gumby240 Posted May 1, 2009 Share Posted May 1, 2009 Hey how much voltage does ms need during cranking ? I am wondering if my battery is just to low during cranking to fire up the car. Quote Link to comment Share on other sites More sharing options...
mikeatrpi Posted May 1, 2009 Share Posted May 1, 2009 Are you seeing resets in megatune while cranking? Ensure that your chosen switched supply is powered while cranking, first of all. Assuming it is - sometimes on my car the voltage dips to around 9v, which is low enough for the relay to trip itself and cut power to the MS briefly. I was thinking of adding a large cap or buying a relay with a lower active voltage, but it hasn't been a huge problem for me so I'm inclined to leave it alone. Quote Link to comment Share on other sites More sharing options...
gumby240 Posted May 1, 2009 Author Share Posted May 1, 2009 Yes it has power while cranking but i noticed that the volt meter was dropping to 8 volts when i went to start it & also noticed that megatune would go from saying "battery ok " to "battery low" Quote Link to comment Share on other sites More sharing options...
mobythevan Posted May 4, 2009 Share Posted May 4, 2009 Low batteries lead to all kinds of weird problems with megasquirt, make sure it is a good battery and fully charged. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted May 6, 2009 Share Posted May 6, 2009 MS needs about 7 volts as a min. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 6, 2009 Share Posted May 6, 2009 Low battery voltage causes problems in ALL ECU's. It was the primary reason for the redesign of the ECCS after 1981. The 81's are especially susceptible to frying the ECU if the battery dips much below 9.6VDC during cranking. It's why Nissan went with the gear reduction starter on the Turbo Models! If you don't have a GR starter, you might consider it to drop your cranking draw... Quote Link to comment Share on other sites More sharing options...
gumby240 Posted May 6, 2009 Author Share Posted May 6, 2009 Well I do have a gear reduction starter but I also thought about wiring up a relay for the starter , wouldn't that help cut some of the voltage drop & amp draw? Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted May 6, 2009 Share Posted May 6, 2009 "I am wondering if my battery is just to low during cranking to fire up the car" Don't wonder, MEASURE IT. Measure the battery directly with a real volt meter and see what the real voltage is during cranking. No sense in re-wiring stuff or changing out starters because that will never "fix" a weak battery. You could save yourself some time/money/confusion if you test the battery first. Next you might also check all the ground wiring since a even a great battery and a good +13V won't deliver enough power to something without a clean ground connection. Quote Link to comment Share on other sites More sharing options...
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