possible bad GP controler
- Thread starter schulhoff
- Start date
rhkcommander
Full Access Member
probably bad glowplugs. one burnt out plug will make it cycle on and off on and off on and....
rhkcommander
Full Access Member
glowplug controller can cycle the plugs on and off too to aid in emissions regulation. Is it truly 4 seconds or is that a guesstimate
argve
Resident Fruitcake
I posted this in an earlier thread but it explains how the glow plug system works so it should help with troubleshooting.
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You have more than likely a bad glow plug or two.
If your timing is not set correctly it will cause glow plugs to burn out early. If you have a sluggish injector that is either lighting off early or late it will change the timing for THAT ONE cylinder. Which would in turn cause that glow plug to burn out sooner.
What you need to do is one of two things.
One is just throw parts at it until it runs - while this works - it's gets very costly.
Two is to troubleshoot the system. I like this way because it makes more sense and is easier on the wallet.
Ok so how do we troubleshoot the system.
First off grab a meter or test light and test each glow plug when it's UNPLUGGED from the circuit. Now you don't have to remove the glow plug from the engine to do this test having it installed is just fine and it's easier (I'm fat and lazy so if I can get by without doing extra work I will).
1st step make sure engine is cold - meaning it hasn't been running for sometime. This does two things for us - 1 it makes it easier to work on and two as glow plugs heat up their resistance value increases.
Now if using a meter place one lead on the bullet end of the connector and the other lead on a solid clean ground, this can either be the nut portion of the glow plug, a clean piece of metal on the engine or the neg terminal of either battery. A good glow plug will measure when COLD 1-2 ohms, a red hot can't touch it will measure around 30 ohms or higher. (this I know from bench testing one years ago - yes I was bored at work).
Test each and everyone of the glow plugs. Replace the ones that are bad.
Now if using a test light....
Place the clip of the test light on the positive post of battery and place the tip of the probe on the bullet end of the connector. If the light comes on then the glow plug is good. if not then that glow plug is bad - replace it.
Now that we have determined which ones are good and which ones are bad you can either replace all (very expensive) or just replace the ones that are bad - I always go with just the ones that are bad - one bad glow plug does not make it harder on the rest it actually makes no difference to the others at all what the other one is doing.
Now look at all connections on the glow plug controller. Make sure they are clean and tight. The reason for this is because the glow plug controller determines how long to keep the glow plugs ON for via measuring the voltage drop across the glow plug circuit vs the voltage drop across the big zig zag piece of metal on the controller. If the connections at any point here is corroded or bad then the time that the glow plugs are ON will suffer. Also make sure that the ground that the glow plug controller uses is good as well. Typically it grounds to one of the mounting bolts for controller.
Look at the harness that supplies power to this circuit as well because bad connection here will effect how long the glow plugs are ON because remember it measures voltage drop across the glow plugs to determine if it's 70 degrees outside or 30 degrees.
One of the fastest ways the system tells you there is a problem is because the WTS on time gets shorter than it should be. Causing a hard start condition. One bad glow plug typically you can limp it through but two bad (has been my experience) requries a lot of faith and recyclinging the key to restart the firing of the glow plugs a couple of times to get her to fire up coughing and belching in 50 degree temps in the morning.
if you have any more questions don't hesitate to ask. Lots of folks on here have knowledge and will pass it along.
*****************************************************
You have more than likely a bad glow plug or two.
If your timing is not set correctly it will cause glow plugs to burn out early. If you have a sluggish injector that is either lighting off early or late it will change the timing for THAT ONE cylinder. Which would in turn cause that glow plug to burn out sooner.
What you need to do is one of two things.
One is just throw parts at it until it runs - while this works - it's gets very costly.
Two is to troubleshoot the system. I like this way because it makes more sense and is easier on the wallet.
Ok so how do we troubleshoot the system.
First off grab a meter or test light and test each glow plug when it's UNPLUGGED from the circuit. Now you don't have to remove the glow plug from the engine to do this test having it installed is just fine and it's easier (I'm fat and lazy so if I can get by without doing extra work I will).
1st step make sure engine is cold - meaning it hasn't been running for sometime. This does two things for us - 1 it makes it easier to work on and two as glow plugs heat up their resistance value increases.
Now if using a meter place one lead on the bullet end of the connector and the other lead on a solid clean ground, this can either be the nut portion of the glow plug, a clean piece of metal on the engine or the neg terminal of either battery. A good glow plug will measure when COLD 1-2 ohms, a red hot can't touch it will measure around 30 ohms or higher. (this I know from bench testing one years ago - yes I was bored at work).
Test each and everyone of the glow plugs. Replace the ones that are bad.
Now if using a test light....
Place the clip of the test light on the positive post of battery and place the tip of the probe on the bullet end of the connector. If the light comes on then the glow plug is good. if not then that glow plug is bad - replace it.
Now that we have determined which ones are good and which ones are bad you can either replace all (very expensive) or just replace the ones that are bad - I always go with just the ones that are bad - one bad glow plug does not make it harder on the rest it actually makes no difference to the others at all what the other one is doing.
Now look at all connections on the glow plug controller. Make sure they are clean and tight. The reason for this is because the glow plug controller determines how long to keep the glow plugs ON for via measuring the voltage drop across the glow plug circuit vs the voltage drop across the big zig zag piece of metal on the controller. If the connections at any point here is corroded or bad then the time that the glow plugs are ON will suffer. Also make sure that the ground that the glow plug controller uses is good as well. Typically it grounds to one of the mounting bolts for controller.
Look at the harness that supplies power to this circuit as well because bad connection here will effect how long the glow plugs are ON because remember it measures voltage drop across the glow plugs to determine if it's 70 degrees outside or 30 degrees.
One of the fastest ways the system tells you there is a problem is because the WTS on time gets shorter than it should be. Causing a hard start condition. One bad glow plug typically you can limp it through but two bad (has been my experience) requries a lot of faith and recyclinging the key to restart the firing of the glow plugs a couple of times to get her to fire up coughing and belching in 50 degree temps in the morning.
if you have any more questions don't hesitate to ask. Lots of folks on here have knowledge and will pass it along.
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