Engine Won't Crank - Battery is Good

[handypilot]

2001 Taurus

So...I've had this problem every once in a while and eventually had the battery changed couple months ago as I thought a bad battery was causing the starter relay to stick. It seemed to fix the problem at the time but now it's back. This is what happens...

I turn the ignition on and everything powers up normally. When I turn the ignition to start there's a louder "click" coming from the engine compartment and nothing happens except all the lights on the dashboard go dim and stay that way. Subsequent turnings of the ignition do nothing...not even any clicking, and the dash lights remain dim.

Also, when this happens, there's a light clicking noise coming from under the steering column...like a small relay clicking.

[intimidator]

Bad battery connections. Clean and check,your problem will go away,trust me.

[behlinla]

Agreed, probably a bad terminal connection or a corroded wire that you can't see under the insulation. Make sure you also check the connections on the starter.

The battery might also be going dead if your alternator is bad or you have a parasitic draw when the car is off.

[handypilot]

Well...the plot thickens.

I checked continuity on all the main leads coming off the battery and all was well. I then went to check the control and supply voltage on the starter relay and it seemed ok, though I didn't know what control voltage to look for (I was getting around 5V). I took the bottom cover off the main fuse box, and had my wife hold the ignition to START while checking the relay from the bottom of the fuse box.

While moving the fuse box around, with my wife holding the ignition, the starter engaged.

I put the fuse box back together and started wiggling things while my wife held the ignition to START. When I wiggled the main lead coming from the battery to the fuse box the starter engaged. I figured that the connection problem was here but I checked the continuity between the battery terminal and the main fuse (175A) while moving the wire and it was just fine. I cleaned everything up with a wire brush just in case...and it still wouldn't start...just a big "CLICK".

Then I had my wife hold the ignition to start again while I started wiggling things. I began with the main lead between the battery and the fuse box...that didn't do anything. Then I started jiggling the whole fuse box, and bam...the car turned over.

I figure something is loose in there or in the wires going into it, but I cant see anything wrong. I also checked the relay again and swapped similar relays around and everything seemed ok.

One thing to mention...with the battery hooked up there is a constant drop of 0.01V every 15-20 seconds on the battery, but with the battery disconnected the battery voltage remains constant or self-recovers slightly. Seems to be a power leak somewhere that may be contributing to the issue.

Anyone have any thoughts?
What voltages should I be looking for at the starter relay terminal?

[behlinla]

Okay, you should have a full 12V coming in on both sides of the relay (terminal 87 light green/violet wire and terminal 85 tan/red wire). If not check fuse #7.

I would also make sure you're getting a full 12V on the white/pink wire at the starter with the key in start. If you do, then the problem is getting the current to the starter and not the relay box. The wires going to the battery terminals might be loose or corroded under the insulation.

The other thing I should make clear is just because a connection has continuity doesn't mean it's good. If something is barely touching it will have continuity but will not be able to handle the current involved which will lead to an excessive voltage drop. Hence the click of the relay closing but not enough current flowing to do anything further.

Based on what you've said I'm almost certain you have a loose connection, but I'm not sure exactly where yet.

Diagram: http://www.revbase.com/BBBMotor/Wd/D...f-b8dc6269532f

Battery should not be running down that fast if the key is off. Make sure all the lights are off in the car. If the voltage drop is still that fast after 40 minutes with the car off (without touching the car), then you should put your meter in series with the battery and measure the current draw.

[handypilot]

Originally Posted by behlinla

Okay, you should have a full 12V coming in on both sides of the relay (terminal 87 light green/violet wire and terminal 85 tan/red wire). If not check fuse #7.

I would also make sure you're getting a full 12V on the white/pink wire at the starter with the key in start. If you do, then the problem is getting the current to the starter and not the relay box. The wires going to the battery terminals might be loose or corroded under the insulation.

The other thing I should make clear is just because a connection has continuity doesn't mean it's good. If something is barely touching it will have continuity but will not be able to handle the current involved which will lead to an excessive voltage drop. Hence the click of the relay closing but not enough current flowing to do anything further.

Based on what you've said I'm almost certain you have a loose connection, but I'm not sure exactly where yet.

Diagram: http://www.revbase.com/BBBMotor/Wd/D...f-b8dc6269532f

Battery should not be running down that fast if the key is off. Make sure all the lights are off in the car. If the voltage drop is still that fast after 40 minutes with the car off (without touching the car), then you should put your meter in series with the battery and measure the current draw.

Thanks behlinla. The one thing I do remember is that the volts at the relay were not 12V. Thanks for the diagram, that will help finding the source of the problem.

I'll check it out.

[handypilot]

Voltage at terminal 87 was +12V (battery voltage), but terminal 85 had precisely 10V. I also checked fuse 27 in the battery junction box and fuse 37 in the central junction box...both were good and voltage at both was 10V. So either the control voltage for the relay is suppose to be 10V or something is amiss upstream of the fuse.

I haven't checked the voltage on the WH/PK wire going to the starter but I'm sure it's fine now because things are currently working.

I'm going to mess with it more in a fews days. In the mean time...Merry Christmas!!!

[behlinla]

If the starter is cranking the engine then 10 volts is not unheard off since the battery voltage has dropped that low under load. If the starter wasn't running and you had 10 volts at fuse #37 (and the battery was still at 12V), then you might have a bad connection upstream of that fuse, perhaps at the ignition switch or one of the other fuses that provide power to #37.

[handypilot]

Update...

So far everything is starting and working ok, but I wanted to check out something with y'all...

When checking the voltage at terminal 85 for the starter relay I get 10V with the ignition switch in RUN and 12V with the ignition in START. Is the 10V normal?

I get this voltage at Fuse 237 in the Central J-box also, and I checked the transmission range sensor to see if it was working correctly and it was.

[behlinla]

When the car is in RUN, you shouldn't have any voltage on terminal 85. The only thing might be if the voltage is back feeding through the radio. Remove fuse #27 (5A) and repeat the test.