My daughter’s blazer won’t start without getting a boost with a battery charger. The battery and the altenator test good. We have replaced the starter, spark plugs and fuel filter. Does anybody have any ideas as to what to do next?
Try thoroughly wire brush cleaning both ends of both battery cables and the connections they attach to.
Yes, I read you said the starter was replaced, but were the connections properly cleaned and reattached WRENCH tight?
It sounds to me that IF the battery AND the charging system is pronounced fit, then the possible fault lies with dirty/poor cable connections.
Your booster clamps attach to the cable connectors and therefore bypass the battery posts.
Then, again, it may be something else entirely eh?
If the battery voltage on the posts is above 10.5 volts when you crank the engine then it would seem something is wrong with the battery cables or connections. Cables can corrode internally and cause this kind of trouble. The high current draw will cause excessive voltage drop across the bad connection inside the cable. Check the ground cable also.
Check the positive side mount battery cable assembly.
Remove both battery cables, and peel back the red rubber cover from over the positive terminals. If you find a lot of corrosion under this red rubber cover, replace the cable assembly.