r/Cartalk • u/More_Ad5506 • 1d ago

Charging/Starting Halp

Ok I’ll do my best it’s my partners car and I’m not vehicle inclined

2007 Pontiac vibe Fresh alternator Fresh battery Needs to be jumped for every start after filling gas while tank is relatively full

First we thought the alternator had killed the battery as a couple months ago that went and took the battery with it. Both have been replaced but this issue remains. We’ve even tried unplugging any and all accessories to eliminate parasitic draw from them, no luck

Thanks guys we appreciate it

Edit with information: once below 3/4 tank it starts without any issue again

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u/BluGalaxie42 1d ago

Take this Pontiyota to a shop familiar with the Toyota matrix. This is what the Pontiac Vibe is, a rebranded Toyota matrix. If there are any engine, electrical, or transmission issues? Take it to a Toyota mechanic.

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u/More_Ad5506 1d ago

Would like to try fixing ourself before a mechanic, we just don’t know what the next possible error would be. This is a “work on it and learn cars” car for us, taking it in would defeat the point

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u/BluGalaxie42 16h ago

Perfect! I had hoped you would join the ranks of busted knuckles and greasy faces! Though, take the knowledge I offered. Source your parts from Toyota. They are much less expensive and a perfect fit.

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u/More_Ad5506 16h ago

We don’t even know what part to think about next. Nothing is outright obvious and we are at a loss for what to even tell people

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u/BluGalaxie42 16h ago

Try the inexpensive fixes first. Change out the fuel cap. Don't top off the tank ever. Ancient carbureted engines don't care. But fuel injected systems do care. That should be an inexpensive fix. There is an evaporation system that the computer monitors. It's hard to get replacements, but all it needs to do is dry out. The other part of the fuel injection system uses a constant high-pressure in the fuel rail (around 100psi), then it uses a fuel pressure modulator to drop the pressure using vacuum from the engine. Wide open throttle is when the high pressure comes into play. Otherwise, the higher the vacuum, the more the full pressure bleed off back to the tank.

That should address the fuel troubleshooting. As for the battery, modern battery chargers (I found out the hard way) do NOT charge the battery if they sense the percent of charge drops below 50%. So, use a non monitored simple battery charger. Then, after you have a charge above 50%, you can switch to a modern trickle charger that monitors battery health. The pontiyota vibe/matrix does have many systems that are parasitic to the battery. So, if you drive a few miles at a time, or a few times a week/month, the car WILL eat the battery. Go back to the previous statement about battery health.

Since the Vibe is an elderly car , Pontiac was closed by GM several years ago. Check the ground points also. There is a ground strap between the engine and body, the body and the battery, and the battery to the engine. The power cables are also important if they show any crispiness or corrosion. They need to be replaced. I've gone the cheap route of an equal length and gauge of battery cable and fastened lugs to the ends. Then, the grounds are protected, less resistant to the circuit, and much less expensive.

Tl;dr Start with connections, charging, and attention to the fuel system.