No Spark Untill I Let Go Of Key

nokia_aid · Post by **nokia_aid** » Thu Nov 07, 2013 12:47 pm

I have a rover v8 and im having trouble starting it, for some reason i dont get a spark untill i let go of the key, iv fitted a new coil and that didnt fix it and i have also tried putting 12v direct to the coil and that made no difference,

anyone have any ideas,

DaveEFI · Post by **DaveEFI** » Thu Nov 07, 2013 1:31 pm

If it has a points dizzy, it will likely have a ballast cold start system. This uses a 9 volts coil with a ballast resistor in series for normal running. When starting, the ignition switch - or starter motor - sends battery volts direct to the coil, bypassing the resistor. I'd guess the problem is in that area.

nokia_aid · Post by **nokia_aid** » Thu Nov 07, 2013 1:40 pm

yes it is an old type dizzy but i thought by putting 12v direct to the coil from an extra battery and the car still not starting this would eliminate that the coil isnt getting enough voltage and the problem must be somewhere else. or am i wrong as im new to these old engines and carbs im used to plugging a laptop into the car lol.

kiwicar · Post by **kiwicar** » Thu Nov 07, 2013 2:56 pm

Hi
Check the relay that does the switch over, then the wiring for brakes after all the loom will not be very new (30+ years?)
Best regards
Mike

DaveEFI · Post by **DaveEFI** » Thu Nov 07, 2013 3:18 pm

nokia_aid wrote:yes it is an old type dizzy but i thought by putting 12v direct to the coil from an extra battery and the car still not starting this would eliminate that the coil isnt getting enough voltage and the problem must be somewhere else. or am i wrong as im new to these old engines and carbs im used to plugging a laptop into the car lol.

If it has a 9 volt coil it may need the ballast resistor in circuit if applying the full 12v to work correctly.

You need to substitute your laptop for a DVM and do some real fault finding.

nokia_aid · Post by **nokia_aid** » Thu Nov 07, 2013 4:48 pm

yeah iv had another look and putting a second car battery earthed to the engine and the positive side to the coil the car starts right away so im tracing the coil wire back and it goes to the starter motor

nokia_aid · Post by **nokia_aid** » Thu Nov 07, 2013 5:03 pm

so is there a relay or something thats part of the starter motor that i can change or is it all built in,

DaveEFI · Post by **DaveEFI** » Thu Nov 07, 2013 5:17 pm

The circuit from the starter motor is full battery volts for when the engine is turning over. As soon as you stop the starter, it stops. The main supply to the coil should be via a ballast resistor, and that should be live all the time the ignition is on.

nokia_aid · Post by **nokia_aid** » Thu Nov 07, 2013 6:01 pm

ah right, my system is kinda home made cos the previous owner put this v8 engine in a capri, i only have 1 wire going to the coil on the + side and that was from the starter motor,

SimpleSimon · Post by **SimpleSimon** » Thu Nov 07, 2013 9:30 pm

nokia_aid wrote:ah right, my system is kinda home made cos the previous owner put this v8 engine in a capri, i only have 1 wire going to the coil on the + side and that was from the starter motor,

If its a Capri it should have a ballast wire a thick cable possibly Blue/Grey with a bullet connector at both ends unless its a MK1 Capri where it will be bound in the loom the 12v + from the starter is the usual ballast wire bypass link and this is normal

DEVONMAN · Post by **DEVONMAN** » Fri Nov 08, 2013 2:17 pm

The ignition switch will have 4 connections.
-power in from battery.
-AUX power out
-IGN power out
-STARTER power out.

The AUX power out goes dead when the starter is turning.
So, it's possible that the feed to the ignition has been connected to the AUX power out terminal and this would give no spark during cranking.

You haven't said but has this fault developed or has the v8 ever run properly in the capri?

nokia_aid · Post by **nokia_aid** » Sun Nov 10, 2013 1:19 pm

yes it was running fine untill this week, iv got it bodged for now so its all running good but i do need to sort out all the wiring at some point, headlights get brighter and duller with the revs etc so somethings not right somewhere

DaveEFI · Post by **DaveEFI** » Sun Nov 10, 2013 2:15 pm

If you have a slow idle it's not unusual for the headlights to get brighter when you rev up. The alternator may not be producing enough output at low revs.

Ian Anderson · Post by **Ian Anderson** » Sun Nov 10, 2013 5:22 pm

My guess
You have a duff battery

Only after you attached a second battery did it start

And now headlights dim and bright point towards a battery not fully charged or holding charge, that said because the lights go bright at revs points towards the alternator working ok

I would swap battery over for a known good one from another running car and try it before fiddling any further

Ian