1995 HDJ81 1HD FT charging issue on cold start (1 Viewer)

[robtaylor]

well, I am hoping someone out there has some advice for me!

On cold starts, the alternator does not appear to be charging. The warning lights on the dash all come on, the amp meter is at zero; so headlight s etc are running on the batteries only.

after a few minutes the warning lights go out, the alternator kicks in and everything works fine. sometimes I can cue it to happen by turning my headlights off, or so I like to think.

This isn't the normal draw down at start up where the headlights are low for 30 seconds or so until the alternator catches up.
This lasts for several minutes, the warning lights all come on and the alternator doesn't seem to be charging the batteries- based on the instrument panel amp meter.
If anything, it has been a progression of the normal draw down taking longer and longer to recover until it turned into the alternator warning light/ zero amp issue.

The alternator was switched out with one that works, batteries switched out. The mechanic checked everything a mechanic would check for voltage, etc. Thinks it might be a fuse or did that he can't see and doesn't have the electrical info for the vehicle. anyway, after all the replacing and checking, the problem is still the same.

It doesn't not happen when the engine is warm; I drive for a while, go into the store, come out, and it starts and charges normally. it is just in the AM or after sitting for several hours ( ie: when I go home from work). It is consistent though. It always happens.

Does anyone have any ideas? My landcruiser mechanic is retiring and can't fit me in, so I'm a bit stuck here...

thanks.

 

[OTBT]

Hi Rob -
It sounds to me like an issue with the voltage regulator.
Glenn

 

[Dork]

I'm gonna suggest the air intake heater as a place to look. There's no glow plugs on the hdft, it uses the intake heater screen thing that draws a TON of current, but stops after about 2 minutes or once the engine is warm. I measured mine at over 100A initially then settles at about 50-60A.

But, if you have a bad connection, or bad battery, or shorted heater, or weak alternator it can suck your voltage down. Once the voltage is below 12, all your dash lights go crazy.

My heater was shorted, so it was the batteries straining to keep up with the load, while the alternator was overwhelmed.

 

[Squash]

You will notice this because the glow system requires significant power easily witnessed by people who try starting a diesel while still in pre-heat phase.
Pre-heat let light go out, start, allow engine to warm up, once charging is back to normal drive away.
Another clue is squealing belts until glow cycle has stopped.

 

[gte343z]

Has it always done this or did this issue just pop up at some point?

I had almost exactly the same behavior from my 91 hdj81, although it would happen anytime the battery was low or there was extra load at startup (headlights or ac). it had a similar effect where I could sometimes pop it out of this condition by turning the headlights or ac off then back on.

Turns out that the po had incorrectly connected the alternator output directly to the LH battery terminal. It should be connected to lug on the voltage switching relay that runs to the LH battery terminal. Seems like a minor detail but it had the effect of placing a fuseable Link between the alternator and the loads. The fuseable link created enough voltage drop such that the alternator never reached closed loop voltage regulation which will cause the charge light to turn on.

a bad ground or 24v switching relay could cause similar problems under large loads.
Do some probing with a voltage meter during cold starts to measure the voltage differential between key points ( LH and rh battery’s, across fusable link and terminals of the voltage switching relay that connects the grounds and also the batteries in parallel).

Not sure as I only have a voltage meter in my instrument cluster, but the stock amperage probably is not a true amp gauge. if you have a dc inductive amp meter you could place it over the alternator output and measure how much current the alternator is actually providing during the issue. You will probably find it is charging but is maxed out at 90-100 amps.

I don’t have the intake heater but I suppose you could disconnect it to verify that it is what is causing the problematic load. You’ll still need to identify if the load is too high or if the charging system just isn’t handling what is a normal co

 

[IanB]

It doesn't not happen when the engine is warm; I drive for a while, go into the store, come out, and it starts and charges normally. it is just in the AM or after sitting for several hours ( ie: when I go home from work). It is consistent though. It always happens.

This sounds like glow screen draw to me. It's a huge draw when it's on, and it's cycle time is coolant temp dependant, makes the difference between my windows rolling back up or not in the winter!

 

[mudandrock]

I agree with above statements about the glow system drawing too much juice for the stock alternator at startup. Pull the fuse or disconnect preheat and see if it still does it. If so, get a bigger alternator.

