6.7 Starter conversion? This one is new to me on a 7.3L.

1. We need batteries with 850 CCA or more
2. The battery cables and connections need to be in optimal condition. If you have a bad ground between one of your batteries and the engine block, this can cause your issue.
3. What is the battery voltage while driving with a warm engine?

 

I'm wondering if they use the same numbers there as we do here. One of the members here made room and put bigger batteries under the hood. IIRC it was idioit who did that. We have plenty of guys here whose stock set up starts their trucks down in the low digits. How many miles are on the truck? Are your injectors getting weary?

 

Yes Mark we have different codes for battery size (physical not electrical capacity) in Europe, I was able to find a UK supplier for Odessey extreme batteries & have been very happy with their performance. My truck starts with just waiting for the WTS lamp to extinguish, even below freezing point. The OP is a bit further north so possibly freezing temperatures already, definitely worth checking cables & earthing points, never heard of a 6.7 starter upgrade either, but any starter has the same basic requirements, good cables & a good current supply.
Edit
EN750 batteries are only around 680CCA so that won't help.

 

Odyssey show a supplier in Norway

 

So I looked at Arendal on Google Earth, and it's a beautiful place. Given I'm an avid boater, that makes it even more appealing. However....

 

Not sure if they are available to you, but try to find some AGM batteries for your truck. They have more than enough CCA to fire off a 7.3 with a good GP system, even a mediocre GP system.

Odyssey is a good choice as well.

 

The OP lives on the coast and the weather just just getting to freezing at night, 40s in the day. Cold but the 7.3 should have no issues starting with
the correct CCA.

Maybe just plug it in for a few hours in the morning until you can get some more powerful batteries.

 

 

Close (to) 10V? Under 10V? Which is it? Where are you measuring the voltage? When are you measuring the voltage? After Key On, but before Crank? During Crank? After Crank? Immediately after Crank or more than 120 seconds later? It all can potentially make a difference in diagnosis.

A voltage drop to 10V when first turning the key on a cold morning could be normal, even on fully charged, perfectly good batteries. The 8 glow plugs, if all working, can consume up to 100 amps altogether. And the glow plugs keep consuming current long after the Wait To Start light extinguishes, unlike older diesels, where the glow plugs job was done as soon as the engine was started. If the resting voltage is 12.6V, and 100 amps are suddenly demanded with key on, then the mere act of supplying that current to the glow plugs will reduce the voltage of the batteries until the alternator can supply power, which obviously can't happen until the engine is running. The combination of powering the glow plugs (which can remain on for up to 3 minutes per key cycle, depending on engine oil temperature) and cranking the engine will pull down battery voltage even more.

Oil viscosity (too thick) in the winter time, especially in northern climates, can delay engine firing as well, since our injectors are oil driven.

I'm just trying to point out that there could be other contributing factors to your sluggish starts... meaning that one doesn't need to run a bank of big rig / lorry batteries under the frame rails just to start the truck.

There might be some benefit to looking beyond just the batteries... as several previous posters have already suggested.

 

Oil... We didn't ask if he's using 15W-40 or 5W-40. I use 5-W40 year-round.