For the first few years I've owned this Van (1993 E-350 7.3L non turbo ambulance) my glow plugs worked perfect. About 2 years ago it started working sometimes, sometimes not. I would turn the key into the ON position and the WTS light would come on, and after 8-10 seconds it would go off and there would be a click, click,click,... Then I'd start it right up... WONDERFUL! Other times I would put it into ON position and the WTS light would go on, and after 8-10 second it would go off and NO CLICK, CLICK, CLICK... And no startup
Sometimes after two or three attempts it would work. Now, I can't get it to work at all... It's pop the hood and spray ether time...

In your opinion, does this sound like a classic case of relay going out, and eventually failing? Or perhaps a different issue?

I haven't tested anything, but I did look at all my wires and i didn't see anything disconnected or signs of melted wires... What I do know is that on my instrument panel (ambulance systems monitor) I used to see a voltage drop to about 10.5 volts when the plugs would cycle, and now it doesn't drop below 12.8 when the WTS light is on.

Thanks in advance for your input! :-)

 

Check your relay sounds like it failed completely now.

 

'93 used the second generation glow plug system. While just as ****ty as the first generation system, it's ****ty in different ways.

1) Check glow plugs. If more than one is dead the system will short-cycle and basically not work.

2) Check wire connections. If there's too much resistance the system will short cycle. And I don't mean just look at them, pull the connections, clean the terminals, reinstall.

3) If you have to replace the module, try to get a Ford or IH part, the aftermarket replacements are crap.

Glow Plugs 101 Tutorial