03 F250 7.3L PSD Will not start need help ASAP please

[m2b1969]

Have a 2003 F250 SD 7.3L PSD. I have changed the glow plugs, GPR, and it still will not start. I plug it in overnight and it fires off without a hitch. The only thing left I think would be the fuel bowl pre-heater or it was a bad glow plug relay I put in. What do you think.

[NoRalPh]

First, verify the GPR is functioning -> Troubleshooting GPR & GP's

Second, what temps are you dealing with?

In really cold weather plugging it IN is the answer (below 20F). Above that to Freezing, your best cold start options are;

Wait for the GPs to do their job (1min AFTER the WTS light goes out) before you start.
Use synthetic engine oil (5W-40).
The batteries are Everything they should be (you get fast enough, and long enough, cranking out of them).
Make sure you're getting Winter Blend Fuel (and you ARE if you're buying it at "the pump". Also the fuel heater isn't an issue 'till under 0F).

If you're still having a problem, and the engine is cranking on the starter as it should, you may have low compression (high miles) or another mechanical problem that requires a good shop to diagnose (or maybe you have the tools & experience?)

[m2b1969]

good deal. I'll check it. Thanks for the link on GPR. The cold is not really an issue. It got down to only 42 last night. Should fire right up. I forgot to mention that it won't start if it has set for 12 hours or more. If I drive it and it is say 29F and it has been setting for say 6 hours it has a hard start, but does start.

If the GPR is working well, what is next. I do have high miles so low compression could be there. Do you know what the ideal compression should be? Are there any additives that could help the compression say like B&G's engine restore or other better products short of a ring job? Let me know and thanks for the initial help. I'll get on that and let you know.

Thanks