V8 rebuilt no spark

General Chat About Electrics, And Ignition Systems.

Moderator: phpBB2 - Administrators

ricey30
Newbie
Newbie
Posts: 16
Joined: Fri Dec 22, 2017 4:27 pm
Location: Chessington

V8 rebuilt no spark

Post by ricey30 »

Hi all

In process of mgb v8 conversion...

Finally got the 3.9 engine in and all set up but having a problem with intermittent spark so cant get it to start. Running on carb with standard electronic dizzy with side module.

It cranks over no problem
I checked the TDC 3 degrees before TDC on number 1 on BOTH revolutions of the crank, and found originally I had the dizzy at No1 when both valves were just closed and starting to rock. Whereas on the other revolution both valves where shut and had no immediate movement as I passed through the TDC 3 deg.

I picked the second option of TDC.... was this right?

with the first option of TDC, I did get a loud bang out of the left right hand bank (with No8 cyl)

When it didn't start I swapped to the second set up of TDC and checked with a spark indicator fitted between the lead and the plug and on initial turn of the key I got a flash for two times on plug number 2 that I had the indicator connected to,and then that was it, no more spark.

It seems that when the ignition is turned off and then turned on again and cranked a get a spark once maybe twice and thats it.

The coil is new but the dizzy with the module bolted to the side came with the engine.

I have the white/green from the loom to the +, then the red from the module on the dizzy to the +, then the white black form the loom to the - along with the white from the module.

One other element is the new starter fitted has the white/brown and white/green jumped together onto the ignition live connection together....is this wrong?

checked for fuel, no issues there and squirted carb cleaner down 1404 but no life.


Any pointers greatly appreciated sorry such Ann rssay



User avatar
Rossco
Moderator Gold
Moderator Gold
Posts: 850
Joined: Sun Nov 19, 2006 11:33 am
Location: Too many to even keep count

Post by Rossco »

I'm probably way off the mark with this.

If you set the gap on the dizzy using a ferrous feeler gauge you can kill the pick-up mounted on the base plate, a non ferrous feeler gauge is needed.

Only remedy if this has happened is to replace the base plate and pick-up assy.

Apologies if I'm off the mark with this but I rarely play with Rover ignitions these days.

User avatar
ChrisJC
Top Dog
Top Dog
Posts: 5039
Joined: Mon Nov 20, 2006 1:13 pm
Location: Northants / Cambs
Contact:

Post by ChrisJC »

I don't know how the ignition interfaces with the fuel injection system, but I do know a bit about the ignition.
Is it a 2 pin ignition amplifier? If it is,
Image
The white/black is coil negative and rev counter. This probably feeds the fuel injection system. The white is the +12V ignition feed and coil positive.

The 3 pin ignition amplifiers have a different connector, but I believe the 3rd pin is just a screen and isn't needed to make it run.

Make sure you have the right coil - I have always used the Bosch ones with the brown turret. Bullshit fancy named ones designed for points ignition aren't worth it. Just get a standard Range Rover one.

Chris.
--
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8

ricey30
Newbie
Newbie
Posts: 16
Joined: Fri Dec 22, 2017 4:27 pm
Location: Chessington

Post by ricey30 »

thanks guys quick update

I sorted the starter motor wiring, the white/green does go to the coil and does connect to the cold start lug on the new starter.

now going to check the Lucas 198 coil that is new is actually doing the job its should.

the 35ldm8 dizzy is a 3 pin module mounted on the side. I have used a 2 wire conversion cable to connect to the coil so + and - appear to be correct

I am running a carb set up so no injection to worry about

I have left the middle pin unconnected to earth....

the fact i get 2 sparks at any plug when I first start cranking, whcih then fade to nothing, makes me wonder if the dizzy and module have had it and need replacing???

thoughts?

DaveEFI
Gold Member
Gold Member
Posts: 4603
Joined: Fri Feb 26, 2010 4:27 pm
Location: SW London, UK

Post by DaveEFI »

Amp failure isn't unknown. I used to carry a spare in my SD1. But easy enough to change. The VR sensor is pretty reliable, though.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y

ricey30
Newbie
Newbie
Posts: 16
Joined: Fri Dec 22, 2017 4:27 pm
Location: Chessington

Post by ricey30 »

Hi all

checked coil for spark with king lead attached to spare plug. on cranking I get 2 -3 tiny sparks then dies.

on disconnecting the - side of the coil that goes to the dizzy, and using a fly lead to touch against good earth in its place I get decent sparks, which leads me to believe the coil is good.

