Dizzy problems std dizzy help needed

Big woof · Post by **Big woof** » Fri Aug 09, 2013 2:24 pm

Hi there every one. I have noticed that on the rotor arms on my 3.9 litre v8 discovery has only burnt on the very edge off the arm like just the tip is making contact with the contacts in the dizzy cap. At the moment I am trying to trace a repair kit for it see if I can recondition it. Il try and upload a pic off the rotor arm. Thanks micheal [/img]

DaveEFI · Post by **DaveEFI** » Fri Aug 09, 2013 4:39 pm

The rotor arm does not touch the contacts in the cap. It wouldn't last for long if it did. There is gap which the spark jumps.

If you're getting burning there, I'd check the king lead (coil to dizzy). If that has gone high resistance (or has a poor connection at either end, corroded etc) it will take more volts to jump the gap between rotor arm and cap, which can cause what you're seeing. Not guaranteeing this is the problem, but it's something I've seen before. And easy to check.

Big woof · Post by **Big woof** » Fri Aug 09, 2013 7:38 pm

Thanks dave il have a look it has magnecor leads fitted to it at the moment that are nearly new it was doing this before the leads went on. Also after being run I am getting a weak spark for the first crank to no spark and then on the second crank it has a massive spark that could be along those lines I shall look in the morning.

DEVONMAN · Post by **DEVONMAN** » Fri Aug 09, 2013 8:21 pm

Hi Big woof,
The trailing edge of the rotor arm is designed to be opposite the posts in the dizzy cap for most of the time so it will show more burn at that point.
This is done because when the vacuum advance is operating, the firing point moves towards the leading edge of the rotor brass strip and is therefore still adjacent to a post in the cap.
So you may not have a problem with the dizzy.

Denis

Big woof · Post by **Big woof** » Fri Aug 09, 2013 9:54 pm

Thanks Dennis I'm trying to find why it isn't sparking first turn off the key but spark's on the second turn off the key when cranking. Some times it's a weak spark but then it will be a very very strong spark on the second attempt at starting the car.

DaveEFI · Post by **DaveEFI** » Fri Aug 09, 2013 10:57 pm

I don't have a dizzy any more, but several who do in the SD1 club have reported problems with modern 'Lucas' parts from Ebay, etc. Especially rotor arms and caps.

Big woof · Post by **Big woof** » Fri Aug 09, 2013 11:32 pm

I have had first hand experience of cheap parts. Fitted a replacement cap and rotor arm they was shot in 3 thousand miles. Now I'm using the cap and the arm that cam on the engine when I bought the car.
I have thought about the fitting of mega squirt or mega jolt and just do away with the dizzy all together only problem is that cost off either kit is quite high just go be able to do away with the dizz

DaveEFI · Post by **DaveEFI** » Sat Aug 10, 2013 8:34 am

Big woof wrote:I have had first hand experience of cheap parts. Fitted a replacement cap and rotor arm they was shot in 3 thousand miles. Now I'm using the cap and the arm that cam on the engine when I bought the car.
I have thought about the fitting of mega squirt or mega jolt and just do away with the dizzy all together only problem is that cost off either kit is quite high just go be able to do away with the dizz

Although I'm very much in favour of getting rid of the dizzy, it's a sledgehammer to crack a nut if you're happy with the dizzy when all is well.

What ignition system are you using? Is it one of the standard Lucas versions?

As regards the lack of spark sometimes when starting, have you checked the 12v supply to the ignition under load - ie connect a DVM to the coil plus and see what it reads on a start. And see if it differs on the next attempt.
(Don't bother doing this with the coil disconnected - you need to see the actual voltage under load.)

I had more of less the same with a near new Mallory dizzy - the cap and rotor arm burnt out. All I could find which was obviously wrong was a badly corroded connection between coil and king lead, and the king lead reading a very high resistance. Something like 100k IIRC, when it should have been under 5k. Cleaned the coil terminal and replaced the faulty parts and had no more trouble.

DEVONMAN · Post by **DEVONMAN** » Sat Aug 10, 2013 9:09 am

Big woof wrote:Thanks Dennis I'm trying to find why it isn't sparking first turn off the key but spark's on the second turn off the key when cranking. Some times it's a weak spark but then it will be a very very strong spark on the second attempt at starting the car.

