I'm afraid my FICM is on its way out. I'm getting voltages dropping to 46.5V about once a minute. Never goes below that. Then it'll bounce up to around 48.5. It gets low when I have to rev up and always coincides with the main voltage dropping to around 12.9V.

Now for my battery condition. They are about a year old. I think I have one with a bad cell. They'll drop into the low 11V range while cranking after glow plug light goes off. While driving, the main voltage never gets below 13.1 except for very short periods ... which coincide with the 46.5V output on the FICM. Gonna have them tested separately at advanced auto and see on has a bad cell.

So, is my FICM starting to go? Second question. What do I tell the folks at Advanced Auto about replacing both an not just one? I suspect they'll want to argue about it with me.

Thanks

 

I believe anything below 45V is the worry point

 

My personal red light is 47.0v.

11v range while cranking is not for me a concern, but main voltage down to 13.1v and lower for short periods to me says you've got a resistance issue with bad connections, or you've got an alternator not producing well. Have the batteries tested as a bad cell can do wonky things. But I'd also check the terminals, the positive bolted connections at the terminals, and there are other things you can do from there.

What pulley do you have on that 140a?

 

I'm using the standard pully that came with the 140 amp alternator. It is an upgraded alternator and not simply a smaller pully on the oem. I checked that before going with that alternator.

Batteries tested good today. Tested separate and completely disconnected from the truck.

Voltage hits 10.7 while cranking with the glow plugs still on...after sitting a few days.

I do have a small spark when connecting the batteries. I expect one, but this is larger than anticipated. I pulled every fuse one at a time and checked the spark. It never went away. I guess i need to learn how to measure the current draw when the truck is sitting. Any advice on how to do that with a simple multi-meter?

Maybe I'll lower my alarm to 46 and keep trucking.

 

We just installed an Ed FICM in my dad's truck. Went from holding 46.5V or better all the time to dropping into the 30s within about a thousand miles. On a trip pulling the RV, which is probably what was the death knell for whichever power supply kicked it. I knew it was going out, tried to stretch it one last time, and it died.

My opinion, you know it's going out. Do it now before it really starts dropping.

Went with Atlas 40, because despite how much I rip on it's lack of MPG improvement on my truck, it's MUCH better than stock. Difference on my truck which had no known issues was ho hum, some tip in throttle response, no big deal really. Difference on his, night and day. So now I can give some credence to the statements that some people make about how much difference it makes if you have a failing FICM and stack a new tune on a repaired unit, it drives likes it's new again. I'll admit I was floored by the difference.

 

That cranking voltage is low for this time of year unless your in a deep freeze in AL.

What size are the batteries and did you get the capacity numbers from Advance?

You will get a good spark connecting the terminals. Electronics are hungry when they are not umbilicaled to batteries.

A 140a alternator is a 140a alternator, it's going to generate only so much current given its rpm.

I think your FICM has been hurt, but you have to sort out the electricals before any further direction.

 

First, 10.7 while cranking is fine.

Second, if your FICM goes BELOW 45 volts, that is the only time you need to worry.

Some people get pretty crazy and paranoid on this subject. My 6oh, which was always in good charging health would fluctuate between 48v-46.5v. FICM's are all different. One truck may keep a constant 48.5v, another may be at 47v and so on, and some don't hold constant voltages. So don't worry about it unless you see it dip below 45v.

If your FICM is truely bad it will continue to drop in voltage. And it will show itself more in the Late Fall and Winter. I would hold off until it goes down further, if in fact it is bad. It is not going to kill the truck if it goes below 45v, it will just need to be repaired.

But, it doesn't hurt to get your batteries load tested cold, and your alternator bench tested cold.

Also, I give Ed at FICMRepair.com credit for information I have just given.

-Preston

 

Thanks, Preston (and Ed) for the info. I will lower the alarm and keep going.

 

Sounds good, I am glad to help.

With these trucks though it is hard not to be paranoid. After my second 6oh purchase I learned what exactly to look for and when to be concerned. But it did take sometime to get comfortable and knowledgeable about it.

 

My 2005 voltage was always 12.6 to 13.2 volts the whole 10 years that I had it. New batteries or alternator changed nothing. Never lost an ficm the whole 10 years I had it.

 

Ok, guys. An update.

I lowered the alarm to 45.5V. Truck sat for 5 days. Went to crank it and got two long cranks (6 sec each) without starting. Got my Torque Pro out to monitor.

Another long crank. HPO is good, sinc was bad, RPMS show 600, but still no sync.
Cam/crank sync is what I measure because I don't know that I can measure FICM sync with Torque Pro.

However, I see that my FICM Main Voltage has dropped to 42V with Logic Voltage and the other one at 11.5V. VBatt is sitting at 10.6V per my notes, but I vaguely recall it going to 9.6V.

Finally the truck starts. I let it run for about 10 seconds and shut it down. Crank again, and the same thing happens. Batteries are a bit low, but FICM Main is between 41 and 42V.

