Hi all,
I'm new to the site as well as new to our recently purchased 2002 E350 7.3L Super Duty 4WD Turbo Diesel with Ambulance package. Heck, I didn't know what any of those words really meant until a few weeks ago.
I've been a VW Vanagon guy my whole life and am comfortable with engine and trans swaps but this diesel is all new territory for me.
I purchased the van from the hospital I work at and then came across this forum while doing some research on how to get it road worthy and its been a great resource!

One of the main reasons the van was sold was because it kept eating up batteries. According to the maintenance records it was taken to a shop for diagnosis. It didn't throw any codes but they said "there was an open circuit somewhere".
I've read that the alternators are the usual culprits so while I waited for my new battery to arrive I pulled the cables off the rear house bank and removed each starter and did a diode check. Unfortunately both passed. I think the next step will be to install the new battery tomorrow and go thru the fuse box under the hood and see if there is a parasitic draw I can track down.

If I don't find anything obvious from the fuse check where should I look next? Is there a test I can perform on the PCM/IDM? Are there any "Usual Suspects" I should know about with these vehicle?

Thanks!

 

You already listed the next step: parasitic draw test. You can also use a thermal imaging camera to see what circuit is drawing amps. There's no "known problem areas" but with all of the extra electronic goodies that's wired in to an ambulance, you'll possibly have more time to invest in the diag.

-- Dave

 

Buy a decent multimeter! I'd start at the battery end, and test for amp draw when engine off. Reading should be around or under 500 mA.

You mention house battery bank... are just the starter batteries being "eaten up" or also the house battery bank? I would definitely disconnect the house batteries while you are doing your diagnosis. With 2 battery banks there must be an isolator or DC-DC charger installed somewhere. I would check the integrity of that component to ensure that it isn't always open and draining the starter batteries.

 

I never like seeing a thread where the OP doesn't post what the answer was so I'll do my best to follow up...

After spending the day with my trusty multi-meter and checking the battery banks, dual alternators and the charging system I've found the drain and its is simpler than I hoped.
I was getting a substantial draw and after isolating the "front" of the ambulance from any parasitic drains I located a very faint humming noise behind an access panel when the engine was off. Someone wired an inverter in the back but never included an On/Off switch so it ran constantly and would drain the batteries. I won't be using it for my purposes so I unplugged it and all is right in the world.

Thanks all for your input. It really helped me get acquainted with these motors and this setup.
Now that its running I'm going to dive into some mods to try and squeeze some more power out of this pig. But I'll start a new thread for that..

 

I don't think a diode test is very helpful for your situation since even new diodes have a reverse current drain consistent with their forward voltage drop.

I would add a capacitor which is supposed to help extended battery life.