i have a f350 superduty with a 7.3 turbo deisel and i pretty much hafta keep it plugged in to get it to start, i have installed all new glow plugs and both relays have been changed and the problem is still there, only other option i have not tried yet was changing the pcm controller but unsure if that is the problem .. anyone have any other ideas to try first ? thx

 

Manually heat the glow plugs for 40 seconds and see if the truck starts. What is the ambient temp when cold starting?

 

approx temp here is around -5 , when it does not start there is a clicking in the dash also, at -5 it should start no prob but i hafta keep it plugged in am at a loss now lol

 

That sounds like batteries to me. How old are they? Have you had them load tested? Are the cables and clamps in good shape and free of corrosion?

 

Ford says you need the block heater at -10 degrees when these trucks were brand new. As the compression lowers with age, cold starting gets tougher. I would say you are in block heater territory or pretty close.

Based on your symptoms, it sounds like the voltage is dropping too low. The clicking sound is a clue that some relays may not be latching properly. Measure the volts while cranking and ensure it is at least 10 or greater.

 

batteries have been tested and have had brand new deep cycle ones in and still does the same thing and all the relays have been changed also , injectors have been tested , glow plugs are brand new ...if i even leave it un plugged for couple hrs it takes over half hr to get it started

 

Deep cycle batteries aren't designed for the fast discharge cranking requires. I've been through several sets of batteries under warranty (Thanks, Pep Boys. Your Bosch batteries suck.), and every time they were on their way out, I had the buzzing under the dash as well. That's what made me think it's battery related. It could also be something else related to power delivery, I suppose.

 

the batteries we temp placed in were brand new and 1020 cold cranking amps , more then enough to crank over the truck but the problem was still there so kinda ruled out a battery issue

 

shake and bake ....
i know there is an issue somewhere but can not figure it out , there is a clicking in the dash that only happens when the truck will not start , i was told maybe the pcm is acting up but thats alot of money to pay out and not have it cure the problem , im thinking it is something else ..... have any other ideas ?

 

FYI, one of the glow plug relays is actually for the AIH so it has zero effect during cold starts. Sounds like you are determined to keep throwing parts at the truck until the issue is fixed. Have you tested the volts while cranking? Is the ground signal from the PCM making it to the GP relay? Does the WTS light come on every time the key is cycled? Do you get any smoke out the exhaust when cranking? Does the engine have excessive blow by when the oil fill cap is removed?

 

What exactly is it doing? I added 3 qts. of Lucas to my Ex last winter, on cold starts he would wrup, wrup, wrup, wrup until I gave it a tad of skinny pedal, then smooth right out,,, if I plug it in, all is good. Never did that till I added Lucas, and I think it is a tad "thick" for colder weather.

 

Yes.
VERIFY that you have at least 10 volts WHILE CRANKING. If the PCM does not see enough volts, the injectors will not be allowed to fire.

Next, manually jump the large terminals on the glow plug relay for 30-40 seconds and then try and start the engine. The glow plug relay is the short one closest to the firewall. A pair of channel lock works good for this purpose...

You can then check the PCM signal to the relay. To do that, you have to lift the wire off the terminal and check for ground when the key is first turned on. There should be a ground signal for up to two minutes depending on the engine temp.

If the WTS light does not come on, then the engine won't start no matter what you do.

 

Also check the oil level. I have seen this cause a no start more times than I can count...

 

the wts light does come on and goes out when to start it and if its clicking in the dash it does not start..... if i leave it plugged in all the time it does start, but i can drive it and go somewhere for couple hrs and then takes me half hr to start it .... i will test the batteries again and try your idea with the relay and then let u know thx

 

This thread has a photo showing what the wires are for. When you check for the PCM signal, make sure you pull the wire from the relay or it will give a false reading.

https://www.ford-trucks.com/forums/1...arly-99-a.html