Problems after installing replacement engine

[i2etributi0n]

Finally have a different engine in my car. Runs fine.. ish.
My confusion is after its started, it'll run for a few minutes, the dash goes black,
and the engine slowly starts to lose power and putters to a stop..
Then in order to start it again, I have to recharge my battery.
Does this sound like an alternator issue? The alternator worked just
fine before swapping blocks so I didn't think I'd run into a problem afterwards.


I did kill my battery once while cleaning the inside of my car while the engine was out...
Was listening to music and it completely drained the battery... Don't know if that would
play a role in this.

I know I could get them both tested, but I wanted to ask to see if there's any relation
to anything regarding this being a different engine block.

Thanks in advance!

[diagnosticator]

No, there is nothing inherent with a different engine and the dead battery symptoms occuring. Check the battery cells for electrolyte level, the level must be above the top of the plates inside the cells. Maintenance free batteries still lose water over time, and eventually the cells need to be topped up with distilled water. IF the electrolyte level is low, exposing the top of the battery plates, the battery will not be able to develop a full charge. The battery could also be sulfated, where the lead plates get coated with an insulating layer of lead sulphate.

The alternator is charging if the red battery light in the dash is turned OFF. However a faulty battery won't develop a full charge regardless.

Typically, a maintenance free battery will have two flat caps with three cells per cap. The sticker on top of the battery will need to be peeled back to allow the cell caps to be pried up out of the cells to check electrolyte level and to add distilled water as needed.

Starting batteries cannot withstand being fully discharged frequently and if left in a discharged state, will usually be damaged. In this case a new battery is required.

After checking the cells for electrolyte levels, connect a battery charger and allow the charger to charge the battery for at least 24 hours, then see if it has a full charge or not.

If it doesn't develope a full charge, and goes flat again right away, replace the battery with a new battery. The stock battery in our A4s is a Group 91R.

[i2etributi0n]

No, there is nothing inherent with a different engine and the dead battery symptoms occuring. Check the battery cells for electrolyte level, the level must be above the top of the plates inside the cells. Maintenance free batteries still lose water over time, and eventually the cells need to be topped up with distilled water. IF the electrolyte level is low, exposing the top of the battery plates, the battery will not be able to develop a full charge. The battery could also be sulfated, where the lead plates get coated with an insulating layer of lead sulphate.

The alternator is charging if the red battery light in the dash is turned OFF. However a faulty battery won't develop a full charge regardless.

Typically, a maintenance free battery will have two flat caps with three cells per cap. The sticker on top of the battery will need to be peeled back to allow the cell caps to be pried up out of the cells to check electrolyte level and to add distilled water as needed.

Starting batteries cannot withstand being fully discharged frequently and if left in a discharged state, will usually be damaged. In this case a new battery is required.

That was a much more detailed answer than I was expecting. I greatly appreciate it.
I'll go check the levels now. I may just replace the battery regardless because if left dead for so long
can damage it... Its been dead for a couple months... So.....

[diagnosticator]

Yeah, sounds like the battery is toast. Walmart has the Group 91R batteries at a good price, excellent quality too.

[rocket1420]

Wouldn't the alternator keep the car going after it starts despite a bad battery?

[diagnosticator]

Wouldn't the alternator keep the car going after it starts despite a bad battery?

It depends. The alternator requires some voltage from the battery to excite the rotor windings, an alternator can usually pull itself up by the boot straps, but if the alternator brushes are worn the alternator may not be able to sustain enough rotor excitation to maintain output voltage.

[old guy]

Also check all of the connections on the alternator harness from the alternator to the starter to the battery. You may have a loose connection somewhere.

[i2etributi0n]

Alternator tested good. Battery tested good. alternator still not charging the battery.,

[Human Garbage]

Well its pretty clear it is wiring then. I had a problem like yours years ago. It ended up being a small nick in the casing of the alternator output wire. That nick had allowed water in and corroded it massively. When I cut it open it was all green copper oxide dust except for maybe two or three strands that were still intact. Replaced it and problem was solved.

Time to break out the multimeter and test for continuity and resistance. I'm sure you will find your issue fairly quickly...

[i2etributi0n]

Is there a diagram or something someone might have handy of points to check so I don't have to go digging through the wiring?

I haven't had to run a test like this before so I'm looking for any pointers I can get.

[old guy]

Here is the alternator wiring harness. It connects the alternator and starter directly to the battery. Check all the connections on this harness:

[Kevin C]

I would also make sure you didn't miss connecting any grounds. If I remember the ground wire from the battery also connects the chassis to the engine.

[i2etributi0n]

Considering how the entire harness looked altogether in the engine, I was expecting more to it than that.... I almost just wanna replace the harness if that's all it is... But I'll test it first to see if I can just fix whatever the problem is.

[i2etributi0n]

The guy that hooked up the starter forgot to connect a cable.