Strange electrical issue - If the car is stalled, the battery is flattened

[maxhag]

Hey guys,

I've had a weird electrical gremlin on one of my engines for a fair while now.....
I know there is no off the shelf answer, but I am more asking here for any suggestions..... Two brains are better than one.....


It's pretty simple..

If the engine is stalled, it instantly flattens the battery, and requires a push/jump start.

All other times are fine......

Engine is a 4AGTE with a Microtech.....

So, it would seem there is a short somewhere, but why only when the car stalls? No one I've asked has been able to shed any light on this so far.....

Any thoughts?

[tottacrolla]

Are you certain that the battery is actually flat ?
The reason I ask is because you may have a fueling issue that gives the impression of a flat battery, essentially the injectors are still filling the cylinders with fuel when the engine is stalled creating an artificially high compression.

[cooter]

alternator?

[Matt]

Bring it up and I'll have a look at a few things

is the starter clicking or just a thud and nothing? Want to measure amperage draw from the starter motor and battery voltage when trying to start

What is the cca of your battery?

[LittleRedSpirit]

How old is the battery?

[maxhag]

Battery goes flat - As in it will just slowly crank over, 1 revolution at a time.... and then dies to the point of "just a thud and nothing" (As Matt said) (no constant clicking)
Starter has NEVER clicked....

Car cranks fine in other situations

Battery is a Small oddessy battery, about 5 years old......... As I said, fine other times...

[maxhag]

Thats a clever theory, but the car will crank normal as soon as I put a jumper pack on it, so it's power related

[Javal]

Check voltage drop to starter under fault conditions, or current if you have a current clamp. When the starter or starter b+ wiring gets hot it could be having a sad time. Easy tests to do and it's always good eliminate the wiring as a possible contributor.

Edit - don't forget to check voltage drop on the ground side too!

[Matt]

Does a warm engine or starter draw more amperage than a cold?

[Matt]

If you put a jumper pack on it and it starts, most likely your battery needs replacing. Unless the alternator isn't charging intermittently etc. when it gets hot.

All the jumper pack does is boost the CCA of the battery.