At work, weve got a 2000 F350 7.3L Manual, with about 140,000 miles. If it goes more than one day without being used, and the temp is below 60°s outside, the truck will crank, but it wont start unless we plug in the block heater for about 15 mins. Is this normal?

We've also got an 02 with 150,000 miles, and have no problems with it.

 

Any takers?

 

Originally posted this in the SuperDuty forum, and got nothing, so I thought I'd give it a try here...

At work, weve got a 2000 F350 7.3L Manual, with about 140,000 miles. If it goes more than one day without being used, and the temp is below 60°outside, the truck will crank, but it wont start unless we plug in the block heater for about 15 mins. Is this normal?

We've also got an 02 with 150,000 miles, and have no problems with it.

 

If it starts easily after being plugged in the problem is the glow plug relay or the glow plugs.

 

Thread moved to 99-2003 7.3L Power Stroke Diesel forum.
Maybe someone here knows...

-Matt

 

Starts easy when plugged in...won't start without it. Glow plugs or glow plug relay is the problem....or possibly weak batteries.

 

weak batteries cause these things to have a female hissy fit. when you check the batteries remove the power wire from driver side or you'll get a false reading. If it is the batteries, prob best to replace both. If not batteries, and it starts with being plugged in , sign of glow plug system problems like cookie stated above.

 

I'd start with the relay. Easy to test. Common problem.

 

Thanks for all the replies. How do I go about checking the relay for the glow plugs?

 

looking at the relay,just behind and to the passenger side of the fuel filter. Two small termials in the center, two large terminals, one left, one right. The large on the left should have 12volts allway's. the termial next to it(small) will get 12volts when the key is turned on which should trigger the relay and close the circuit and put power to the large terminal on the right.
Or just hook test light to the right terminal and turn key to run position. should be power for about 20 seconds. I think, maybe 15?

 

I have attached a small photo of the glow plug relay, as seen from looking from the front of the truck.

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

 

Thanks SpringerPop....that should really help me diagnose my problem. I wont be able to get to the truck until tomorrow morning....so I'll post later, and let you know what I find out.

Thanks again

 

Glow Plug Relay, Changed mine last winter and what a difference.

 

Don't be alarmed by all the double posts NDrum2005. When your post from the SD/HD forum got moved down here I merged them into a single thread.

 

I believe that the blue wire goes to the fuel bowl heater. Not 100% sure on that though.