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Oooops, I jump started my 928-help!

Old 03-21-2019, 04:34 PM
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Location: Prescott AZ
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Default Oooops, I jump started my 928-help!

In the back of my mind I knew I shouldn’t do it. I knew I should pull the battery. But I was late so I jumped my 928 using the post/strut mount.
Now it’ll turn over, it’ll pop once or twice, but it will not start. All the lights on the dash are on and they will not go out until the key off. I don’t think I’ve ever really seen all the lights on the dash on before.
The 928 has been great for the past 4-5 years. I’ve put maybe 8,000 on it since it’s Resurrection.
In fact, I was going to do the timing belt just for something to do with it.
Dual exhaust, Porken, rebuilt Maf, new injectors etc.
Im worried I fried the computer, but hopefully someone may have done the same and found a different solution.
Quick research showed that if all the dash lights are on, it could be a box? under the drivers left foot rest?
any ideas is very much appreciated!
I am so sad right now,
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Old 03-21-2019, 04:51 PM
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take out the battery and charge it properly with a 6 amp charger for 4 hours.
Install it make sure the ground connection and the terminals are clean,
Hold your foot to the floor till it starts then let it up
report what you find after you start the engine
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Old 03-21-2019, 04:52 PM
James Bailey
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Given that you have an 85 model it is quite possible that you fried the brain.....the most common fault seems to be the loss of the signal to turn on the fuel pump. AS A TEST you could supply 12 volts directly to the fuel pump and try starting the car but note that with the pump running all the time you can fill a cylinder with fuel and possibly hydraulic the engine. It was a common hack for "mechanics" to jumper the pump on the fuse board to make the car run and get it out of their shop........
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Old 03-21-2019, 05:50 PM
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Having all the lights turn on before the car starts is completely normal. the intent is to give the driver visibility to check that all lights work. If you have one that doesn't light it is a sign that the bulb may be out or the system isn't functioning correctly. the bulbs should extinguish after start up, unless it sees a fault then the corresponding light should stay illuminated.
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Old 03-21-2019, 07:08 PM
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please follow the advice I posted then report what you find.
Since your starting a dead battery with a jump,
the options for failure are a few.

Get back to a good battery state and see if it will start and run with your foot to the floor to clear the plugs,
NOTE since you have the Porken chips it needs to run to hot temps before you shut it off or it can foul the plugs.
the lamps being on with a turn of the key is a normal state till the engine starts ,
Once the alternator is online the warning lamps will go out.
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