305 E to small block 400. Battery dying problem. - Engine Swap - Third Generation F-Body Message Boards

Tbuck2007 · 09-10-2006, 09:29 PM

Hey guys,
I have a 1989 Firebird that I swapped a 400 small block into. The motor was freshly rebuilt, runs like a champ. We replaced the batter, alternator, starter, and wired up everything correctly. However. After running the car, even for a minute, sometimes the car will like to not start, the starter will click sometimes, or grind. The battery cant hold a charge for some reason..could this have anythign to do with the engine not being timed corectly? The alternator is brand new, so is the starter. both fit for the 400 smallblock. (alternator is for the 305, fit it to the car, not motor..) but it just keeps killing batteries..Whats the deal? I have nothing going to the batt that coudl be draining it..

KrisW · 09-11-2006, 03:10 PM

Speaking from prior auto parts store experience, I have had new parts returned for what you describe.

Take off the starter and have it tested. Especially if it is a reman or rebuilt unit.

Good luck!

QwkTrip · 09-11-2006, 08:52 PM

You either have,

(A) A charging system problem where either the battery or alternator could be bad.

(B) Starting system problem where either the starting motor is bad or the cabling and connections are bad.

(C) A ground fault that drains the battery quickly.

Get to a situation where the car won't start again. Turn on the headlights. If they are nice and bright then the battery is likely okay. If the headlights are dim then you need to isolate whether it's the battery or alternator.

To do this get the car started WITHOUT charging the battery. If the headlights get bright again within a minute or two then the alternator is likely okay. At this point get the battery load tested. It's the only way you will know how much reserve capacity it has. If it load tests good then you need to keep searching.

It concerns me that the battery keeps going dead. Go buy a clamp-on ammeter from Sears or somewhere else. Zero the ammeter so it read 0 amps. With the car off (and every switch off), place the ammeter over the cable that goes to the battery positive terminal. If it reads anything but zero then you have an electrical load somewhere that is continually discharging the battery. Your mission is to find the culprit. If it stills read zero, then turn on the headlights and measure the current through the cable that goes to the battery positive cable. You don't care what the number is but you do care whether the number is positive or negative. Flip over the ammeter until the numbers are negative in value. Now negative means "battery discharging" and positive means "battery charging". Turn on the car and check the current again. If the values change to positive then the alternator is charging the battery and you need to diagnose the starting motor next. If the number stays negative then you have a very high electrical load that is taking all the alternator can give and more, thereby discharging the battery at all times. You either have a honkin' amount of electronics on board or you hooked up something wrong and it's causing a ground fault (electrical short).

To diagnose the starting motor, first make sure all electrical connections between the battery and starting motor are clean and tight. If the problem persists then you should replace the starting motor.