Truck surges on startup from cold, fine after running a few minutes

[tmuller]

Hi all,

I installed a new alternator (not stock, 200A 6G version) and my truck has started surging when idling. It only does it cold and the only thing I notice happening is that the voltage is spiking when it's doing it, jumping between 15.8V and 13.4V (or 12.4V, not sure on low end). At the time of the install, I installed 1/0 AWG from the alternator to the passenger side battery and again from the driver side to the passenger side. I also used 1/0 ground wire from the battery to the ground point on both the engine and frame on the driver side.

It does this for about a minute and then suddenly the truck is idling fine, seems to not have a problem with voltage, nothing abnormal. No squealing sounds, no grinding sounds, nothing I can identify as the issue. Truck is throwing no codes at all, regardless of this happening or not.

Thoughts?

Thanks,

 

[DaveBen]

I would keep an eye on it. Does it drive OK? Turn on the headlights just after it starts and see if they change in brightness.

 

[79jasper]

Can you watch the ficm voltage?

Dave, the 7.3 will activate the glowplugs to draw the system down. Kind of A voltage regulator. Lol do you know if the 6.0 will do it also?

Sent from my SAMSUNG-SM-G935A using Tapatalk

 

[DaveBen]

Yes it does cycle the glow plugs.

 

[tmuller]

I would keep an eye on it. Does it drive OK? Turn on the headlights just after it starts and see if they change in brightness.

Drives fine and headlights do get brighter, but not 'sustained' just a blip several times and then they are fine after the truck runs a minute. Acts like the VR on the alternator is trying to fight against the truck.

I never see the FICM voltage ever change that much, just the voltage as shown outside of that. If the FICM moves at all, it's like .5V in either direction from 49V (have seen it 48). I have a BulletProof FICM installed for 2 years now (redundant circuits).

 

[tmuller]

Yes it does cycle the glow plugs.

That's what it sounds / feels like to me. Not sure if it's because they are in warm cycle and then they turn off and then on/off/on/off/on/off. Not sure, maybe the relay that works the glow plugs is starting to fail. My old 7.3 had that happen, glow plugs just quit working one day without any codes. The relay was bad, replaced, fine.

 

[tmuller]

Since the truck supplies power via the plugin for the VR to monitor, could it be that I have a issue with the link between the on hot wire and the truck such that this occurs for some strange reason, as if it can't get a good reading all the time on that wire? I've heard about that before and putting in a wire to the battery directly seems to have rectified that issue.

I will go back and try that (and put a fuse on it) after I check all the connections again.

 

[79jasper]

Iirc, the 7.3 had a computer update to make them quit doing it.
Could be the same for the 6.0.
Could try running a light to the glowplugs to see if that's what's going on.

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[bismic1]

Surging at idle is commonly an ICP sensor issue. Disconnect the sensor and see if the surging goes away.

 

[tmuller]

Surging at idle is commonly an ICP sensor issue. Disconnect the sensor and see if the surging goes away.

But it only does it when it first starts cold. It's as if something suddenly "turns" off and the problem goes away. It never does it idling once it stops after it runs a minute or two after it is a cold start.