ErickBaker Posted January 24, 2007 Share Posted January 24, 2007 We had a 1992 F-250 towed in today for a no start and customer informs us they replaced all 8 glow plugs about a month ago due to a hard start condition. I decided to check out the relay first since the truck was supposed to have "known-good" glow plugs. The relay comes on and works like should but when I measured voltage drop across the contacts it was .6 volts. I felt like this was too high so I condemned the relay. Knowing how things tend to go when customers try to "fix" their own vehicles I decide to test glow plugs. As it turned out all glow plugs where electrically open. FWIW the customer used Autolite glow plugs. I replaced the relay and voltage drop decreased to .03V and the glow plugs all worked properly. I guess what I'm looking for is a reason all 8 glow plugs would die after a month. I've been mulling it over all day and can't come up with a reason. I don't see how the weak contacts in the relay could cause the failure. Could it be poor quality aftermarket parts? The truck is fixed but I'm not sure if I got to the root cause. /forums/images/%%GRAEMLIN_URL%%/hammer2.gif Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted January 24, 2007 Share Posted January 24, 2007 We had a 1992 F-250 towed in today for a no start and customer informs us they replaced all 8 glow plugs about a month ago due to a hard start condition. I decided to check out the relay first since the truck was supposed to have "known-good" glow plugs. The relay comes on and works like should but when I measured voltage drop across the contacts it was .6 volts. I felt like this was too high so I condemned the relay. .6v is on the high side, but probably wouldn't cause a hard start. Knowing how things tend to go when customers try to "fix" their own vehicles I decide to test glow plugs. As it turned out all glow plugs where electrically open. FWIW the customer used Autolite glow plugs. I replaced the relay and voltage drop decreased to .03V and the glow plugs all worked properly. I guess what I'm looking for is a reason all 8 glow plugs would die after a month. I've been mulling it over all day and can't come up with a reason. I don't see how the weak contacts in the relay could cause the failure. Could it be poor quality aftermarket parts? Yes. The truck is fixed but I'm not sure if I got to the root cause. /forums/images/%%GRAEMLIN_URL%%/hammer2.gif Did you change just the relay, or the whole controller? I've had nightmares with these old IDI's and aftermarket parts, and in this situation I'd only install 8 OE plugs and an OE controller, and the problem won't come back. This is one area where OE really matters. Good Luck! Quote Link to comment Share on other sites More sharing options...
ErickBaker Posted January 24, 2007 Author Share Posted January 24, 2007 I replaced the whole controller and all 8 glow plugs with Motorcraft parts. /forums/images/%%GRAEMLIN_URL%%/thumbup.gif Quote Link to comment Share on other sites More sharing options...
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