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Charlie,
I wouldn't hesitate to give it a shot, I would guesstimate that a shop would charge you $600-700 to replace the glow plugs.
You can probably do it in a couple of hours max, including breaks, and the glow plugs should cost around $120 or so for all 8.
Have you done the electric/resistance tests on each plug connector? This can really help pinpoint which plugs are bad and can help you determine if you need to replace all of them, or maybe one bank has a bad under valve cover harness.....
Here's a write-up I found that might help- I especially could have used the trick about spinning the plugs in and out using a short piece of tubing- I used the socket but it was slow going IIRC.
When replacing the glow plugs on these trucks they can put up one heck of a fight if they have been in there for awhile or have alot of carbon buildup, this article will help make them a little more cooprative.
This is a straight-forward service. After removing the valve covers and unplugging the glow plug(s), loosen the glow plug a couple of turns (10mm deep socket, 1/4" drive). Then push a 4-6" piece of vacuum line over the end of he glow plug and use the hose to unscrew and remove it. Use the hose to install and screw in the glow plug, then tighten with the socket. The socket will contact the rocker arms if used to remove the glow plug. If the glow plug is difficult to turn you may be able to loosen it by working it back and forth--turn counter clockwise one turn then clockwise half a turn--until it turns freely enough that it can be loosened with the hose. If the glow plug probe is severely carboned up or swollen, the barrel may screw out of the head leaving the probe stuck in the hole. In this instance you may be able to remove the probe by removing the adjancent rocker arm and push rod to gain enough room to get ahold of the probe with a pair of needle-nose pliers. Have someone hold the pliers to prevent the probe from falling into the cylinder and use a long punch to loosen the probe by tapping it down. Once the probe is broken loose, work it up and down in the hole until it can be pulled out--some WD 40 or other solvent may help to loosen any carbon on the probe once it can moved, just remember not to use too much and to remove any residual by cranking over the engine with the glow plug out. You may be able to dislodge the seize probe by cranking over the engine, just remember to reinstall the rocker and pushrod if removed, and place a blanket or fender cover over the glow plug to keep it from shooting out. If the probe falls into the cylinder or cannot be loosened, the head will have to be removed to extract the probe. To prevent damage, remove all the glow plugs on the head to be removed and install them after the head has been reinstalled.
And this for checking the relay and glow plug resistance (without removing the plugs or the valve covers):
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
Also let me add, that if your GPR does test pad you can use a Napa model #109, their book will call for the #110 but the 110 is around $60+ where the 109 is low $20's. They are the same exact sensor spec wise, the only difference is the mounting tabs are rotated 180 degrees, don't worry the wires make it fine. However if you really want a HD relay and one you won't have to change yearly, you should replace it with the HD Stancor unit, the model # is 586-902 and it is made to handle the 200 amp draw, whereas the others are made very cheaply.
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