Longer than usual cranking time

Am97

New member
Jul 30, 2020
2
0
1
I have a 2006 Chevrolet duramax LBZ 200,000 miles. I only drive the truck about once a week. And for the last few weeks, it takes longer than usual to fire up. I’ll turn the key and let the glow plugs warm for about 5-10 seconds. When I try cranking, it will turn over for a solid 5 seconds or so before firing. Usually, it only takes 1-2 seconds, especially with it being in the mid to high 80’s lately.
it turns over very strong (no dead batteries). But I did check both batteries and the were fine.
I tried the sea foam in the fuel and fuel filter yesterday, and tried cranking today and no luck. Same long cranking issue.
After the truck is warmed up, it will fire up in 1-2 seconds after turning off. After it sits for an hour or so, it takes 2-3 seconds to fire up. Any ideas?
 

matthew86

Member
Mar 15, 2018
41
0
6
Eastern WA
Sounds like it could be losing prime. Do you have a lift pump? Stock fuel filter or some sort of adapter to run a different style fuel filter? Do you still have the plastic bleeder screw? It could be time for a filter head rebuild.


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Am97

New member
Jul 30, 2020
2
0
1
Sounds like it could be losing prime. Do you have a lift pump? Stock fuel filter or some sort of adapter to run a different style fuel filter? Do you still have the plastic bleeder screw? It could be time for a filter head rebuild.


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Yes I do have an airdog lift pump that’s been on the truck over a year. The regular fuel filter has abt 50% life left. Was replaced about a year ago.
 

matthew86

Member
Mar 15, 2018
41
0
6
Eastern WA
Something I would try before your first start where it cranks more is try manually priming the system. See if there is any air that comes out of the bleeder screw or if the manual pump isn’t firm and you can push it down. It’s possible you might have a leak of some sort allowing a little air into the system and your lift pump can push it though and start the truck. Also, you could pull the fuse for the lift pump and try starting it without the air dog and see how it behaves. Barring anything coming up with those two thoughts, next thing I would try is a bottle test and see if your FPRV is working properly. That’s probably not as likely, but a possibility and something similar to your symptoms I had on a buddies truck.


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