I bought an older 753 F-series. So far I installed a new cylinder head, went through valve body and rebuilt the drive motors;however, I'm still at a loss why my glow plugs won't engage. On my model, you turn the key to the left to energize the glow plug relay by the air cleaner. The machine doeshave the early BOSS set-up. Looking at the schematic I see that the power coming from the ignition switch (when turning left) goes to the glow plug relay but also it feeds into the BOSS controller. Would the BOSS controller some how control and not allow the power to go to the glow plug relay if not needed? I have continuity at the terminal on the switch and the glow plug relay but when I put 12 volts to the terminal at the switch, I have no voltage at the glow plug relay. Any thoughts or suggestions?
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have you checked if power is coming out the relay when it clicks, is power getting to the relay power pin not the actual coil, that relay should have 12v on the center relay pin, when coil is energised it pulls relay to switch power to the terminal which on my machine is straight to the glow plugs, mine is a older model
I rechecked everything and I do not have continuity from the switch to the relay. The green/yellow wire must release pressure in the auxiliary hydraulics. When cold I have a blue wire at the glow plug relay with no power when the ignition is turned on nor do my Boss gauges indicate glow plug countdown. I packed ice around the engine coolant temp sensor (which is new) and I don't ever get the boss display to signal glow plugs. I'm not sure, but I'm assuming that the temp sensor signal feeds the Boss module and if it's cold enough, would call to energize the blue wire at the relay. I could always run a separate wire from the ignyswitch using a momentary switch, but I'm kind of a purist. I assume I need a Boss diagnostic tester to see the temp sensor signal input and outputs from the controller to determine if it's a bad Boss controller?
cdmccul
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It's my impression that diesel glow plugs would fire on every start....
Also, glow plugs often do not run at a full 12 volts, they run at more like 8 volts. Also, they are a variable resistance...the warmer they are, the higher the resistance. So, in Los scull diesel, you cycle the key. The glow plugs get power via the relay. The power then goes to a lamp in series (causing a voltage drop) them to all 4/6/8/etc glow plugs in parallel. As each glow plug warms up, the resistance goes up. When the last glow plug warms up to infinite resistance, the glow plug light goes out, signaling to you too crank over.
But I'm not sure what the BOSS is doing, in this case.
Do you have main (12 or 8/etc volts) power to the relay, and no signal triggers the relay, or do you have a signal to it, but no main power for it to switch?
Also, glow plugs often do not run at a full 12 volts, they run at more like 8 volts. Also, they are a variable resistance...the warmer they are, the higher the resistance. So, in Los scull diesel, you cycle the key. The glow plugs get power via the relay. The power then goes to a lamp in series (causing a voltage drop) them to all 4/6/8/etc glow plugs in parallel. As each glow plug warms up, the resistance goes up. When the last glow plug warms up to infinite resistance, the glow plug light goes out, signaling to you too crank over.
But I'm not sure what the BOSS is doing, in this case.
Do you have main (12 or 8/etc volts) power to the relay, and no signal triggers the relay, or do you have a signal to it, but no main power for it to switch?
Figured this one out. It wasn't cold enough. I would have thought the glow plugs would come on at 55 degrees or colder as my diesel truck. When I went to start it this spring, the BOSS controller displayed GLOW and I had about 9-10 volts going to the glow plug relay. In my haste, I also installed a momentary switch on the control panel with a diode, so that I can also operate the glow plugs manually.
