How far will an EA EFI go on a flat battery

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Wed Nov 28, 2007 10:54 pm

I had impending failure of my battery in the last week but its been noticable for a few months now, ie not being able to crank the engine with the AC on etc, but this morning i had to jump start it then drive into Brisbane.

It all went well till it cut out while reversing into a parking spot (the fans came on) I then clutched it in reverse and headed off again but this time the alternator chose not to charge the battery, ended up being a blown fuse. I was able to rev the engine to about 4000rpm at 10volts but as the battery voltage dropped it became less.

Finally at 6.7 volts the car would rev to only 1500rpm and the engine fans would work without stalling the engine but they only just where spinning and the engine just running. So at this point i took out the fuse for the fans knowing that i didnt have any traffic lights for a while and i was travelling into the wind. The engine still revved to about 2000rpm but if you accelerated quickly it would misfire so i kept driving till i reached Battery World and Larry fixed me up with a new battery.

Before i swapped the battery out i tested the voltage and i still had the 6.7 volts i had an hour ago, so without fans engine and heater and radio off they dont use alot of power. Then the battery was load tested and it failed miserably which is understandable. Probably the bit that annoyed me the most was the battery was only 3years old and has always been checked weekly. It was also a name brand battery as well.

Subafury · Post by **Subafury** » Wed Nov 28, 2007 10:58 pm

battery problems are annoying. and alsways seem to happen at the orst possible times. good to see the old girl kept going all that way tho

Gannon · Post by **Gannon** » Thu Nov 29, 2007 5:42 am

Definately check your alternator

Your alternator should be able to supply more than enough juice to run the engine, even if your battery was disconnected.

What fuse on the alternator? i didnt think it had a fuse.

It has a fusable link, but that shouldnt blow unless you had a dead short somewhere.

Are you getting over 14v at the battery with the engine running?

discopotato03 · Post by **discopotato03** » Thu Nov 29, 2007 7:30 am

EFI systems go pear shaped with falling voltage because of whats available to drive the injectors and the computer can only compensate so much . Also the low tension supply to the coil means less spark voltage and eventually it falls in a heap - cough splutter silence (CSS syndrome !) .

Its not a bad idea to be on good terms with an auto sparky and get you alternator checked out every 12 - 18 months . Generally all they need is a clean , a pair of bearings and new carbon brushes . If your a bit mechanically minded you could do this yourself with basic tools . The brush straps are generally soldered in and your WSM shows you how to test diodes etc though if it worked ok before it should again if all you changed was the bearings and brushes .
If your going bush often its easy to carry and fit a spare alternator as well . Just test it first !

Cheers A .

SUBYDAZZ · Post by **SUBYDAZZ** » Thu Nov 29, 2007 11:02 am

What did the alternator bench test at current-wise? Seemed like you got a damn good run out of that battery after it was buggered.

Xtreme_RX · Post by **Xtreme_RX** » Thu Nov 29, 2007 11:18 am

Must have gotten a bit of distance out of the dead battery....
What size was the battery?

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Thu Nov 29, 2007 10:49 pm

The Battery was a 520cca unit. Alternator is a 80amp off an EJ modified to suit the EA engine and has nothing wrong with it putting out a healthy 14.6v at idle. Yes there is a fuse in the setup i have which controls the trigger for alternator charge. It blew but i know whay and its fixed now so its all good. Point of the post was to bring to your attention that even if your alternator dies on an EFI engine that you can still get a fair amount of distance before the engine will stop. Not that i recomend you kill your battery but sometimes it can be your only choice.

D3V1L · Post by **D3V1L** » Thu Nov 29, 2007 11:05 pm

we have run brendans old touring wagon off battery before....right down to dead...had a pathfinder charge it up for 20 seconds and we where off again for another 5 minutes...heh..was quite funny actually

dave

PeeJay · Post by **PeeJay** » Fri Nov 30, 2007 6:18 pm

I've actually ran my EJ conversion with the battery disconnected just to see what would happen. Ran fine