Wiring Conundrum(s) I. : Busted GPs and Tachometer

[Zion]

Truck in question is a 1984 6.9
-GPs

I'm not sure what the issue is, but my glow plugs burn out within a week of installation. After replacing them the first time I got about a week out of them before 6~ out of the 8 plugs went bad, which were then replaced again with similar results. My plugs are wired to a deadman switch, bypass the GP controller, and from what I can tell, the wiring is done correctly. With my limited knowledge on the subject, my best guesses are a stripped wire somewhere in the harness/wiring or where the plugs draw power from the fuse panel. Currently the power wire is pinched under a fuse, I don't know if the ohm rating has much effect on the whole circuit though. I have an add-a-key fuse, but I'm not certain this will fix the issue.

- Tach

I pulled the instrument cluster/panel out of (what I think was) a diesel F600 straight truck that had a tachometer. I've seen a write up about the styles of tachs found in bullnoses and their adaptability, but I don't believe it mentioned much about whether it could be grafted into an IDI. From what I see, the orientation and poles of the tach unit are identical to those used in IDIs, but I have no clue if my truck even has the ribbon wiring for one since it came factory without a gauge. If it works, and since I forgot to snag a wiring harness from the truck I got the timing gear cover off of, could I modify my current harness to accept the magnetic sensor?

 

[rreegg]

what symptoms are the GPs showing and how do you know they're burning out, is it a resistance measurement across the GP? i would assume you'd be able to see if they're getting voltage when they're not supposed to with a voltmeter

 

[Zion]

what symptoms are the GPs showing and how do you know they're burning out, is it a resistance measurement across the GP? i would assume you'd be able to see if they're getting voltage when they're not supposed to with a voltmeter

For symptoms, it will start hard starting after a few days or won't start without excessive effort. Each time I've determined bad plugs using a multimeter and a test light, most of the plugs read too much resistance and/or won't light the tester. I've tried to determine if there's voltage being sent outside of activating the switch, but no luck so far. The plug circuit only has power in accessory, so I don't think there's a passive voltage leak. Haven't observed any power going to the plugs while the engine is running unless the toggle switch is being held.

 

[franklin2]

I do not have any experience with this, but have heard guys talking on here that excessive timing can burn out the glowplugs on these engines.

 

[rhkcommander]

Glow plugs should only be used for 5-8 seconds depending on the brand. Some can go longer but not by much.