Won't crank/start/run

[RBMC]

'99 Mystique; 2.5L V6, 5 sp. manuel, 62K miles. Battery, charging system are fine. Computer is not displaying any codes. All fuses/relays/breakers are ok/properly set.

Turn the key to "on": everything works as it should. Continue turning to "start": the fuel pump will prime but nothing else happens-no clicks, cranking, not sounds/action at all.

Bypass the clutch interlock switch, turn key to "start": the engine will crank but the electrical feed to the fuel pump has been interrupted (although it has primed it will not continue to pump fuel due to no electrical supply). It is not the pump: it is lack of electricity to the pump which has been shut off/not turned on somewhere by something else in the electrical system/computers. If we feed the engine starting fluid it will start and continue to run on the starting fluid.

The electrical system has been thoroughly checked out by a qualified mechanic (not me) who has access to all the OBDII data/diagrams/measurements and all the reference sources a professional/equipped shop should have, including online. No visual defects or smells in the electrical system. A '99 Contour (different engine, unfortunately) was borrowed and the electrical systems in the two cars were compared with no apparent defects discovered in mine (couldn't swap computers due to different engines).

This happened a month ago and after I made arrangements to have it towed I went out to clean out the car (4 hrs. after previous failure to start). When I turned the key to "start" it cranked, backfired, started then ran fine for four weeks until the problem reoccured.

HELP!
Thanks.

 

[2X95SEs]

When you turn the key to ON does all the idiot lamps come on? Does the CHECK ENGINE lamp light? If it doesn't the computer isn't powering up. You can have all the fuel pressure in the world but without the EEC nothing will fire - injectors, ignition.

 

[RBMC]

All idiot lamps, check engine lights come on, seat belt system works. Chimes work, lights work, power windows work, radio works. If we bypass the clutch interlock the engine will run on starter fluid so we have ignition.

 

[twocontours]

When you bypass the clutch interlock are you shorting across the switch or applying 12 v to it? When you go from run to start with the key some of the dash light will go off and some should come on. What happens on yours?

 

[RBMC]

Shorting arcoss the switch. Don't know about the dash lights; car's in a shop which I will have to visit or call the mechanic. Don't want to bother him too much 'cause so far he isn't charging me for most of his time as long as I don't annoy him. He feels "challanged" and committed to solving the problem but clearly doesn't want to be pressured. He told me that he has, for all practical purposes, as much access to data as does Mercury except for someone who may have run across the problem before in one of their dealerships.

 

[RBMC]

It's fixed: it's interesting

It's fixed: it's interesting

I had it at an outside shop who did everyting he could then told me he thought my own security system was not letting me start the car and only a dealer could access the security system. It then went to the Mercury dealer, who had to go to Ford, who, after two days, THOUGHT, it could be repaired by replacing the PCM as it appeared that the security portion of the PCM was not recognizing the chip in the ignition key. They were right (as was the outside mechanic). New PCM, new key, started the car and somehow activated the old keys also. It's fixed but an expensive repair that really shouldn't have happened.