Glow Plug Ground Wire?

[ripfish]

Ok, Let me give you some details.
Checked all glow plugs. Beru's. Working. Hard Starting when cold. Block heater makes start much easier. WTS light cycles on for 10-15 seconds. Battery voltage drops from 12.6 to 11.5v when glow plug circuit clicks on. I get 7 volts to the glow plug caps. I think maybe I am having a bad ground on the glow plug circuit and the glow plugs are not getting enough voltage/current. Where exactly is that ground located? The solenoid looks to be chasis grounded, but is there a specific ground wire that should be coming off of the smaller studs?

[BuilderBob]

Let clear alittle confusion.
The GP circuit is grounded by the GP's.
The GP controller is grounded by a small wire.
For proper operation the GP controller requires a good connection to the block.
The GP's themselves are grounded by threading into the block, traditionally this ground does not cause a problem, unless you use many turns of teflon tape on the thread, "anti-seize", yes.
The voltage measurements need clarification, are the voltage measurements made with the 8 wires attached to the 8 GP's? Or how were these measurement made.
On edit, from OKGringo
[ QUOTE ]
http://photos.thedieselstop.com/show...;thecat=998<br />
[/ QUOTE ]

Refer to this schematic

[BuilderBob]

On the schematic you will see the ground symbol on the bottom of each GP, fine.

Again on the schematic, just on the top side of of the GP controller, you will see a small wire labeled BK, (BK=Black), note the ground symbol, this must be a perfect ground, clean, &amp; tight!!!

[ripfish]

Voltage drop of 1 volt is measured at the battery and with entire system plugged in. Voltage at the glow plug is measured with the entire system plugged in also. I can put my lead in the top of the cap to measure. I believe I see the ground wire in the back right hand corner of the motor. It appears like a good connection. Only a couple inches away from the relay. If my voltage drop is not very big and I am getting a limited 7 volts to the plug, is that ok or are the plugs not getting hot enough.

[tim94f250]

Another member just last night was asking the same question. He only had 7 or 8 volts to the glow plugs. I went out to my truck and tested my glow plugs and I had over 11 volts to the glow plugs. The controller ground is very important. It goes to the back of drivers side head. Make sure it is clean and tight. Tim

[BuilderBob]

I understand the circuit completely, I don't understand you measurements, with that said I believe that you missing another component.
There is a large resistor that is hung on the side of the relay.
This, I call the zig zag resistor, made of stainless steel. It is on the schematic, looks like a backwards "L".
The ZZ resistor has 2 functions, first it limits current. If it limits current, then it has a voltage drop, when the relay is closed.
The voltage drop across the ZZ resistor added to the voltage drop across the GP, will equal battery.
Now with that said, it is assuming you have a relay in good condition.
If the relay is worn, with the contacts arc &amp; pitted, you have added another resistance. This relay can be replaced.
Refer to the schematic,
The GP circuit goes like this;
Battery(+) to the 2 yellow 10 gauge to the engine connector, engine connector to 2 yellow 10 gauge, to the side of the relay.
On the other side of the relay to the ZZ resistor, through the ZZ resistor to the 2 brown 10 gauge wires, each wire feeds 4 GP's, thru the GP's to Battery(-)
Again this description will make no sense unless you refer to the schematic, plus it is not a good schematic, it is more of a wiring diagram.

Your description speaks of one meter lead, it does tell me where the other is being placed.

[ QUOTE ]
I believe I see the ground wire in the back right hand corner of the motor. It appears like a good connection.

[/ QUOTE ]

That is not good enough, remove it, clean it with scotchbrite and brake cleaner, clean the back side of the engine block. Look for wire integrity, solder the connection from the (blk) wire to the ring terminal, if required.

[BuilderBob]

The small Black wire has nothing to do with the voltage at the GP's.
The Black wire has EVERYTHING to do with irratic operation, poor timing, short dwell time.

Another subject,
Refer to the schematic, it show a #6 Red wire, its connection to battery must be clean, the opposite end of the #6 Red is made at the starter relay on the fender well must be clean and secure.
Refer to the schematic

[ripfish]

Thanks for the help. I bought the 88 F350 with 210,000 miles on it. Has bout 220 now. Not knowing if the solenoid has ever been changed, should I just change it out while I am at it? It appears to be functioning, but still concerned the glow plugs are not getting to the appropriate temp before turning over the motor. I have gone through my fuel system very thoroughly and know I have tigtened that up since purchase. However I have not messed with IP or Injectors. New return kit, new fuel and air filters, clear line to watch for air before the filter.(That worked great to find issues). Fuel pressure is 4 psi at filter s valve. When warm this baby starts and runs great. New starter and batteries working fine also. Beyond the plugs I am wondering if some of the "cold" hard starting is due to poor performing injectors or IP. My mileage is pretty bad. Was about 15+ when I first brought it home, now down to 10 or 11 mpg. I just put some Injector cleaner in the last tank. Maybe that will help.

Edit: By the way. This truck does blow quite a bit of "blue" smoke when it starts up and runs while somewhat cold. I think that is normal, but maybe related to unburned fuel and poor injector/pump performance. I think I may have the injectors tested. Any thoughts.