shut off valve (held open electrically as long as the ignition switch is supplying power to the coil).

It would be interesting if you could find a name and model number on the valve.

Don

[rgoff]

A solenoid valve would make sense. The original post said the electric pump was not connected to the oil pressure safety switch (the normal method).

[rondahart]

Thanks gentlemen, I will check it out. Is the solenoid valve an added safety measure to be considered? Or would you recommend scraping the solenoid measure and pursue the oil pressure safety switch only.

Ron

[Don Moyer]

Ron,

I believe you're confusing a fuel shut-off valve (automatic or manual) with an oil safety switch in the electric fuel pump circuit, the primary function of which is to shut off the electric fuel pump whenever the oil pressure drops below 10 psi. Oil pressure safety switches don't really have any built-in valve to shut the fuel off, they simply shut off the electric pump.


In terms of fuel shut-off valves, I like the idea of an electrical solenoid to serve as an automatic fuel shut-off feature. If you want to be very cautious you might also have a manual shut-off valve for times that you want (for whatever reason) to be sure the fuel is shut off and don't want to rely on an electrical device.

Don