Hey guys,

I'm trying to help a friend who has an early 90's Ford 7.3 IDI work truck with some hard starting issues. He has replaced the glow plug timer himself but I'm fairly sure he has at least a few cooked glow plugs. What I need to know is how do you test them? Is there a specific Ohm rating that needs to be verified?

Any help would be appreciated as I have very little experience with these older 7.3 IDI's......

 

I'm thinkin you can take a test light & hook it to the pos. post on the battery then turn on the key & with the plug on top of the glow plug unhooked, just touch the test light to the top of the glow plug, if it lights up then the glow plug is good, if not it's fried, someone else chime in here, but I think that's how I used to check them on my old 7.3L, it's been many years though so hopefully someone else will jump in here, Dusty

 

I owned a 7.3, you need to replace them all, if you replace a couple then the new ones won't last nearly as long.

 

I think Dusty is right.. Anytime I tried to use an ohm meter to test them I couldn't get a good read on good or bad. The test light seems to work best.. For the cost, its worth just chuckin a new set in. Also check the relay, I know they sometimes give grief...

 

My 95 PS went through glow plug relays about every 30k.

 

Thanks for the advice.....but why would the key need to be on? If the test light is on + power and the probe end is on the glow plug terminal, if the glow plug element is good, shouldn't it be grounding the test light? No ground would mean a dead plug, no? Maybe there is a specific Ohm rating for the element if it is good?

 

OK, I'll try the test light route.....is what I just described the correct way to test the glow plugs with a test light? Is the relay part of the timer or is it located somewhere else?

 

As an ex IDI owner I can tell you if they have been in longer than 50,000 mi. they probably need to be replaced.
Joe

 

If you do change the glow plugs make sure you replace them with motorcraft (beru) glow plugs, and as was said before replace all eight, AutoZone carries them for about $8 a piece.

DO NOT, I repeat do not use autolight they have a tendancy for the tip to swell up making it a real bear to remove which you will be doing sooner than you want because they don't last.

On one of the other sights I frequent the word autolight is used instead of sh**. If that gives you any indication as to how the idi crowd feels about thier glow plugs

Cam

 

I would think using a postive on one end of the lite and touch the glow plug spade. Should complete the circuit right?

From what I remember the relay is separate from the controler.. The relay looks like an HD starter relay with a large lead from the battery and out to the intake manifold for distribution to the plugs.. I can't remember where it is exactly, never owned one, just worked on them..

 

Got an old 6.9 IDI got tired of replacing glow plugs ,controlers. Put on an either injection system and unhooked the glow plug system. Now turn the key hit the button and starts with about 3 seconds of cranking. Truck starts better then ever and have absolutly no engine nock from the either.

 

One easy way to "ear check" for glow plugs on an IDI is to listen to how long the relay stays engaged when the key is on and engine is off. Rapid cycling means you have at least one glow plug gone.
Make sure if you replace the controller (back of engine) that the terminals are all clean and no corrosion and tight. It will melt very fast with loose wires.As stated test glow plugs with a test light. Clip to + on battery, key off, glow plug wire off of glow plug and check for continuity. A wee bit of antisieze (again a wee bit) will help next time they need replacing.

 

Ok, thanks for all the help.....I'm going to look at the truck in a few hours and will test all the plugs and the solenoid.....I guess the dealer is the best source for OEM Motorcraft glow plugs?

 

"If you do change the glow plugs make sure you replace them with motorcraft (beru) glow plugs, and as was said before replace all eight, AutoZone carries them for about $8 a piece."


The guy said Autozone had em.

 

Yeah, I know.....but we don't have Autozone up here in Canada.....NAPA is probably the single biggest US auto parts chain around here...