voltage issue

dcletten · Post by **dcletten** » Sun Jun 12, 2011 1:05 pm

i seem to be having an issue that has been bugging me for the last couple months since ive got my car back on the road. car ran perfectly fine before i tore it down(tuned by topmountgsr, thanks buddy

). the only reason i tore it down was to clean up some wiring(note i did not touch any alt wiring) and paint my bay. anyways, i noticed the other day that the voltage my battery sees, and the voltage that ectune is seeing is way off. say 1.5-2v just now running in the garage, it idles at say 16-18 sometimes even 20s at sub 500ish rpm. but with voltmeter on batt it reads ~14v but ectune is only seeing 12ish. even when its off i see only 10-11v in ectune and mid 12s at the batt. ive cleaned up all my grounds 4-5 times thinking the paint had something to do with it. tried looking for good alt info to check my wiring but cant. eld has been disabled but i am still seeing eld voltage(not sure if thats correct or not). i really think this is my whole issue i just cant seem to pinpoint where. if anyone has any suggestions please let me know because im about to blow this bitch up. :-/

dcletten · Post by **dcletten** » Sun Jun 12, 2011 4:05 pm

ok, ran some more tests today, narrowed it down to whatever is feeding my main relay, sometimes ill get proper voltage at terminal 1 on the relay, sometimes i wont. but as far as i knew, it goes, battery, to main pgmfi fuse, ecu fuse, to the relay. could this be affected by my ignition switch? or is this possible that the main relay could be giving me this issue? i know they go out, and mine does act up every once in a while, but give it a couple seconds and itll click my fuel pump like normal if it helps, i litterally, had the issue, turned the key off, turned it back on and it wasnt there, cruised for a good 30 min fine, blew the plate gasket to the iac(how thats even possible i dont know) so it started to get warm, turned it off, then when i restarted it the issue was back.

Bindegal · Post by **Bindegal** » Mon Jun 13, 2011 7:48 am

Ensure all ground connections are perfect. That goes for the wires themselves (if in doubt replace) as well as where they go. I have solved the weirdest electrical problems this way during the years

The most interesting one by far was a customer with a car that was seemingly perfect everywhere, yet voltages and temperatures were all over the place, misfires, ECU reboots, the works. Well, turned out the head had been painted - causing a bad electrical connection to the thermostat housing where the ECU ground wires are connected

/Allan

dcletten · Post by **dcletten** » Mon Jun 13, 2011 10:12 am

yea this is definatly the last time im painting anything. caused me more headaches than i ever wanted. im still gonna buy a new main relay, today, then i guess redo the thermostat ground. i checked the relay yesterday, one second i would ohm out, then id kinda tap it on my battery, n would read 10ohms, then it would slowly drop, sometimes an unstable ohm reading. is that where that relay grounds through? was thinking of just cutting and rerunning those grounds directly to the batt

Bindegal · Post by **Bindegal** » Mon Jun 13, 2011 11:16 am

You want the ECU ground to end at the engine somehow, not the battery - for the sake of not offsetting the voltage measured at various sensors when there is a current draw. Addiitionally.. Engine needs both of the big chassis ground connections to ensure reliable operation. From memory thereÂ´s usually one at the gearbox and one at the valve cover. /Allan

dcletten · Post by **dcletten** » Mon Jun 13, 2011 9:21 pm

well, not totally convinced its gone yet, but i changed the main relay, and went ground happy and threw a 4g from trans to chassis, and 6g for vc ground and ran a 6g from the thermo housing to trans ground. took it for a cruise, bout an hour and no issues \"knock on wood\" so hopefully its gone but not totally sure. thanks for your help