Fuel priming device for mechanical pump

[hatman]

If an engine is not started for some considerable time ? then long cranking may be of some benefit.

Must admit, I thought that's what this whole thread was about as it's the only time that a healthy, well set-up twink needs any cranking, ie to get some petrol into the carbs. Otherwise it's one turn and off you go.

[Emma-Knight]

Brian, is the mechanical pump on your car in line with the Facet pump / will the Facet let the fuel pass through when turned off?

I' m confused about the oil pressure issue


Anna

[bcmc33]

Anna,

I fitted the Facet pump as a test prior to eventually removing the mechanical pump. I did this simply to see if it was of any real benefit in priming as I was only using the car every 3 to 4 weeks by which time the feed line had emptied back into the tank to some degree, and it took about 10 seconds of cranking to fill the carbs. It has reduced the cranking time, but whether it?s really worth it, I?m not sure.
If you use the car regularly the carbs should stay reasonably full and starting should only take a couple of seconds cranking.
To answer your question ? I don?t think the electric pump will send fuel past the mechanical pump ? it will only prime the pump. If you don?t start the engine for some time the only benefit is the time it takes for the mechanical pump to be primed.

Your original point regarding the bulb primer for outboard motors - this will do exactly what the Facet pump is doing for me.

Now regarding the oil pressure issue ? IMHO I don?t think this is worth any consideration at all. What I should have said in my last message was: ?If an engine is not started for some considerable time ? then long cranking may be of some benefit ? but I doubt it.?

[robertverhey]

I have a Facet type electric pump fitted on the bulkhead before the mechanical pump. My float chambers were emptying over one week (it's a weekend car), and I have a spring toggle switch so I can prime, using the electric pump for a few seconds prior to cranking, and then the electric pump goes off, and the mechanical takes over.

The valves in the mechanical pump are arranged for one-way flow, so yes the electrically pumped fuel does flow freely through the mechanical pump, up to the needle valve.

If planning to use an electric pump permanently, I suggest a fairly low pressure one (2-3 lbs), otherwise you'll force fuel past the needle valve and your float level will be too high

[bcmc33]

Robert,

Thank's for the lesson on the mechanical pump.

The Facet pump I fitted was a 2.5 to 3.0 PSI unit which is the same as the mechanical pump and designed to suit Weber/Dellorto carbs.

[bcmc33]

Anna,

I can confirm that Robert was correct in saying that the electric pump sends fuel through the mechanical pump to fill the carbs.

First start today after 2 weeks in the garage was instant after waiting a few seconds for the pump to do it's work was instant. The following eight starts during the day were also instant.

So you can do what I've done, if you wish, and leave the electric pump permanently in operation.