Ignition Amp wiring
Discussion
Evening all, hoping someone on here can give me a steer on the connections from the dizzy mounted amp to the coil on a rover v8?
Confession time, its not in a TVR, its not even a TVR engine...and the TVR I do own is a griff...but, it is a rover v8 in an MGB roadster and of a similar vintage to a wedge so thought this was a decent place to post a query.
A bit of context to the issue. The car sat in a dryish garage for a year having driven there under its own power. when I returned to collect it, it started and ran. over the next 500 yards things got progressively worse until it conked out and had to be recovered home.
Regarding fuel, I have swapped the fuel for fresh stuff, confirmed fuel pump is working, removed carb (weber 500) and cleaned with carb cleaners, reset floats, confirmed everything free, tipped out old fuel and reinstalled. Regarding electrics, I removed and cleaned plugs, checked cap and rotor and gave them a light rub with fine sandpaper, swapped coil, removed dizzy and turned manually to trigger spark on each plug in turn - all seems ok so assume dizzy pickup is OK.
I get an occasional backfire or pop back through the carb and have had one or two occasions where I thought it might run - few cylinders firing in succession on cranking, otherwise it is totally dead.
The one thing I can't check is the amp (aftermarket with the dizzy), but I have a spare lucas dizzy mounted unit I could swap in. due to space I can't connect the unit to the dizzy and I don't have the lead for the connection plug to the coil. I'm going to rig up some homemade wiring to see if this confirms the issue, but of the 3 pins coming from the amp, which one goes to positive and which to negative on the coil? the pins are on a bit of a limb out from the body of the amp, otherwise its a small box a little squarer than a credit card.
Thanks in advance, any guidance greatly received!
Chris
Confession time, its not in a TVR, its not even a TVR engine...and the TVR I do own is a griff...but, it is a rover v8 in an MGB roadster and of a similar vintage to a wedge so thought this was a decent place to post a query.
A bit of context to the issue. The car sat in a dryish garage for a year having driven there under its own power. when I returned to collect it, it started and ran. over the next 500 yards things got progressively worse until it conked out and had to be recovered home.
Regarding fuel, I have swapped the fuel for fresh stuff, confirmed fuel pump is working, removed carb (weber 500) and cleaned with carb cleaners, reset floats, confirmed everything free, tipped out old fuel and reinstalled. Regarding electrics, I removed and cleaned plugs, checked cap and rotor and gave them a light rub with fine sandpaper, swapped coil, removed dizzy and turned manually to trigger spark on each plug in turn - all seems ok so assume dizzy pickup is OK.
I get an occasional backfire or pop back through the carb and have had one or two occasions where I thought it might run - few cylinders firing in succession on cranking, otherwise it is totally dead.
The one thing I can't check is the amp (aftermarket with the dizzy), but I have a spare lucas dizzy mounted unit I could swap in. due to space I can't connect the unit to the dizzy and I don't have the lead for the connection plug to the coil. I'm going to rig up some homemade wiring to see if this confirms the issue, but of the 3 pins coming from the amp, which one goes to positive and which to negative on the coil? the pins are on a bit of a limb out from the body of the amp, otherwise its a small box a little squarer than a credit card.
Thanks in advance, any guidance greatly received!
Chris
Happy Easter all, wee workshop update following HT test. The spark happily jumps a >5mm gap from king lead to radiator.
Fuel pump had a dodgy earth but thats been cleaned and it pumps fuel well to the carb.
In conclusion then, I have sparks (and presumably at approx the right time because the car did run for a bit) and I have fuel.
I've disconnected and blocked all vacuum ports ( servo etc).
Still nothing but the occasional backfire or pop back up the carb and very occasionally I get a few cylinders in a row - just enough to get my hopes up!
Fuel pump had a dodgy earth but thats been cleaned and it pumps fuel well to the carb.
In conclusion then, I have sparks (and presumably at approx the right time because the car did run for a bit) and I have fuel.
I've disconnected and blocked all vacuum ports ( servo etc).
Still nothing but the occasional backfire or pop back up the carb and very occasionally I get a few cylinders in a row - just enough to get my hopes up!
I've got a couple of can of easy start on order so will give that a go. plug seems wet and on cranking I get a bit of a slow crank after a few revolutions as the fuel presumably sits there and causes a better seal. not sure the term for that? floats seemed free when I took the carb apart, although one bank of plugs was pretty back.
I know the fuel is old (about a year), but the car did run for a bit on it. I've also tried putting the fuel pump pickup in a fresh can of fuel, but no change
I know the fuel is old (about a year), but the car did run for a bit on it. I've also tried putting the fuel pump pickup in a fresh can of fuel, but no change
The carb is actually an edelbrock 1404 (weber 500). I've had it out and on the bench - one of the floats was bent and the valve sticking open flooding one bank, but I've sorted that I think. Gave it a good dose of carb cleaner. Can see the fuel from the accelerator pump being sprayed in and the plugs are wet...
