Wait to start Light
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Wait to start Light
I have just recently purchased a 1993 F250 4x4 with a 7.3L diesel. The wait to start engine light has been working fine up until a day or two ago, now it will not go off no matter how long I wait. The previous owner had no knowlegde of it doing this, and claims he just put in new glow plugs, module and whatever else there is pertaining to the glow plugs.....I think he said relay. Does anyone have any ideas of what is causing this or where I could start trouble shooting my problem? Thanks in advance.
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Joined: Dec 2004
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From: Mackinaw, IL
Sounds like the relay is hung up... Not sure though... I suppose you could turn the key on with the engine cold and use a digital Thermometer to see if the glow plugs in deed are getting warm.... You don't want you glow plugs to constantly be getting hotter and hotter thought.... Not too much good on the glow plug system but just a couple ideas
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Originally Posted by bigblu78
Sounds like the relay is hung up... Not sure though... I suppose you could turn the key on with the engine cold and use a digital Thermometer to see if the glow plugs in deed are getting warm.... You don't want you glow plugs to constantly be getting hotter and hotter thought.... Not too much good on the glow plug system but just a couple ideas
Senior User
Joined: Dec 2004
Posts: 317
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From: Mackinaw, IL
I know there is a way to disable the relay an make your glowplugs manual but I don't know how.... I know there is a thread somewhere about the workings and location of your glowplug parts.... I will see what I can find for you..
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Joined: Dec 2004
Posts: 317
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From: Mackinaw, IL
Found this for you.... Hopefully this will help you out a little....
Originally Posted by PLC7.3
Email me and I will send some info.....click on my name.
How the system works.......93-4
The Glow Plug Control circuit applies power to the Glow Plugs, which heat the combustion chambers so that the diesel engine can be started.
Glow Plug Controller
The solid-state Glow Plug Controller, attached to the top of the engine block, controls the Glow Plug pre-glow and after-glow time. It also controls the circuit's operation by sensing engine temperature, Glow Plug voltage and after-glow voltage from the start/run circuit.
When the Ignition Switch is turned to START or RUN, voltage from Maxi-fuse K is applied through the Glow Plug Controller to the Wait-To-Start Indicator Lamp.
The Glow Plugs heat up in zero to fifteen seconds, depending on engine coolant temperature. After the Glow Plugs heat up, the controller cycling switch opens and turns the Wait-To-Start Indicator Lamp off. The Glow Plugs are now warm enough for the engine to be started.
At the same time the Ignition Switch is turned to RUN, voltage from Maxi-fuse K is applied to the after-glow timer (located inside the Glow Plug Controller). The after-glow timer cycles the Glow Plugs for up to two minutes, depending on engine temperature. The after-glow timer then opens. The Wait-To-Start Indicator Lamp will not light during the after-glow period.
If the Ignition Switch is turned OFF, it can be turned to ON immediately, and the Glow Plug heating cycle will start again.
Diesel Start/Run
The diesel engine uses two batteries to provide extra power for starting and glow plug heating. Power is applied from the batteries, through heavy gauge wires, to the Starter Solenoid (located in the Starter Motor assembly). When the Wait-To-Start Indicator goes out, the Ignition Switch can be turned to START.
With the Ignition Switch in START or RUN, voltage is supplied to the Fuel Heater, Fuel Shutoff Solenoid, and the Engine Temperature Switch through Maxi-fuses K and U.
The Fuel Heater is in the Fuel Filter/Separator. It heats the diesel fuel, melting any wax that might clog the filter. The heater has an internal thermostat to turn it on as needed.
The Fuel Shutoff Solenoid controls the flow of fuel into the injection pump. With the Ignition Switch in START or RUN, the Solenoid is energized, and fuel is allowed to flow into the injection pump. When the Ignition Switch is turned off, the solenoid is deenergized, fuel flow stops, and the engine stops running.
