Well I finally got the FICM changed and went with the Atlas40 tunes. Starts and runs much better now. Just changed it this afternoon, so I haven't had a truly cold start with it yet. We're getting some temps in the teens next week, so that'll change soon.

Truck wasn't getting up to temp earlier this winter, so I decided to change the thermostat while doing the alternator. While doing that I cleaned the EBP sensor and tube. That made it run pretty choppy. I replaced the sensor while doing this work, it's like a new truck now. Nice even idle and no surge on takeoff, I love it. And the extra 40HP ain't no joke either!

If my problems are solved without changing any injectors, I'll be one happy camper.

 

I have a reasonably new 140a alternator with small pulley and good batteries... however when I do a cold start at low ambient temps my battery voltage sits at 11.0v for 45-60 seconds until the glow plugs finally shut off. System voltage then goes to 13.8 - 14.0 and stays there.


Suppliers of upgrade kits are telling me this is killing my FICM and that I need at least a 230a alternator and upgraded cables... to the tune of $500 or more.


I have no cold starting problems AT ALL, even down to single digits without plugging in, so I'm reluctant to shell out that kind of cash unless my FICM is truly doomed ! My current FICM is a 7yr old Swamps 58v unit that has performed just great !


Sorry if this has been answered before... but there are truly over 1000 posts on alternator/charging system/FICM... etc.. Way to much to wade through.


Thanks in advance for the wisdom of the experienced !

 

Then either you have a bad 140a alternator or someone slipped you a 110a.

This is a Bosch 140a from Amazon with a small pulley in temps well under freezing.

Volts, glow plug amps, time, alternator amps.

If the video is blurry hit the top frame title to go to YouTube direct, tap the three dots top right, and increase your resolution as this was recorded in HD.

 

Interesting.... Thanks Jack.


Your battery voltage, right after starting... starts around 12.5 and slowly creeps up to over 14v... over a period of 60 seconds.


My voltage stays at 11.0 for the entire 60 sec then JUMPS to 14 immediately as soon as glow plugs shut off.


Does that give you any further clues ? Cold it be high cable resistance (your cable mod is on my list of things to do) or do you still think the alternator is weak ?

 

The 11v value is typical for the 110a alternator. Unfortunately I lost the 110a video with a batch of other videos in my iCloud snafu. But around 15s after start it's already breaking 13v as soon as the batteries start to slow acceptance of charge.

I would have a hard time thinking that was a wiring issue. The stock cables can handle about a 200a alternator, although it's not best practice. And while voltage drop is proportional to current flow, your post GP voltage numbers are not that low. At that point each battery is only accepting about 8a.

But then I'm not sure where your measuring voltage from. If it's off the OBD2 port, then you could be down 0.5v due to the resistance stack over all the cables and connections, plus OBD2 reports low.

You can try to clean the connections at the alternator and alternator output connection at the pass batt, as well as your other up top connections. But it's really at that initial alternator post where a poor connection would be most problematic since the glow plugs are drawing 80-100a temperature dependent which is never seen at the battery connection once the motor starts.

The definitive test would be to put an ammeter on the cable off the alternator, but my gut is it's the alternator. You could get it checked although I can't say the AutoZones and Advance of the world don't get the tests right 100%. I've got 3 ammeters, to me there are as important as a voltmeter.

On the starter cable improvement, that would not do a thing for this situation that a connection cleaning wouldn't do. And if I get my act together I may be redoing the whole starter cable thing after some calculation work I just did.

 

What cold start temperatures you talking? It's my understanding that the glow plugs run for several minutes at startup - well after the dash light shuts off.

I've got the Bosch 140a alternator now, it came with the stock size pulley. I believe mine dips down to about 11v while cranking and then jumps in the mid 12's at startup. It's probably hitting 14v at about the 60 second mark I would guess. It's warm now, but I'll see if I can get an OBD/scanguage video later - if that'll help.

 

My data was from a cold start (overnight soak) with a 12 deg F ambient.


I let the glow plug light go off then started up. The ScanGauge voltage stayed around 11.0 v for another minute after the truck started.


I think I'll clean connections and see if it improves..... then probably swap my Alternator for another 140a unit.

 

I cleaned every connection I could get to from up top......at the alternator, batteries, clamps..etc. I swapped drivers and passenger batteries as well.


Did not change my symptoms.......


I just ordered the Bosch 140a alternator from Amazon.


When cleaning/checking batteries, I found the battery electrolyte to be low in both batteries. This used to be a symptom of overcharging ? Batteries are two years old. Maybe time for replacement ?

 

Did clean the Frame grds? That is very important. Jack has a whole thread on the importance of good grounds.

 

No.... I just cleaned the "up top" connections as Jack suggested in post #20 above. If we get some decent weather, I'll crawl under and do the frame grounds, if you think it will make a difference.

 

Remember, the ScanGauge2 reads voltage ~.4-.5V lower than the actual reading at the battery using a meter. Always measure at the battery with a meter.

 

Since we're referencing my vid a few posts back, with decent grounds this is the OBD2 loss after the glow plugs are off.

 

That's very typical for a 110a though. After GP operation, the 110a will be up to 13.8-14.2v, situation depended. I just don't think that's a 140a.