Not done a specific compression check, but have turned it over with all the plugs out and it spun round quite happy, then when I put the plugs back in it struggled much more (just like it usually does when starting), so I think I have compression
Wondering if the leads and plugs are knackered? I've tested the king lead to get the spark to jump, but used another plug previously to test the dizzy. Seems odd that all magnicore leads or all plugs would expire at the same time though.
Only one way to find out I guess...
Also, is there a way to check is the main jets are blocked with the carb in situ?
Wondering if the leads and plugs are knackered? I've tested the king lead to get the spark to jump, but used another plug previously to test the dizzy. Seems odd that all magnicore leads or all plugs would expire at the same time though.
Only one way to find out I guess...
Also, is there a way to check is the main jets are blocked with the carb in situ?
Hi all, spending another few hours on the MG today. So far, taken carb off again, used air compressor to blow through everything, loaded with new clean fuel and reinstalled.
Leads have the resistance suggested, all tested with spark plug and can see the spark in all cases. all plugs tried and replaced and tried again.
Just done a compression test (cold unfortunately). cylinders 5&7 showing up lower than the others. the rest are all 125psi or thereabout, 5&7 are 100psi. Could this be the problem?
I've messed about with timing and fueling and no material change. The only thing I have noticed, after I crank it for about 10 cycles or so and the engine is struggling to turn as its getting flooded then I get a fire - i little effort that gives me hope.
I'm out of ideas now. I guess I have to choose between taking the heads off and seeing if there is a problem there or giving up and getting it off to a specialist with greater diagnostic abilities.
Leads have the resistance suggested, all tested with spark plug and can see the spark in all cases. all plugs tried and replaced and tried again.
Just done a compression test (cold unfortunately). cylinders 5&7 showing up lower than the others. the rest are all 125psi or thereabout, 5&7 are 100psi. Could this be the problem?
I've messed about with timing and fueling and no material change. The only thing I have noticed, after I crank it for about 10 cycles or so and the engine is struggling to turn as its getting flooded then I get a fire - i little effort that gives me hope.
I'm out of ideas now. I guess I have to choose between taking the heads off and seeing if there is a problem there or giving up and getting it off to a specialist with greater diagnostic abilities.
Yeah, I think I may have under thought the timing - both valves always closed at TDC! may have just mucked the timing up. Will recheck and correct as necessary.
I've check all hoses for air leaks and all seem fine (actually is just servo hose and a bunch of blanks. Inlet manifold could be leaking. Must be really bad for the engine to not even attempt to run!
I get the occasional cough and plenty of bangs and pops so there must be spark and fuel meeting somewhere.
When it died, it did die progressively, it wasn't an instant cut out.
I've check all hoses for air leaks and all seem fine (actually is just servo hose and a bunch of blanks. Inlet manifold could be leaking. Must be really bad for the engine to not even attempt to run!
I get the occasional cough and plenty of bangs and pops so there must be spark and fuel meeting somewhere.
When it died, it did die progressively, it wasn't an instant cut out.
Further reflection today (not been near the car)
I've definitely butchered the timing, but its easily restored. That's job number 1 on the list.
I'm more convinced its the carb than the sparks - sparks jumped a decent gap, and when I tested the dizzy by hand I got sparks to each plug.
I can't clean the carb any more, and its so simple I cant imagine what is causing something so totally catastrophic I can't see it. I've had a rocker cover off and the valves are moving, but the plugs didn't seem as soaked as I would have expected given the amount of cranking. Oddly the threads are soaked but the actual tip is dry - could this mean anything?
Could I have a massive inlet manifold leak? I would still think I would get some hints that it would start, that it was trying to run. Instead I just get the odd backfire and flames out the carb. I've got he old SUs in the garage I could put back on. Would need to change the inlet manifold too but that's not a problem.
I never thought I would got to EFI because I thought a carb is easier to look after, but when I bought the Griff I convinced myself all would be fine. The irony now is the Griff runs like a dream (oh that's tempting fate) and the MG won't start!
Thanks for your continued ideas.
I've definitely butchered the timing, but its easily restored. That's job number 1 on the list.
I'm more convinced its the carb than the sparks - sparks jumped a decent gap, and when I tested the dizzy by hand I got sparks to each plug.
I can't clean the carb any more, and its so simple I cant imagine what is causing something so totally catastrophic I can't see it. I've had a rocker cover off and the valves are moving, but the plugs didn't seem as soaked as I would have expected given the amount of cranking. Oddly the threads are soaked but the actual tip is dry - could this mean anything?
