MSD ignition problem
Discussion
Had a bit of a problem today, was out for a cruise in the Ultima, and noticed a strange knock from the rear...only slight, but then the engine started to miss and sounded like it was firing on 7. Then it got worse and worse. By this time I had turned around and headed for home. 7 miles seemed like 50!!! There was no power, engine misfiring like a b*****d. When I finally got home, stuck my head in the engine bay for a look. Popped dizzy cap off and all seemed ok, dont think its plugs or leads (1 or 2 yes, but 6+ ??)I put a multitester on the coil to measure resistance etc, and I got a circuit albeit very low resistance (002) is this normal? I didnt remove the low tension leads though... I think it could be the coil or MSD box, anyone on here any ideas? made the mistake of taking the black cover off from under the rotor arm... didnt realise it contained the magnets for the inductive sensor in the dizzy!!! had to take the whole distributor out to get them back in!! what a nightmare. Just for info, I am not getting a spark from the HT (king lead). Tomorrow I am going to see if I am getting a pulse from the low tension side when the engine is being cranked. If I am then its the coil.. If not then 
In the morning first check you still have the problem. It may be heat related which many MSD failures are and one of the reasons many mount the 6AL low down in the engine bay or inside the cockpit.
Disconnect coil low tension. Earth the negative and make/break a 12V to the positive. This should produce a spark at the king lead. If not coil is dead.
If coil OK reconnect.
Can you locate the white lead into the 6AL?
With ingition on and imobiliser disabled (if you have one) splash the white lead against earth and you should get a spark at the king lead. If not then 6AL is dead.
If you get a spark then the fault is most likely in the trigger circuit in the dizzy or the connecting wires. It may still be in the 6AL as the green purple trigger wires use a different circuit inside the 6AL than the White (Which is for a points dizzy).
Steve
Disconnect coil low tension. Earth the negative and make/break a 12V to the positive. This should produce a spark at the king lead. If not coil is dead.
If coil OK reconnect.
Can you locate the white lead into the 6AL?
With ingition on and imobiliser disabled (if you have one) splash the white lead against earth and you should get a spark at the king lead. If not then 6AL is dead.
If you get a spark then the fault is most likely in the trigger circuit in the dizzy or the connecting wires. It may still be in the 6AL as the green purple trigger wires use a different circuit inside the 6AL than the White (Which is for a points dizzy).
Steve
Hi Steve,
I thought it may be heat related, but not so sure... will check in the morning anyway. MSD unit is mounted on bulkhead at the bottom N/S. Think it may be the coil, so will run your suggested test and see.
hopefully it is the coil! if not, who can service/repair the MSD unit over here?
I thought it may be heat related, but not so sure... will check in the morning anyway. MSD unit is mounted on bulkhead at the bottom N/S. Think it may be the coil, so will run your suggested test and see.
hopefully it is the coil! if not, who can service/repair the MSD unit over here?
hi, i worked on a friends GTR that had exactly the same symptoms that you have described, he thought it may have been a fuel pump giving up. it eventually stopped the car from starting at all. turned out to be the MSD box. i suspect the thing frys in the engine bay.
Steve is it you that has a cover over the MSD, it may phil now i think of it. seems like a good idea to me , acting like a heat sink.
Dave
Steve is it you that has a cover over the MSD, it may phil now i think of it. seems like a good idea to me , acting like a heat sink.
Dave
Had a mate round today that owns a well known tuning company, he brought along a few boxes of tricks etc and checked it out, I am getting feeds to the coil and pulses from the dizzy, but no positive feed out of the MSD box. so its dead. However, he sells a 2D ecu called "Go-Tek" which is capable of running injection should I wish to change at a later date. He will supply, fit and map for £300. Unfortunately, the MSD box is sealed (and riveted) so getting in it to repair is a no go.
Had a mate round today that owns a well known tuning company, he brought along a few boxes of tricks etc and checked it out, I am getting feeds to the coil and pulses from the dizzy, but no positive feed out of the MSD box. so its dead. However, he sells a 2D ecu called "Go-Tek" which is capable of running injection should I wish to change at a later date. He will supply, fit and map for £300. Unfortunately, the MSD box is sealed (and riveted) so getting in it to repair is a no go.
not with a 750 cfm 4 barrel Holley eliot said:
the multispark function is only at low revs anyway. Once over a couple or three thousand revs it reverts to single spark mode.
True! Mine drops to single spark mode over 3,300rpm. But it does help with a smooth idle and at cruising speeds. The multiple sparks at idle assists more with the people running carbs as they tend to run richer.
Regards Dave
got the gotech system, but found that the hall effect sensor in the dizzy isnt working 
either that or I have disturbed something in my eagerness to try and repair the MSD system. So the dizzy is off at the workshop to replace the pickup with an "optical wheel" trigger, and it goes back in tomorrow for initial fire up. Then its off to the rolling road for some mapping and more importantly a power run 
either that or I have disturbed something in my eagerness to try and repair the MSD system. So the dizzy is off at the workshop to replace the pickup with an "optical wheel" trigger, and it goes back in tomorrow for initial fire up. Then its off to the rolling road for some mapping and more importantly a power run Getting there slowly...have found that the hall effect sensor has died. If anyone knows where I can get a Pertronix ML-181 unit for my Mallory dizzy (in the UK)I would be grateful. Other than that, has anyone any ideas what other hall sensor I could use in its place?? Someone told me that a Landrover uses something similar??
I would have thought any industrial / automotive spec hall sensor should do the trick (eg RS Components (rswww.com) part number 235-5706) as all you're trying to do is provide a single pulse on every rev of the dizzy). Gotech unit seems pretty flexible as to what input it'll accept, it's just trying to get the physical fit of the sensor
Summit racing seem to do the exact replacment part you're looking for (although it's in the US..is that a problem). Can Mallory maybe do a pickup?
Summit racing seem to do the exact replacment part you're looking for (although it's in the US..is that a problem). Can Mallory maybe do a pickup?
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