Question need help 7.3 wont start in the morning

[jpciron]

Hey guys
I need a littel help. My 2003 7.3 wouldnt start this morning. I need this truck for work had to drive the 2005 f250 intead not as much fun. It was 32 out when I tried to fire it up. It sounded like poop and didnt stat after two attempts. I think it might be the glow plug relay or a relay that controls that relay. if anyone has any info about this or what i should look for please let me know. JPC

 

[creeper]

if the glow plug relay or glow plugs were bad it wouldnt effect the way the engine sounds while cranking. it would blow white smoke. its an easy check though. check to make sure you have 12 volts on both big terminals on the glow plug relay( thats the smaller one behind the taller one if there are two there) with the key in the run position. you need to check quickly though because it does time out. if you have 12 volts on both of those then you have another issue. or to rule out the glow plug system entirely just plug in the block heater for awhile if you have one


note: make sure the check engine light goes out while cranking. if the light stays on then the cam sensor is bad and the rpm signal is not being detected. your truck may have a recall for an updated sensor

 

[jpciron]

creeper
the post with a boot on it has constant currant. Had my wife turn the key to ignition with the coil light on nothing on the other post. any ideas? thanks for the help.

 

[creeper]

if there is no voltage on the other terminal then the relay is junk. the post with the constant current is direct battery voltage. the relay closes with a pcm signal which allows current to flow to the glow plugs. the glow plugs ground through the block.

 

[jpciron]

gotcha
thanks creeper.
You think my tuner may have screwed something up or its just what it is. We dropped 20 degrees in temp the last week.

 

[creeper]

havent seen any tuners causing issues on the 7.3. more than likely just age and mileage.
good luck. need any more info just ask

 

[jpciron]

ok i will ask thanks!
What is before the relay might cause a problem and where should I look? That relay is a valve basically getting power to the coil then closing it giving power to the plugs. There must be a time delay relay that shuts this off perhaps this is the problem? Thank you for all info...jpc

 

[creeper]

the pcm controls the glow plug relay on/off time based on a few inputs like engine oil temp, intake air temp. thats why when the engine is hot the wait to start light barely stays on. you have already diagnosed a bad glow plug relay. you need to get that replaced. if it was a pcm related or wiring issue you would have had a check engine light on previously ( even with the tuner ). recheck the condition with a new relay that is working properly. if the no start persist you will need to check a few other things. there are a few items you listed that make me think you may have another issue. like the sound of the engine when cranking and the lack of white exhaust smoke.

 

[DaveBen]

Cold weather brings a lot of starting problems. More current (amps) is required to heat the glow plugs and run the starter and this shows the weak link. Relays do fail and this is how they fail. Glow Plugs also.

Dave

 

[JLDickmon]

ok i will ask thanks!
What is before the relay might cause a problem and where should I look? That relay is a valve basically getting power to the coil then closing it giving power to the plugs. There must be a time delay relay that shuts this off perhaps this is the problem? Thank you for all info...jpc

dude, relax.
The glow plug relay is junk.
Replace it.
It's a common failure.