This is the first slow start I've had when I had more than 1/8 tank of fuel.

Is it time to call Ed?

I need some thoughts on this slow start please.

Background: For about a year I've had longer starts than normal after the truck sits for a few days. I now wonder if its the FICM. Can a FICM going bad cause this behavior only after it sites a few days? And typically when the fuel is low? If not, then what.

I thought it was a HPO leak (2004 model), but my gauges show its not. Whenever this happens, I'm not getting sync. I assumed it was a loose cam or crank wire. I installed a new cam sensor about 18 months ago because the old one didn't have a robust lock to the pigtail.

Another potential factor: Its a bear to crank if its close to empty. I ran it close to empty a few times. After a few try cranks, it starts really slow and slowly revs to idle speed...vs hitting it hard. This only happened when the fuel light was on. I actually ran out of fuel while towing the camper this summer. I know I hurt my injectors some. After putting in 4 gallons of diesel, I cycled the key 3 times and it started on the first try, but slowly came up to idle speed.

I didn't notice the low FICM voltages then.

Don't these trucks hate to start with low fuel with a dirty fuel filter? So, the next thing I did was changed both fuel filters. I did this after the last crank and no start episode when I noticed low FICM voltage. The filters had about 15k miles on them (I think). But they were very clean when removed. I started the truck after cycling the key 3 times without fail. I haven't cranked it since then. I'll do that tomorrow to see if it is still hard to start.

My fuel mileage has not been very good lately either. Could that also be FICM?

So, the big question is what has been causing these hard starts? 1) FICM acting funny only after sitting a few days or 2) Dirty fuel filters when its close to empty. I drove it daily for 4 weeks while camping this summer without a problem.

Could a FICM going bad cause a non-sync? If so, I think its been my FICM the whole time. Perhaps the slow starts (when it takes 3 seconds to come to idle speed) is a separate issue (maybe fuel filter).

Thanks for any thoughts.

Ps, while searching the baords on this issue, I stumbled across Eric's (Rusty's) spool valve/low power thread. What an experience for someone that helps a ton of people on this board. And its not a short trip between Tideman and Rusty...so kudos to Tideman for the effort. After reading that thread, I'll be adding some wires to ensure my FICM is happy and my battery load is balanced. I'll also not try and polish my spool valves when it comes time to change injectors.

 

42V, it's done.

My opinion: get the FICM repaired, put in a new FICM relay, load test the batteries. Do the electrical first before you start throwing more parts at it, or really even worrying about it. The combination of low voltage and an old relay causes weird problems; inconsistent crank times, lack of power, sometimes works A++ perfect. Weird, rolling, hard starts can be a FICM issue. When I was stringing a FICM along at 46V it would roll to start even with brand new batteries.

If the filters are at 15k, change them because they need it. But if the secondary filter is filling up and it runs fine at WOT once it's warmed up, I'm still thinking electrical over fuel pressure. I don't know what being close to empty has to do with it, unless you have marginal fuel pressure and the FICM is struggling to shuttle the valves fast enough on time and the injector body isn't filling up fast enough. Low voltage impacting the HFCM during the GP cycle? You mentioned a sub 10V main power reading.

 

As I said before, I think the FICM is hurt. IMO, what I would do is send it out to FICMRepair or Circuit Medics to have it checked and repaired if necessary. While it's out get the batteries capacity tested. Even if one battery is deminished it's going to hurt the FICM as well as starting. Report back what the two batteries are at capacity wise, but keep in mind that brand new batteries test out higher then they are spec'd for, and batteries will be declared unuseful at 50%. That's a wide dispersion for a diesel truck, and the low end too far for me. 10.7v when starting in this temp is OK, but not great.

If batts are OK to keep, put them on a trickle charger for the days the FICM is away. It will flip the most lead to an active state. Batteries should not be dropping much over 5 days unless there's an external or internal drain.

"A bear to crank when low" ???? On fuel??? The fuel level should have nothing to do with the starters cranking ability. However if you meant hard to get it to run, there's a chance you have a fuel pickup problem. That needs to be taken care of or not let the fuel go below 1/4 to 1/3 tank.

Once the FICM and starting reserve (batteries) are taken care of, then troubleshoot.

 

Thanks for the help, guys. I got the batteries load tested, separate, disconnected from the truck 2 weeks ago. They tested good. I'll find the results and post.

Glad to hear a hurt FICM can cause a slow roll start and other wierd things. Yes, i meant slow start, not slow crank. The crank has always been strong since i changed the starter 4 years ago.

I've got a trickle charger / maintainer I'll put on the batteries while Ed works his magic. I'll clean all the contacts and order the extra cables for balancing the battery load in the meantime.

Someone once told me some 6.0s slow start when filters are dirty and full is below 1/8 tank. I guess that's not true.

 

While you have things out you also might as well take the ALT in
and have it bench tested just for S&Gs. You never know what you'll
find unless you test it.