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I've been intermittently working on a no start problem with my 92 Spider. Knowing how important the starting voltage is I've tried to charge the battery with my old analog charger. The charging starts okay but after about a minute the amp meter goes to 0 and then back up to 6amps and then back to 0 and up again as if it was shorting out. I tried the charger on another car and it worked normally. Here is where it gets really weird. Since the battery was still under warrantee I brought it back and got a new battery in exchange. I hooked up my charger and it behaved normally. I then hooked it up and tried to start the car. The engine turned over normally but wouldn't start and the voltage during the cranking was only 11.1V. I hooked up my charger and the new battery now behaved like the old one.

I figure the heaviest load would be the starter but since it turns the engine at a normal speed I don't think that's the problem.

What else could put enough load on a battery to kill it with one 5 second attempt to start it?
 

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Generally the motronic requires 'about' 11.5V cranking to start.

I would first remove the ground cable from the battery where it bolts to the trunk floor.....clean and check the cable ends are tight and clean the metal from any paint/rust under the bolt and refit it back with some copper grease or similar.
retest cranking voltage.

btw. it is not wise on the S4 to charge the battery, with the battery still connected to the car....it can damage the 'motronic red stripe' relay.
 

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Discussion Starter #3
The terminals are clean and the battery is new. The on/off/on behavior of the charger is happening now whether the battery is connected or not and I don't know how to explain this happening to a new battery after one crank.

BTW since I couldn't get a decent ohm reading on the Bosch relay I hooked it up to a 12v source and verified that its is working.
 

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What else could put enough load on a battery to kill it with one 5 second attempt to start it?
Nothing I can think of, unless your new battery is also bad or your charger is bad.
I would forget the charger for now.

so is your battery now dead or do you still get 11.1V cranking voltage? That is not bad cranking voltage at all, not even sure if it wouldn't in fact fire up with that (even though one says 11.5v cranking is needed)

try jump starting the car with another vehicle and jump leads?
or push start it (get a couple of friends to push it)....
if it doesn't fire up with a jump start or a push start then it is something other than battery.....and we are back to "do you have spark" ?

as here, your old thread....
https://www.alfabb.com/threads/motronic-red-stripe-relay.688510/#post-8484874
 

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Discussion Starter #5
I've got spark, tested the fuel pump, checked the relays and the voltage to the relays but I know I've got to fix the battery issue before I can diagnose the problem. Your previous post has me wondering about the cables. Maybe they're corroded or their connections (starter, ground) are corroded.

BTW its not the charger since it worked fine on another car and on the new battery until after I tried to start it.
 

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Many battery chargers have overload protection and if they sense the battery is low, will charge it at a high rate, momentarily, until they sense it won't accept that charge rate, so then shut down and later try again. If you can control your battery charge rate, set it for 3A and let it charge like that for 24 hours. Then try again.
Some batteries have a static (not under load) charge that seem Ok until you try starting with them, then the load drops the charge QUICKLY to low enough not to do much of anything. Again, try a trickle charger on the battery for 24 hours to see if it will then have adequate starting power. Lead acid batteries charge differently than those in most portable devices (LI) and need a longer charge for starting power.
From my experience.
 

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I've got spark, tested the fuel pump, checked the relays and the voltage to the relays but I know I've got to fix the battery issue before I can diagnose the problem. Your previous post has me wondering about the cables. Maybe they're corroded or their connections (starter, ground) are corroded.

BTW its not the charger since it worked fine on another car and on the new battery until after I tried to start it.
if you have spark, then your cranking voltage is fine....if it were not, the ecu would not awake and you'd get nothing!
That means when you crank the starter, the tach needle jumps a bit, correct? (That is the tacymetric signal)

so we are left with no fuel (OK, could be no compression, but let's leave that for the moment!)
Your fuel pump works when jumped direct, so it is either a relay OR a break in the cable between relay and pump(s) or the pump grounds or the G107 connection between relay and pumps...I believe G107 is right near the ecu....just follow the pink/white wire from pin #87 of the fuel relay.

Exactly what relays are you using for the fuel and for the auxiliary relay....? there was a similar problem thread and it turned out he was using a similar, but not exactly correct 5 pin relay!
see here: https://www.alfabb.com/threads/spider-still-wont-start-need-help.174919/page-2#post-963069

Have you tested BOTH pumps, the in-tank one as well? Just power in-tank pump up with 12V live to the pink/white stripe wire and ground to the black terminal....nice and easy as battery is in trunk! you will hear it hum quite clearly if it is working.

yep: get those grounds clean, clean grounds can't harm anything:)
1. Battery negative lead to trunk floor - remove it, it might look good but could be rusty underneath!
2. Main ECU ground bundle on head, near injector 4
 

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Discussion Starter #8
Many battery chargers have overload protection and if they sense the battery is low, will charge it at a high rate, momentarily, until they sense it won't accept that charge rate, so then shut down and later try again. If you can control your battery charge rate, set it for 3A and let it charge like that for 24 hours. Then try again.
Some batteries have a static (not under load) charge that seem Ok until you try starting with them, then the load drops the charge QUICKLY to low enough not to do much of anything. Again, try a trickle charger on the battery for 24 hours to see if it will then have adequate starting power. Lead acid batteries charge differently than those in most portable devices (LI) and need a longer charge for starting power.
From my experience.
My 8amp charger only has 6 and 12V settings. Since the battery is new (only cranked once) it shouldn't be an issue unless the battery was damaged in that one crank.
 

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Discussion Starter #9
if you have spark, then your cranking voltage is fine....if it were not, the ecu would not awake and you'd get nothing!
That means when you crank the starter, the tach needle jumps a bit, correct? (That is the tacymetric signal)

so we are left with no fuel (OK, could be no compression, but let's leave that for the moment!)
Your fuel pump works when jumped direct, so it is either a relay OR a break in the cable between relay and pump(s) or the pump grounds or the G107 connection between relay and pumps...I believe G107 is right near the ecu....just follow the pink/white wire from pin #87 of the fuel relay.

Exactly what relays are you using for the fuel and for the auxiliary relay....? there was a similar problem thread and it turned out he was using a similar, but not exactly correct 5 pin relay!
see here: https://www.alfabb.com/threads/spider-still-wont-start-need-help.174919/page-2#post-963069

Have you tested BOTH pumps, the in-tank one as well? Just power in-tank pump up with 12V live to the pink/white stripe wire and ground to the black terminal....nice and easy as battery is in trunk! you will hear it hum quite clearly if it is working.

yep: get those grounds clean, clean grounds can't harm anything:)
1. Battery negative lead to trunk floor - remove it, it might look good but could be rusty underneath!
2. Main ECU ground bundle on head, near injector 4
The only relay I changed was the red stripe. The others all tested good.
I only jumped the main fuel pump but it should be easy enough to check the in tank pump.
I'll check the G107 connector, battery cables and grounds this weekend.
 

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Do your battery cables have any of those bolt-on repair ends? In my experience they are OK for temporary repairs but after a while there is corrosion in the bolt-on area (even though the battery clamp area itself may be clean). Also, I've had issues with those green knob battery disconnects. I use them when testing automotive electric circuits but not for regular driving.

And the advice to follow the battery ground cable to where it bolts on to the boot floor is spot-on. That location is sort of out-of-sight; out-of-mind. Another thing to check is the ground strap between the bellhousing and the transmission tunnel. Corrosion there will prevent the starter from being able to get all the electrons it needs for proper operation.
 
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