starter problem
garyt - 9/1/16 at 01:29 PM
hi folks I need some help with this one, its an mx5 1.8 2003 motor etc, it was starting but hadn't started it for a few months went to start it
after charging the battery and its not turning over
battery is giving a healthy 12.8 v static and still reads 12.6 when key is in the cranking position
12.8 v at the hot solenoid terminal
9 - 10 v at the thin solenoid wire when key in cranking position
all other electrics working as far as I can work out
when I bridge the hot 12v terminal on the solenoid to the starter one , starter motor spins but doesn't turn engine, swapped over starter motors
for another "new" second hand one and all exactly the same........
haven't tried bumping it yet need some extra bods for that one.
any ideas or something obvious I'm missing
rusty nuts - 9/1/16 at 02:15 PM
Clean the battery terminals and leads also the main earth lead connection on both ends
obfripper - 9/1/16 at 02:44 PM
You can also put a jump lead from the battery negative to the engine block to rule out a poor earth & try cranking.
It'll start if the earth is your problem.
The 12.6v at the starter cranking is indicating there is very little current being used & it is not due to the condition of the battery.
Arced/corroded contacts inside the starter solenoid could be at fault, if you get an assistant to hold the key in crank position and bridge the 2
contacts you span the motor with before, it should crank and start.
If you're lucky the solenoid will be a servicable type, unsolder the solenoid wires from the connectors, remove the contact cap , the contacts
inside want a quick clean with some fine wet&dry to get them working again.
Dave
sprintB+ - 9/1/16 at 02:58 PM
That battery voltage is low, I'd expect at least 13.7 after a charge.
garyt - 9/1/16 at 03:14 PM
thanks guys my mates gonna try and pop round tomorrow, and we will try jumping it from a known "starting car" or / and bumping it, starting
(no pun) to lose light and its getting b'#';'#y cold out there now.
if its the solenoid contacts then why is it on both starters maybe just unlucky......
when I bridge the contacts and the starter spins should it not engage the flywheel and turn the engine?
obfripper - 9/1/16 at 03:56 PM
When you bridge the 2 main contacts you are replicating what happens internally in the solenoid after the pinion has engaged.
Because you were operating only the motor, it was still disengaged and so just spun freely.
An occasionally used starter solenoid is more likely to fail due to corrosion than an often used one, a second hand starter can be pot luck if
it's been off & unused for a while.
If your solenoid is the non servicable crimped tube type, there are replacements like MAZDA 323F MX-5 B1600 B2000 89- E2000 87-
STARTER SOLENOID SWITCH
that should be compatible and cheaper than a whole new starter.
Dave
garyt - 9/1/16 at 04:29 PM
cheers Dave, found this ont internet
"you should have battery voltage at the starter lead wires (12) and with the key in the crank position you should get battery voltage to the
small wire. make sure in neutral if a standard tranny. the 12 volts applies current to windings in the solenoid called pull in they move the metal
center to engage the hold in windings another set of wires in the solenoid and at this time the starter motor gets power and starts turning. when it
is pulled in the starter drive is engaged"
so IF I use a length of wire , ignition on and take the 12v to the wee wire it should engage and turn... right ... if it does then I need to find out
why I have a voltage drop between the key and the solenoid wee wire if it don't then its the solenoid
starting to think a handle in the front was a good idea back in the day 
britishtrident - 9/1/16 at 05:04 PM
quote:
Originally posted by sprintB+
That battery voltage is low, I'd expect at least 13.7 after a charge.
If anything the battery is overcharged.
A fully charged battery will read 12.6 to 12.7v depending on temperature it may read 12.8 v after it is taken immediately off charge but the
voltage will drop slightly as the surface charge on the plates dissipates. In a modern tintop a voltage 12.4v or so after being parked overnight
is not uncommon as low currents drawn by the cars ECUs even in sleep mode.
britishtrident - 9/1/16 at 05:09 PM
After reading through the original post I will ask the question nobody has asked ---Is the engine free to turn by hand ?
garyt - 9/1/16 at 05:46 PM
yes , should have put that , checked that one and it turns freely as expected.
Lander - 9/1/16 at 05:51 PM
If the starter motor is spinning and not engaging the flywheel then the problem is that it isn't shooting forward when activated. Remove the
starter motor and test it on the bench to see if it is moving forward when it spins, they sometimes get stuck.
Cheers,
Ian
britishtrident - 9/1/16 at 07:57 PM
This is what normally happens to battery voltage during a normal cold start when everything is is perfect condition.
Engine Starting Voltage Curve
garyt - 10/1/16 at 03:34 PM
Sorted, I checked the ignition switch voltage and it was fine on start so after running a gash line from there to the solenoid she started straight
away. After some investigating I found that I had picked up an ignition feed for the switches from ig1 wire which stays live on start this caused
enough of a voltage drop to prevent the solenoid working.
so a wee bit of rewiring and all is ok.
thanks for all the help and suggestions guys
