F250 7.3L Diesel starting quirk

[RoyKing]

Maybe I got the initials wrong PCM? It the main computer, it won't throw any error codes and humid seems to make it worse. It will crank but never a hiccup, then it will just start and run fine. It the box under the hood drivers side, I think there a label of the breakers under the cover, I bought a new one and spare off ebay

 

[terryknight]

late to the party as usual, there has been some good advice.

does it eventually start every time? can you plug it in and have it start easier? you could have issues with the GPs and relay, you could have bad/weak batteries however i'm thinking and oil issue. if it is low it won't start. if the oil is thicker (cold or heavier weight) it is harder to start. next time you have issues pull the plug on the HPO reservoir and see how much oil is in it. they can leak down giving a hard to start when cold issue. the motor has to fill the reservoir before it can send pressurized oil to fire the injectors

 

[Citydude]

Sounds just like my 7.3 symptoms last year with a bad glow plugs relay. Still trying to wrap my head around a 7.3 with 24 thousand miles on it. It probably still has that new car smell?

 

[RoyKing]

Bad glow plugs won't keep a engine from starting on warm day. I have same year truck, same symptoms, bad relay to the computer, easy to check swap the relay from AC, or in my case the relay that comes in the towing package for battery charging the trailer which I never installed. Tapping on the relay won't help

 

[jmc]

OP here. Sorry I can't try these suggestions yet. In the meantime, if the glowplug dashboard light is operation normally, does that mean the system is working or is that light just on a simple timer?

Thanks, all.

 

[Langanobob]

That light is just a timer to let you know when the glow plugs have heated things up to the point where the engine should start. The glow plugs stay on after that light goes out, they turn off when the engine oil temperature reaches about 140F.

If you look at the dashboard Voltmeter, you can tell when the glowplugs are on. They draw enough current to drag the voltage way down to what looks like 8 Volts or so.

 

[4570Man]

That light is just a timer to let you know when the glow plugs have heated things up to the point where the engine should start. The glow plugs stay on after that light goes out, they turn off when the engine oil temperature reaches about 140F.

If you look at the dashboard Voltmeter, you can tell when the glowplugs are on. They draw enough current to drag the voltage way down to what looks like 8 Volts or so.

The light and the glow plugs on my truck are wires wired together. With the exception of if the bulb burned out no light equals no glow plugs.

 

[skipmarcy]

On a 99 and later 7.3 the light DOES NOT indicate that the glow plugs are actually on - that light ontime is pcm generated and timed according to air, oil and coolant temps. As already mentioned, the glow plugs may stay on after the engine starts and the light is off - up to over 2 minutes after depending on conditions. This is out of the factory Ford manual. On my Calif. emission 99 F250, when the pcm sees a mismatch in amp draw for one bank of glow plugs over the other, it turns the check engine light on and throws a code.

Engine cranking rpms is the next critical start factor along with the glow plug function and oil quality/level. The 99 and up only have glow plugs, no intake heaters unless aftermarket. You don't have to wait for the "wait to start" light to go out IF you have good batteries & oil and the glow system works. You have to watch the battery cables on these trucks too, for corrosion. That positive cable in Motorcraft is in the $125 - 150 range, I've replaced mine once and always run Interstate Megatrons bought in pairs and my truck always starts. I also keep a spare cam sensor in the toolbox for when it doesn't start !!!

 

[Btown]

Sounds just like my 7.3 symptoms last year with a bad glow plugs relay. Still trying to wrap my head around a 7.3 with 24 thousand miles on it. It probably still has that new car smell?

I just broke 89,000 on mine last week. No new vehicle smell left in mine.

 

[4570Man]

I’d guess your cranking speed is too low or glow plugs are bad. If it’s a straight shift try rolling it off. You could just about forgot about starting my Chevy diesel with the starter but it rolled off perfectly. A new starter fixed the problem. The difference in cranking rpm was very noticeable. But check the batteries are good with a load test and all the battery connections are good before coming to that conclusion.