I have a 1991 7.3 i always wanted a diesel but not so sure now.I replaced the glow plugs and the relay or controller now when i turn the key the wait to start light flashes and goes right back off can hear the relay clicking rapidly but won't start unless i plug it in overnight
someone please help

 

Test for voltage relating to glow plugs and relay
Check the voltage drop to the glow plug controller relay terminal. You should have battery voltage with the key off, and the voltage should not drop below 8 volts when the relay kicks on. If the voltage is low with the key off, check the fuse links at the starter relay. If the voltage drops with the key on when the glow plug relay closes, check the connector between the engine and chassis harness at the passenger side fender, and the fuse links.
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Glow plug resistance
Check the resistance of the glow plugs to ground They each should be between 0.6 to 2.0 ohms. If over 2.0 ohms replace the glow plug. These engines will start with several glow plugs bad depending on out side temp.

welcome to diesel bombers and try this out and see if it helps you with your problem

 

I will check that today and let you know what I find out. thank you very much for your help.

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thank you truck back up and running. It had two fired fuse links at starter relay.Just spliced them back to see if that was the problem and it was.Going now to get parts to fix it right. thanks again for all your help