glow plug problems on 6.9
 

I'm new to the forums and need some help. I've read everything but still in the dark a bit. I have a 1987 f-250 with 6.9 diesel and it has 220,000 miles on it. It has the later version controller and relay on the rear of the intake. It hard to start when cold but starts right up when warm and runs great. First my glow light stays on for 3-4 seconds maybe, and then goes out when cold. I also hear what I believe is the relay clicking but not on every cold start. I've also seen the light come on for a sec when driving down the road in the last year or so. I had the IP and injectors done a couple of years ago and 3 or four GP's replaced. I'm not sure of the brand. Last year it was getting hard to start and a different mechanic replaced 3 or 4 GP and that last about 5000 miles. Once again not sure of the brand. I tested them today and found the front three on the right bank bad.
1. I thought I would replace all 8 GP's with Motorola ZD9 plugs.
2. Should I replace the relay and controller or first the plugs and give it a try?
3. I also have the bullet connecters.
4.
5. I pray they come out ok.
6. The dealer wants $19.95 per for the plugs and $211.00 for the controller.
7.I can get the plug for $11.99 from the local AP store but they don't show the controller. I think I need to tell them a later year. Sorry for such a long post. Thank You

The light coming on for short time when first turning the key indicates one or more bad glow plugs. I'm betting you mechaic used aftermarket plugs. Replace all the GPs with motorcraft/Beru ZD9 plugs your First start problem will be solved. Someone reported that Rockauto.com sells the ZD9s for between 10 and 11 bucks.

agreed. rock auto or riffraff diesel for glow plugs, they are between 10 and 11 dollars.
ZD-1 for spade connector plugs, ZD-9 for bullet connector.
start with the plugs. i bet the controller is fine.

Yeah, start with new plugs. O'reilly also sells them for around $11.

x3,4,5,6,7 whatever its at...its your plugs...i bet two nickels your controller is just dandy...

And if you glow plugs seem to be coming out rather tight, don't force 'em or anything, spray alot of WD40 or any kind of good penetrate and turn 'em side to side while pulling so wiggle 'em out.

You don't want to break the tip in the head.

Good news guy's,
All eight came out with no problems at all. I had six autolites and two Bosch. Both Bosch and one Autolite were the bad ones. The Bosch had been in for 5000 miles and I believe the Autolites had been in for 20,000. I installed the Motorcraft/Beru ZD-9 plugs. The glow light stays on for about 4-5 secs and it started right up. No clicking from the relay. What I was wondering is do you think the light should stay on a little longer? It was a 70 degree day here in San Diego so maybe if it was colder it might stay on longer. If anything weird happens I'm going to replace the controller/relay and be done with it. I didn't check voltage to the glow plug and I'm curious what would be the proper way to do it? Could I pull all the connecters and turn the key on and check all of them or just one at a time and have someone just turn the key on for a sec and then turn off? And also I forgot to mention the light did cycle once after starting and it stayed on for a sec or two. I understand that is normal. Thank you fellows!!

It "should" stay on for minimum 10 seconds dead cold. And you should hear clicking after, witch is the plugs cycling.

Yeah, the light should be on longer when it's colder, but 4-5 sec at 70 degrees is fine.

agreed at 70 degrees i do not even bother waiting for the light. just turn the key and fire it up .
but at -10 degrees, the WTS light may stay on for 25 seconds, and then cycle for 2 minutes..

Motorcraft ZD9s are what you want especially with the controller. Most likely its just bad glowplugs. When a few go bad the relay will click on and off because the controller is stupid :-roll :-wink. Unless all 8 are 'working', it will act up. The controller triggers the relay to click on and off. If there is any bad glowplugs it will make it click on and off on and off on and off. A lot of people love the newest style controller but without the right load it will go haywire. Motorcraft BERUs can take the extra cycles that it places on them too.

When everything is setup perfectly, the controller setup can work reliably from what I've heard. I prefer manual control since everything else is manual on my truck, and I trust my finger more than a nearly 2-decade old device but to each their own.

Otherwise you can go manual control for the cost of a button and some wire. No more controller to buy and if a few glowplugs are burnt out you can glow the rest and hopefully still start it just fine, versus the relay clicking on and off sporadically. Then you cut out having another possible problem (the controller), and wont have to fork out the $ for it. Relays are nice and cheap. Also if you need to heat your glowplugs up that do still work, and the relay is clicking on and off you could manually trigger the relay OR jump the two big posts (high amperage will likely eat the metal up that you use though)

Hopefully they come out ok, just spray it with your favorite stuff if they feel like they dont wanna come out. There is a tool you can use to help remove stuck plugs too. Also if your really afraid it might bust off, rotate the engine until that piston is at top. Then if it breaks off you can take the injector out and use compressed air in the glow plug hole to blast it out the injector hole hopefully

Goodluck :-X22

the clicking of the relay is a normal condition on a properly working system to keep the glow plugs warmed up after starting to help keep the engine running. on my 88 i have seen them click on-off for up to 2 minutes when it is really really cold out

Right, I meant rapidly clicking. From what I've gathered it's more for emissions than to keep the engine running.

I have another problem. After engine start when my glow plugs cycle my volt meter drops to 9 or 10 volts for a few seconds and then goes up to 14 volts. Even after the engine is at normal operating temp my plugs cycle sometimes and the volt meter with drop. Sometimes I see the volt meter drop and no WTS light. Could the GP's be coming on and no light? I would think they could cycle but the high drop in voltage seems wrong. Even my instrument lights and headlights will dim. This can't be normal. any Idea's?

I'm going to replace the controller/relay next weekend and sure hope that fixes it.

When the plugs are on, the voltage will drop. The plugs draw more than 200 amps. That level of current draw will pull the voltage down. After the WTS light goes out, the controller cycles the plugs on to help a cold engine stay running. On mine, even when it's pretty warm, the controller will run the plugs...