Cold cranking problem with 7.3 ford

There can be several reasons for this. The cheapest reasons to look at are spark to the glow-plugs and fuel to the cylinders. If you have a "ready light" on the dash that tells you when the glow-plugs are ready, you need to listen for the clicking of the glow-plug relay and the blinking of every other light that is on in sync with the clicking sound.

If the clicking and light dimming is not observed your power relay to the glow-plug relay is probably bad. A voltmeter will be needed to test for juice passing through the the power relay. If you have juice going to the glow-plug relay from the power box relay and it does not cycle off and on, your glow-plug relay is bad or the glow-plugs are bad.

You can test the power to each glow-plug with a test light or meter (when the power relay and glow-plug relay are cycling). Glow-plugs are similar to spark plugs and they can be tested. It can be tricky or you can just replace them.

Fuel, this time of year is subject to freeze-ups. Additive will help, noting Diesel additive and NOT gasoline additives. In short, Pyroil makes a starting fuel which has protective oil in the spray to help the cylinders. A spray of starting fluid will diagnose that fuel starvation is the problem. It is tricky to use when the glow-plugs are hot. On injector systems with O rings the cold weather can sometimes cause the O rings to shrink when sitting and leak. Your fuel will run back to the tank. Cranking will not be enough to draw up the fuel. Another way is to change fuel filters BUT to put some diesel into the fuel filter to prime the system. No guaranty that the problem will not reoccur because you have not permanently fixed anything. Hope this helps, if not then something has let loose like a fuelpump.

unlikely
it is more likely that the cranking speed is too slow for the compression pressure to get hot enough to ignite the fuel
2 possible fixes
the battery has to be in top condition for cold weather starting
and
the injectors may be squirting and not atomizing so have them professionally checked at a specialist diesel shop

why?

I have replaced all the glow plugs and injectors along with new relay and still can't get the thing to crank in cold weather. any ideas

year model? Engine size? I need a little more information than ford won't start when cold. I would guess either the glow plug relay or the actual glow plugs themselves are bad, but usually the glow plug relay, because if it were just one or two glow plugs it would start, but run like ****.

Have you checked the glowplug relay.

your glow plugs not working or glow plug relay or controller not working.

just crack the injector nut crank it over till fuel comes out tighten nut,and so on to the others.

Yes, my 2003 did the same with about 75k miles on it, stranded me on days it stayed under 40F unless I plugged in the block heater the night before, then it started like a champ. Dealer replaced the relay and a control unit under ESP warranty. There's no way to fix this one without throwing parts at it.

you will have to look for your plug
not all came with the frost plug heater but you can add one
i use the ZERO START brand and have had good luck
your local auto parts store should have it
part #
3100043