Advice sought - stalling under elec load
Discussion
I have searched previous threads and whilst it looks like a common fault there doesn't appear to be a simple solution.
Symptoms are that it tries to stall whenever a major electrical load is put onto the alternator i.e. cooling fans or headlights.
If the belt is taken off of the alternator it runs fine but when fitted with the highest output alternator available it still tries to stall i.e. revs die, AFM flap closes and it runs very rich.
Battery is ok, all earths ok, seperate direct earths run to ECU and all other major items and still does it. ECU connections ok and all other wiring checked and ok.
The strange thing is it never did it before it went in to have work carried out - cooling system altered and camshafts refitted correctly (were loose allowing 30deg rotation under load). Engine is 4.5 with Jag AFM and injectors with a 404 cam. Idle is set at 1000 with CO of 2.5% - throttle pot set correctly - CSV ok and to all intents and purposes everything is fine until an electrical load is put on it.
Anyone have any ideas ? Is setting idle to 1300 the next step ?
>>> Edited by chunder on Friday 4th June 06:53
Symptoms are that it tries to stall whenever a major electrical load is put onto the alternator i.e. cooling fans or headlights.
If the belt is taken off of the alternator it runs fine but when fitted with the highest output alternator available it still tries to stall i.e. revs die, AFM flap closes and it runs very rich.
Battery is ok, all earths ok, seperate direct earths run to ECU and all other major items and still does it. ECU connections ok and all other wiring checked and ok.
The strange thing is it never did it before it went in to have work carried out - cooling system altered and camshafts refitted correctly (were loose allowing 30deg rotation under load). Engine is 4.5 with Jag AFM and injectors with a 404 cam. Idle is set at 1000 with CO of 2.5% - throttle pot set correctly - CSV ok and to all intents and purposes everything is fine until an electrical load is put on it.
Anyone have any ideas ? Is setting idle to 1300 the next step ?
>>> Edited by chunder on Friday 4th June 06:53
What fan setup did you go for after? When i fitted twin fans to my 350i it gave me similar problems when they cut in.(drawing more ampage). Had to increase tickover to suit.
Also after the new cam was fitted i had to increase the throttle pot voltage to about 380mV.With an increased butterfly gap of about 0.004"
Also after the new cam was fitted i had to increase the throttle pot voltage to about 380mV.With an increased butterfly gap of about 0.004"
I recently replaced a cooling fan on my Griff. It was corroded inside badly and prior to replacing it the current drain when they cut in was enought to cause the idle to drop. With the faulty unit replaced it is now fine.
The fan showed no external signs of the problem and I only found out when it finally jammed and kept blowing fuses.
The fan showed no external signs of the problem and I only found out when it finally jammed and kept blowing fuses.
dickymint said:
What fan setup did you go for after? When i fitted twin fans to my 350i it gave me similar problems when they cut in.(drawing more ampage). Had to increase tickover to suit.
Also after the new cam was fitted i had to increase the throttle pot voltage to about 380mV.With an increased butterfly gap of about 0.004"
Went for a twin fan set up - they are around 350mm diameter and came with a cowl that as luck would have it fitted almost exactly (few brackets made up) across the full width / height of the radiator. They are controlled by an adjustable sensor mounted on the wing with a capillary tube sensing temp at the inlet to the rad. They were wired from scratch leaving the existing cooling fan wiring and relay alone and at the moment cut in together and pull 20A on start and around 14A continuous. With the rest of the mods to the cooling system temp is no longer an issue - may though fit a second sensor and relay so they can cut in sequentially as this will reduce current draw and the second fan is unlikely to be on when the headlights are on with it being cooler (relatively speaking) when dark.
Not sure what the throttle butterfly gap is now but the throttle pot voltage was set to 325mV. The car is at a specialists around an hours drive away so I haven't seen it for four weeks now - getting very frustrating as I still don't have it registered for the road.
It sounds like increasing the idle speed is the way to go - thanks Richard - does anyone else have any thoughts ? Why would 20A put such a strain on a good alternator that it pulls the idle down that much - I have a disco with the 3.9 and even with air con and everything running it doesn't affect the idle ! Is it anything to do with the lack of any idle speed control compared to the hotwire systems or the lack of grunt at idle of a cammy engine ?
Thinking about it surely the SD1 and early Land / Range Rovers used the flapper type set up and some of these would have had power steering / electric fans / air con / spot - driving lights etc.
Does anyone know if they had this problem also and if not what was different - never heard of a 3.5 Land Rover needing it's idle set at 1300 !
Does anyone know if they had this problem also and if not what was different - never heard of a 3.5 Land Rover needing it's idle set at 1300 !
The SEAC you were intersted in and Dicky now has never suffered anything like this. I think it has the same cam and flapper, and whether it was hot, cold, idling at 1500 or 1k, putting the lights on or the twin fans cutting in only ever made the very very slightest of differences to the engine note or speed.
I have had issues with "good" batteries causing problems before, I think it is worth testing with another. Failing that get the alternator tested but it's bound to be one of those annoying little simple things that takes you ages to sort.
I have had issues with "good" batteries causing problems before, I think it is worth testing with another. Failing that get the alternator tested but it's bound to be one of those annoying little simple things that takes you ages to sort.
Thanks Steve, had thought of asking them to try another battery but would have thought that if the battery is capable of supplying cranking current then it should be ok.
Having looked through the bible and at the wiring diagrams it apears that I need to go down there and check the following -
1. The ancilliaries are only pulling the 20A stated.
2. There is no major voltage drop on any main terminals when something is switched on.
3. The actual cable between the alternator and battery is there and current is being drawn on this cable when something is switched on.
It seems like the car has two positive circuits with the battery supplying the starter and the alternator supplying everything else direct as this would induce the symptoms described. Not sure how this could occur though.
If anyone knows anything about auto electrics and I am barking up the wrong tree please let me know.
Having looked through the bible and at the wiring diagrams it apears that I need to go down there and check the following -
1. The ancilliaries are only pulling the 20A stated.
2. There is no major voltage drop on any main terminals when something is switched on.
3. The actual cable between the alternator and battery is there and current is being drawn on this cable when something is switched on.
It seems like the car has two positive circuits with the battery supplying the starter and the alternator supplying everything else direct as this would induce the symptoms described. Not sure how this could occur though.
If anyone knows anything about auto electrics and I am barking up the wrong tree please let me know.
Just in case this helps anyone else then after extensive testing and trying of new bits the concensus of opinion is that it is a characteristic of the engine which does not produce enough power low down to cope with the mechanical load from the alternator / power steering.
With the idle set at 1200 then turning everything on whilst loading up the power steering pump drops it down to 900 but at least it doesn't stall !
Registration (preceded no doubt by a big bill) now beckons.
With the idle set at 1200 then turning everything on whilst loading up the power steering pump drops it down to 900 but at least it doesn't stall !
Registration (preceded no doubt by a big bill) now beckons.
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