The"ignition" system is shutting off the pump once adequate head pressure is obtained. Its not the engine starting that directly triggers the pump. Its the engine using the fuel in the rail, lowering the pressure below the triggering threshold on some pressure sensor somewhere, causing a logic circuit to turn the pump back on. The feedback loop in this situation is based on fuel pressure.
 
Dave

William wrote:

Paul,

If your ignition system shuts off the pump with no spark, isn't the following going to happen?

 

Pump 1 on -- engine running,

pump 1 fuse blows, engine shuts down very quickly,

Pump 2 turned on, but no spark since engine has stopped, therefore it shuts off right away.

 

Sounds like if engine stops, you have to crank it to get it started again

Bill Schertz
KIS Cruiser # 4045

----- Original Message -----

From: sqpilot@bellsouth.net

To: Rotary motors in aircraft

Sent: Monday, May 02, 2005 1:42 PM

Subject: [FlyRotary] Re: fuel pumps/forced landing

 Turned on the other pump, but the engine had already quit. (yes, it happens very fast)  

 

      I now recall reading in the MicroTech manual that the fuel pumps shut off if it detects no spark from the coils, so that it would not continue pumping fuel into an engine that has no spark. This is obviously why the pump only runs for a few seconds when I first turn on the ignition switch, then quickly stops pumping. We put a voltmeter to the inline fuse, and found that it had 12.9 volts as soon as the ignition was turned on, but after a few seconds, the pump stopped and there was no longer any voltage at the fuse.

    I'm hoping we can find what caused the slight fuel obstruction in front of the gascolator....if we can't find the cause, it would be difficult to regain confidence in the fuel system. Too bad, because the engine was running strong and smooth, and the temps were great!!!  Paul aka deadstick Conner