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Discussion Starter #1
I've got a Motronic Spider that requires 11+Volts to start but with a new fully charged battery I'm only getting 10.5V. I've looked at and cleaned the terminal ends and while the positive clamp is corroded on the outside it appears clean on the inside.I'm wondering if that external corrosion could extend to the cable coming into the clamp. Its the original pressed on clamps so I can't tell.

Another possibility is the starter/solenoid is part of the problem but I'm not sure how to diagnose this. In addition the problem first reared its head while driving so it doesn't seem likely.

A third possibility would be the cable running from the starter to the trunk but an external examination didn't show any obvious problems.

I've also cleaned the ground near the battery.

Any good ways to diagnose the problem?

Mitch
Denver, CO
 

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Many auto parts stores will do a free battery load & starter draw test. (If needed, they hope to sell you a new battery). Once you are sure all the connections in the battery to starter circuit are 100% clean & tight this would be my next step. It won't be the first time I've seen a new battery be defective. Did you also do the ones at the starter motor itself? And the ground strap between the bell housing & transmission tunnel - under the car?
 

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But Mad North-Northwest
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You're seeing 10.5V where: on the gauge? Is this with just ignition on or during cranking?

The gauge is switched power and will include the voltage drop across the ignition switch, which can be significant. So just because it's showing <11 during cranking doesn't mean the computer is seeing <11V

What exactly happened while you were driving and what are the symptoms now?
 

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Discussion Starter #5
Its on my VOM which has a Min/Max capability.

I was pulling up to the house and coasting in neutral and the car start stumbling and then died (great timing). I originally thought it was the coil but that wasn't it. I've got spark and if I jump the fuel pump I can hear it run. I've checked the red stripe relay and despite an incorrect ohm reading it actually works when I apply voltage directly.
 

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I agree with Tom - a dash gauge is not wired for proper testing of system voltage during cranking. Connect a voltmeter directly to the battery. A fully charged lead/acid battery should show 12.6V. 12.3V is half charged. Then see what it reads during cranking.

I've had a (new) motorcycle battery that'd short out internally when going over a bump. The engine would die and then sometimes re-start and sometimes not - I assume depending on whether the internal fault remained or not.
 

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But Mad North-Northwest
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Well, if you've got spark then the Motronic computer is working, right? So it's not low voltage causing the Motronic to not start up, I think.

Where and when are you measuring the 10.5V? Is the fuel pump running during cranking? Is the fuse behind the Motronic aux relay good?
 

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Discussion Starter #8
I'm measuring at the battery. I've checked for voltage at the red stripe socket but I'll need to check the fuse.If I remember correctly I was getting voltage to the fuel pump and when I hot wired the pump I could hear it run.
 

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so what exactly is the problem?
car just died as you got home and now will crank over (with spark) but will not start?
that means fuel (or lack thereof)

your fuel pump works when directly jumped, correct?
But you do not know if the pumps work when cranking?

I'd confirm fuel is getting to the injector rail - remove hose at rail and have someone crank the starter...does fuel come out? (have rags at the ready to catch it)

What "fuse" do you need to check?

If fuel does not come out the hose at the fuel rail, then that's what we need to check for next.

and your battery needs to be checked by a professional: a post of yours not long ago was talking about how when you charge it, the charger reading was jumping between 0 and 6 amps.....to me that is a sure sign your battery is shorting.
 

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Discussion Starter #10
Crank, spark but no start.
The fuse behind the relay.
The battery is new and I got a new charger that works without issues.
I have checked the fuel pressure regulator but will try the fuel rail test when I get a chance.
 
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