Yesterday I got a 94 F250 7.3 non turbo. when I arrived at the sellers residence he had already had the truck started so it started easy for me. After I got it home and it sat awhile and cooled down it became hard to start, this morning it wouldn't start until I gave it a shot of starting fluid and I hope to not do that much, then it started right up. The wait to start light is not coming on, so how do I know if the glow plugs are working? What can I check to verify they do or don't work? Thanks for your help

 

You may need to check the bulb for the wait to start light. It is supposed to come on when the key is first turned on as a bulb check. The glow plugs if working correctly can stay on even if the "WAIT" lamp goes out depending on engine temp.

You might also check the glow plug relay for operation when engine temp is below approx. 131 degrees F Relay is usually located on top rear of engine, when commanded on, will provide power to the glow plugs. This can be verified with a test light or voltmeter.

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I wound up putting in a set of new glow plugs and also had to put in a new glow plug module. Starts right up now.