 

[Squash]

Patience!
Allow things to warm up, diesels mellow out once warm especially in cold climates.

 

[roscoFJ73]

What rpms are you starting with? I always always hand throttle my diesels up to about 1100rpm on a cold start

 

[gte343z]

I agree with the comments about letting things warm up, but in my case the charge light would stay on well after the glow plugs turned off. In fact sometimes it would not turn off at all unless I switched either the headlights or ac off and on. Just saying that a wiring issue can cause similar effects.

 

[robtaylor]

Hi Rob -
It sounds to me like an issue with the voltage regulator.
Glenn

thanks for the tip!

 

[robtaylor]

I'm gonna suggest the air intake heater as a place to look. There's no glow plugs on the hdft, it uses the intake heater screen thing that draws a TON of current, but stops after about 2 minutes or once the engine is warm. I measured mine at over 100A initially then settles at about 50-60A.

But, if you have a bad connection, or bad battery, or shorted heater, or weak alternator it can suck your voltage down. Once the voltage is below 12, all your dash lights go crazy.

My heater was shorted, so it was the batteries straining to keep up with the load, while the alternator was overwhelmed.

ok I can check that out, thanks!

 

[robtaylor]

Has it always done this or did this issue just pop up at some point?

I had almost exactly the same behavior from my 91 hdj81, although it would happen anytime the battery was low or there was extra load at startup (headlights or ac). it had a similar effect where I could sometimes pop it out of this condition by turning the headlights or ac off then back on.

Turns out that the po had incorrectly connected the alternator output directly to the LH battery terminal. It should be connected to lug on the voltage switching relay that runs to the LH battery terminal. Seems like a minor detail but it had the effect of placing a fuseable Link between the alternator and the loads. The fuseable link created enough voltage drop such that the alternator never reached closed loop voltage regulation which will cause the charge light to turn on.

a bad ground or 24v switching relay could cause similar problems under large loads.
Do some probing with a voltage meter during cold starts to measure the voltage differential between key points ( LH and rh battery’s, across fusable link and terminals of the voltage switching relay that connects the grounds and also the batteries in parallel).

Not sure as I only have a voltage meter in my instrument cluster, but the stock amperage probably is not a true amp gauge. if you have a dc inductive amp meter you could place it over the alternator output and measure how much current the alternator is actually providing during the issue. You will probably find it is charging but is maxed out at 90-100 amps.

I don’t have the intake heater but I suppose you could disconnect it to verify that it is what is causing the problematic load. You’ll still need to identify if the load is too high or if the charging system just isn’t handling what is a normal co

no, it has not always done this, and like your vehicle, I can sometimes pop it out of it the same way you did.
So, this sounds promising!

 

[robtaylor]

This sounds like glow screen draw to me. It's a huge draw when it's on, and it's cycle time is coolant temp dependant, makes the difference between my windows rolling back up or not in the winter!

ok, thanks. I don't think there are glow plugs on this engine, but the alternative might be the air intake heater mentioned elsewhere. Thanks!

 

[robtaylor]

You will notice this because the glow system requires significant power easily witnessed by people who try starting a diesel while still in pre-heat phase.
Pre-heat let light go out, start, allow engine to warm up, once charging is back to normal drive away.
Another clue is squealing belts until glow cycle has stopped.

I always let the pre heat cycle play out, even go through the process twice on cold (-15C or so) mornings thinking it will help ( I do not really know, though). I do have some squealing belts, though...

 

[robtaylor]

What rpms are you starting with? I always always hand throttle my diesels up to about 1100rpm on a cold start

I'll try that. The manual throttle is set at about 700 I think.

 

[roscoFJ73]

I'll try that. The manual throttle is set at about 700 I think.

The alternator is borderline making enough power at 700.

 

[gte343z]

I always let the pre heat cycle play out, even go through the process twice on cold (-15C or so) mornings thinking it will help ( I do not really know, though). I do have some squealing belts, though...

Is it the dual v belt setup? I forgot to mention that it took several times adjusting the tension because the V belts stretched. If the belts are slipping at all, you won’t get full output from the alternator. Especially at low rpm. This definitely made the problem worse in my case.