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Losing fuel pressure when in wot


V8 Beast

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Its the alternator. Couldnt get the battery to hold a charge. Scott and I took a spin to Advanced and they told us the flux capacitor was loose and that the voltage majiggy in the alternator wasnt charging it enough... Now I know why I ended up in 2008 instead of 1985.
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  • 1 month later...
Oh glad to see it was an easy fix. I was goin go with bad battery, bad connection or alternator.

 

I finally had a chance to do some more tests on it. The alternator is keeping the battery charged at about 13.4. I turned everything on with the engine off, then started it up minutes later. The alternator had no problem taking the battery back up from 12 to 13.4. While watching it I noticed that when the battery was freshly charged the fuel pressure was at 61. After driving around for a while and loosing some of the battery's charge the pressure dropped down to 59 (cruising and idle.. still crapping out at wot).

 

When I first purchased the battery it would stay between 14-16, now it staying between 12.8 - 13.5.. alternator still? Charging but not charging enough????

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  • 2 weeks later...
I finally had a chance to do some more tests on it. The alternator is keeping the battery charged at about 13.4. I turned everything on with the engine off, then started it up minutes later. The alternator had no problem taking the battery back up from 12 to 13.4. While watching it I noticed that when the battery was freshly charged the fuel pressure was at 61. After driving around for a while and loosing some of the battery's charge the pressure dropped down to 59 (cruising and idle.. still crapping out at wot).

 

When I first purchased the battery it would stay between 14-16, now it staying between 12.8 - 13.5.. alternator still? Charging but not charging enough????

 

did you figure this out then? Have you put a voltmeter across the battery with the engine running to see what your alternator is putting out? Should be ~14.4volts at idle.

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13.2 isnt bad. You just have extra load in the system somewhere. When we built car stereo systems back in the late 90's (god that sounds weird), we looked for 13.8 as being strong... let the caps do the hard work. Granted technology has come a long way in 10yrs, but the principals remain the same.
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When I looked at the car we didn't have a load tester, but you could watch the voltage drop off pretty quick. It acts like a really weak alternator. Just because there is voltage doesn't mean it's capable of putting out much ampereage. Amps being the capacity of the alternator, and it's ability to charge.

 

Brian, I don't see the point in the voltage booster because a properly working charging system will increase output on demand. In my opinion if you have a quality alternator, and a high output battery is all you should ever need.

When you are at the track or where ever, do you run the bottle heater, stereo, other electrical stuff while the car is off? I know you'd had battery problems, and having a discharged battery will cause the charging system to go to it's max output trying to recharge the battery. This causes the alternator to get hot, build up carbon, and burn the brushes inside the alternator. These are things that keep it from having much amp capacity. The battery and the alternator work together to keep each other alive, this is why I have an Optima battery and OEM alternator in my car. The Optima isn't just a name, it has one of the highest reserve capacities and ability to hold a charge of any battery you can get.

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Its 13.2. I'm getting this to see if it helps http://www.speedinc.com/cont.cfm?cid=C0000096

I had one and a freind in cleveland had one. Mine lasted about a year, then I had really low voltage all the time. Took it off and it all went back to normal. waste of money IMHO

Not sure how long the one in my freinds car lasted but it did the same thing to him. He was the one that put me on to taking it off.

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did you figure this out then? Have you put a voltmeter across the battery with the engine running to see what your alternator is putting out? Should be ~14.4volts at idle.

 

IMHO this tells you nothing.

If the load on the system exceeds the output of the alternator the voltage can read low while the charging system is working as designed.

You need to measure the load using a clamp on amp meter after the alternator and after the battery.

Have you tried a different battery?

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IMHO this tells you nothing.

If the load on the system exceeds the output of the alternator the voltage can read low while the charging system is working as designed.

You need to measure the load using a clamp on amp meter after the alternator and after the battery.

Have you tried a different battery?

 

Just had the battery recharged and tested, Came back with no issues at all.

 

So the alternator does charge, Its a little low at idle but when I turn everything in the car on it jumps to 13.7

 

When I hit the gas the fuel pressure drops but none of the lights in the car flicker or dim. If I was really losing power I would see it in more than just the fuel pressure.

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