Hey guys,
I've got my 88 F350 running pretty well now thanks to the information on this site, but I have one issue with the WTS light that still bothers me. I have new glow plugs (motorcraft) and they all test good. I get a 6-7 second WTS light yet the relay is still engaged for another 5-6 seconds. Is this normal or is the controller malfunctioning? It's almost like the glow plugs don't have time to heat fully because it usually takes two GP cycles for it to start.

Craig

 

if i understand correctly, coolant temp affects the cycle time, and they can cycle on and off after the wts light goes out to help the engine warm better...

 

what your experiencing is after glow.our trucks do that to keep the cylinders hot until the engine produces enough heat for combustion.thats the way it was explained to me.5-6 is well within the norm.

 

How ...The Solid State Circuit Works ........

This is 93 info, but other than the "maxi fuse" operation is same.


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.

 

What I am experiencing is that the by watching the volt meter gage, I hear the relay open the meter voltage rises but the light had gone out 5-6 seconds earlier. I have had no luck starting it if I use the WTS light only.

My fast idle is operating correctly and drops the idle once the engine warms up. I would think that means the temp switch is ok.

Good info so far-Thanks

 

I would check the ground wire on the controller/relay and make sure it has a good ground connection.

I would also check the engine harness to chassis harness connector near the dip stick for signs of overheating on the end that has two large AWG wires, either yellow or tan in color.