Wont start unless plugged in

[dmaciborski]

I know this has probably been brought up before but ny 99 7.3 will not start in cold weather unless it is plugged in. The glow plug system checks OK. I just replaced the batteries and that didnt help. Anybody had this issue in the past and how did you fix it.

[Sinac]

I had a similiar issue, but it was the glow plug relay...

[haulin99spd]

how cold is the weather....

[haulin99spd]

you might check your fuel heater........the glow plugs heat the air to a set temp. and one or more might be heating up but not heating enough...........ohm the glow plugs...they should be at least 1.5 to 5.0 ohm's......

[alabamafrog]

Sounds like glow plug system, double check the relay then might have to check the amp draw on the plugs. That’s much better than my other thought of low compression.

[Dave]

Most likely the Glow plug relay

[haulin99spd]

i agree with dave...prolly the relay...doulde check...

[dmaciborski]

Thanks for the responses. Numerous items were checked by "scanner" including the glow plug system. Everything checked out "OK". I requested my mechanic to physically remove the covers and look at the glow plugs himself. With much hesitation (because the ^&%^ing scanner showed that the plugs were OK) he agreed. Sure enough - they weren't "OK". After market glow plugs were installed prior to me buying the truck and 3 weren't "grounding". Once again - the scanner showed that the glow plug system was "OK". Ford plugs were put in an no further issues. Thank you all for your input.

[alabamafrog]

Glad you got it going. I’d look into getting a new mechanic that knows what he is doing instead of trusting a scanner. How the heck can a scanner diagnose the glow plug system? All the computer controls is one little ground wire and the is no feedback. That’s why I do all my own work, I don’t trust mechanics.

[hildyjill]

My truck has 2 controlers on top buy the feul filter when the switch is turned on one cycles and one doesn't. Which one is the one I'm after