Yesterday I went to start the Excursion (2000, 7.3L PSD), and the engine cranked, and then started, and then about 2 seconds later completely shut down. I went to try to start again and it was like the batteries were completely dead -- nothing.

At the same time I was hearing one of my relays in the fuse panel constantly 'kicking', even with the key out of the ignition.

I opened the fuse panel to find it was relay #2, which is what's called 'Battery Saver Relay'.

At any rate, upon trying to jump start the truck I found it would not crank at all, so, I pulled that relay out and since I don't have a bunch of spare relays handy used the relay from #1 (Interior Lamp Relay) in it's place as both were identical relays (same part #'s anyway).

When I had swapped the relay in, it no longer kept 'kicking' and now I was able to actually get the starter to 'attempt' to crank. But, my batteries were in fact completely dead (which is strange because recall the truck actually 'did' start before it completely died).

Long story short, I ended up having to call AAA because I just don't have access to a vehicle with a powerful enough alternator to start the Excursion if the batteries are completely dead. Once AAA arrived with tow truck, AND a mini van both jump starting me, plus their 2 power packs (i.e. a total of 4 jump sources) we got the Excursion to start. It ran fine for a good 10 minutes while parked. I shook hands with the AAA guys and they drove off. I then was about to take the Excursion for a small drive to get it charged back up again (i.e. to Autozone to go and find myself a new relay), put the Excursion into drive, and drove about 20 feet when... It just completely SHUT DOWN again!!!

And again, back to what appears completely dead batteries, like nothing will work, lights on the dash are completely dim, no radio, etc.

Has anyone seen something like this before? Is it possible I've got some really bad short in the system some where? Enough to 'instantly' drain two batteries -- which, I just don't think is possible, but, this is what it 'appears' to be.

If any one has any idea, I'd welcome them.

Thanks.

 

It could be one of your batteries may have a bad cell and you were able to run on the other battery until it died from the drain from the bad battery. I would either get 2 new batteries or borrow 2 batteries whidch you know are good and start there. Good luck finding the problem. Let us know what you find out.

 

Batteries wouldn't have an effect after the truck was running. However, a bad ground from the battery to the body could. Remember all ground is pulled from the negative side of the battery. I would say alternator and the the truck was dying once the voltage got low enough for the pcm to not be able to function properly if the truck wouldn't have started the first time. Bad ground between battery and body is the only thing that makes sense to me.

 

If one or both of the batteries is severly sulfated and is suffering shorted cells, it will not run properly on just alternator power alone. There has to be some battery power for the field circuit to work properly. In addition, if the batteries are really flat, then the alternator can also be overloaded and you can be flirting with blown diodes or worse in the alternator.

If the batteries are really flat, first try a hygrometer test on the cells and you can buy an inexpensive one at any auto parts store. On a discharged battery, the cells will show low specifig gravity, but will show similar readings on all cells and may actually "taper" slightly in specific gravity from one end of the battery to the other. If one cell is markedly lower than the others, then you've got a bad battery that will have to be replaced. If one battery is bad, go ahead and replace both.

Again, it's not a good idea to rely on your alternator to recover your discharged batteries if at all possible. If you do, you very well could damage your alternator. Your best bet is to put a full charge on your batteries with an external battery charger and then start the vehicle. Most replacement alternator rebuilders will not honor their warranty if you don't charge the battery first and there's a reason for this.

Right now, I'd bet that you've got some battery issues.

 

I had the same thing happen when I had the 01' PSD X. My #2 relay was also clicking. I replaced both batteries and all was good. No more problems.