When i hold key on,glow plug light never turns off but it starts and runs ok.light used to go off after 1 second

Probably out of fuel

I have an 83 300SD. Have you actually tested the glow plugs? You can remove and with a jump wire or even battery charger test to see if they are working. Attach negative to the body and + to the tip. Be careful they get HOT. If they are working (test them ALL because even if 1 or 2 are out it can cause hard start) make sure you have power to the plugs themselves. Maybe start there to make sure the relay is working. Test light while turning key on (may need a helper with this).

Sounds like the timer is bad. Since you have power when warm, the power relay must be giving the timer juice. The way it is suppose to work is you wait until the glow plug light goes out and then try to start. In cold weather it should take longer for the glow plug light to go out.

i think glow plug replacement needed. ever used starting fluid in cold to start?try this, next time no start, cycle your key and let the light come on, wait till it goes off, turn key again until light goes off, if you have to do this more than 3 times, and it runs fine, replace the glow plugs only then. thank you for choosing fixya.com!

Sounds like the glow plugs are frazzled. There is one electrical wire going to a plug, then each plug is connected in sequence. The glow plugs are heating devices used to get the fuel up to temperature before ignition.

They are fiddly to replace, but are relatively inexpensive and the most common source of issues with cold-starting diesel engines (first thing to fail).

Some cars had a 'pre-heat' available with glow plugs, where you simply turn the key part-way to 'on' and you would see a glow plug light come on (looks a bit like a picture of a spring). If you see this light on your van, you can turn the key to turn on the glow plugs and they will pre-heat your engine slightly and make starting easier

check fuel pump or relay,run scanner for trouble codes, some auto parts stores will do this for free

Yes you have a defective glow plug relay if you have your owners manual you can find it and replace it, the unit also has a timer on it, if you don't have a book look for the glow plugs and follow the wires from the glow plugs to where they terminate there you will find the relay unit and replace it, to test the glow plugs you remove the wires and test each plug by pulling off the wire and with a cheep ohm meter touch one end to the glow plug and one end to ground if it swings almost al the way over it is ok, if it dos not move then that glow plug is bad. if you find 2 or more bad then replace them all, and if a glow plug has shorted and caused this problem you will have to replace the glow plug relay. Good luck.

99 vw passat 1.9tdi was driving sound but just died just turns but wont fire up

if you need connectors and terminals for the glow plug connections under the valve cover, Ford sells then so you don't need a whole $600 harness.

info for your use

Section 03-07B: Glow Plug System 1996 F-250, F-350, F-Super Duty Equipped with 7.3L Diesel Engines Workshop Manual
DESCRIPTION AND OPERATION Glow Plug System The 7.3L diesel engine uses a glow plug system which preheats air in the combustion chamber to improve cold engine starting. The system consists of eight glow plugs, the glow plug control module (12B533), powertrain control module (PCM) (12A650), engine oil temperature (EOT) sensor and barometric pressure sensor (BARO sensor) (12A644). The glow plug system is electronically controlled by the powertrain control module. The powertrain control module energizes the glow plugs immediately after the key is placed in the ON position and then determines how long the glow plugs will be on according to the engine oil temperature and the barometric pressure. The required time for the glow plugs to be energized decreases as the engine oil temperature and barometric pressure increase. The glow plugs are self-regulating, and the powertrain control module controls relay ON time. The powertrain control module protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high.

Possible Causes: Insufficient glow plug ON time will not allow enough heat to accumulate in the combustion chamber to easily facilitate starting. If the glow plug system ON time does not meet any of the specifications in the accompanying chart the problem is most likely a faulty wire harness connection, ground connections or glow plug relay.

