2000 Hard starting when cool or cold.

[Cat Fuzz]

Hi all. Looks like a great board here.

Anyway, I have a 2000 7.3L in an F-650. Now, this is an International build but I think everything to do with the engine itself are the same. I have read and searched the forums and done all the suggested tests. The test light on the glow plugs checks out ok. I tested the glow plug relay, it's new and good. I tested for voltage at the harness connector on all eight pins for the glow plugs. That checks out. This thing is still hard starting a lot of the time and it's parked inside a heated shop. When it's been running it starts easy.

Started somewhat easy today but there have been times we've had to use ether to get it going (I know, that's not the best idea).

The only thing that stands out to me is that the GP relay doesn't cut-off voltage when the 'wait to start' light goes out on the dash. Not sure if this indicates a problem or if it's normal.

Anyone have any tips on what might be wrong here?

Thanks ahead of time.

[RadarRider]

I'd say checking the relay is your best bet. If it checks out ok, the next item would be the glow plug timer. They're known to go too.

[Cat Fuzz]

I may be wrong here, but I would think that if the relay or glow plug timer were bad, I wouldn't be getting power to the glow plugs. I am getting power to the glow plugs.

[RadarRider]

To the relay: yes. But to the timer no. The timer is what initiates the delay of your glow plugs cycling. If it's malfunctioning, there is a possibility your glow plugs aren't cycling at the time they're supposed to or even cycle them at all sometimes. It's worth a shot.

[adfields]

Originally Posted by Cat Fuzz

I may be wrong here, but I would think that if the relay or glow plug timer were bad, I wouldn't be getting power to the glow plugs. I am getting power to the glow plugs.

Pull out one of the plugs and see if it's all carbon up on the end. When they get old they can get a layer of gunk on them that keeps the heat transfer down.

Another thing to check is the battery voltage when the glow plugs and starter is both on. If it is dropping under 11 volts or so the injector driver may not be working right till you let off the starter or the gpr kicks off. This would say week batterers and need replacement.

The glow plugs do stay on after the wait to start light goes out, thats the way it works. They can stay on for a long time after and even cycle on and off when it's cold out.

One more thing is the air temp sensor could be bad and the computer thinks it's a worm day. It is the sensor in the air filter box. Your temp sending unit in the motor also has a hand in glow plug control and must be working.

[Cat Fuzz]

Ok, thanks for the tips. The next time the truck is available, I'll check those things. It's a flat-bed tow truck, so I don't know when I'll get another chance to fiddle with it.

[timmytimmy2000]

guys im having the same issue with four trucks 99 to 01 F550's just a big headache new glow plugs and harness just dont know where to go next but i never use either really bad idea on glow plug engine thanks everybody

[adfields]

It is very important to have an oil with exultant cold flow for PSD cold winter starts, a thick oil may not operate the injectors right. That is the first thing to look into, try a 10w30 or even a 5w30ro40 oil for winter. Make sure your temp sensors and glow plug systems are working. Then you need very hot batteries as the glow plugs and starter combined draw can pull the voltage low enough that the injectors wont work.

[adfields]

I forgot the

[Cat Fuzz]

Well, I just found out that this truck has been run very low on oil at some point and another mechanic declared the engine toasted but then changed his mind. So, it could very well be low compression that is making this thing hard to start. I don't have any diesel diagnostic equipment so I can't confirm anything to that regard. But I do know that when the engine is at operating temp and you rev it up, there is quite a bit of exhaust smoke. Any thoughts on this?