Hard start 7.3. Glow plug relay? Glow plugs?

BronKitis · Jan 11, 2014

Hey all. I've got a 1999 F250 with the powerstroke 7.3. Here is WA, weather has been kinda cold, but not super cold. Maybe down to freezing at night.... Maybe.... I didn't plug my truck inand the next morning I went to fire it up and I had very long crank times. She did not want to start, and when she did, she was bblowing some stinky blueish smoke. Ran fine though, no misses or grumbles and what not.

I decided to test my glow plug relay and it shows that it was fine? I should add that these "cold starts" have become normal, even in 45-50 degree weather. One thing I noticed is that even though my WTS light was off, I was still Recieving voltage on both sides on the relay. Is that normal? Would that indicate power being sent to the glow plugs all the time or could it have been a fluke? I'm stumped and really do not like how my truck is starting. Any help is appreciated.

1badexplorer · Jan 11, 2014

If the relay tests good I'd look at the glow plugs and the wiring harness and connectors under the valve covers.

BronKitis · Jan 11, 2014

That is my next quest. I guess I'm mainly concerned as to how long I should be getting 12V on the glow plug side of the relay. The light had been shut off for a while and I was still getting 12V on both sides of the solenoid. Can the "relay" have intermittent issues? I only tested with one key cycle.

bobbywalter · Jan 11, 2014

ohm the plugs and see where they are at. when its running and cold it will kick the relay a few times...maybe you caught it there....if the relay is stuck closed and always pushing then the plugs are all likely dead and gone and gonna be a motherfawker to get out. though when that happens it usually kills the truck when your driving....the voltage gets too low to pop the injectors.

adsm08 · Jan 11, 2014

The powertrain control module protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high.

The glow plug ON time varies from 0-120 seconds depending on battery voltage, engine oil temperature and barometric pressure.

The wiring diagrams show a dedicated line from the PCM to the IC for the WTS light. I know on the 6.0s that the WTS being on or off does not directly translate into the glow plugs being powered or not. I don't know for sure that that applies to the 7.3, but with PCM controlled glow plugs it is a distinct possibility that it does.

I would begin to suspect, at this point, that the plugs are getting worn out, although compression could play a role in it as well.

BronKitis · Jan 11, 2014

Here's a question: What about batteries...? I bought two new batteries last year from a vendor at work and he gave me 650CCA's rather than the 750's that came out...

I sure hope that it's not the plugs.... What's weird is that it happened overnight. Also, if it were low compression would the truck stumble and run rough? She's got 180K on her and has been very well maintained.

bobbywalter · Jan 11, 2014

well maintained i expect 400 k of gettin it miles out of a 7.3.

if its a overnight thing then its something like a bad connection at the vc gasket or bad relay or wire from the pcm or something...

i was suspicious the plugs been bad for some time and its just cold. i just plug the bastards in for now till you have time to get to it.

BronKitis · Jan 12, 2014

OK guys.... So I went to test the relay again today and it was fine. While under the hood, I had my better half attempt to start the truck. While she was cranking away, a rather large plume of what looked like white exhaust and smelled strongly like diesel came up from the engine compartment. I couldn't get a good look as to where it was coming from, but it looked like everywhere! I first noticed the smoke by the heater box, then again under the engine on the drivers side. After a few more attempts, the truck started and ran fine with no sign of the diesel smoke. Shut it off after about 30 seconds of run time and then it fired right back up with no issue and no sign of the exhaust cloud thingamajig.... What in tarnations could this be? I am TOTALLY at a loss. Please help! Truck sits during the week as I have a company vehicle but a back injury may be changing that soon.

adsm08 · Jan 12, 2014

Leaking injector maybe?

BronKitis · Jan 12, 2014

OK, apparently the white smoke I saw was the unburned fuel forcing it's way back up since there wasn't any pressure to push it through the exhaust.

Tested the glow plugs and sure enough they're bad. Looks like a fun job too....

Thanks for all the help guys. Really appreciate it.

1badexplorer · Jan 13, 2014

The glow plugs aren't too bad to do in those trucks. the drivers side is easier than the pass side. the hardest part about the pass side is getting the valve cover off. You can get it out with the a/c compressor still on if you turn it right and pull the header hoses out of the way.

Will · Jan 15, 2014

My 7.3 Powerstroke is the worst thing I have for winter starting. I have to leave the block heater plugged in all night (an hour in the morning doesn't do it) and a 10amp charger on the batteries. It has a pair of new Walmart (Exide) 1,000CCA batteries.

My 6.2 has a pair of Optima yellow tops and a 1.5 amp automatic charger permanently installed. Without the block heater plugged in, it always starts. Even when we were at -7 and I had to go pull out a girl stuck in my sisters driveway. Those Optimas are far superior to any plate-type battery I've used. They will crank forever. I have an air leak on my 6.2 and it takes a while even in the summer to clear it. In the winter, the Optimas crank it endlessly and start it. This was a government truck and it had Optimas when I bought it. They were 4 years old at the time and lasted another 8 years. I replaced them with plate batteries and this 21:1 compression engine killed them in one year. I put Optimas back in it and it's back to always starting no matter what.

Buy Optimas if you have a diesel.

But my #1 starting diesel is the DTA360 in my Skoolie. It's my only diesel without glow plugs (the motor in my boat, trackloader and VW tdi all have glowplugs) and it always starts at the first blip of the key. I don't know what the difference is. It has plate batteries, but they are huge--not little car batteries.

1badexplorer · Jan 16, 2014

My 7.3 powerstroke starts better than any other diesel I've had. I've had 7.3 idi, and 12v cummins trucks. This psd fires up without any plug at 10 degrees. I'm started in when it was -10 without a plug if you cycle the glowplugs a couple times.

Will · Jan 16, 2014

Well, I've never had an idi Navistar or a Cummins so that bit isn't relevant. And you haven't had a GM 6.2 or Perkins or Kubota or DTA360 Navistar or VW tdi. So I think all of this doesn't equate to an argument.

The 7.3 Powerstroke starts easier than all the stuff you had and worse than all the stuff I have.

And to me the Optimas are the best.

BronKitis · Jan 16, 2014

Did the plugs today and she starts great! Good thing too because Tonto is supposed to go on it's maiden voyage for a snow run this Saturday. It was a PITA due to the 6" lift and my short stature, even with the tires deflated. But, all in all, not bad. Glad you can get to some of the valve cover bolts through the fender well and a chunk of vacuum line worked great for actually getting the plugs in and out. Even the harness for the plugs and injectors looked to be in good shape! Thanks for all the responses guys. Truly.

Sent from my SPH-L710 using Tapatalk

Hard start 7.3. Glow plug relay? Glow plugs?

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