Voltage drop through floor when cranking
Thread Starter
Joined: Jul 2010
Posts: 1,768
Likes: 22
From: Nashville / Tampa
Voltage drop through floor when cranking I generally try to bump older semi-relevant threads when possible but there are potentially lots of variables here and that approach could get confusing.
Anyway, when I crank the car to start the voltage drops like a rock then it's 50/50 that it'll come back then start. Battery is new, checked and charged. Once the car gets going the alternator keeps things above 14v, but getting it started is the hard part.
Here is a video of what is going on, voltage is top right gauge. Is there a general sort of thing that usually causes this? It's been going on for a while but this is the first chance I've had to try to fix it.
Anyway, when I crank the car to start the voltage drops like a rock then it's 50/50 that it'll come back then start. Battery is new, checked and charged. Once the car gets going the alternator keeps things above 14v, but getting it started is the hard part.
Here is a video of what is going on, voltage is top right gauge. Is there a general sort of thing that usually causes this? It's been going on for a while but this is the first chance I've had to try to fix it.
Thread Starter
Joined: Jul 2010
Posts: 1,768
Likes: 22
From: Nashville / Tampa
Compression checked out okay when the motor was put together, tune is recent but that of course doesn't mean perfect.
The battery cables are short and good quality (I took them from a newesh wrecked BMW that had the battery in the trunk but am using 2 feet of it instead of 20). I had planned on replacing both it and the grounds anyway. Perhaps the starter is going bad, I can try and replace it tomorrow. The guy I had tune it is left town for a couple weeks but I'm going to have him check it out again next time I get into town.
The battery cables are short and good quality (I took them from a newesh wrecked BMW that had the battery in the trunk but am using 2 feet of it instead of 20). I had planned on replacing both it and the grounds anyway. Perhaps the starter is going bad, I can try and replace it tomorrow. The guy I had tune it is left town for a couple weeks but I'm going to have him check it out again next time I get into town.
Yours sounds more like a timing issue, but here is what I ran into.
The voltage meter is reading the voltage as is seen on the dash board, not at the starter itself. If the wiring going from the dash (ignition switch) to the solenoid is small, you will get what you (and I) were/are getting. There isn't enough voltage amperage to activate the solenoid correctly.
I added a relay before the solenoid. The solenoid wire now goes to activate the relay. I ran a larger wire into the relay and from the relay to the solenoid. The car turns over faster and there is no drop anymore. Not sure if it will work for you or not.
The voltage meter is reading the voltage as is seen on the dash board, not at the starter itself. If the wiring going from the dash (ignition switch) to the solenoid is small, you will get what you (and I) were/are getting. There isn't enough voltage amperage to activate the solenoid correctly.
I added a relay before the solenoid. The solenoid wire now goes to activate the relay. I ran a larger wire into the relay and from the relay to the solenoid. The car turns over faster and there is no drop anymore. Not sure if it will work for you or not.
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Verdad Gallardo I just stated what fixed the same situation in my car. You are not supplying enough voltage to the starter solenoid. Try running the starter solenoid off a relay instead of directly from the ignition switch.