Glow Plug Question

[boosted_diesel_84]

i searched on here and in my Bentley and could not find the proper procedure for testing my glow plugs with an ohmeter,

how much resistance should i have? how much is too much? and where to where do i need to probe? thanks!!

[theman53]

I don't know about an ohm meter, I am sure there is a procedure. I have always just hooked a live wire to the battery and brushed it on the stud. If  it sparks then that GP is good, or at least all of the bosch ones I have tested were that way. You can pull them out and run them on the wire and see if they glow or not as well, but I have never did the ohm meter.

[boosted_diesel_84]

well probing from the threads to where the wire connects i am getting .08 in the 200 range of my meter across the board, so they are all consistant, so i am assuming they are good, they only have about 400 miles on them, but i am trying to see if one was bad, that could help explain my cold start problem where it misses and has a cloud of white smoke for about a minute until it gets some heat in it

[the caveman]

If you want to go through the trouble of disconnecting them all [possibly for no reason in the end] then they can be checked with a test light . 99.99 % of the time if the test lamp lights when touched between the glow plug center contact and battery positive it's good. The ONLY real way to test the circuit propery is to use an ammeter. With the motor cold [disconnect the temp sensors anyways] each GP should pull 10 amps when it settles [after initial lighting and just before they shut off] . There fore with all 4 connected you'll get an initial 56-70 amps ,then 36- 48 amps .It really depends how cold the motor is. Around freezing 13 amps each, warm 8 amps. If you are still not sure do the same proccedure but remove the buss bar from # 3 & 4 cylinders and see what you get.

[Vincent Waldon]

The resistance of a glow plug is very small.... beyond the ability of most cheap ohmmeters to differentiate accurately, so the Bentley doesn't recommend a resistance test.

Same goes for continuity using a test light... they may have enough continuity to light the light but not to heat properly. Mind you, they often fail open, so you might spot bad ones that way.

Current pull at each individual glowplug (after removing the buss bar) is a good way to go, as previously posted.   I usually start by testing for current to the buss bar... look for the 40-50 Amps for all 4 in parallel, and if I see less than that I pull the buss bar and measure the current to each one individually.

An el-cheapo current meter from Napa or Autosource works just fine... I put mine in a box with some alligator clips  and 10ga leads, just to be fancy:

[Quantum TD]

Poor Man's method:

Pull the buss-bar. Take a lead from the positive terminal of the battery, and touch it to the terminal tips of each glow plug.

There should be solid spark emanating from the contact point. If the spark is faint, or non-existent, then the plug is bad.

Using the test light trick will show you only if a plug is working, the positive-lead will give you an indication (via spark output), of how well the plug is working. It's subjecitve, yes, but once you now what to look for, it's pretty effective, especially if you don't have a test light or an ohmeter.

Once I have a plug out, I'll often hook it up to my booster pack to double check marginal plugs (clamp the negative terminal around the chrome body of the plug, and then connect the positive terminal to the power lead). If they glow solid orange, I'll keep them as spares. If not, I toss them.