3.9 V8 won't start (after stupid mistake)

Hello everybody,

I made a horrible mistake.. in a rush I thought I could disconnect the battery with the headswitch installed in my car. Ofcourse that switch is placed between the postive and not negative..
So.. i've been welding on the car with battery in place.
After I was finished welding I tried to start the car.. and it started.. I drove 5meters after it shut down...
Then I started to check everything..

maybe it was flooded?
- spark plugs wet
- spark plug sparks
- changed ignition module
- changed ECU
- no fault codes (14cax)
- TPS sensor disconnect, no difference
- fuel pressure 2.5bar
- no difference with step motor disconnected
(battery, rotor, cap, cables are new)

after I was so done it with it, I did'nt try anything for a week. After this week, it started?!
2days later, same problem, it was starting, but running very poor and shut down.
Now it won't start again..

I made a log with rovergauge..



Can somebody tell me if this MAF and throtle position is correct? Or does anybody has an other idea?


It is a late 3.9 v8 cux14 (97) without lamda sensors

Is that with the engine running.. ignition on etc?
Why is the voltage so low?
Not familiar, do you have points or electronic ignition?

Your battery is knackered?

If that's the battery voltage it suggests your battery is knackered or deeply discharged.
With the engine off put a multimeter set to 20 volts DC across the battery terminals.
What reading do you get?
Start the engine - if it will. What does the multimeter read? Increase the rpm - what does the multimeter read?

This is the moment from start.

I made another one with jump cables on it.
Looks like almost no difference in enginespeed. But at the first log reaction at 163rpm and now at 150rpm, but i won't go higher.. to less rpm to start?

Volts are just continuously dropping aren't they?
I bet when it gets below a certain threshhold the fuel pump/coil/coil-packs all cease to want to play.
You've probably blown your alternator up so it isn't charging at all and the battery is so poor it just runs out of "power" to keep everything going.
I'd be replacing both the Alternator and the battery, and being a bit more careful in my wiring/connecting up in future. Good Luck!

Hi DanClarke (and others!) thanks for your reply,
but when you tyring to start the engine, it is normal that the voltage will drop +-1,5V right?

sorry, i was writinng that this was the moment from start. But is the the moment of the starter, it wont turn on

A fully charged battery should read 12.7v with nothing switched on. It should drop to approx 11v during engine cranking, before it starts running, but that figure depends on the health and charge of the battery

DanClarke said:

You've probably blown your alternator up so it isn't charging at all

Click to expand...

+1.. either rectifier or regulator.. probably rectifier … to test it:- set a DMM to AC voltage and measure battery voltage with the engine running… should be less than 15mV.. this is also called charging system ripple voltage.. a good indication of the state of the alternator … start on a large AC scale, just in case the rectifier is completely kaput..

Regulator might be kaput too, given the low output voltage … should be 14V or slightly higher…

I was busy searching the problem yesterday evening when it became dark. What made clear it had nothing to do withing the welding.. My coil / spark plug cable is losing sparks near the coil connection . Ordered new cables and coil..

ambuland said:

I was busy searching the problem yesterday evening when it became dark. What made clear it had nothing to do withing the welding.. My coil / spark plug cable is losing sparks near the coil connection . Ordered new cables and coil..

Click to expand...

And..... so now it is all fixed, but you won't tell us?

Im not to sure yet After it still didn't started. Changed the sparks because they were wet. Than it started! But the next thing I wanted to do i changing the exhaust (was waiting for 8weaks for that). But I also want to change the manifold bolts because they didn't look good to use them again. So now im waiting for that. After fitting the new exhaust I can tell if it is still starting