Originally Posted by FallstonYJ

How does one go about testing the injectors?

If the seals are bad on the turbo, would that explain the loss of power, rough running and white smoke under load?

Thanks for your time,
Tom

Originally Posted by BombThreat

Hey guys I read through the first 6-7 pages and couldn't find out exact readings on testing my glow plug system 1997 dual 5 pin wiring. Could someone point me to a good write up on doing this? A lot of good info in here but hard to sift through it to find the info I'm looking for.

Thanks guys

Originally Posted by BombThreat

I checked the GPR and the old one was getting 12.4 volts on the constant hot (same as battery terminal volts). Checked the GP terminal and that was reading 10.5 volts. So I replaced the GPR with a new one and it reads exactly the same? Any ideas?

Originally Posted by ealbertson

I found this in the link below. If you go there you can see the picture of the GPR that is mentioned in the first line.
Book on Ford Pickups on sale - Ford Truck Enthusiasts Forums

I have attached a small photo of the glow plug relay, as seen from looking from the front of the truck. (Goto link above to see the picture)

The large terminal on the left with a rubber boot over it goes directly to the batteries. It has +12 volts all the time.

The other large terminal, without a boot, is the switched +12 volts that is fed to the glow plugs when they are supposed to be on. That current gets fed to the glow plugs through the brown and yellow wires (below). I don't know where the blue wire goes. Anybody got those factory wiring diagrams?

The smaller terminal at the bottom has no voltage when the key is off, but gets +12 volts any time the key is on, engine running or not. It is the incoming current supply for the relay's coil.

The other smaller terminal, closer to the firewall, is the other side of the relay's coil. It is looking for a ground to activate the relay. When the key is first turned on, and glow plug heat is called for by the PCM (the engine computer), the PCM outputs a ground, thereby causing current to flow through the relay's coil, activating the relay, and sending current (at +12 volts) to the glow plugs. When glow plug heat is no longer called for, the ground that is output by the PCM goes "open", causing the relay to turn off. If you put a volt meter on this pin after the relay opens, you will see +12 volts here, too. Why? The wire in the relay's coil is feeding it to your volt meter.

If you short this terminal to ground through a switch, you can manually control the current to the glow plugs any time the key is on.

Since the winter weather is usually not that cold here in Southern California, I intend to install a switch inside the cab that opens the connection to this terminal. That will allow the timer to control the glow plugs normally ONLY when I want it to. Otherwise, when I don't need the glow plugs to be heated, I'll save myself the current drain on the batteries.

You could also wire a momentary-contact push button switch in the cab and have glow plugs only when you push the button, and complete manual control if you want it. I wouldn't use a toggle switch, as it could be forgotten and the glow plugs would be on all the time. Not a good thing.

Pop

Originally Posted by Bart Earnest

When glow plug heat is no longer called for, the ground that is output by the PCM goes "open", causing the relay to turn off.
Now based on the above quote, would the big terminal that transfers 12v to glow plugs stop sending the voltage to the glow plugs? While testing my gpr the big terminal that sends 12v to glow plugs stopped reading voltage once the gpr "clicked". Is this normal? I have 12v on that terminal once the turned is turned to start.
Thanks.

Originally Posted by IDMooseMan

When the GPR goes "click, click, click, click, click, click, click..." (you get the idea), you have a problem and it's time to replace the GPR.

One of the big terminals should always have 12V going to it, (that's from the battery), and the other big terminal, like Nate stated, will have 12V when you turn the key to "On" or "Start", but will have 0V when the key is turned "Off".