I tried a couple of tests on the dizzy to see if I got a on/off output on the - wire coming from the module to the coil and the + of the coil, but I just got a steady 13v dc, and when I tried to rotate the rotor arm against the advance mech of the dizzy to induce the fluctuation of the signal, the rotor wouldn't budge it just clicked like a switch about 3 degrees and then clicked back.

secondly i tried measuring for a resistance in ohms across the two outer terminals on the module and this showed an open circuit?

Does this sound like just put a new dizzy in? I have absolutely no knowledge of the one that came from the donor, it could be 150K old!

Any thoughts greatly recieved

Merry xmas

DEVONMAN
Top Dog
Top Dog
Posts: 1440
Joined: Sat Dec 13, 2008 2:46 pm
Location: Croydon UK

Post by DEVONMAN »

From what you have described, the fault would seem to be a duff module on the side of the distributor. No too expensive.

Put a couple of drops of oil into the shaft under the rotor. The expanding weights will not move smoothly if the shaft is seizing slightly.
1950 A40 Devon Hotrod with 5.0 twin turbo RV8.
EDIS8 wasted spark, Holley Injection.
Been as far as the Moon and back in 57 years of driving. Same Car, 5 engine upgrades !!!


Image

ricey30
Newbie
Newbie
Posts: 16
Joined: Fri Dec 22, 2017 4:27 pm
Location: Chessington

Post by ricey30 »

Guys thanks for the responses on xmas eve.

I am going to bite the bullet and buy a new dizzy from Powerspark in Bromsgrove (simonbbc.com)

Has anybody used these before?

DaveEFI
Gold Member
Gold Member
Posts: 4603
Joined: Fri Feb 26, 2010 4:27 pm
Location: SW London, UK

Post by DaveEFI »

I've read many reports of these not being as well made/reliable as the original. Unless the old is worn, I'd stick with it. Try a new amp first.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y

ricey30
Newbie
Newbie
Posts: 16
Joined: Fri Dec 22, 2017 4:27 pm
Location: Chessington

Post by ricey30 »

Hi Dave

Thanks for that I will grab a new module and pullit apart innext few days thanks for your input I’ll feed back the end result cheers

User avatar
ChrisJC
Top Dog
Top Dog
Posts: 5039
Joined: Mon Nov 20, 2006 1:13 pm
Location: Northants / Cambs
Contact:

Post by ChrisJC »

Also check the gap between the reluctor (spider shaped thing on the shaft) and the pickup. You need a brass feeler gauge. It's 15 thou from memory.
If the gap is too big, you won't get a spark. This can be caused by a distributor shaft being wobbly in the distributor body.

Also check that the rotor arm is pointing at one of the exit connections at the instant you expect a spark. Otherwise you might be having a spark getting onto the rotor arm, but with nowhere to go!

Chris.
--
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8

DaveEFI
Gold Member
Gold Member
Posts: 4603
Joined: Fri Feb 26, 2010 4:27 pm
Location: SW London, UK

Post by DaveEFI »

IIRC, reluctor gap is 0.006in/0.15mm. Says to use a brass or plastic gauge.

0.015in was the old points setting.

Obviously check all of the distributor for side play. Unless it's very worn, it will be negligible.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y

unstable load
Top Dog
Top Dog
Posts: 1278
Joined: Mon May 04, 2009 6:53 am

Post by unstable load »

DaveEFI wrote:Says to use a brass or plastic gauge.
Is this because brass isn't conductive?? 8) :?
Cheers,
John

DaveEFI
Gold Member
Gold Member
Posts: 4603
Joined: Fri Feb 26, 2010 4:27 pm
Location: SW London, UK

Post by DaveEFI »

Think it's to do with being magnetic. If you used a steel gauge which had become magnetised I suppose there's the possibility of transferring that?

As it happens, I had an old magneto service set of gauges which are brass, so used those to check the gap. Which was OK. You could check yours using layers of paper or whatever - then measure that? Unless someone has played with it, it will likely be fine. I doubt it's super critical.

The VR sensor on EDIS works over a wide range, 0.5-1.5mm
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y

ricey30
Newbie
Newbie
Posts: 16
Joined: Fri Dec 22, 2017 4:27 pm
Location: Chessington

Post by ricey30 »

Thanks for the points to try out. I’m away until new year but have got
New Lucas module and New pick up base from rimmers. Plus I def need a continuous 12v as the old Mgb loom def has a resistance wire built into it.

I’ll do this sbcheck the gaps etc then report back hopefully with a result in a few days cheers all

Post Reply

Return to “Electrical & Ignition Area”