The Good, the Bad and, hopefully not the Ugly

[ducatist]

Here are a few pics of my engine finding its way home...a welcome sight to me after some fairly long delays in the process (most notably sourcing an in-spec piston to replace the one I broke during disassembly - Thanks again Henry Schmidt). Anyone who's done this project knows how I feel seeing the engine back in the car, but I have to admit to the reassembly and reinstallation being much smoother and easier than I'd imagined possible...everything was quiet...too quite, it seems. Now, I have encountered a problem...any ideas or advice would be most welcome.

After reinstalling the engine, I got a big spark when reattaching the negative wire to the negative battery post - quickly removed it and broke out my multimeter. It turns out that the body of the car behaves just like the positive post on the battery. I get 12.4 volts on the meter by touching the black probe to the negative terminal and the red probe to the body of the car. If I touch the red probe to the positive battery post and the black probe to the car's body, I get 0 volts - exactly opposite of what should be the case. I reviewed all my connections and even disconnected them all (the quick release wiring harness connections in the engine compartment as well as the wires on the starter and alternator), but the condition persists. I then reconnected everything and went through my fuses one by one - removing them did not remedy the short. The condition exists without the key being in the ignition so I really didn't expect the fuse exercise to yield any positive results. Somewhere, I seem to have an always hot wire in direct contact with the car's body - have to assume it's related to the engine removal and re-installation as the car was fine prior to that and has been sitting untouched on jack stands for two and a half months.

Hopefully I'm missing something simple or even stupid simple...don't worry about insulting me if I am. At this point I'd be willing to sacrifice a little ego for an answer

Does anyone know of a "usual suspect" for this sort of short?

[timmy2]

Did you somehow manage to pinch the wire that runs directly from the battery to the starter where it passes through the tunnel when re-installing the engine?

[ducatist]

Originally Posted by timmy2

Did you somehow manage to pinch the wire that runs directly from the battery to the starter where it passes through the tunnel when re-installing the engine?

It certainly seems like I've pinched some "always hot" wire...I'm getting 12.4 volts from the car's frame when I only have the positive wire on the battery. I only removed the engine - left the transmission in the car, so the only wires I noticed were the ones that go to the starter from the engine and they were free and clear. I'm going to double check on it though...and make a good inspection of the seal between the transmission and engine to make sure nothing got caught in there.

Thanks for the suggestion.

[ducatist]

for "always hot" wires that might be shorted are on the starter and the alternator. I pulled back the rubber boots to better display the actual connections. Looks right to me, you?

[kyle242gt]

Is the 12v+ wire for the alt to the insulated terminal? Hard to tell from that angle.

[Dan J]

Originally Posted by kyle242gt

Is the 12v+ wire for the alt to the insulated terminal? Hard to tell from that angle.

I think Kyle is right make sure that's the B+ terminal or disconnect and isolate the wire and see if your problem goes away

[timmy2]

As others mentioned, Starter looks OK, can't see what is connected to what on the ALT.

[ducatist]

Thanks to all of you who provided me with the benefit of your better (or at least fresher and more objective) minds…especially those of you who kept telling me (in effect) when in doubt; blame the alternator. You guys were right…sort of. Truth be told, I’m more to blame than the alternator since I used a spacer on the plastic alternator cover that had just enough excess diameter to make contact with the metal plate on the back of the alternator where the connectors are mounted. Instant arc…just add 12 volts. I discovered it after determining the grounding problem went away after I removed the plastic cover, but returned once I reinstalled it – another clue was the arc popping (and heart stopping) sound that emanated from the engine compartment the instant I connected the negative wire to the battery. The oversized spacer was blackened where the arc hit it – a dead giveaway of a dead short to ground.

So, a properly sized spacer was substituted and the problem was solved.
Not one to dwell on unpleasantness, I moved on to the test cranking of the engine. After a minute or so of turning it over, it cranked up, seemed to need and not get enough fuel and it died. I repeated the process a few times and it cranked and idled on its own, but there are some rattling sounds that seem to be coming from the driver’s side intake rocker bank – maybe the oil hasn’t gotten to that side in sufficient quantities. There were also a few minor back fires through the pop off valve, but nothing worse than you might expect of a cold SC. I can’t accurately check the oil level without the car running at idle for a while, but the dipstick looks a little low. I’ll pick up a few quarts of oil tomorrow and see if that quiets the rattle. Very little smoke on first startup, but there is a rich smell of unburned fuel.

I guess I wasn’t expecting it to crank up and purr like a kitten, but hopefully, with the addition of a little more oil, it’ll at least sound like an SC again.

Thanks again.

[jsoderbe]

Hi, the risk is greater to add too much oil than the opposite. When I change oil in my Carrera I add 7.5 quarts, and only add more oil once I get it fully warmed up and can check the actual level.

You should not see oil on the dip stick when you have had it parked overnight, since the oil drains back into the engine.

Also, I question if it should backfire, at least my SC did not. Check so you got the plug wires set up in order, and the dizzy resonably well adjusted.

Congrats on finding the short!


Johan

[ducatist]

I started out with 8 qts, but it ended up needing about 10...still didn't stop the rattle/knocking that seems to be coming from either the left timing chain cover or the left intake valve cover. I'm thinking maybe the mechanical chain tensioner didn't pump up - allowing the rattle.

The engine idles roughly and seems to be starved for fuel, but the knocking is really troubling as well.

Here's a link to an audio recording I made of the engine during a test start and idle. I hope someone with a keen ear can help me zero in on the culprit.

911 engine sound.mp3