I've seen glow plugs go at 20k and some last over 100k. Testing them and how your engine starts when cold is the only way to tell.

 

GLOW PLUGS

ARE THEY HARD TO REPLACE TRUCK ALWAYS STARTED GOOD BUT NOW IT TAKES SEVERAL ATTEMTS BUT WHEN PLUGGED IN UT STARTS FINE:ford:

 

I believe i saw another post by NCHornet that said the block heater has nothing to do with the GP's or the GPR.

 

They are not related, but they are. If it started when it has been plugged in (and cold outside), then I would look at the glow plugs and/or relay. If it is still warm out, and it needs to be plugged in... other issues exist.

 

If it is still warm out, and it needs to be plugged in... other issues exist.

what are these issues?

 

Start with the troubleshooting below. If it starts fine with the block heater plugged in than you probably have problems with the GP system. Changing the GP's are easy, pulling the VC's is most of the work. Most of the time it is just the GPR, and if that is bad I highly suggest going with the Stancor model (586-902, IIRC)

How to check Glow Plug System

To check the Glow Plug Relay (GPR)
· Be sure the engine is cold, so that the PCM will tell the GPR to turn on. If the engine is hot, you won’t have as much time to check.
· Locate the GPR – Its behind the fuel filter on top of the engine, a little bit toward the passenger side of the valley. There may be two relays there. If so, the rear one is the GPR. It will have two fairly large wires (yellow and brown) connected to one of the large posts.
· With your multitmeter set to DC volts, and 15 V range (if not autoranging), clip the positive (red) lead to the output terminal (with yellow and brown wires connected), and the negative (black) lead to a good ground point (like the battery ground terminal or someplace metal directly on the engine block.)
· Turn the key to ON (do not start)
· If your GPR is good, it should click, and you’ll see 11 volts or so on your meter, then, depending on temperature, it will click off up to 2 minutes later. You should do this a couple of times to make sure it consistently makes the connection.
· If you don’t get voltage with this test, confirm by retesting as follows.
· Remove the two small wires from the smaller two of the four GPR terminals.
· With jumper wires, apply voltage from the battery across the two small terminals. If your voltmeter now reads voltage on the output terminal, your GPR is OK, and your problem is in the PCM circuit that tells the GPR to activate.

If your GPR is bad you can use the factory replacement for around $75, Napa's GP110 is close to this price maybe $10 cheaper. But you can get a GPR 109 from Napa for around $22.00 This is the same exact relay as the GP110 except the mounting holes are rotated 180 degrees, which is no big deal as the wires stretch just fine.
Now if you are tired of replacing your GPR and want a H.D. alternative may I suggest the Stancor 586-902. This is a large relay and it can truly handle the large AMP draw our trucks call for at start up. Gopher Electronics has these for under $40. I know several folks that live way up North (Alaska, Canada) where they know about serious cold starts and they all swear by the Stancor. I am very happy with mine, I believe I have pics of mine installed in my webshots.

To check Glow Plugs.
· Remove the electrical connector on the inboard side of valve cover at the gasket. Press down on the top of the connector latch and pry gently with a screwdriver. Photo of disconnecting one and another Photo of it loose.
· There will be 9 pins on the valve cover gasket where you removed the connector. The two pins furthest forward and the two pins furthest back are for your glow plugs.
· With your multimeter set to resistance (ohms) and low range (single digits) if not autoranging, clip the negative (black) lead to a good ground point.
· Probe each of the 4 outer pins individually with the positive (red) lead, noting the resistance. Good glow plugs will have a resistance between 0.6 and 2 ohms. If you get infinite resistance on any glow plug, that one is either bad or the connector under the valve cover has come loose.
Take Care
Kevin

 

NCH (kevin)
First of all, Awesome GP write up!

I just tested my glow plugs and i was getting 9-16 ohms out of them. Much more than 2. Does that mean mine are bad?

I have 120k on them and live where its cold

Thanks

 

Is the Stancor Stancor 586-902 also available at Napa?

Thanks

 

opcorn2:

 

good to know kevin. thanks!

 

i highly recommend the stancor also, got it on both my trucks, if it lasts twice as long as the stock glow plug relay it will pay for itself.

 

great write up I am having the same problems I will have to check my relay before I change my gp.
Thanks

 

Man somebody went digging for this thread, but glad it is still being used. FWIW it is also posted in the maintenance section, it really needs to be a sticky when the weather starts getting cold. If yours are reading that high they are shot!!
The Stancor isn't available at Napa but Graingers has it or just google it. The Stancor lasts a lot longer than twice the life of the stock unit, more like 10 or 20 times as long. The stock unit just can't handle a continuous 200 amp draw for up to two min!!
Anyway y'all have a good one!!

NCH

 

Man somebody went digging for this thread, but glad it is still being used.

NCH

Haha, thats me. I hate starting new topics that have been talked about a few times. I figured this is a common question.

:icon_ford:

 

Just throwin it out there: I've got a tad over 273k miles and my cold starts are fine still. BUT I've never tested the GPR or the GPs but I'm assuming that they are all working or enough are working to start fine in the cold.

 

Wheres a good place to get glow plugs?

 

i live in michigan and i have 265k miles on them, still start great. never changed.

 

advance auto was like 9 each.
there was a set of fords on ebay for approx 110.

 

The Beru GP's have gone up through the roof, I haven't seen them for under $10 in almost 2 years, around my parts $15 is about right. Don't use anything other than the Beru's unless you like changing GP's.

NCH

 

They better than Ford GPs?
And where do you get em at. Just an auto store?

 

whats beru's? what brand is that?

 

The Motorcraft ZD-11's are made by Beru. I bought ZD-11's at O'Reilly's. Advance only had Autolite.

 

Hopefully I am not posting to a dead thread here, but ALL of my plugs measure 0.2 Ohms using a high quality and regularly calibrated meter.

I know the plugs at least work a little because my GPR was completely dead and after being replaced, my truck actually starts (I could still use thinner oil though).

Do you think there are just some aftermarket GPs in there? I have a hard time believing that all of my GPs would be off by the same identical value no matter how evenly worn my engine is unless that 0.2 Ohms suggests something else.

 

Is there a video anywhere of a glow plug replacment for a 7.3?

 

I have never tested a glow plug that would give a low reading like that, if they are bad it will be a infinite or real high reading. Strange!! They could be another brand plug and therefore he lower ohm reading?????
And yes Beru makes the Motorcraft units.
NCH

 

Are the Bosch glow plugs any good? That was the best they have at autozone, and the ones at ford at $30 a piece

 

I've heard the Bosch plugs are actually the worst.

 

Well I ended up ordering motorcraft plugs.
Is there any special tricks or tools needed for replacing GP's?

 

Cool!

One tip, once you loosen the gp, you cant take it all the way out with a socket because it will the injector (i think, it hits something lol). So once you lossen it, you need rubber hose (i used a small ID pvc pipe) to slide over where the elec connector goes. It needs to be kinda tight. Then just twist it out using that hose. I test fitted a hose on the new ones.

And on the Pass side, its easiest if you move the AC compressor and take off the idler pulley. But thats what i was told, i have only replaced my driver side bank so far haha

Good Luck.

and also, i like the bike in your Screen Name!

 

Does the stanco relay just bolt in place of the factory one. If not what do I need to do.

 

I have a write up in the 7.3 Mod section on the Stancor relay with pics!! The search feature will turn up what you are looking for!!!

NCH