Anybody Else Notice This?

[Billrog]

There's power to the alternator the sec. you turn the key on , so if it doesn't charge until running the fuse is blown.

 

[Highgear]

1200 - 1500 rpm at start ! Yikes ! I would never let it rev that high at start !

 

[Oaktree]

Okay, sorry, you're right. No excuse, guess I'm just getting old.

My Tach, once the engine starts, just stays around 800 or so RPM or so. Stays there.

Then after a minute or three it jumps up to show the correct RPM and I can hear/feel a change in the engine tone that tells me the alternator just kicked in.

I'm confused. Does the engine speed up after a couple minutes, or is the tach reading low at first? A change in engine tone would imply the former.
I don't know what the electrical differences are between a CK and my LK series, but on mine there's nothing fancy on the charging system to make it only start charging after running a few minutes. Are you sure it's got anything to do with the charging system at all? It's not like there's much, if any electrical draw once it's running. Maybe hydraulic fluid is thick-ish when you first start and is loading down the pump a bit?

 

[Username Taken]

I'm confused. Does the engine speed up after a couple minutes, or is the tach reading low at first? A change in engine tone would imply the former.
I don't know what the electrical differences are between a CK and my LK series, but on mine there's nothing fancy on the charging system to make it only start charging after running a few minutes. Are you sure it's got anything to do with the charging system at all? It's not like there's much, if any electrical draw once it's running. Maybe hydraulic fluid is thick-ish when you first start and is loading down the pump a bit?

No, the tach freezes at 900RPM more or less. After a minute or three, the tach will show correct RPM. Before that -- No, it won't. It just stays in that one spot. And when it does start working, I can hear/feel a very, very subtle change in the engine. Like a load but more likely, the alternator kicking on. It lights up, it goes from 0 to 900 (more or less, don't remember) but it stays there until what I think is the alternator kicking in.

It is electrical, I know that. I've been around professional mechanics for decades and, while I am by no means a mechanic, I can tell when something isn't working quite right.

Like I said, it starts and charges just fine. Perfectly, in fact. It's just that little quirk I was curious about.

I'm thinking maybe the ECU shuts down the alternator for a certain period if it thinks the Glow Plugs are operating. Otherwise, to the ECU, it could put a strain on the alternator.

Don't know why it would show up on the tach, though. weird

 

[Oaktree]

Have you put a voltmeter on the battery or output of the alternator to see if the voltage jumps up when you notice the engine sound change? That would tell you if it's the charging circuit or something else.

 

[Username Taken]

Have you put a voltmeter on the battery or output of the alternator to see if the voltage jumps up when you notice the engine sound change? That would tell you if it's the charging circuit or something else.

I will when I get up there.

Thanks for trying to help and I'll let you know what's what when I find out.

Buddy of mine is a cracker-jack diesel mechanic so when I see him next, I'll ask him. I'll most likely get a big 'DUH' so I'll probably have to wait until I get up there in June or so.

It's not a big deal yet. If it ever will be. Just kinda curious.

Thanks again

 

[Retired guy]

Okay, sorry, you're right. No excuse, guess I'm just getting old.

My Tach, once the engine starts, just stays around 800 or so RPM or so. Stays there.

Then after a minute or three it jumps up to show the correct RPM and I can hear/feel a change in the engine tone that tells me the alternator just kicked in.

The change in RPM is due to the hydraulic fluid warming up and offering less resistance to flow drawing less engine power to run the pump.

 

[pirogue1]

Not the fan belt by any chance? I had Ltd of trouble with my belt with a new CX2510. I purchased a 25-7400 belt from NAPA and had no more trouble with the tach which is driven by the speed of the alternator.

 

[Tinhack]

Ditto on the belt. It could be loose and slipping. Slipping causes heat and once the belt is hot, it grabs and charges. Check the belt.

 

[deezler]

Okay, sorry, you're right. No excuse, guess I'm just getting old.

My Tach, once the engine starts, just stays around 800 or so RPM or so. Stays there.

Then after a minute or three it jumps up to show the correct RPM and I can hear/feel a change in the engine tone that tells me the alternator just kicked in.

Haha, no worries man we've all had that kind of brain fart when it comes to engine instrumentation.

I'm commenting to this post before finishing reading the thread, just to point out that a change in engine tone does not only indicate a minor load increase from alternator load and thus battery charging. It could be many things, but most likely IMO is a change in fuel injection pattern/timing associated with the physical warmup of the engine.

If you want to know if the alternator kicked in, clamp a multimeter to your battery and watch the voltage right after startup. My bet is that the alternator is working more or less right away (why would they delay this?).