. I'm pretty sure that fuel system is now ruled out (Carbs, muck, fuel flow etc etc). The rest of the iginition is new, and I now have an as new distributor fitted. 
BTW, anyone tried MSD ignition systems?
C.D. Unit Breakdown - Change to MSD??
Moderators: hot66, impmad2000, Barry, Viv_Surby, Derek, Mike Usiskin
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Barry
- Nurse, I think I need some assistance
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C.D. Unit Breakdown - Change to MSD??
Has anyone had a C.D. Unit fail, if so, do they tend simply to completely die, or do they break down bit by bit? I'm getting a heavy missfire that starts around 2700 rpm, and won't allow the engine to pass 3200 rpm . I'm pretty sure that fuel system is now ruled out (Carbs, muck, fuel flow etc etc). The rest of the iginition is new, and I now have an as new distributor fitted.
BTW, anyone tried MSD ignition systems?
. I'm pretty sure that fuel system is now ruled out (Carbs, muck, fuel flow etc etc). The rest of the iginition is new, and I now have an as new distributor fitted. BTW, anyone tried MSD ignition systems?
Last edited by Barry on Sun Nov 21, 2004 5:39 pm, edited 1 time in total.
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drummerboytom
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I would be suprised if it is your c-d unit from what you've said ( see reply to your p.m ) , but it is only a twenty minute job to change it .
If you can borrow a "known good" unit it could rule out ( or confirm ) the spark-box as the culprit before you splash the cash on M.S.D.
Any friendly early 911 owners near Barry brave enough for a transplant .....?
If you can borrow a "known good" unit it could rule out ( or confirm ) the spark-box as the culprit before you splash the cash on M.S.D.
Any friendly early 911 owners near Barry brave enough for a transplant .....?
drummerboytom
1970 914 / 6 Irish Green
1974 914 / 4 Giallo Fly ( yellow ! )
gone to a new DDK home - 1972 911 2.4T coupe with '73 2.4T CIS motor
gone to a new home - 1970 911 T Targa
1970 914 / 6 Irish Green
1974 914 / 4 Giallo Fly ( yellow ! )
gone to a new DDK home - 1972 911 2.4T coupe with '73 2.4T CIS motor
gone to a new home - 1970 911 T Targa
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Barry
- Nurse, I think I need some assistance
- Posts: 4319
- Joined: Tue Aug 24, 2004 8:50 pm
- Location: East Sussex
Thanks chaps! Just a quick update: in view of the fact that any replacement for the C.D. unit is likely to be a) Hard to find, and b) Less than cheap, I thought I had better carry on with my investigations. Hooked king lead upto a champion plug with 1/4 inch gap (good power test for ignition): Bang! massive blue spark that could be heard across the workshop. Checked resistances on: leads, dist. cap (including springy carbon thingy), rotor arm, (all fine) then went to check plugs. These were new Bosch Platinums, but don't look it now: very carboned up. The question is are they carboned up because the engine wasn't running well, or was the engine not running well because they were carboned up? Anyway their resistances were very low (correct, like all above), nonetheless will try a new set of low tech plugs tomorrow and see how they affect the running..... Will also recheck all earths around engine and ignition units, plus power supply.
Another update, did all of above, BTW all original plugs evenly fouled, which would suggest any problem is common to all cylinders. Now have tested C.D. unit as best as pos: not too hard if you have a friend who knows how to use an oscilloscope. We were a bit limited by not having a circuit diagram, and having to test it 'static' though. It did have a poor earth, which was rectified. The unit is back on the car, with all of its triggering harness well away from the H.T. side. Aditional earth leads have been fitted between all ignition componants. Still missfire still there, so business as usual .
Now beginning to consider again simply changing the ignition to a MSD 6AL system (or equivelent), which matching coil. At least by doing this theoretically you are actually upgrading the system (therefore saving face!). Any thoughts??
Another update, did all of above, BTW all original plugs evenly fouled, which would suggest any problem is common to all cylinders. Now have tested C.D. unit as best as pos: not too hard if you have a friend who knows how to use an oscilloscope. We were a bit limited by not having a circuit diagram, and having to test it 'static' though. It did have a poor earth, which was rectified. The unit is back on the car, with all of its triggering harness well away from the H.T. side. Aditional earth leads have been fitted between all ignition componants. Still missfire still there, so business as usual
.Now beginning to consider again simply changing the ignition to a MSD 6AL system (or equivelent), which matching coil. At least by doing this theoretically you are actually upgrading the system (therefore saving face!). Any thoughts??