Ignition Amp wiring
Discussion
Little_Blue_Car said:
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.
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It seems strange that your engine is struggling to turn over after 10ish cycles - maybe your timing is massively retarded and it is effictively trying to stop the engine turning as it attempts to fire. I would be surprised if this is a result of flooding as it would require lots of fuel in the cylinders to cause a 'lock' - I'm sure you would have noticed this much excess fuel!..
I had an issue with my 2500M (I know it's different but the principles are the same!) where it would only attempt to fire when I stopped cranking the engine over. It turned out to be my Lumenition system failing because of the cranking voltage drop. I replaced my Lumenition with Powerspark (nice & cheap!!!) and it sorted the problem.
It might be worth trying a cheap Powerspark system in your dissy to see what happens :-)
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.
Compression sounds on the low side but it might be a land rover engine, which is tuned for torque.
Usually with an Sdi/Vitesse/TVR engine you would be looking at 160-170 everywhere.
It will run though with that compression. Can you adjust the carb to be A LOT leaner? Maybe turn off the fuel pump and then crank it. If it start to run (and then dies due to lack of fuel) you know where the problem is.
Usually with an Sdi/Vitesse/TVR engine you would be looking at 160-170 everywhere.
It will run though with that compression. Can you adjust the carb to be A LOT leaner? Maybe turn off the fuel pump and then crank it. If it start to run (and then dies due to lack of fuel) you know where the problem is.
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.
Little_Blue_Car said:
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
How was this missed?Yes there is a big problem with the compression ratios
Ok, agreed with whoever, sorting the engine may not solve the problem but why attempt to sort an engine with a problem or a problem with an engine?
Not sure I've missed something here, but there have been several references to trying either neat fuel or easy start straight down the throat of the carb, ideally with the fuel pump disconnected. Have you actually tried this??
As Penelope says, compression is low, but not low enough not to run. Personally I wouldn't be too worried if the engine hasn't run properly for a while. When you do get it running, then bring it up to temperature and let it have a decent run which will ensure the piston rings and bores are clean and lubricated. If after a decent run compression is still low then time to investigate. I wouldn't be surprised however that compressions improve with a bit of use.
Re carb verse EFi, I'm a fan of the EFi and once you get to know it, there's actually very little to break down. Typically bad wiring faults, poor connections, coolant temperature sensor or ignition module, which isn't actually ERFI related but a HT issue.
As Penelope says, compression is low, but not low enough not to run. Personally I wouldn't be too worried if the engine hasn't run properly for a while. When you do get it running, then bring it up to temperature and let it have a decent run which will ensure the piston rings and bores are clean and lubricated. If after a decent run compression is still low then time to investigate. I wouldn't be surprised however that compressions improve with a bit of use.
Re carb verse EFi, I'm a fan of the EFi and once you get to know it, there's actually very little to break down. Typically bad wiring faults, poor connections, coolant temperature sensor or ignition module, which isn't actually ERFI related but a HT issue.
I agree with KKson.
As you have spark, and squeeze, I would have thought it can only be fuel and time of spark, as you have spit back it must be igniting at some point.
1st - Spitting back through carb I agree sounds like a timing issue. Basic quick static timing (not wanting to teach anyone how to suck eggs) Get #1 to the top check crank pulley graduation is at zero and with the dizzy cap off rotor pointing to #1 lead. If piston #1 is up the crank indicator is not in view likely it is 180 deg out.
2nd - double check HT leads firing order, in relation to rotor rotation.
3rd - As indicated the other day easy start straight into the carb no fuel lines connected (after checking 1 & 2)
If none of that works stamp your feet, and throw the dummy in the corner
As you have spark, and squeeze, I would have thought it can only be fuel and time of spark, as you have spit back it must be igniting at some point.
1st - Spitting back through carb I agree sounds like a timing issue. Basic quick static timing (not wanting to teach anyone how to suck eggs) Get #1 to the top check crank pulley graduation is at zero and with the dizzy cap off rotor pointing to #1 lead. If piston #1 is up the crank indicator is not in view likely it is 180 deg out.
2nd - double check HT leads firing order, in relation to rotor rotation.
3rd - As indicated the other day easy start straight into the carb no fuel lines connected (after checking 1 & 2)
If none of that works stamp your feet, and throw the dummy in the corner
Why don't you just put a strobe light on number 1 and get someone to crank it over? I'm presuming that you haven't removed the dissy so it shouldn't be 180 out. Then at least you can assess your ignition timing and either rule it out or investigate further as required - it's a nice quick test!
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
Little_Blue_Car said:
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
And fuel or easy start direct into the carb throat??????? Have you tried this yet?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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