So this all started with me replacing a busted steering column shift tube in my 92 f-150. The mistake I made was I took the ignition switch off of the column instead of just unplugging it from the back of said switch. I put the column back together and tried starting the truck to find out that it will crank but won't fire. I looked up the proper installation of the ignition switch and followed the instructions.... nothing changed. I went to O'Reillys and purchased a new one. Following the directions on installation once again and now the truck won't even crank. Took the new one off put the old switch back on and bought a new key lock cylinder and the result is it will crank but won't fire......again. so I'm at a loss. I've had people tell me its the fuel pump (which is hard for me to believe that because before the shift tube broke the truck was running fine) or something inside the steering column. Im at a loss and probably overlooking a very simple fix but If anyone has any ideas or solutions it would be greatly appreciated.

 

Hi Benny,
Do you have a simple test light to use or a voltmeter?

When the key is in the on position /or start, there should be power to one of the terminals of the ign coil . If not, go back and check the fuses.
Do you hear the in tank fuel pump run for the usual 2 seconds ? Did you check the inertia switch, I believe it is located under the dash just over the trans tunnel.at the firewall.
Lets see what you find before going further.

 

So after much deliberation, we thought it was the fuel pump. I had test the pressure in the fuel line and had zero. On top of that I checked the interia switch and it was was ok. Now when starting the truck I would hear just a click but the fuel pump was not turning on. Had someone help me that had the voltmeter with the clamps. Hooked up the fuel pump to the battery and it was working. So he crawled under the truck to the plug the connected to the fuel pump and is getting no volts. We checked relays, fuses and interia switch (they’re all fine) only to end up at the ecm. Which he has a coder that he is bringing over to hook up later today and see what it’s telling us. But as of right now, I have no idea what it is.

 

You checked the inertia for power distribution on through? The fuel pump relay supplies voltage to the pump through the closed inertia. Ground for the pump motor is supplied by the PCM..

 

So what he did was he checked power to the inertia switch by checking the green yellow wire. And then popped off the inertia switch and checked to see if it was working properly with the voltmeter. He said everything was good.

 

Until Hayapower gets back , maybe we can provide a little of what is supposed to happen.

There are 2 relays involved.
One is the ECA relay that is activated by turning the key on and the other is the fuel pump relay. The ECA relay supplies power for the fuel pump relay so that when you first turn the key on the ECA grounds (activates) the fuel pump relay sending power on down to the inertia sw.then on down to the fuel pump. It only does this for 2-3 seconds then if no RPM signal is received from the ign system, opens the fuel pump relay. When cranking the engine the RPM signal keeps the fuel pump relay energized..and the fuel pump running. The 2 relays are the same and are interchangable. They are usually mounted on the firewall, passenger side, but don't have to be there..
That is some of how the fuel pump gets powered. There is a diagnostic plug that you already know what it looks like. If you are looking at the plug front , you should see a Letter shaped H in the center and 2 what look like hats on the bottom of the plug.at each end.. If you ground the right hand end terminal,with the key on the fuel pump relay gets energized and you should hear the fuel pump run. Does it?

 

No fuel pump noise. Hooked the coder up and we now are getting codes of 542 and 636

 

The missing power distribution at the fuel pump connector seems to be the key. You should, as hanky mentioned, see voltage in/out of the inertia for a few seconds only each time the key is cycled. If not or missing, look backwards towards the relay ect. If it’s present, then towards the pump be it harness/connector issues etc. You can as mentioned , bridge/ground the EEC connector and run the pump ‘continuous’ as long as the key is ON (helps to test and pinpoint a fail point and remove the timed control) If no ground is supplied by the computer, bridging the EEC will manually supply the ground and close the relay for a pump run as long as power distribution is there. If the pump test fine on the bench, or in place, power distribution or ground control most likely is missing.. I can supply you with an EEC fuel pump run test image, or you can find them on the net fairly easy..

 

Thank you all for the help. Finally figured it out and I’m quite embarrassed.... so my truck is a single fuel tank, seeing how previously I was working on the steering column when this all happened, my dash was apart. We just happened upon a plug that connects to the back of the dash where a tank selector switch would be for duel tanks (left side of steering wheel). Coder was reading 542 (PCM to GROUND) FYI. So connected the plug, turn the key and the pump kicked on, turned the key to start and boom, truck started! Just have to laugh at how stupid of a fix it was. But again, thank you for the help

 

Glad it was a simple fix..

Things get overlooked all the time,, one of the reasons were all here