The Engine Temperature Switch provides voltage to the Cold Timing Advance Solenoid and the Cold Idle Solenoid. When the engine temperature is below 112 °F (44 °C), the Engine Temperature Switch is closed. When the Ignition Switch is turned to START or RUN, the solenoids are energized, advancing injection pump timing and engine idle, allowing the engine to run more smoothly when cold. When the engine temperature reaches 112 °F (44 °C), the Engine Temperature Switch opens. This denergizes the solenoids, returning the timing and idle to normal.
To start turn key on press fuel pedal to the floor, then if above 30*F hold at 1/2 throttle, if below 30*F hold at 3/4-full throttle start engine. Once started release the fuel pedal to the fast idle setting or feather pedal to keep running.
The WTS light is the Black purple wire at the controller to the firewal' connector, it uses fuse #17 power and the controller is the ground until cycling starts.
How the system works.......93-4
The Glow Plug Control circuit applies power to the Glow Plugs, which heat the combustion chambers so that the diesel engine can be started.
Glow Plug Controller
The solid-state Glow Plug Controller, attached to the top of the engine block, controls the Glow Plug pre-glow and after-glow time. It also controls the circuit's operation by sensing engine temperature, Glow Plug voltage and after-glow voltage from the start/run circuit.
When the Ignition Switch is turned to START or RUN, voltage from Maxi-fuse K is applied through the Glow Plug Controller to the Wait-To-Start Indicator Lamp.
The Glow Plugs heat up in zero to fifteen seconds, depending on engine coolant temperature. After the Glow Plugs heat up, the controller cycling switch opens and turns the Wait-To-Start Indicator Lamp off. The Glow Plugs are now warm enough for the engine to be started.
At the same time the Ignition Switch is turned to RUN, voltage from Maxi-fuse K is applied to the after-glow timer (located inside the Glow Plug Controller). The after-glow timer cycles the Glow Plugs for up to two minutes, depending on engine temperature. The after-glow timer then opens. The Wait-To-Start Indicator Lamp will not light during the after-glow period.
If the Ignition Switch is turned OFF, it can be turned to ON immediately, and the Glow Plug heating cycle will start again.
Diesel Start/Run
The diesel engine uses two batteries to provide extra power for starting and glow plug heating. Power is applied from the batteries, through heavy gauge wires, to the Starter Solenoid (located in the Starter Motor assembly). When the Wait-To-Start Indicator goes out, the Ignition Switch can be turned to START.
With the Ignition Switch in START or RUN, voltage is supplied to the Fuel Heater, Fuel Shutoff Solenoid, and the Engine Temperature Switch through Maxi-fuses K and U.
The Fuel Heater is in the Fuel Filter/Separator. It heats the diesel fuel, melting any wax that might clog the filter. The heater has an internal thermostat to turn it on as needed.
The Fuel Shutoff Solenoid controls the flow of fuel into the injection pump. With the Ignition Switch in START or RUN, the Solenoid is energized, and fuel is allowed to flow into the injection pump. When the Ignition Switch is turned off, the solenoid is deenergized, fuel flow stops, and the engine stops running.
The Engine Temperature Switch provides voltage to the Cold Timing Advance Solenoid and the Cold Idle Solenoid. When the engine temperature is below 112 °F (44 °C), the Engine Temperature Switch is closed. When the Ignition Switch is turned to START or RUN, the solenoids are energized, advancing injection pump timing and engine idle, allowing the engine to run more smoothly when cold. When the engine temperature reaches 112 °F (44 °C), the Engine Temperature Switch opens. This denergizes the solenoids, returning the timing and idle to normal.
To start turn key on press fuel pedal to the floor, then if above 30*F hold at 1/2 throttle, if below 30*F hold at 3/4-full throttle start engine. Once started release the fuel pedal to the fast idle setting or feather pedal to keep running.
The WTS light is the Black purple wire at the controller to the firewal' connector, it uses fuse #17 power and the controller is the ground until cycling starts.
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New User
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Originally Posted by bigblu78
I know there is a way to disable the relay an make your glowplugs manual but I don't know how.... I know there is a thread somewhere about the workings and location of your glowplug parts.... I will see what I can find for you..
