Something of a thread resurrection here.
When the new '87 arrived last Saturday, later that evening I went out to see how the glow plugs performed and how easily the engine cranked over. I plugged in my cigar lighter digital voltmeter I'd used on the wrecked MB.
Surprised the heck out of me when the GP's yanked that big Group 49 battery down to 10 volts, and only recovered to 10.7 volts before cycling off - wrecked '87 would start at 10.9 and be at 11.6 (where I would normally crank it) long before the relay cycled off at that ambient temps.
I cycled the GP's again and cranked the engine. Fired up quite easily and ran smoothly. But then I looked down at the voltmeter. Alternator was only putting out 12.5 volts. Revving it up kicked the voltage to 13, then dies back down when I let off the pedal. Turning on the parking and head lights dragged voltage down to 12, so low it triggered the exterior lamp failure warning light.
PO had installed a brand new Autocraft Titanium battery a couple weeks before putting the vehicle up for sale. He had commented to me that the old battery must have been in rough shape, as the GP's warmed up much faster and the engine cranked over quicker with the new battery.
Well, no s### sherlock, it DID perform better with the new battery - because you'd killed off the old battery by being too stupid to realize YOUR ALTERNATOR WAS FRIED!
He'd installed a larger 90 amp alternator from a later model MB gasser - a used alternator from a picnpull junkyard. When I pulled it out of the vehicle yesterday, of the 3 bolts that held the two halves of the case together, one was missing, one was backed out over 1/4", and only one was tightened down holding the bloody thing together.
Fortunately, the new battery hadn't been damaged - it charged up nicely once out of the vehicle and several days later is still reading over 12.8 volts.
It occurred to me that the CRD had been cranking rather slowly since driving it full time again. I took my voltmeter and plugged it into the dash outlet. I'd driven it for 40 miles not 8 hours before. Voltage was down to 12.2 volts. Starting it up, the alternator struggled to get it up to 14 volts at idle. I had to drive it for several miles before it climbed up to 14.4, and as soon as I'd come to a stop for more than a minute, it'd drop back down to 14. As soon as I shut it off, battery voltage would immediately drop back to 12.8 or less, and after a few minutes was back down to 12.2.
No doubt about it, that cheap Chrysler speced bean counter version of an Optima was nearly dead.
I went to Advance and got one of the 34/78-4 Autocraft Titanium batteries to replace it. I gave it a full cycle on the charger first and checked that the cells were topped off before installing it.
As soon as I plugged in the voltmeter, voltage was reading 12.8. Key on with the glow plugs and lift pump only pulled it down to 12.2, and as soon as the engine fired, the alternator had voltage jacked up to 14.4 immediately.
And I have NEVER seen that engine crank over that fast, even when brand new - it fired as quick as any gasser I've seen. Thinking back to summer of '07, when I first tried a Scangauge II, even back then voltage at idle was only 14 volts - that Chrysler version Optima was already defective way back.
I tried putting the Optima on the same charger, and after a few minutes got an F03 code - battery was internally shorted. I'm willing to bet that battery was defective when it was installed on the assembly line over 3 years ago.
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