If the glow plug resistance to ground is high, the most likely causes are an open UVC (under valve cover) harness or open glow plug.
--------------------------------------------------------
Relay Operation
Install a DVOM on the glow plug feed side of the glow plug relay (large stud with two wires connected). Turn the ignition key to the ON position but do not attempt to start. Note the time in seconds from when the key is turned on and the glow plug relay energizes until the glow plug relay de-energizes. The glow plug relay makes a loud click noise which is easily heard when it energizes and de-energizes. The dome light will dim and the dash voltmeter will dip when the glow plugs are drawing current from the battery. Compare the times measured to the table (time will be affected by engine temperature, battery condition and vehicle altitude). The voltage at the glow plug feed terminal may vary from 9 to 12 volts depending upon battery condition.
--------------------------------------

-----
If battery voltage not present check for B+ at power supply terminal (terminal with single large wire). Power for glow plug power supply is supplied from starter relay through two fusible links at solenoid.
Glow Plug Operation
Disconnect all of the glow plug/injector harness connectors from the valve cover gaskets. With the pigtail installed, measure glow plug resistance to ground (preferably B-). A resistance measurement of .1 to 6 ohms indicates a good glow plug.



Glow Plug Harness Continuity
Measure for continuity from the connector harness to the glow plug feed terminal on the glow plug relay. Resistance should be less than 5 ohms.
Incorrect measurements will result if all glow plug/injector connectors to valve cover are not disconnected.

---------------------------------------------------
Glow Plug Relay The glow plug relay (12A343) has a plastic base and two mounting bolts. It is operated by the powertrain control module (PCM) (12A650) which senses engine oil temperature, PCM voltage and barometric pressure. When the engine oil temperature or the barometric pressure is low, the PCM activates the glow plug relay and the glow plugs. If the PCM voltage is too high, the powertrain control module deactivates the glow plug relay and the glow plugs immediately energize for a shorter duration, decreasing the modulation of the duty cycle.
-----------------------------------------------
Glow Plug Removal

1. WARNING: THE RED-STRIPED WIRING HARNESS CARRIES 115V DC. SEVERE ELECTRICAL SHOCK MAY BE RECEIVED. DO NOT PIERCE.
   Remove valve cover (6582). Refer to Section 03-01D .
   

1. Disconnect glow plug electrical connector using a pair of pliers.
   

1. Remove glow plug using 10mm socket.
   

1. Clean and inspect glow plug tip for damage. Replace if damaged.
   

Installation

1. Install glow plug and tighten to 19 Nm (14 lb-ft).
   

1. Connect glow plug electrical connector. Make sure glow plug wiring is routed to avoid moving parts.
   

--------------------------------------------------------------
Glow Plug Control Glow plugs are used to warm the cylinders to improve cold-engine starting. The PCM uses the engine oil temperature (EOT) sensor and barometric pressure (BARO) sensor to determine how long the glow plugs will be on. The PCM energizes the glow plugs longer if the engine is very cold or if the barometric pressure is low at high altitudes.
The PCM controls the relay that supplies power to the glow plugs with the glow plug control (GPC) signal. When the GPC signal is grounded by the PCM the relay closes, turning the glow plugs on.
The glow plugs are controlled by the following sequence:

1. PCM energizes the glow plugs.

1. The PCM energizes the glow plugs immediately after the ignition is placed in the ON position.

1. The PCM then determines how long glow plugs will be on based on EOT sensor and the BARO sensor. The required time to warm up the cylinder decreases the engine oil temperature and barometric pressure increases at low altitudes.

Glow Plug Lamp Control The glow plug lamp (GPL) signal controls the WAIT TO START light located on the instrument panel. This light is used to indicate when to start the engine. The cylinders are being warmed by the glow plugs during and after this light is lit. The PCM energizes the glow plug lamp longer if the engine is very cold or if the barometric pressure is low.
When the GPL signal is brought low, the "Wait to Start" lamp is turned on.
The glow plug lamp is controlled by the following sequence:

1. PCM lights the WAIT TO START light after a key on reset occurs.

The PCM determines the glow plug lamp activation time based on engine oil temperature, barometric pressure and battery voltage.

1. PCM turns off the WAIT TO START light.

The glow plug lamp is turned off when the timer counts to the number of seconds specified by the PCM. The glow plugs will normally remain on longer than the "Wait to Start" lamp.
-----------------------------------