I have a 95 powerstoke with 183,xxx miles on it.. It is hard starting on days that are a little cool without being plugged in.. I have replace the glow plugs and relay but still having problems... Any other suggestions on what the problem could be??

 

More than likely you are going to need injectors. Could be compression but it would have to be real bad and have some serious crankcase pressure.

 

but why will it start being plugged in but not when its not??

 

Have you TESTED the glow plug relay, glow plugs and associated wiring?

 

yes. actually I have replaced it with a new one and still have the problem...

 

Plugging it in warms the oil, the injectors are fired by oil so thick oil will delay the poppet from opening fast retarding the timing. The clearances under the poppet are more than likely wore out. Could be part of the problem. Also you could have a plunger issue in the injector causing poor atomization.

 

Matt knows these injectors..listen to what he has to say.

Also...

Check voltage drop acrosss the solenoid? Just because its new dosent mean its good. also valve cover connections for burnt pins? Power wire from supply to solenoid and to the vcs..voltage drop test will be your friend and will get you to your cure the fastest

 

So what are the results of the tests with the new glow plugs and relay? Specifically:
* Voltage drop of the contact circuit while energized
* Resistance of each plug, measured at the UVCH connection
* Continuity of wiring between the relay and the UVCHs