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Glow plugs aren''t heating up

2K views 16 replies 5 participants last post by  samiam 
#1 ·
Can someone who's been here tell me an easy way to decipher whether my glow plugs are bad, or the relay? I've had serious cold weather issues at even 50 degrees, but when i use my block heater regardless of temperature, the trucks starts and runs perfectly. Any ideas?
 
#5 ·
thanks ,yes you can test the glow plug relay with a test light , one side has
battery voltage all the time ,the other should light up test light when key is turned on ,if you have two relays on top of the motor ,only one is the glow plug relay , the other and intake air heater ,glow plug relay is the farthest back and is shorter
 
#6 ·
A light will work, but you should check voltage drop across the relay. because you could be losing a couple of volts across the relay and not all 12 volts and it will still light up the test light, but you won't be getting full voltage to the glowplugs. Take a Digital volt meter and hook the pos to one of the big terminals on the relay and neg to the other big terminal. With key off you should read battery voltage, with key on the reading should drop below .02 volts. if it is above this replace the relay.
 
#7 ·
I have a 2000 F-350 powerstroke diesel that has no signal/ trigger to the glow plug solonoid (mounted on the intake manifold). I have 12V constant at the battery cable end of the solonoid, I have 12V ignition at the (S) terminal of the solonoid, I get power at the (load) side of the solonoid (to glow plugs) when I manually ground out the (I) or ground signal of the solonoid. The pink wire on the (I) terminal has to be controlled by the PCM or some other device. I need a wiring schematic to trace it (pink wire). It would also be helpful to know what component supplies the ground signal to the solonoid, via the pink wire. Thanks!
 
#8 ·
the processor sends ground signal to that wire to turn on relay , if you have an i and an s on your glow plugf relay sounds to me like someone put a starter solenoid on in place of a glow plug relay and it will not work right , could be the reason ,why your having problems ,starter relay will not carry the voltage you need to keep glow plug operating properly ,need to replace it with a glow plug relay
 
#13 ·
if you trace wires back to processor and wiring is good , it will probably take a pcm to fix it , i have run a toggle switch in that circuit which will work to get glow plug relay operating ,but some people dont like doing it that way
 
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