Could I have a massive inlet manifold leak? I would still think I would get some hints that it would start, that it was trying to run. Instead I just get the odd backfire and flames out the carb. I've got he old SUs in the garage I could put back on. Would need to change the inlet manifold too but that's not a problem.
I never thought I would got to EFI because I thought a carb is easier to look after, but when I bought the Griff I convinced myself all would be fine. The irony now is the Griff runs like a dream (oh that's tempting fate) and the MG won't start!
Thanks for your continued ideas.
Thanks for the advice guys - adding it all to the list for the weekend.
My dad has been refurbing his taimar and has my strobe up in Glasgow for the time being so I'm having to go a bit old skool regarding timing. I've had the car so long I'm confident I know where the dizzy sits when its set correctly (ie with the stobe).
I've been barking up the wrong tree with the timing itself moving I think - it was either a component failure or something else entirely. I think I've ruled out component failure by now (bob weights seem free, spark is being triggered and jumps a decent gap) so now I need to just get it all back how it was and concentrate on fuel
My dad has been refurbing his taimar and has my strobe up in Glasgow for the time being so I'm having to go a bit old skool regarding timing. I've had the car so long I'm confident I know where the dizzy sits when its set correctly (ie with the stobe).
I've been barking up the wrong tree with the timing itself moving I think - it was either a component failure or something else entirely. I think I've ruled out component failure by now (bob weights seem free, spark is being triggered and jumps a decent gap) so now I need to just get it all back how it was and concentrate on fuel
Yes, tried the easy start - no reaction although I didn't do it while cranking (needed more brave pills and an assistant - there have been some serious flames out the top of the carb!)
I also took the top off the carb and filled it with fresh fuel then tried - no obvious difference.
I'll put pouring fuel directly in on the list too
I also took the top off the carb and filled it with fresh fuel then tried - no obvious difference.
I'll put pouring fuel directly in on the list too
Afternoon all,
The problem has been identified! Not by me unfortunately - ran out of time and talent.
The skew gear on the end of the camshaft has worn down teeth to such an extent that they are failing to turn the dizzy consistently and the sparks are all over the place as a result.
Hands up if you had that as the answer!!! Its a Piper cam with about 20k on it so disappointed to find out this was the issue, but apparently so.
So - that's the diagnosis, confirmation here when its running again
The problem has been identified! Not by me unfortunately - ran out of time and talent.
The skew gear on the end of the camshaft has worn down teeth to such an extent that they are failing to turn the dizzy consistently and the sparks are all over the place as a result.
Hands up if you had that as the answer!!! Its a Piper cam with about 20k on it so disappointed to find out this was the issue, but apparently so.
So - that's the diagnosis, confirmation here when its running again
I'm back in business!
Thought I would summarise the outcome here in case anyone else stumbles across the thread in the future.
The skew gear on the end of the cam that meshes with the gear on the bottom of dizzy was virtually completely worn down - never seen anything like it. This was causing the dizzy to jump teeth and not rotate freely and evenly, firing sparks off at completely random intervals.
When that was fixed, the car would start but wouldn't rev over 2,500rpm. Suspected the dizzy itself wasnt up to it any longer (only replaced a few years ago from well marketed Rover V8 specialist). Replaced with Powerspark unit and that solved that problem.
Finally, it was reluctant to start when hot. Turns out the bosch coil resistance was too low and it was cooking the amp. Lucas sports coil switched in and now she starts with barely a crank and drives like an absolute dream. Huge thanks to Leighten at GM Autotech in Harleston, Norfolk - that guy knows his engines.
Sad news now - she's up for sale in the classifieds and may be heading for Collecting Cars soon too as I need the space.
Thanks to all who commented with suggestions, very appreciative of the community.
Chris
Thought I would summarise the outcome here in case anyone else stumbles across the thread in the future.
The skew gear on the end of the cam that meshes with the gear on the bottom of dizzy was virtually completely worn down - never seen anything like it. This was causing the dizzy to jump teeth and not rotate freely and evenly, firing sparks off at completely random intervals.
When that was fixed, the car would start but wouldn't rev over 2,500rpm. Suspected the dizzy itself wasnt up to it any longer (only replaced a few years ago from well marketed Rover V8 specialist). Replaced with Powerspark unit and that solved that problem.
Finally, it was reluctant to start when hot. Turns out the bosch coil resistance was too low and it was cooking the amp. Lucas sports coil switched in and now she starts with barely a crank and drives like an absolute dream. Huge thanks to Leighten at GM Autotech in Harleston, Norfolk - that guy knows his engines.
Sad news now - she's up for sale in the classifieds and may be heading for Collecting Cars soon too as I need the space.
Thanks to all who commented with suggestions, very appreciative of the community.
Chris
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