V8 fires but wont start

Cornish lad

New Member
Hi I have a rover v8 SD1 in my late stepdads TR7. It hasn't been run in over 7 years, did top end rebuild, new leads/plugs went to start no spark or oil pressure. Located the fault to dizzy ripped out old coil/dizzy/resistor fitted new coil and electronic dizzy. Ensured timing was correct before removing dizzy fitted new. When I tried to start it it sounded like it was firing across the wrong cylinders. Wipped the dizzy out did the old trick of 12mm bar with slot on a cordless drill got oil pressure up. Wipped rocker cover off, double checked I was 6 deg before TDC compression no.1 refitted dizzy rotor arm contacting no.1. It will fire but not run! Again it sounds like it's firing on the wrong cylinders! Plenty of fuel to carbs. It's doing my head in, I am a landbased engineer so know engines inside out but really miffed on this one! Checked and double checked timing, to me I would say its firing on the wrong stroke
 
Two questions. Are you sure it's No1 at TDC and not No6? It sounds like it's getting voltage from the ballast bypass wire from the starter but not the ignition switch, have you checked that?

So you just put the egg in your mouth...

Colin
 
In terms of TDC is what I am thinking? It sounds like it is firing on an off stroke not compression. When I fitted the new ignition coil I took the heavy of the 3 feeds going to the ballast resistor and used that as the feed to the coil.
 
In terms of TDC is what I am thinking? It sounds like it is firing on an off stroke not compression. When I fitted the new ignition coil I took the heavy of the 3 feeds going to the ballast resistor and used that as the feed to the coil.
can you confirm re "heavy" if you mean the heavy feed wire, then that is a problem, This wire only goes live when turning engine over and at full 12v and comes from starter motor, then goes dead (bar the ballasted voltage) once the car has started, car the reverts to ballasted feed, there are a few wire there as they take a trip through taco in the dash as well.
 
can you confirm re "heavy" if you mean the heavy feed wire, then that is a problem, This wire only goes live when turning engine over and at full 12v and comes from starter motor, then goes dead (bar the ballasted voltage) once the car has started, car the reverts to ballasted feed, there are a few wire there as they take a trip through taco in the dash as well.
Just checked and re checked timing all as it should be, made better job of spacing leads apart, fires smooth now but only when cranking. I had 2x 1mm wires going to original ballast resistor and 1x 2mm spliced off one of the 1mms. Only got switched voltage down one nothing on other, given it fires when cranking my assumption would be the supply to coil isnt consistent! Got a battery lead point in engine bay gonna run a feed from that direct to coil tmw and see if it will run.
 
Just checked and re checked timing all as it should be, made better job of spacing leads apart, fires smooth now but only when cranking. I had 2x 1mm wires going to original ballast resistor and 1x 2mm spliced off one of the 1mms. Only got switched voltage down one nothing on other, given it fires when cranking my assumption would be the supply to coil isnt consistent! Got a battery lead point in engine bay gonna run a feed from that direct to coil tmw and see if it will run.
Sounds like a newer P6 v8 (D or E versions) and wired differently to earlier ones. Disconnect the large white and yellow wire (insulate as it goes live on cranking,) connect the white and black that comes from inside the car that appears next to coil to the distributor, (not the coil) .Connect the other white and yellow (smaller wire) to the + on the coil, Connect the white and grey that comes from inside car to the Neg coil terminal. BUT! The large disconnected white and yellow wire was there to assist on starting, I do not use that wire anymore as i run a newer type starter and not required. Also need to check the required voltage for the new electronic ignition fitted.
 
Sounds like a newer P6 v8 (D or E versions) and wired differently to earlier ones. Disconnect the large white and yellow wire (insulate as it goes live on cranking,) connect the white and black that comes from inside the car that appears next to coil to the distributor, (not the coil) .Connect the other white and yellow (smaller wire) to the + on the coil, Connect the white and grey that comes from inside car to the Neg coil terminal. BUT! The large disconnected white and yellow wire was there to assist on starting, I do not use that wire anymore as i run a newer type starter and not required. Also need to check the required voltage for the new electronic ignition fitted.
Ran a 2mm cable from battery to ignition coil this morning bypassing wiring loom altogether fired up and ran sweet. My logic now is to pick up a new switched live off of ignition switch fit a relay and fuse inline to feed ignition coil and forget about the old loom.
 
Ran a 2mm cable from battery to ignition coil this morning bypassing wiring loom altogether fired up and ran sweet. My logic now is to pick up a new switched live off of ignition switch fit a relay and fuse inline to feed ignition coil and forget about the old loom.
I personally would not do that, the cars originally ran on a ballasted supply lowering the voltage, if you are going to run on 12 v permanently you could damage other items on the ignition system, hence wiring as i stated above!
 
I personally would not do that, the cars originally ran on a ballasted supply lowering the voltage, if you are going to run on 12 v permanently you could damage other items on the ignition system, hence wiring as i stated above!
My new coil is unbalanced.
 
I wouldn't relay or fuse the ignition supply you are introducing things that could fail and leave you stranded, traditionally ignition supply is unfused.
 
OK just a thought, will make life easier. Is there more than one switched supply coming off ignition switch?
Yes sort off, 1st is the ballasted supply when ignition is on,2nd is a full 12v when cranking the engine over by the starter motor
 
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