I have a 2002 F50 7.3 liter. I've had it about 3 years. The 1st Winter I had it I never had to use the block heater, I would go out in the morning when it was below freezing in my truck would start right up. The past 2 winters if I don't plug it in to the block heater the truck doesn't want to start or has a really hard time starting. Now that the Winter is over in the temperatures are warming up my truck still has difficulty Starting in the morning when it's somewhat cold out even if it's only getting down to 50ﾟ or so. I replaced the glow plugs 3 or 4 months ago with Motorcraft plugs but I did not replace the valve cover gasket and wire harness, they seemed to be in good shape. I also replaced the fuel bowl because of a leak so it has a new fuel heater I also replaced the glow plug relay, anybody have any ideas on why it has trouble starting in the cold?

Edit: in the morning when I goto start it, it'll crank but not fire, it sounds like it's slow to crank but the batteries are brand new, I'll usually crank it for 5-8 seconds and it might putter once then sounds slow to crank, so I'll turn the key off and on let the plugs warm up again and crank it another 5-8 seconds, it's usually the 3rd or 4th attempt that it'll finally start, at which point it'll shoot out a cloud of white smoke for a couple seconds then it's good to go, it runs and idles fine and there are no service lights or codes. Just reading thru some forums I'm thinking it might have something to do with the injectors? Again any insight is appreciated. The truck has 205k miles, and if I plug the block heater in for a hour or 2 in the morning it'll start right up, first crank and no white smoke.

Thank you.

 

Sounds to me that if it fires with the heater plugged in for a few hours but not without you injectors are about done. Others may have something else to say but that is one of the trouble shooting steps commonly followed for diagnosing said problem.

New 5W-40 may help for a bit on stretching the replacement of the injectors. Not saying you are one of them but way too many owners are pushing the oil way too far between oil changes and it does have effects on the way our trucks run...

 

I appreciate the reply, thank you. Is 200k an average life for injectors? Also if I replace them, what are some good injectors? Should I just get stock Motorcraft? My truck isn't tuned but I do use it 5 days a week for towing.

 

I am not sure it's the injectors, they weren't a weak point in the 7.3. The 6.0 yes but not the 7.3. You are getting a big cloud of white smoke, so it sounds like your injectors are working fine.

I would check to make sure your glow plug relay is functioning first. Its health is NOT indicated by the 'wait to start' light (the little curly light on your dash). That light is on a timer and doesn't actually tell you if the glow plugs are ready to crank. You can check it alone but it's easier with help, you'll need to check across the big lugs on it while someone else turns the key to on. If the ohms reading drops to something near zero you're good, if it stays at infinite you have an issue.

I think you also have an intake air heater (early '99s did not, late '99s and after did I think), which uses an exact duplicate of this relay. If this one is bad it will ALSO cause a hard-to-start situation. Checking is the same as for the glow plug relay.

If both of these check okay, then you need to check your glow plugs themselves, make sure they aren't burned off (they should be replaced every 100k as preventative maintenance, but I have heard of stock ones reaching 300k+). You will need to pull the valve covers to do this, which also means pulling the turbo pipes to and from the intercooler (an easy job). Be careful not to damage the valve cover gaskets, but while you're there check them for any damage, and throw a ohmmeter on the pass-through connections to make sure you don't have a break there too.

If, after all of this, it is still hard to start without the block heater, then you have bigger issues. It could be your HPOP failing, bad wiring somewhere (it is an older truck, chafing is always possible on a wiring harness), or any number of other issues. But definitely start with the GPR and IAHR.

EDIT: I just re-read your post and see that you've replaced glow plugs and the relay for them. I would still suggest the intake air heater relay before going after injectors. I have seen this relay being bad cause a 7.3 to refuse to start, even in warmer temperatures, and give the exact same symptoms you are describing.

 

Agreed on testing a few things before dropping $1500 ,give or take, on reman injectors. If you don't have it already, start with a $40ish compatible bluetooth OBDII dongle and the Forscan app. This page may have the info too, but I know for sure it's in the tech section of the 99-03 7.3 forum for this site, for tutorials and hardware requirements so you get what you need the first time. Here's a lint to the tech section to help find your way.

https://www.ford-trucks.com/forums/1...-7-3l-psd.html