PLEASE HELP! Wont Start unless plugged in

[truck7575]

I have a 2003 Ford Excursion 7.3 that will not start unless plugged in. It will crank and crank and act like it wants to start but never does. When plugged in it cranks a couple of times and fires up. I do notice the power isnt what it used to be but it has 300K miles on it. I have replaced the Glow plugs, 2 injectors that were bad and the glow plug control module. Someone told me that it might be the under valve cover wire harness, could these cause a no start when not plugged in and a start when plugged in? I have also put in a new starter and still same symptoms. PLease help! Anybody have any ideas where to go next? I just got this truck and It is my first diesel, I am not a mechanic but i have mechanical ability. I also have a oil leak somewhere that is causing oil to pool on top of the engine on the intake plenum and off also it seems to be running down the back side of the passerger side of the engine. could these problems be related? the oil leak was there before the start problem? Any Ideas would be a huge help!
Thanks
Rick

[jesilvas]

The UVCH supplies power to the glow plugs. So yes, if they get no power, it could be that.
What about your batteries?
The oil leak could be related to the high pressure oil system that fires your HEUI injectors, could be turbo pedestal orings, or EBPV actuator rod if it's pooling up in the valley. There is a sticky and many threads about common oil leaks on 7.3s.

[truck7575]

Batteries are both less than a year old.. When I pull te valve covers if the harness looks intact is there any testing I can do to confirm they are good? Or shoul I just replace both of them?

[jesilvas]

What is the CCA of the batts?
You can look at the pins at the connection where they go under the VCs. You can also look for chaffed wires under VC.
But, never hurts to have new harnesses and pigtail connectors.

[truck7575]

Do u happen to know the part numbers to te harnesses and pigtail connectors

[jesilvas]

No. There's plenty of websites who sell them.

[jesilvas]

Dieselorings is a great site, and instructions too
Replacement O-rings for Ford Diesel Engines
RiffRaff is good too.
Riffraff Diesel: Ford Valve Cover Gasket 99-03
Riffraff Diesel: Ford Under Valve Cover Harness 99-03
Riffraff Diesel: Valve Cover Gasket Connector Pigtail 99-03

[truck7575]

Ok I will order and changeout those uvch and pigtails and report back... Any one with more ideas let me know... Thanks!

[truck7575]

HUGE help! Thanks man!

[jesilvas]

I hope that's problem