Senior User
Joined: Dec 2004
Posts: 317
Likes: 0
From: Mackinaw, IL
I wish I could help you out more..... Check out my previous post....
Remember the only dumb question is the one that isn't asked....
Remember the only dumb question is the one that isn't asked....
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Senior User
Joined: Mar 2006
Posts: 201
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Dont discount a manual switch, I spent 2 days elimanating what could be the cause of my glow plugs not working correctly. I installed a push button switch in 25 minutes, now if my controller fails, I just push the button, works great. lol
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Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
kyle01041981,
Welcome to FTE and the IDI diesel forum.
If you crawl on top of the engine to the passenger side rear of the intake manifold you will see the controller and relay.
It is covered by a vented plastic cover that pops off.
All the connections are bolted on except the wait to start light connection is a snap connector.
Once you remove the top you will see this.
Pay close attention to the black grounding wire, if it is not properly grounded to a clean connection, it may exibit the symptoms you are describing.
Do you hear the relay clicking?
Do you see the amp or volt meter dropping way down while the glow plugs heat?
Are your glow plugs good?
The small red wires on the ignition terminal in the picture can be removed and insulated to disable the glow plug controller, but yor engine may not start very easy this way. When you have them unhooked, one goes down to the controller, leave it on the relay. The other that goes into the engine wiring harness goes to the ignition key ON terminal and will be hot when the key is on at all times. Also the battery terminal on the relay has large wires that run straight to the positive terminal of the battery.
If you short it out with a wrench, it will melt the wrench and your fingers, USE CAUTION and unhook both positive battery terminals before attempting to loosen the nuts.
If it did stick on for any length of time, your glow plugs are burnt out. All the bad ones need to be replaced for it to work correctly. If you do have a bad relay or controller that is staying on, don't replace the glow plugs till it is fixed or it will just burn them out again at 10 dollars each. Only replace the glow plugs with Motorcraft/Beru ZD 9 glow plugs, the rest are junk and cause problems you do not want.
If you have more questions, I will be back on tomorrow night or there are others in here that also know this system well.
Welcome to FTE and the IDI diesel forum.
If you crawl on top of the engine to the passenger side rear of the intake manifold you will see the controller and relay.
It is covered by a vented plastic cover that pops off.
All the connections are bolted on except the wait to start light connection is a snap connector.
Once you remove the top you will see this.
Pay close attention to the black grounding wire, if it is not properly grounded to a clean connection, it may exibit the symptoms you are describing.
Do you hear the relay clicking?
Do you see the amp or volt meter dropping way down while the glow plugs heat?
Are your glow plugs good?
The small red wires on the ignition terminal in the picture can be removed and insulated to disable the glow plug controller, but yor engine may not start very easy this way. When you have them unhooked, one goes down to the controller, leave it on the relay. The other that goes into the engine wiring harness goes to the ignition key ON terminal and will be hot when the key is on at all times. Also the battery terminal on the relay has large wires that run straight to the positive terminal of the battery.
If you short it out with a wrench, it will melt the wrench and your fingers, USE CAUTION and unhook both positive battery terminals before attempting to loosen the nuts.
If it did stick on for any length of time, your glow plugs are burnt out. All the bad ones need to be replaced for it to work correctly. If you do have a bad relay or controller that is staying on, don't replace the glow plugs till it is fixed or it will just burn them out again at 10 dollars each. Only replace the glow plugs with Motorcraft/Beru ZD 9 glow plugs, the rest are junk and cause problems you do not want.
If you have more questions, I will be back on tomorrow night or there are others in here that also know this system well.
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
If you want the GP controller test click on my name and email me..........
Subject: GP controller test.
Double check the Blue Purple wire and connector to firewall.
Subject: GP controller test.
Double check the Blue Purple wire and connector to firewall.
Last edited by PLC7.3; Jun 6, 2006 at 08:37 AM.
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