Fixed my glow plug problem.

[ida34]

Some may remember my post asking about the glow plug temp sensor. I found that at around 60 degrees the resistance was at 5000 ohms and it went down to 300 ohms after idling for about 20-30 minutes.

Before putting in my new to me glow plug controller board I replaced the relay. I noticed that it had been bypass improperly so I checked the -20 wiring diagram f-7. The small orange voltage sensing line for the contoller was connected to the glow plug side of the relay and the diagram showed it on the resister side of the relay. I figured the diagram was right. It is wrong. The line belongs on the glow plug side of the relay. Do not trust the wiring diagram on this one. When I put the small orange wire back on the side with the big orange wires everything worked great. I still have the backup button in case of failure.

The person that had hooked in the glow plug contoller bypass had run a positive trigger to the negative side of the relay. This may have burned out the relay or made it not fully engage and click alot. They also had hot wires with no short protection running through a hole in the firewall with no grommet or other chaffing protection. It is truely scary what some people do who do not know what they are doing.[/img]

 

[dirtyfingernails]

Chuck,
I'm new to this engine (heck I'm new to the diesel setup). Anyway, I have one of these vehicles lined up to buy and I don't quite understand the glowplug problem. I'm assuming that glow plugs are designed to heat the cylinders to facilitate starting the engine--especially when cold. As I currently understand it, glow plugs in this engine swell if amperage draw is too little or much during startup causing the temperature to expand the plug? Please set me straight. Also, are the plugs (swollen or not) easy to replace? And are they expensive? Thank you!
DFN

 

[ida34]

I am learning more and more myself. First off, I have been told that these engines will not start without help from the glow plugs. The system on the cucv is different from the civy set up so that they can be jumped with 24 volt vehicles. When the system messes up people bypass the timer/controller and install a manual switch. The problem occurs when the plugs are overheated by keeping them on to long. Kind of like running the water heater with no water in it. Many newer plugs are self regulating meaning they shut themselves down before they swell. I don't know how exactly they do it. Changing them is not to hard except for the back plug on both sided. When I changed mine I found that all had been changed before except for the back ones. It took me about 2 hours to do along with some other stuff I did at the same time.

The military system uses a large resister bank to drop the voltage to the plugs. When they go bad the extra voltage kills the controller and many people make the manual set up because of this. The system senses the current draw from the plugs. When one goes bad the others work harder and stay on longer making them swell. People have removed swelled plugs but the worst case scenario is when a part of the plug breaks off into the cylinder.

The swelling comes from the plugs getting to hot so the low amperage draw you are talking about does not effect anything unless it is just one plug not working and that causes the other plugs to overheat and swell.

The controller can by bypassed by providing a switched ground to the ground side of the relay. One of the small terminals is a positive off the ignition switch. The other side is a negative that is supplied by the controller or by your bypass switch. The switch must be a normally open self returning switch. This part is very important.

I am home sick today and may not be thinking to clear. I hope this all makes sense. I am sure if I have left anything out someone else will pipe up.

Good Luck
Chuck

 

[mangus580]

You did good chuck

One other note.... the contorller is 'supposed' to protect itself from overvoltage, but I dont think it always does. It is commonly one chip on the controller that goes, and its a really cheap part, if you know how to soldier to a board....

I for one suggest using the self limiting, fast heating glow plugs that www.ssdieselsupply.com carries (althouh, i have yet to save the $ to put them in mine )

BTW, my temp switch is shot too.... They werent turning on at all, I had to bypass the switch, now they come on every time you start the truck.

 

[ida34]

Thanks Mike. I used to be a mechanic more than a few years back but the diesels have not been my cup of tea until now. I am slowing learning the system.