First off an introduction. First time poster, long time lurker on your forum. Bought a 90 f250 regular cab 4x4 idi a few weeks ago with unknown mileage. I don't know a great deal about diesels, but have been working on gassers for years. Right now the truck is a project, but I hope to get it to the point that it is a daily driver.

The truck runs well and doesn't smoke at all when warm. Now the temps are dropping and the truck starts great plugged in but is very hard to start without being plugged in ( have to crank in a few 5 or 10 second bursts to get it to start). The truck also runs very rough for about a minute after being started and blows a lot of white smoke ( fills the whole driveway). Glow plugs are new motorcrafts and the light stays on for about 10 seconds. I had the batteries checked and they both passed. The starter is also new and cranks the motor at about 400 to 500 rpm on the tach.

For the first week or 2 after replacing the glow plugs I could leave the truck unplugged at work for 10 hours and it would still fire right up in about 50 degree weather. The temps at night are around freezing now and I am worried how it will start when the temps drop below zero.

Sorry for the long post.
Any ideas? Would this be air intrusion? Thanks.

 

check your glow plugs even though they are new you may have gotten a bad one or two. With 2 bad ones that engine will start very hard. you can check with a test light hooked to the positive post of battery and touching the end of glow plug where the wire hooks up, if it lights the glow plug is good, no light it is bad.

 

I checked all of the glow plugs and they passed. I did however find out that if fully charged, the batteries will be nearly dead by morning. I did a parasitic draw test and found that something was drawing around 3 amps with the truck off. Traced it to the alternator.

Had the alternator tested and it failed. Question now is what amperage alternator I need? I didn't see any markings on the alternator. When tested they told me it was around 70 amps. Does this sound right?

Thanks

 

bigger is better as far asi am concerned when it comes to a alternator. I recamend getting one at the dealer if you can afford it i have had BAD luck with electrical parts from napa, aotuzone, etc.. You did make sure that you were getting power at the glow plug when you had the terminal off when you tested them? make sure you have even voltage at all plugs you may have high resistance in the glow plug harness.

 

If it fires right up when warm, it shouldn't be air intrusion. Instead of watching the WTS light, watch your battery guage. It should show a huge draw while your glow plugs are on. It should show a draw for a little while after the light goes off. Wait until your battery guage returns to normal then try and start it. I have an LED attached to my GPC that tells me when my plugs shut off and it usually stays on 10-20 seconds longer than the WTS light.