This is topic battery in trunk in forum Tech Talk at Northern California Ford Owners  .


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Posted by xchpstang (Member # 1206) on :
 
(Ignore the first incomplete post)
To those who have their battery in the trunk:

Did you run ground wires back to the engine block and to the frame near the washer bottle? If not, did this affect your performance? I recently installed Edelbrock heads, TFS intake, Comp Cam, BBK full lengths, off road H-pipe, Pro-M 75 meter, and MAC cold air induction. The battery had been relocated to the trunk a few weeks before. The car now runs terrible. It "wheezes" just to get to 4K RPM. When I let off the gas I hear backfiring and popping through the exhaust. The car feels like it has less power than stock. I haven't even tried full throttle because like it's running on 5 cylinders. I read at the Pro-Flow website that not running ground wires back to the engine compartment will cause this lean condition and backfiring due to the EEC not getting proper ground. Would running ground wires solve this problem and if not where should I start? Any suggestions would be appreciated before I drive the car off the cliff.
 
Posted by shade-tree (Member # 298) on :
 
I thought the ground for a trunk battery is supposed to be the frame rail closest to the trunk? Only long run should be the 'hot' wire, right up to the stock location (near the coil)?
 
Posted by xchpstang (Member # 1206) on :
 
This is exactly where I have the ground: a short wire goes from the negative terminal to the nearest frame rail in the trunk. However Pro-M tech support said this was exactly the WRONG way to do it on a fuel injected Mustang. They told me that for proper grounding of the EEC and thus proper operation of the computer I needed to run ground wires back to the original places in the engine compartment (the frame near the washer bottle and the engine block.) I am still puzzled as if this is what's causing all the mentioned woes.
 
Posted by 1sicklx (Member # 1018) on :
 
the only wire going to the front on mine is the positive, the grond is bolted to the frame... [patriot]
 
Posted by st5150 (Member # 51) on :
 
If you have a digital volt meter, load up the car electricly (run the A/C, defefroster, electric fan, ratio, headlights + high beams, ect) and measure the voltage from the point where you grounded it in the trunk to where the EEC grounds on next to the washer fluid cap. Then measure the voltage from the point where you grounded it in the trunk to where the motor grounds to the firewall. You should get almost no voltage. If you do get any significant amount of voltage, then that means the chassis has too much internal resistance and you'd probably benifit from running an extra ground strap to the front of the car. Even if you're unsure, extra ground straps can never hurt you [Smile]
 
Posted by PunkINa5.SLOW (Member # 10) on :
 
quote:
Originally posted by st5150:
Even if you're unsure, extra ground straps can never hurt you [Smile]
There is the key to your fix [Smile]

Run another ground strap

Like ST says cant do anything, but good [Smile]
 
Posted by xchpstang (Member # 1206) on :
 
Thanks for all your input guys. I'm off to my nearest hardware store to buy about 20' of 2 gauge welding cable and 20' of 10 gauge wire. I hope this solves my problem.
 
Posted by shade-tree (Member # 298) on :
 
nah that stuff is too heavy. get the silver braided cable with 'eyes' so that you can bolt it to the frame.

no need to weigh the car down with another 10-20 lbs. of welding cable!
 




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