Strange Glow Plug Issues

[Petri317]

Let me start off by saying I am about as good at wiring as Britney Spears is at singing . The previous owner of my truck wired in a push-button system to bypass the solid state controller. I assumed it worked. (Never assume!!! ) So, I go to start the truck for the first time with the new motor. It took 10 minutes and starting fluid, but it fired up, and ran quite nice one all of the air had purged the lines. I've had to start it 2 or 3 times since then to move it around in the driveway (no exhaust or turbo on it yet) and the glow plugs don't work. Pushing the button on the dash doesn't even dim the lights or move the voltmeter. But a quick shot of ether the few times I've started it and it fires right up. I've ran it for close to 10 minutes (pissed the neighbors of with straight manifolds) and it runs great. So from that, and checking all of my fuel lines, I can rule out air leaking as a possible contributing factor.

So far, I've checked the fender mounted solenoid which is controlled by the push-button, and the wire leading from it to the glow-plug controller. When the button is pushed (whether the ignition be in run or acc) 12.something volts is present, so I know that works. I've used a test light and ohmmeter to check the glow plugs (which all lit the light, and all had .3 ohms of resistance cold, or was it .03? One of those) I even pulled a few out and they looked brand new!!! (I put them in when the engine was on the stand about 4 months ago. I checked the PO's wiring against the tech article here on bypassing solid state controllers and it all looks to be correct.

Here's the weird (scary) part, I've found, using a multimeter, that with the Ignition on run, 12.something volts is Constantly present at the terminal on the controller across from the always hot terminal!!! (I'm talking about the one momentary power is supposed to go to) And this is with NO wires going to it, including the white wire (which was taped off) or the wire from the solenoid/pushbutton setup. Furthermore, with the ignition in run, and all of the bullet-connectors disconnected, I've checked each one (connector) and they all read 11.6V constantly!!!

I am amazed (and still a bit skeptical ) that my glow plugs are still good, but 2 tests and an eyeball check (I've seen burnt-out plugs with swollen tips before) seem to confirm this. All of this being said, I am not very good at electrical stuff and could use any tips/suggestions you more-experienced wrenchers can provide.
Thanks in advance,
Peter A

 

[highest_vision]

I don't know what wire feeds the WTS light on your truck, but it sounds like whenever the p/o bypassed the controller they bypassed that too. It also sounds like they wired the relay poorly. Or your push button or relay is shot (always on).
Get a diagram and compare factory wires to where they are now. Chances are you don't have to unhook much to disable the solid state portion of the system, and you only have to run one wire to the relay (the other goes to a hot via a momentary switch).
James

 

[Agnem]

I am about as good at wiring as Britney Spears is at singing

So what your saying is, even though your wiring doesn't work well, it looks great?

 

[dsblack]

As part of the mod, did they move the solenoid? On my 7.3 it is at the back of the motor, the one on the fender is for the starter, Maybe looking at the wrong one?
IF it ohms good it should be ok, It is possible to have voltage and verry little current if the wires are too small.
May try removing one, and grounfing it where you can see it and see what the results are.

Just ideas, my system is still OEM style.

 

[Petri317]

So what your saying is, even though your wiring doesn't work well, it looks great?

Well, It used to look great, like 5 years ago.

DSBlack: For some reason there are 2 fender-mounted solenoids as well as the controller. One is the starting solenoid, and the other has 1 wire from the pushbutton going TO it, one from the positive battery cable going TO it, and one wire that goes FROM it to the terminal on the GP controller on the engine. When I push the button (even with ignition off) 12.something volts is present in the wire going to the controller. The problem lies in that even with that wire NOT attached to the terminal on the controller (as per the previous owner's wiring and the bypass article) the terminal is always hot with ignition on, and it shouldn't be. On the attached file, it's the one with the red tag. The terminal across from it (not the resistor) is the ONLY one supposed to always be hot. I guess my controller may be bad.

P.S. I would kill for my system to be stock and not screwed up by the moron PO. On your stock system, are there any wires going directly from the starting solenoid to the controller. If my controller isn't bad, I want to go back to a stock setup, that is, if it hasn't been too butchered to do so. I have wiring diagrams which I'm trying to make sense of, but this second fender-mounted solenoid is really confusing me.

 

[Agnem]

Peter, just to clarify then. This is the 7.3 factory glow plug system which was modified with a push button? I've never modded a 7.3 glow plug system, or looked too hard at a schematic for one, but I was under the impression that the common mod for this is to remove the ground wire, and run that to the push button to ground. If this is true, then you probably would see 12V there all the time, but the relay should not be engergized, so there should be no voltage at the secondary high amperage terminal. Like I said, I haven't studied the schematic, but if there is a sense wire in this circuit that examines the voltage going to the glow plugs, this could be putting the 12 volts out there, but with the glow plugs connected that should go away.

 

[Petri317]

Yes, It is the 7.3 factory glow plug system which was modified with a push button, but the push-button energized a relay on the fender (next to the starter relay) which sent 12v via a 10 gauge wire to the terminal. I don't know what this bozo did, but I'm pretty sure he fried the controller. Idiot!!

 

[Petri317]

I have ordered a new controller and 8 new Beru Glow plugs. It is my goal to get back to the stock system. For those of you with the 7.3 (and late 6.9) Solid state glowplug system, is a fender-mounted relay (next to the starter relay) part of the system, and if so, how? Are there wires going from that relay to the engine-mounted controller? Any relevant Pics would be great!!! I understand the stock wiring to the engine mounted controller (I think) but how or if a fender-mounted solenoid comes into play is a mystery to me. I will get pics of the setup (If you can call it that ) on my truck tomorrow.
Thanks for the tips and suggestions so far,
Peter A.

 

[Mr_Roboto]

The 7.3IDI system uses a controller with a relay on top of it, they are mounted on the rear of the intake manifold right in front of the CDR valve. There is absolutely nothing GP related on the fender.

It would be entirely possible to use a standard starter relay to power the GP's, however I think 10 awg is a little light. The system draws somewhere around 100 amps. I would guess the factory wiring to be somewhere around 6 awg.

Mel, the mod isn't to disconnect the ground wire (to chassis ground), but to run a parallel ground wire to the relay itself. The controller uses the ground side to switch the relay. If you wanted to completely disable automatic operation, you would remove the ground wire from the controller to the relay.

 

[Petri317]

Been so busy, I just finally got around to working on the truck. The new controller I ordered did the trick, wired stock it works perfectly. Thanks again for all of the help guys!!!!