Diesel turns over slow, then fast ?
 

ive had this ongoing problem in the colder months with the 1772. the issue... the starter will turn over slow then, fast then back to slow then fast and then it will start. all this takes place in about 5-10 seconds. i have two interstate SP-40 batters which put out 425 CA and 340 CCA each. so with the two combined i have 850 CA and 680 CCA. i think that should be plenty of power for the starter. i also have a quality battery tender hooked up all the time so i know the batteries are topped off. all the battery cables are new and tight. starter is 1.5 years old. this problem only happens when its cold(45 and below). once its warm it turns over fast and fires right up. could the voltage regulator be going out?? im at a loss. any ideas??

have you put an amp meter on it to see what the draw is while cranking?

Are the glow plugs working? Gear reduction or regular starter? What do you have in it for oil? How long do you run the glow plugs? VR would only affect it charging not starting. I like to heat diesels some before starting them in cold weather, ask Andy2182.

all the glow plugs are working. i usually give it 15-20 seconds. i have a regular starter. using 10w-30 oil. i put a magnetic heater on the oil pan if it gets below 30. i feel like its got to be electrical related. when i say cranks slow i mean its sounds like the battery is dead. then like magic its starts cranking fast and might fire up or go back to slow crank.

Have you done the glow plug upgrade - adding the solenoid? Mine was behaving in a similar way, and after the upgrade no more problems. Glow plugs get power while cranking, and best way to explain the problem is resistance in the harness. Adding that solenoid pulls all that draw off the main harness. Mine starts fine now with only 1 battery. At least this was my experience. Also double check your grounds.

i did read up on the glow plug mod. it seems that the early diesels only got 7 or so volts to the glow plugs. i checked voltage on my GPs and im getting 9. it would be nice to get 12.

My experience with slow and then fast starting is that there is a lot of resistance when the ignition is first turned on but as the amperage builds the resistance begins to drop. I would look for some bad terminals or corrosion.:beerchug:

How old is the starter?

starter is not even two years old.

Being that it goes from fast to slow and back during a crank cycle, I'd be leaning toward a wiring issue. Find out if the slow crank corresponds to the glow plugs. In other words, when it's slow are they on, when it's fast are they off. If nothing there, I'd be looking at the starter.