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TR5/TR250 No spark... again
- Thread starter mcqin
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poolboy
Yoda
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I don't think it's necessary to have a LUCAS coil, but you do need one with the proper resistance. For a 250 that would be a 3.0 ohm coil. If you do get Lucas brand the DLB 105 is probably the one I'd spring for. And if that doesn't cure the ills, it's coming from the distributor "components".
dklawson
Yoda
Offline
It would normally be unusual for a coil to fail that quickly but it could happen... particularly if the local parts store was wrong with their recommendation.
If it's a 3 Ohm coil you need, I am a big fan of Bosch Blue coils (from Brazil). There are Bosch Blues from other locations that are not as good. Jeff at Advanced Distributors was selling the Brazilian coil. It's a bit more expensive but it is epoxy filled so it doesn't leak oil and is very tough and vibration resistant.
If it's a 3 Ohm coil you need, I am a big fan of Bosch Blue coils (from Brazil). There are Bosch Blues from other locations that are not as good. Jeff at Advanced Distributors was selling the Brazilian coil. It's a bit more expensive but it is epoxy filled so it doesn't leak oil and is very tough and vibration resistant.
SASSAMON
Senior Member
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Hello All,
One new source of intermittent electrical failures to consider.
When I was starting out in the electronics industry an Engineer I was working with told me that over 90% of electrical problems were mechanical in nature. Over the years I have confirmed this observation to be true.
The most common problem has been in connections between components. This includes the connections between wires and the connectors crimped or soldered onto them.
If you find that there is an intermittent connection give the connectors a pull to see if they are attached. Many connectors have a plastic shroud that will help the connector to stay attached while there is no electrical conductivity. Poor crimps can occur from using an incorrectly sized crimp for the wire, the improper tool for the crimp or from operator error while making the crimp. Broken wires at the connector will also show up with the pull test.
Corrosion at the connectors also cause headaches. We talk about having good grounds at body connecting points but there is also corrosion to worry about at the bullet connectors and where a bare wire goes into a screw connection. Often times an electrical problem can be fixed just by undoing a connection and reconnecting, because this will break up the corrosion. On my TR3 as I was installing the wiring I used a coper based electrical dielectric grease in all connections to reduce corrosion.
A suggestion for your current problem, check the earth lead inside the distributor. This is a wire that is under the points plate that connects the points plate to the body of the distributor. This wire is flexing when the advance mechanism changes and could over time fail.
Good luck and I hope your problem is solved soon.
One new source of intermittent electrical failures to consider.
When I was starting out in the electronics industry an Engineer I was working with told me that over 90% of electrical problems were mechanical in nature. Over the years I have confirmed this observation to be true.
The most common problem has been in connections between components. This includes the connections between wires and the connectors crimped or soldered onto them.
If you find that there is an intermittent connection give the connectors a pull to see if they are attached. Many connectors have a plastic shroud that will help the connector to stay attached while there is no electrical conductivity. Poor crimps can occur from using an incorrectly sized crimp for the wire, the improper tool for the crimp or from operator error while making the crimp. Broken wires at the connector will also show up with the pull test.
Corrosion at the connectors also cause headaches. We talk about having good grounds at body connecting points but there is also corrosion to worry about at the bullet connectors and where a bare wire goes into a screw connection. Often times an electrical problem can be fixed just by undoing a connection and reconnecting, because this will break up the corrosion. On my TR3 as I was installing the wiring I used a coper based electrical dielectric grease in all connections to reduce corrosion.
A suggestion for your current problem, check the earth lead inside the distributor. This is a wire that is under the points plate that connects the points plate to the body of the distributor. This wire is flexing when the advance mechanism changes and could over time fail.
Good luck and I hope your problem is solved soon.
I've suspected that wire that connects the distributor body to below the points plate as it looks a bit ragged, but I've checked continuity several times and it seems ok. I do have a Lucas DLB 105 coil on order (ordered before I saw the note on Bosch units), so I'm going to give that a go. Thanks again for the suggestions. I'll let you know how it goes.
Geo Hahn
Yoda
Offline
Or that little wire from the coil to the distributor (White/Black on 4 cyl engines, maybe the same on a 6).
That wire can fail w/o a visible break -- losing it connectivity inside the insulation. That type of break can also be intermittent. A few moments with an ohmmeter and some wiggling will tell.
TBU_Triumph
Member
Offline
My first vote is for a break in the wire inside the distributor from the terminal block to the to the terminal on the points. My second vote is a crack in one of the insulator pieces either where the terminal block enters the distributor or in points mounting. Both are very hard to find! And the heat from a running engine could trigger either failure compared to a cold engine.
I had both and found them using an ohmmeter with the distributor out of the car. The clue was that the ohmmeter would not change reading as the points opened and closed. First it always showed continuity because of the break in the insulator because the points plate was always grounded to the distributor. After I fixed that then it would never show continuity when the points closed because of the break in the wire.
Best of luck troubleshooting!
Rusty
I had both and found them using an ohmmeter with the distributor out of the car. The clue was that the ohmmeter would not change reading as the points opened and closed. First it always showed continuity because of the break in the insulator because the points plate was always grounded to the distributor. After I fixed that then it would never show continuity when the points closed because of the break in the wire.
Best of luck troubleshooting!
Rusty
You called it Rusty! It was the wire inside the distributor connecting from the terminal block to the points. Definitely a bad wire. Whew... don't know how I missed it for so long. Thanks everybody! Now I can finally move to everything else. I'm sure I'll be back with more questions.
Thanks again, Bob
Thanks again, Bob