Hopefully quick glow plug/wait light issue.

[tony2wd]

Hello, recently bought a 84 m1008. Been using this site for heplfull info on getting some problems taken care of. Thank you to all of you for the great posts.

I put a test light on a glow plug and when i turn the key on it light lights up. Then after about 4-5 seconds the wait light comes on and the test light shuts off while its on. ive been cycling the ign key a few times to heat up the plugs before the wait light comes on. The test light comes back on when cranking but after it starts the wait lights comes back on and glow plugs turn off. Really want to get it working right. Ive checked the TM and it says that if i ground the dark blue wire it should turn on the wait light, which it does. But does not actually turn on the plugs. any one have and idea of what i should check next or if getting a new card should fix this?

Btw its still 24v and seemes to be unaltered. It came from a sherrifs department that got if from the military.

 

[cucvrus]

Check the battery cable grounds and all the grounds from the 24 volt buss bar behind the rear battery. Make sure the metal plate in behind the negative buss bar connection is not burnt. It is hard to diagnose via internet but that is a few of the issues I have seen in the past. I hope it helps. Once you have it diagnosed keep it stock. I will work for years as it already has. That is my opinion. I hope it don't offend anyone.

 

[cpf240]

Have you tested the glow plugs themselves as per the directions in the TM? From the test with the test light, that just confirms that the GP relay is working enough to light the test light, but doesn't verify the voltage getting to the glow plug, or that the glow plug is working.

 

[tony2wd]

I have not tested every plug. I changed three. On one the terminal was broken when I got it. I ended up breaking the terminals on another 2 as well. While they were out I grounded to test and see how the work,My first diesel, and they did glow. That's when I noticed that they weren't in sync with the wait. Light. That explained the hard starting. Since I've been cycling the key to heat them up till the wait light comes on its been starting great.

As soon as I turn the key I hear the solenoid click(turning on) and the click again when the wait light comes on (turning off the plugs). Should the relay and wait light be on the same page when they turn on. I guess I can check all th e grounds, good practice anyways. Thanks.

 

[cpf240]

The light and the plugs are not necessarily going to be on at the same time. You might find this useful: http://www.steelsoldiers.com/showthread.php?62477-GP-Module-Theory-of-Operation

 

[tony2wd]

Alright. I've changed the rest of the plugs to 60g's. They were 13g. The solenoid was not consistently working so also replaced with a 85a continuous isolated type. And bypassed the resistor to 12v on first battery. Still only firing the plugs for about 4 seconds and wait light comes on when they turn off. Then they come on when cranking. But when they turn off and the wait light comes on the relay clicks like crazy for about a half second. Would really like to have it stock. Buy would hate to spend $100 on a card and still end up putting in a momentary switch if that doesn't work. Once it starts the wait light stays on till the high idle drops. Any ideas? If I jump the relay and preheat the glugs it fires right up.

 

[tony2wd]

Alright. I've changed the rest of the plugs to 60g's. They were 13g. The solenoid was not consistently working so also replaced with a 85a continuous isolated type. And bypassed the resistor to 12v on first battery. Still only firing the plugs for about 4 seconds and wait light comes on when they turn off. Then they come on when cranking. But when they turn off and the wait light comes on the relay clicks like crazy for about a half second. Would really like to have it stock. Buy would hate to spend $100 on a card and still end up putting in a momentary switch if that doesn't work. Once it starts the wait light stays on till the high idle drops. Any ideas? If I jump the relay and preheat the glugs it fires right up.

 

[antennaclimber]

Tony, Can you verify that all all of the Orange wires connected to the glow plug side of the relay?

Also, try disconnecting the temperature sensor and see if the issue still happens.

The wait light staying on until the high idle drops is really odd. It's possible that the wiring has been compromised, you will need to verify that the GP card is wired correctly.

The GP system needs to wired as described in the GP Module Theory of Operation. The GP system wiring diagram in the TM is incorrect.
Karl

 

[rsh4364]

Ever since re-wiring my manual only glowplug push button switch to the light blue wire and then to ground my wait lite also stays on till cold start solenoid kicks idle down.Since card was in-op,I cut light blue wire and simply tied switch to it.

 

[tony2wd]

Climber, All wires appear to be correct on relay. I unplugged the temp sensor and the glow plugs stayed constant on even after starting. But no wait light. Plugged sensor back in(while running) and plugs turned off but then wait light came on and stayed on even after idle dropped,about 2-3 min. Is the 12v feed to the relay to stay on even after engine up to temp?

 

[tony2wd]

I failed to mention that gen 2 is not working. I keep the battery which is new charged but I noticed in the videos that the card responds to voltage increases. I have the resistor eliminated and relay connected straight to front battery. Gen 2 has been off again on again but glow plug issue constant.

 

[antennaclimber]

Climber, All wires appear to be correct on relay. I unplugged the temp sensor and the glow plugs stayed constant on even after starting. But no wait light. Plugged sensor back in(while running) and plugs turned off but then wait light came on and stayed on even after idle dropped,about 2-3 min. Is the 12v feed to the relay to stay on even after engine up to temp?

The glow plugs can stay on for as long as 45 seconds after the engine is started. By disconnecting the temp sensor you have a high resistance to the GP card in a cold condition. Plugging the temp sensor back in gave the GP card a lower resistance and it turned the relay off as it should. The GP controller switches the ground to the relay to turn it on and off as needed. The relay +12 volts is not switched by the GP card. It will stay on after the engine is running.

As for the Wait light issue, the GP card again sends a ground to the wait light to turn it on and off. It sounds as if the relay side of your card is working and the Wait light side has an issue.

The wait light and the relay are not in sync with each other. The GP relay can be on after the engine starts (afterglow) and the wait light will be out during the afterglow period. Again, the relay can be closed up to about 45 seconds depending on the temperature of the engine.
Karl

 

[tony2wd]

Karl, I tried to run it today when everything is cold. With the temp sensor unplugged. Glow plugs came on with wait light, both were on longer than usual,abuot 10 sec. Then wait light turned off, glow plugs stayed on, started truck easily. Then plugs stayed on about 40sec as you said. Wait light stand off after starting.

Is it possible temp sensor is bad? Or is that a GP card problem. Works good with the sensor unplugged. Just leave it that way?

 

[antennaclimber]

Seems like the card is working properly with the temperature sensor disconnected. If possible measure the resistance of the temperature sensor when it is cold and again when it is hot. It should have a high resistance (around 3000 ohms) when cold and low resistance (around 250 ohms) when hot. Disconnect the sensor from the vehicle before measuring the resistance.

Otherwise, it sounds as if you have a bad or incorrect temp sensor.