GP Cycle time
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Joined: Dec 2004
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GP Cycle time
I have 89 F250 with IDL 7.3l. The "On" time for the glow plugs has suddelny dropped dramaticaly, like one second, and then goes directly into the relays cycling. This occurs first thing in the morning when it is cold, so I know that it should take longer. I have no idea of where to start to troubleshoot this. Could it be a controller problem? Is there a sensor that determines when it is hot enough? Where is the contoller?
Thanks in advance
Thanks in advance
Logistics Pro
Joined: Apr 2004
Posts: 4,292
Likes: 5
From: NJ where fun comes to die
Start by checking your glow plugs. Test each one. Replace with Motorcraft/Beru from Autozone. About $8 each. Test to see if you get power to each gp while you are at it. I have a 90 7.3 and I just by-passed the controller with a push button. I am very happy with it. I hardly use the gps. They should last alot longer. The controller is on the top rear of the engine, almost at the trans. It should have a black plastic cover over it with alot of wires coming out. It has a relay on top if it, also under the cover. If the relay is working you can hear it click. Good luck with it.
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
I think this is good info.........
If you have 2 or more bad GPs, the controller may not cycle at all.
Two problems that occur with the solid state ( 1987 to 1994 IDI engines ) GP systems. If a GP burns out ( circuit resistance goes up ), the controller cycles the GPs at a faster rate which doesn't let them get to max operating temp. If 2 or more GPs fail, the controller may not cycle the GPs at all ( very rapid or no clicking heard ). When you check the GPs, use an ohmmeter. A high resistance ( not necessarily burned out ) GP can cause circuit resistance to go up and the controller will then cycle the GPs too fast. You probably will not find this problem with a test light. Resistance spec for GPs = .5 to 1 ohm cold. Second problem. A poor controller ground ( black wire attached to valve cover stud ) will cause the controller to leave the GPs on longer, often damaging or failing them. If you are having mulitple GP failures, I would check closely the controller ground. Now the confusing part. Bad ground --> longer GP on time ( slower cycling ). Burned out GPs --> faster cycling If you have both situations, it may appear that the controller is cycling the GPs at the proper rate. Bad ground slows it up while the burned GPs speed it up ---> normal cycling. The system acts/sounds like it's working normally, but you have a hard starting concern.
DieselDon
Glow plug torque is 12 ft lbs, I always use antisieze on the threads.
If you have 2 or more bad GPs, the controller may not cycle at all.
Two problems that occur with the solid state ( 1987 to 1994 IDI engines ) GP systems. If a GP burns out ( circuit resistance goes up ), the controller cycles the GPs at a faster rate which doesn't let them get to max operating temp. If 2 or more GPs fail, the controller may not cycle the GPs at all ( very rapid or no clicking heard ). When you check the GPs, use an ohmmeter. A high resistance ( not necessarily burned out ) GP can cause circuit resistance to go up and the controller will then cycle the GPs too fast. You probably will not find this problem with a test light. Resistance spec for GPs = .5 to 1 ohm cold. Second problem. A poor controller ground ( black wire attached to valve cover stud ) will cause the controller to leave the GPs on longer, often damaging or failing them. If you are having mulitple GP failures, I would check closely the controller ground. Now the confusing part. Bad ground --> longer GP on time ( slower cycling ). Burned out GPs --> faster cycling If you have both situations, it may appear that the controller is cycling the GPs at the proper rate. Bad ground slows it up while the burned GPs speed it up ---> normal cycling. The system acts/sounds like it's working normally, but you have a hard starting concern.
DieselDon
Glow plug torque is 12 ft lbs, I always use antisieze on the threads.
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