Some suggestions:-
-I would check that the earth strap between the chassis and engine has good clean connections.
-Check that the ignition switch is delivering 12v to the coil/dizzy every time you turn it to the starter position. The switch could be iffy.
-On initial turn, the starter could be draining too much power and leaving insufficient for the ignition system etc.

As you have called the car Christine, you got to expect problems

Denis

Big woof · Post by **Big woof** » Sat Aug 10, 2013 9:32 am

That's true fella she is nicknamed Christine. Thing is with the car is the ignition system is a std Lucas one I replaced the ignition module and a new coil a while ago but the problems persisted. Next on the list fuel supply replaced all the fuel components like the pump/sender unit fuel pressure regulator lamba sensors fuel filter. Done a pressure test that is right i will have to see if I can find my multi meter.
When you say plus side off the coil is that both prongs on the plus side off the coil the red and black leads on the same side off the coil terminals.

The problem is also there if the car has been run and stood for 4 hours or in direct sun light there is no spark or very weak spark. But yet from clap cold it fires up stright away and from hot if it has been stood around ten minutes it also fires up. I have no clue what to do with it. Just short off buying the rpi power amp replacement and a new coil and trying it which will cost me just shy off £250 just for the two parts off the ignition system but that then does away with the Lucas amplifier. And the amp is currently in front off the head light panel.

DEVONMAN · Post by **DEVONMAN** » Sat Aug 10, 2013 11:00 am

Big woof wrote:
When you say plus side off the coil is that both prongs on the plus side off the coil the red and black leads on the same side off the coil terminals.

To test that you are getting a supply to the coil every time you turn the key to the start position just connect a test lamp to the positive terminal of the coil. A 12v bulb with one side connected to earth and the other to the coil +ve terminal will do the job. It won't tell you what the voltage is (Like a test meter) but at least you will know the ignition supply /switch is ok.
You can eliminate the rotor/dissy as likely suspects by checking to see if the spark at the king lead is ok. Pull the king lead from the dizzy cap and position the end 6mm from the rocker cover. If you are NOT getting a spark every time you crank, the cap and rotor are not the problem.

Denis

DaveEFI · Post by **DaveEFI** » Sat Aug 10, 2013 11:27 am

If an injection RV8 is hard to start after getting good and hot, it's more usually fuel evaporation (vapour lock) Will often start fine shortly after stopping, but not after a bit longer - depending on ambient temp. After it cools down things return to normal.

Mine did this with the Lucas (flapper) injection - and still does with the MegaSquirt, although not quite as badly. Often just called heat soak. For some reason, it's much worse with modern fuels - compared to what was around when my SD1 was new.

What I've done is fit a switch to run the fuel pump before starting - for about 30 seconds. Circulating the fuel seems to help. With a whiff of throttle it then starts ok. A Rover factory mod was to raise the fuel pressure when heat soak occurred, just for the start.

Big woof · Post by **Big woof** » Sat Aug 10, 2013 3:06 pm

I thought that too mate but the problem isn't fuel it's defo on the ignition side off the motor. I have stood cranked the car and I can watch the spark from no spark to very weak spark to a stronger spark switch off crank again and I can watch the spark stright away strong engine runs.
What I am thinking off if I keep the car is to replace the ignition module with rpi ignition amp as that replace's the wiring from the dizzy to the coil. Plus the wires are quite long so I can place it any where In the engine bay for cooler air. Replace the cheap pattern coil for a Bosch coil off the correct part number and try that after a run if it works then I shall be buying a mark Adams optimax chip to alter the fueling off the engine to what ever mr Adams sets the fueling to be and that should be more then the car needs on that side off things.
Just to add the car does this even if it has been stood in direct sun light for 4 hours. I just need to get to the bottom off it. Thanks all micheal

Big woof · Post by **Big woof** » Sat Aug 10, 2013 11:43 pm

The rpi power amps would any one recommend one of them I am considering the upgrade as the ignition modules are not lasting the course cheap nasty manufacturing process and just a little bit of heat seems to cause it to break down even though it has been moved to down by the head light panel to keep it cool and ment to last longer using a genuine kit.

Reading the advert from rpi is that there hand made with a lot more electronics inside to prevent heat soak and boost the power up.

sidecar · Post by **sidecar** » Sun Aug 11, 2013 6:58 am

In my humble the RPI amp is a waste of time, I'm sure that I saw an independent test of it some where and it either made no difference or the engine produced less power!

If you want a simple ignition system go for a Mallory system (not dual points though).

If you want a more tuneable system then there a few more options, MSD being one of them.