so your saying the battery regulates the voltage? not the voltage regulator in the alternator? I'm confused by this.

 

It provides a load. That load may be required. Also, if you disconnect it as the engine is running you may cause a voltage spike. With so many modules that sounds a risk I would not take unless I was certain it could never cause damage. As I see no reason to disconnect the battery when the engine is running, but risks of damage, I would not do it. Feel free with your own car of course....

 

I have worked on hundreds of vehicles....I have been an electrician/engineer for over 20 years, I have never had an issue doing this. If the alternator fails, all the conditions you describe would be caused to the system regardless if the battery were connected or not. There is no massive load through the battery while the car is running unless something is seriouslly wrong, this whole theory in my experience is not right. The voltage regulator in the alternator/car is protecting the circuits, not to mention fuses. And I will continue to test this way.

 

Up to you but you do not sound to understand that a battery is a low impedance/resistance load nor do you appear to know that the battery is required to provide the peak currents these cars need when the engine is running to power injectors and coils. An alternator does not have a fast response.

 

I understand all of that, but as a very simple prodedure for determining if your alternator is failing and depending on that battery to run those items, I'm not sure any of this applys. Running at idle, parked, quick test, no big deal. People have been diagnosing alternators this way for probably a century, and now all of a sudden its bad. I dont believe that to be true.

Just make sure you dont disconnect the positive while driving at 50mph accelarating hard running from the law expecting to make it, and you will be ok, in my opinion.

But, I will research our problem and see what I can find.

Removing the alternator and having it bench tested is the best way to know and do it right, hands down. So if in doubt, take it out!

 

Two things:
1. why did you post about alternators in this thread? (I don't see its relevance)
2. do you understand now that your statement that the car when running does not rely on the alternator is wrong? (maybe it was different for old cars but this isn't a forum for them)

 

So your saying I cant start a car with a bad alternator, not totally correct, if there is enough voltage in battery then it will start, but might not continue for long.

Are you saying a car doesnt totally run on an alternator when its running, completely incorrect, it does.

So what are you saying?

Im not going to post to this thread anymore for sake of arguing with V8. I only continued to post on one thought because of the first rebutal to my comments, thats it. I have no argument with anyones opinions, do as you will.

 

I think I've been clear but you have not been. You have not provided wise advice for our cars and it was not relevant to this thread as far as I can see.

I haven't stated those things you just made up.

 

both points of view noted, now please lets get back on topic

 

In summary ...

System voltage is relevant to the problems described by the OP.

However, running an alternator without a battery in the circuit is ill advised. The electronic modules in the vehicle are expensive and sensitive. Subjecting them to avoidable risk is ill advised.

In any case, there are multiple ways to test alternator output that are more deterministic than disconnecting the battery. Two of the generally accepted ways are:

1. load test by instrument

2. load test by vehicle load, eg. look at headlight brightness and system voltage as more and more electrical devices are turned on

Greater detail for both of these can be found by using a search engine.

It should be noted that even extended sparking while connecting a battery too slowly has been known to cause random failures in modules.

 

my ecu on my 2004 f150 tells me what cylinder is misfiring. but the xkr didn't. 1 plug 1 coil 4 trys and success!

 

More recent PCMs tend to be more powerful, with larger software and faster CPUs (this may not be a surprise when you think about it) and thus more able to diagnose misfires.

 

So i pulled all of the coil packs off on the passenger side, with the exception of f #7, and looked down the hole as well as inspected the plug boots. #1 had visible pool of oil at the bottom. Now, it was a very little bit of oil but it was indeed there. I didnt see any oil persay in hte #3 and #7 plug but saw what i think is evidence that oil had been there before. Or perhaps it could be water causing misfires in the other cylinders.

In searching the forums and with the help from you all on this post It seems that the fix for this is new cam cover gaskets for the oil, and a combination of fixes for damming the water coming through the cowl running from the windscreen. I took a look at the gasket kit online and it looks like your standard valve cover gasket as in around the exterier perimeter of the valve cover. With that said, I am confused as to how the new cam cover gasket will prevent oil from getting into the spark plug wells? Any help with this question would be greatly appreciated. My overall plan currently includes the following tasks next weekend:

1. remove cowl @ windscreen. apply RTV silicone "DAMM" to prevent water from getting into the bonnet. Additionally I will install the plastic patch fix discussed in TSB S303-S159. Change cabin filter while i am at it and replace cowl.

2. Replace spark plugs with NDK iridium plugs all around. I also think I found online where I can replace the rubber boots that go over the spark plug without having to change the actual Coil pack itself. At 50$ a shot I would like to only replace the ones I have to, If any. Has anyone ever changed out just the boots and reused existing coils?

3 Change cam cover gaskets???? Now to the best of my knowledge the cam covers themselves are not leaking, or seeping for that matter, an oil at all. I only saw a little oil in the number 1 plug and found traces of what could be oil or could be accumulated gunk i guess as well in the other plug holes. I did not pull the other side (2-8)because they have not thrown any codes. and what i do to one side i will do to the other anyway. If changing the cam cover gasket is the usual fix for this then I will do it but if not then What else would cause it?

When I complete the work next weekend I will take photos and do a write up for the forum.

I also need to track down a fuel smell in the cab especially when cold, but one thing at a time.

 

The advice to disconnect the Positive terminal is ,,,,

 

We don't have F1 cars. Please ignore the above comment as regards our cars. The battery should be there. Period.

 

In addition to the cam/valve cover gaskets, the four seals around the spark plug wells and the seal around the VVT solenoid should also be renewed.

 

Change all the gaskets. You are not seeing the complete picture. All your gaskets are old. Some of them have started to leak. When do you think the rest of them will start?? If you plan to sell the car do the minimum needed but if you are keeping it don't be short sighted at this point. This will fix your problems for a long time!

Yes make sure you get the gasket kit. Then check that it has two cam cover gaskets and 8 plug well seals and 2 VVT seals.

I like to use a small layer of silicone on all spark plug well seals as added insurance. I have had new ones seep a bit after install. Go lightly on the cam cover bolts. They are very small and easy to damage.
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Refer to the JTIS manual for the correct tightening sequence of the cam/valve cover to avoid distortion and future leaks from the new gasket and seals.

A small amount of silicone sealant should be applied to the cam/valve cover mating surface where the front timing cover meets the front of the cylinder head.

 

Do you know that the 2005 S Type had only one recall and that was for the fuel tank?

I would not delay in getting it fixed. People have reported gas spilling on the ground when refueling because of this problem. On my 2005 the dealer replaced the entire fuel tank. I am at 85K miles with no problems.
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You may think that but it isn't true for our cars. You can read any number of threads on here and the UK forum where a failing battery shows up during driving by failing to provide enough sudden peak current. What you say is, for our cars, an approximation but an inaccurate one. Sudden currents lasting for a few ms (milliseconds) come from the battery and are replaced over a longer timescale by the alternator.