I got some good advice a couple of weeks ago on a no start situation, and now I need more advice concerning I think a related problem. I changed the glow plug relay as the "wait to start" light wasn't coming on. This fixed the problem and my truck started for a couple of weeks. Now as I turn the key to initiate the "wait to start" but just as fast as I see the light, it goes out and the 30amp fuse blows. Again It won't start. I have checked the wiring as much as I can. The wiring that I worked on is fine. Help Please thanks, plumbr

 

Sounds like a short-circuit

 

unplug the fuel heater on the back of the fuel filter housing....sounds like the heater element has came apart....sorta a common problem on 7.3s....we had one of those in the shop last week....dorman makes a replacement now that you can get at the parts stores but most of them have to order it

 

Will a OBD-II Scan give me a specific error? Is it possible to use a multi-meter to get a reading, and if yes how do i connect? thanks for the help!!

 

the fuel heater pulls juice from the same circuit as the glow plugs???

 

It was not the fuel heater. Anybody have any suggestions? Again many thanks!!

 

that wiring harness for the glow plugs is a crappy design after a while it will fall apart and short out check it under the valve covers

 

You know it was not the fuel bowl heater? That is about the only thing that will blow that fuse. If not, check over everything on the top of the motor, all the wire harnesses.

Sometimes the main harness will rub thru where it goes under the intake track. Look there.

My bet is still on the fuel bowl heater. Unplug it.

 

The wait to start light and the glow plug relay have nothing to do with one another... Your problem was not the GPR to begin with... You could completely remove the GPR and the WTS light would still come on, and then PCM would not even know the difference.

Keep digging, there is something else going on there.

 

30 amperes in a glow plug circuit?
I have a 100A fuse in my Jeep- are you sure it is the right fuse value? Check back with the manual!

Did you changed or touched the glow plugs themself lately? The ring gap closes real quick if you apply to much torque to the plug while screwing in- causing a constant short!!! Reason for replacement!

Check the wiring and the plugs with a multimeter. Use the resistance circuit for the glowplugs. Use the lowest setting. One lead on the tip, the other on the body. Reading should be similar low in all plugs.
If you have no resistance at all you have found a short. You don't have to screw the plugs out- just measure on the tip and to the engine block. But make sure the wire to the plug is disconnected.
Check the wiring also in the lowest resistor setting. Disconnect the wiring on both sides and put the leads on the ends- Do not hold the wires with your fingertip- your body is a conductor.
Resistance must be also very low.
A short is always caused by very high current flow. Check the conductors if the insulation is damaged, has kinks or scuff marks to the body metal. Replace with the same diameter, if so.
report back!