I assume, being new to diesels, that my '01 f250 has glow plugs. And I'm also assuming they are working. However, my truck wants to be slow to fire on occasion and I'm just checking. How do I check to see if they work? Also, I have a "wait to start" light, but no "glow plug" light. Should I have one?

 

The wait to start lamp is the glow plug lamp. The glow plugs are under the valve cover, along with your injectors, there is a simple way to test them do you have a OHM meter. If you unplug the harness that goes into the valve cover on top, ground one lead of your meter, and if you look inside the female plug on the valve cover gasket you will see 4 big pins and 4 skinny pins, the fat pins are your glow plugs, just take the other lead and touch the fat terminals one at a time. you should get 4 OHMs, if it reads OL or open that plug is bad. Also check the glow plug relay, passenger side mounted on engine and make sure terminals are not burnt and tight.

 

Glow plug relays on the old 7.3's were known to go bad after a period of time. I would consider replacing it first even if the problem ends up being a wiring harness or bad glow plug(s).

 

Thanks guys, I'll check on it this weekend.