Moved Battery, got problems

Jamesl · Post by **Jamesl** » Thu Mar 23, 2006 8:06 am

Could moving the battery to the opposite end of the car -- and changing grounding points -- have an affect on performance of MegaSquirt? I'm using MSnS-Extra to control ignition on a version 2.2 board.

I made several changes to the car and now have a terrible miss and odd ignition problems. It just hit me that one of the changes was moving the battery from the engine compartment to the trunk. My ground strap for the battery runs to the body in the trunk, and then from a fender to the engine where the grounding strap originally terminated.

Could this new arrangement create some sort of ground-value separation that would adversely impact how MS does its thing?

EstateAgent · Post by **EstateAgent** » Thu Mar 23, 2006 9:33 am

Perhaps if the new power wire runs past the MS or sensitive wires (e.g VR pickup).

Maybe running an earthed shielding around the wires or new power wire could help/cure the problem. Or routing the power cable down the prop tunnel/othe side of car.

Jamesl · Post by **Jamesl** » Thu Mar 23, 2006 11:47 am

The main power wire doesn't come anywhere near MS or critical wires. I was mainly wondering if a ground-source variation could cause erratic behavior.

bleoh · Post by **bleoh** » Thu Mar 23, 2006 12:47 pm

I assume this is a uni-body so frame grouning isn't an issue.
Did the original battery location ground to the body or the engine?
If it was to the engine do you have a good ground strap from the engine to the body?

If all else fails maybe you could run a dedicated ground from where you are grounding the trunk mounted battery up to where you are grounding your MS.

Jamesl · Post by **Jamesl** » Thu Mar 23, 2006 2:33 pm

Thanks. I'm just going to put the battery back in the stock location and see if the problem goes away. I will have to redo the battery terminal connections, but it should be the easiest test to see if the battery relocation is the problem.

Fastest95PGT · Post by **Fastest95PGT** » Fri Mar 24, 2006 8:04 am

Make sure that your ground in the relocated area is a good, clean, and solid connection to the chasis. Then make sure the original battery location is grounded just as well to the chasis.

I don't recommend running a ground all the way back to the original battery location.

Jack · Post by **Jack** » Fri Mar 24, 2006 11:38 am

Fastest95PGT wrote:I don't recommend running a ground all the way back to the original battery location.

Unless it's big enough to carry the full cranking load because if it's a better ground path, it will carry more load. My TR3's choke cable did this once, because the ground strap had gotten corroded. The choke cable would glow cherry red during engine cranking. the cranking was much slower than it should have been too. Oops!

jib

Jamesl · Post by **Jamesl** » Fri Mar 24, 2006 12:55 pm

As a test, I hooked a set of long jumper cables to the negative terminal of the battery and the stock ground location on the engine. It didn't help the problem, so I'm reasonably certain it's not the battery location.

Not sure what's going on. The car seems to run fine for the first few minutes, when it's cold, but when it warms up a bit it starts missing -- with the miss getting worse the warmer the car gets.

It's an apparently random miss on all four cylinders. Watching the AFR, you can see it jumping lean -- I'm assuming that's actually the result of unburned gasoline passing thru. The injectors were recently cleaned and I have listened to each one with a stethoscope and can hear them clicking away just fine.

I've already replaced the distributor cap, rotor, plug wires and plugs, without benefit. I've borrowed a spare coil & ignitor from a fellow MR2 owner and will swap them in tonight, although the basic resitance tests indicate mine are fine. Edit: they were. No help

I'm down to clutching at straws.....

By the way, the car's been running fine for over a year now on MS. I guess it's possible something is going amiss inside the case somewhere.

bleoh · Post by **bleoh** » Tue Mar 28, 2006 10:54 am

Check the connections in your ms harness, specially the ones involving spark. Maybe all the work you were doing moving stuff around exposed a weak solder/crimp in the harness.
Brian.

Jamesl · Post by **Jamesl** » Tue Mar 28, 2006 11:49 am

Sorry, should have closed this thread. Since the battery location wasn't the issue, I started a new thread on this problem. I did have some loose/bad solders on the harness connector.