glow plugs

[bill smith]

my truck is hard to start and wandering if the glow plugs may be going out and what should i put back in,

[Dave]

Test the glow plug relay if you havent already. Its more common to fail then the glow plugs themselves

heres how

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.

[alabamafrog]

Also check voltage between the two big terminals, if there is 1/2 volt or more between them then replace the relay. Best way to test the plugs themselves is to do an amp draw test but you can measure the resistance at the valve covers. I prefer Bosh durotherm plugs (~$100). Don't use the cheap brands, they draw more amps and heat up slower and have been known to swell up and break off in the heads.