94 7.3idi testing GP relay

[ISPKI]

Hello Oilburners! I am working through the issues with my 94 f250 7.3idi. The vehicle has not been able to start in a few weeks. I had found that it had some major air intrusion problems and a bad lift pump. All the injector rings have been replaced as well as half the caps ( currently do not see any leaks). Lift pump was also replaced along with the fuel filter.

My current issue is: The WTS light does not come on when the key is turned the "on" and the truck does not start. It is receiving fuel although some air is still slipping into the system. The ignition switch has always felt extremely worn out and I found through testing the system that it might be bad. I tested the Large + terminal on the GP relay (that is the supply from the batteries) and it had 12.4v at all times. I turned the key to "on" and tested the smaller terminal on the relay with the red wires coming out of it feeding into the controller and had no voltage. I am going to remove the controller and relay to clean the contacts and ground as general maintenance but I believe there must be an issue with the switch given that I get NO reading with the key in the ON position. I am thinking that I may eliminate the ignition switch completely by wiring in a manual GP switch in the dash. AAAaaannnd I should probably resize that before attaching...

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[mblaney]

My opinion is to not use a manual GP switch... healthy relay and glow plugs works great. With a manual system you really can't tell when you lose a GP... the WTS cycle time will tell you right away that something is up. Many here like the manual system but I don't; do you think my wife will be able to remember to "only run the GP's for five seconds if it is warm, ten if it is cool, 25 if snowing..."?

The ignition switch is cheap (if that's the problem). Fusible links ok? If you suspect a problem with the relay then consider upgrading it! See the link in my signature.

 

[BDCarrillo]

check for power at the white wire with "Key ON"

If that one sees zero volts, you have an issue between the key and GPC. If you get 12v, and nothing on the GPC output, she's likely toast (or every single glowplug is dead, breaking the ground)

 

[ISPKI]

I have to assume all the GPs are good since they are new motorcraft zd9 that I installed a few months ago. I noticed a small black wire with a 90 degree plastic connector coming out of the GP harness over by the fuel filter that is not plugged into anything and I do not see a plug for it

 

[cpdenton]

That wire should be the water in fuel light. The sensor it plugs in to is on the bottom of the fuel filter. I changed my filter to one that doesn't have the sensor and mine is unplugged.

That's not your problem.

Check the ground wire really good. It comes out of the controller and should be grounded to the bolt holding the solenoid.

 

[FORDF250HDXLT]

I changed my filter to one that doesn't have the sensor and mine is unplugged.

 

[ISPKI]

Not much of an update, was raining all weekend but I did test the white wire with key onand read no voltage. Ground wire is attached and not corroded, looks like its never been removed. My next step is the switch. When turned to the on position, several lights around the WTS light used to come on but now the only light that comes on is the battery light. Its acting like the swich is not engaging.

 

[laserjock]

Are you getting power to the other things that should get power with the key on? For example the fuel shutoff switch?