Runs & Guns but does not start w/o starting fluid

[txhorseman7]

Hello to all the great folks on the forum. My first post.
I've got a starting problem thats got me stumpted.
Details:
2000 F-250 7.3 powerstroke, 199K and only changed the water pump(1yr ago), stock chip
Friday morning I get in her and she does not start.
engine turns over but, No Start
In troubleshooting, i found that a 2 sec. shot of starting fluid, and she starts!
She runs, guns and drives normal turn it off and then on again, No Start unless i use starting fluid
Here's what i can tell you so far.

All fuses are good. injector relay exchanges with another same relay
Batterys are charged, clean terminals, disconnected for 30 min.
fuel pump sings with key on
no "check engine" lights are on, "Wait to start" light acts normal
50 miles into a motor oil changed and full tank of die$el
Changed CPS and can see movement on the tach
I have not checked for codes and my have erased them.
I have not changed the fuel filter in some time.

What is not working at start-up that seems to work while running?
Please help! I may have to saddle my horse and ride her work.

[Big AL]

Welcome to the Site!
Someone is gonna' be able to help you more than I can.
I will tell you this, though ; The engine has to turn over with at least a certain rpm, & there is a minimum voltage required to fire it off. That info is here somewhere - I'll try to find it.

[bigcountrysg]

I am thinking maybe the IDM is not working. This would be the Injector Drive Module. I Or maybe the UVC which is Under Valve Cover Wiring Harness. If the harness has a bad connection the injectors will not fire. You can check the connection on the driverside and passenger side valve cover. If those connections look ok. Remove valve covers and look at the UVC check the connections. The UVC is not as common as the CPS but it is known to get hot and melt and short out.

You need 10.5 volts minimum to have the PCM work. If you do not have that then charge the batteries.

Also don't use starting fluid either can damage the pistons. I prefer carb cleaner if the truck needs something to fire it up.

[txhorseman7]

Thanks for welcome and the advise.
The cranking RPM is normal, but not sure of the voltage at the PCM whrn the batteries are under the load of cranking.
I'll check the voltage at the PCM while cranking.
The condition of UVC connectors and test the IDM and let you know.
This should be a simple fix sense the truck runs (with a little help).
Thanks again.

[Logan]

to the ORG. WD40 works instead of starter fluid too.

[westcoaststrokin]

to the ORG!!

[StarDriver]

Ether won't damage the pistons, BUT, the glow plugs may pre-ignite the ether and may damage the rods, bend pushrods, blow headgaskets, etc. If you have to use ether to start it, disable the glow plugs.

[txhorseman7]

Thanks for the advise. I'm saving my starting fluid for the lawn mowers.
She still won't start.
The voltage at the CPM was about 9 volts while cranking. Took the batteries out and had them tested. One of the batteries tested bad, so she two new batteries. I tried several attempts to start it but she just cranks. Also got her scanned, no codes were retrieved.

[pipelayerjdh]

Check the Glow plug relay. If that works, you may need glow plugs.

[lilredpowerstroke]

I know you got two new batteries but did you check them to see if they were fully charged and good??? When using starting fluid (which is a bad idea)was there any white smoke when it started?? Did you check the alternator??