replaced glow plugs, controller and relay but still won't start

[davidpippenger]

I gather from some of the other posts that the clicking sound that comes from the glow plug relay is normal (after the wait light goes out).

how long is normal before the clicking sound? How hot does the tip of the glow plug (in the engine) get?

We've replaced everything but the wiring harness, and that is on order.

[cdnsarguy]

Well since we don't know what year truck you have here is the 93 year info.....


How The Circuit Works


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.

[Mr_Roboto]

Were the GP's and other parts replaced in an attempt to cure a no-start problem? If you plug in the block heater for a couple hours, it should start without GP's..(provided the block heater works). That will help you determine if it is a GP problem or something else.

[OkieGringo]

Pipp, we need MUCH more info to help you. There are lotsa other reasons for "no start", getting fuel out of IP to injectors. Have you inadvertantly introduced air into the fuel lines. What work have you done. Check the following to determine if the wiring to the IP is in correct order. It is VERY important.
To check the connections to the IP, here's what you need to do. Turn on key to 'run' position. Check the main wire that comes from the loom to the IP (injection pump), does it have juice. The wire runs to the FSS (fuel shutoff switch) connector first, then to one side of the Cold Engine Switch(two-prong sensor, located in hole behind the upper radiator hose connection). When the engine is cold 'juice' will pass thru the sensor, if the sensor is good, and go to either the FIS (fast idle solenoid) or the CTA (cold timing advance), then to the other. If the engine is cold and sensor is good it will be 'closed' and allow 'juice' to get to the FIS plunger which holds the idle speed up. If FIS plunger is working, but not pushing up far enough, use a 1/4" wrench to turn/extend it until the idle speed is ~1000 rpm. The CTA (cold timing advance) near the spider/distribution end of the IP 'advances the timing' to make engine run smoother/run cleaner/less smoke. The Cold Engine Switch opens/shuts off the electricity to the FIS and CTA after engine reaches 112 degrees, and engine speed/rpm will/should drop to ~650 rpm. If these three items are working correctly, when you go to start engine, hold the throttle pedal at least 1/2 way to floor to allow the FIS plunger to 'set' itself. Use a test light to check for electricity/juice at each of the solenoids, FSS, FIS and CTA. Let me know if this helps. Good luck, OkieGringo