Can 9v 7.3 GPs handle 12v if used carefully?

[Ferdy Mint]

After discussing options with Tim at Accurate Diesel, we installed 12v 6.9 GPs in our latest 7.3 build. Ground on the GPR is wired directly to a pushbutton on the dash, GP controller and Z resistor are bypassed. Had to replace the bullet connectors on the GP wires with spades, but we had some spares. Works great.

Now @Minty Ferd has another 7.3 that still has 9v GPs in it. Well, almost. Minty burnt them up by forgetting to turn them off. Doh. But we have good spare 7.3 GPs that ohm out fine. As soon as he replaces his dumb GP toggle switch with a pushbutton, we'll put in the good GPs.

The question is, if we bypass the Z resistor and go full manual pushbutton, sending 12v to the 9v GPs, will they burn out right quick? Or - we live in Texas and almost never need GPs - can we just be careful never to run them for more than 3 seconds, and expect to get a few years out of them?

I don't have any more of those big 6.9 spade GP wires on hand. Or any spare 6.9 GPs either. That would be the perfect solution.

 

[snicklas]

All that Z resistor is for is to measure voltage drop so the 7.3 controller knows when to shut off. From what I have read the ZD-1A (6.9) and the ZD-9 (7.3) glow plugs are 6 volt rated. This was done so they heat up faster than a 12 volt plug. The 6.9 "dumb" controller was know to fail on, and burn up all the plugs. If they were 12 volt plugs I don't think that would happen. The Z-Resistor is so close to a dead short, it doesn't drop the voltage buy much. If you were to pull it off and ohm it out... I would be surprised if it even registered an ohm.

To be able to leave them on and not have issues, you would need to use a 12 volt regulated Glow Plug, like the ones that are in the 6.2/6.5 GM Diesels. Just know, they tale a while to heat up.... like 30 seconds, not 10 or so...

Plus, if the complete replacement harness, and the controller eliminator that Wes at CDD sells, it would have some kind of resistor built into it. As far as I know, it is just wiring.

 

[nitroguy]

For what it's worth, I built my own harness using just a solenoid and a push button and completely removing any and all trace of the controller. Using bullet style plugs, shooting them with a full 12v straight from the battery (yeah yeah, via the solenoid, technically).

Here in NW Montana I start my truck up every morning (it's my daily driver) and not always plugged in. 8-12 seconds on the button and away she goes, every morning.
Been running that way for a year now, plugs look great. No telling how long they'll last, but shoot, if you're in TX, the amount you'll use them vs the amount I have to, I'd say give 'em the full 12v and they'll last forever!

 

[1mouse3]

I have been using 60g plug and the nut end has been trimed back like how is mentioned in this thread, I did it crude with a die grinder. I dont have a controller hooked up and just have a starter relay triggered off a button. They do good at 5 sec hot, 13 sec cold above 40f and 20 sec below 40f for glow times that gives a start below 3 sec crank time.

trimed plug

For the heads on a 7.3 Im rebuilding, I took a 7/16 bit to the holes to allow uncut plugs. At a depth of .28 is adequate to get the plug down on the seat, a light smear of grease shows such.

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