Hi guys, I'm a fairly new owner of an '86 F-250 with the 6.9L IDI.

The previous owner said that he had all the glow plugs replaced very recently with Motorcraft brand, so I'm fairly certain the plugs are good.

Somebody wired up a manual switch, but I guess the glow plug controller is still hooked up too, because when I turn the key on, the "Glow Plugs" light comes on for about ten seconds then turns off. It starts cycling if I leave the key on.

So it seems the glow plugs are doing something, but I can't get the engine to start without starting fluid. Not to worry -- I disconnect the purple wire before I use it, so the plugs don't accidentally come on and explode my prechamber.

But I've been trying to get the engine to start without starting fluid and just can't seem to make it happen.

I've cleaned the connectors on the glow plug relay and on the battery, and I've confirmed that I have +12V at the glow plug side of the relay when the relay activates. I haven't been able to see any significant voltage drop when the plugs are on, however, and my charge meter on the dashboard doesn't seem to move much when the plugs are on. Is that normal?

I read somewhere else that this might not be the plugs at all, rather I might be losing fuel prime on one or more injectors. One of them at least leaks a little fuel. I tightened them all yesterday, hoping that would take care of it, but it didn't fix the starting problem.

If the engine runs fine after I get it started (using starting fluid), but refuses to start with just glow plugs, does that point to a fuel prime problem?

Thanks for the help. Lots of great info here.

 

When you crank it with just the glow plugs do you get white somke out the exhaust? First off test the plugs by clamping a test light to the + side of the bat. pull the connector off the plug touch the test light to the top of the plug. If its good it will light up. If theres a button bypass the controller all together.

 

I tried the check-for-smoke test, but it's already warm outside and the engine fired right up. I guess that test will have to wait for another chilly morning. I'll report back.

I took my LED test light (which lights up green or red depending on which way the current flows), hooked the alligator clip to battery positive, and checked several glow plugs. I couldn't get it to light on any of them!

Interestingly, though, I was able to get it to light up by touching it to the glow plug wire (while it was disconnected from the plug). I saw this behavior on each glow plug.

Now that doesn't make sense to me. I thought those wires were only connected to +12V when the relay was activated, and even if they did have +12V on them, wouldn't the test light be connected positive-to-positive (and therefore should not light)?

I'm not sure what's going on here.

 

I don't mean to sound insulting, but are you sure that you have a regular test light? Most glow white and polarity is not a factor. Try using an ohm meter for both tests. A good glow plug will read between .5 to 1 ohm while bad ones will read higher. (review the read first thread on glow plugs in this forum for more info.) Check continuity to ground on your plug wires. If I am not mistaken, the only way a regular test light will light from your positive terminal to your glow plug wire is if it is shorted to ground. If your plugs test ok, check for air intrusion, since fuel molecules are much larger than air molecules, fuel out means air in, and you will lose prime and starting is very difficult.

Good luck, and keep reading, I am a fairly new diesel owner also and almost everything I know about them I have learned here! Thanks guys!

Macgyver.

 

2x Macgyver!

 

If the glow plugs are working right, you should definitly notice it when they activate. I know on my F250 when the glow plugs on all the lights will dim and the gauge on the dash will drop some. Will it start without ether if you hold the switch down for 10 seconds first? Try turning the key to the ON position and immediately hold the switch down for 10 seconds, after that start cranking away and see if it makes any difference.

 

I guess I don't really know. I bought it a while ago at Wallyworld, and I thought it was a normal test light, but it uses an LED rather than an incandescent bulb. LEDs will only let current flow one way (since they're a diode) but this one actually has two LEDs in one -- a red and a green, and they're hooked opposite of each other, so if the current flows one way it lights up green, if it flows the other way, it lights up red.

That's what I was thinking too. Something strange is going on if I can get the tester to light up while touching the positive battery post and the glow plug wire. I will use my multimeter on the plugs as soon as I get a chance. The challenge is getting to the rearmost plugs with the turbo air box (ATS) in the way.

Huh, I kind of thought that since the lift pump and injector pump keep the fuel under pressure, that the fuel could leak out of the lines without air getting in. Is that incorrect?

 

When I hit the switch, I get no lights dimming and no movement on the charge gauge. Which, combined with using a multimeter and determining that there is no voltage drop when I hit the switch (yet I can hear the relay click) leads me to believe the glow plugs are not doing anything. The folks over at The Diesel Stop think that's because they're burned up.

No it will not. Even a second cycle of the button seems to make no difference. Just crank, crank, crank, nothing. Little shot of starter fluid and it starts within 2-3 seconds of cranking, even in high-30s and sitting for eight hours.

 

what you need to do is have someone turn the key on while you have a volt meter connected to ground and the glow plugs to see if you get power to the plugs when the WTS light is lit.
then see if you get power to the glow plugs with the push button.
my thinking on this is that sonething in the glow circuite was disconnected, and you are not getting power to the glow plugs at all.

 

Your plugs ain't working i suspect. If the controller still works and you have a button someone didn't wire that switch in right. Read the sticky at the top for the early system and you should fined the proper way to bypass the controller and just use a button thats what i did and no I'm in command of my plugs and the advantage with that is you really only need them at first startup so you save wear on them.

 

Great minds think alike -- I did exactly what you describe yesterday. Had the girlfriend in the cab pushing the button while I was using the multimeter between the battery and the glow plug relay. Didn't see any significant voltage drop when she hits the button.

 

Yeah, I'm going to do a little more troubleshooting, but the jury seems to say that the glow plugs (which apparently were replaced recently, darn it) are burned up.

How tough a job is it to replace the plugs? I've read that you've got to have each cylinder at TDC, which means a lot of rotating the engine to replace each plug. Otherwise if they're swelled up the tip can break off and stay in the chamber. Is that a huge concern, or should I just not worry about it?

Anybody got any pointers on how to get to the rearmost glow plugs? I've got this huge ATS airbox on top of the turbo, and it makes access really difficult.

 

pull the glow plugs out--useing a 12v charger put the black(-) on the gp threads
and touch the red (+) to the top of the gp you'll know if there good, count to 10 sec,
they get red hot, but if you have them held by the neg clamp , you'll be fine

 

check for power first. motorcraft plugs rarely go bad.

 

Pulll a plug and look for the brand. Let us know If its motorcraft or beru they may be good yet and its just wiring. If you see autolite ac bosh wap they belong somewhere else besides the motor. Motorcraft/beru only