hey everybody I bought a 1989 F 350 7.3 IDI it has set for about nine years it has a rebuilt injector pump a new starter ,a new ignition switch new glow plug relay and control box this thing should run but the wait to start light comes on for like one onehundreth of a second goes off and the relay just clicks for about one min would bad glow plugs cause this?can anyone please help thanks

 

Glow plugs can be tested while in the block. Two ways.

Use an ohm meter between ground and the connector tip. Should be 2 ohms or less.

The other way is to use a 12V light bulb between positive and the connector tip. The bulb should light. No light no good.

I think, and would like verification, that if some of the glow plugs are bad, the wait to start stays on longer. If your wait light goes out so fast it usually means that the engine is hot. May be it thinks that the engine is hot.

Also you can't beat fully charged good batteries and a good starter to start up a diesel. The faster it turns over, the better chance for a start. I have also heard that you can plug in the block heater for a couple of hours to simulate a warm start and the glow plugs should not be needed at all.

 

I would bet you have more than 2 bad glowplugs.The 87 and newer controlers use resistance to know how long to heat the plugs. Get a set of Motorcraft ZD9 plugs and be done with plug problems.

 

the light will go out fast if you have two or more burnt out you should for sure use motorcraft plugs.

 

Thanks guys I will put in new plugs in the morning and will let you know if it solves my issue

 

Ensure all the wires have been installed correctly on the GP controller and it has a very good ground.

Dave S has great pictures re the GP controller........

93 year info.......other than some fuses mentioned the 7.3 system 87-94 is basically the same.

GLOW PLUG CONTROL
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 at 32*F.

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 deenergizes the solenoids, returning the timing and idle to normal.