WHICH COIL CAN I USE

[Lrob143]

Sorry to start a new thread, but, I could not find the answer in my search.
I'm new to this forum, but I've worked previously on MGA's, the Sprite's cousin.
I am restoring a 1959 Bugeye which we found.
The old coil is a strange piece and not functioning.
There was an external ceramic ballast resistor which needed replacement as it read 0 ohms.I replaced it with a 1.5 ohm ballast resistor.
I was shipped a new Lucas DLB 101 coil which measures about 3 ohms.
Can I bypass the ballast resistor and use this 3 ohm coil, or must I get a DLB102 which is 1.5 ohms?
Information I found online states I must use a DLB102 with the ballast resistor, but, if the coil measures 3 ohms, why can't 'I merely bypass the ballast resistor and use it?
What's the difference?
Thanks.
Larry

[Charlie Tolman]

It appears that Lucas wants 3.0 ohms in the primary ignition circuit.

Coil DLB-101 has 3.0 ohms, and is intended for use without an external ballast resistor.
Coil DLB-102 has 1.5 ohms, and is intended for use with a 1.5 to 1.6 ohm external ballast resistor.
Either coil should work well with your engine.

Sprites & Midgets did not use an external ballast resistor coil until the mid-1970s, I believe.

Charlie T.

[Lrob143]

Thanks Charlie.
Strange but this car HAS an exterior ballast resistor. Not sure why. It's been modified extensively for racing...probably the reason. I'll bypass it and use the 3.0 ohm DLB101 I think. I haven't gotten it started yet, so we'll see.

[Charlie Tolman]

There are several coils on the market, other than original Lucas units, that require an external ballast resistor. I had one several years ago, and had problems with the supplied resistor having an intermittent internal continuity issue. I tried another manufacturer's coil, which needed an external ballast resistor, and the electrical tachometer went wild. This coil had a plastic case, and it did not shield the electromagnetic radiation from the coil, which was picked-up by the tach wire.

I went back to the Lucas Sport coil, which did not need an external ballast resistor. No issues.

Charlie T.
SCCA H/P 40, Retired

[Lrob143]

I installed the new coil and it works and tests fine. But now I found there's a short in the distributor after going through some diagnostic tests. I pulled the distributor out to set the points last week and again today, but....no spark during the tests by shorting out the points.
I connected a spark plug to the coil and grounded it to the engine. Then took the wire from the distributor and when I grounded it, I had spark. The diagnostic chart indicates the distributor is shorted out.
Any ideas?
I'm thinking of replacing the distributor with an electronic Petronix.
Larry

[Charlie Tolman]

What are the steps, and conclusions, stated on the diagnostic chart ?

About the only place where the distributor points can short to ground, is the insulator that fits between the threaded electrical connection and the end of the points spring. A rare situation is that the condenser (capacitor) is shorted.

The plug should spark when the distributor points wire is removed from ground after initially being connected to ground. This the same as the points opening after initially being closed.

Charlie T.

[Lrob143]

Charlie, Here is the web page with the methodical diagnosis.

http://home.mindspring.com/~purlawson/f ... itions.pdf

See pages 4 and 5.
I was able to get a spark in Test 4 on Page 5. But when I went back to Test 2...nothing.
What do you think?

Larry

[Charlie Tolman]

My old computer / browser was not able to display the flow chart,
which did not allow me to determine the test procedures.
Maybe you can briefly describe the two test? Thanks.

Charlie T.

[Lrob143]

Charlie,
I FINALLY was able to get it started tonight!! The distributor had a ground. I installed the points and created the ground in error.
It is now running and I was able to set the timing. But since it's a race car there is no choke that I can find. And, it runs rich. I have to find the mixture adjustment which I think is on the bottom of the SU carb.
I cannot find the starter either. I've been using the solenoid on the firewall.

Here is the flow chart which I cut/pasted. See if you can make it out.
If not I can scan and send to you.

Larry

"Test 1: Remove the ignition wire from the coil’s center terminal and hold 1/8”
from the entrance to the coil while an assistant cranks the engine.
If No Spark Use a jumper wire with clips to attach a test spark plug to the coil’s center
terminal. (See Figures 1 & 2)

Test 2: Remove the distributor cap, bump engine over until points are open. Turn
ignition on and watch test plug while repeatedly shorting points with a screwdriver Spark Check cap, rotor, & points gap

If No Spark

Test 3: At the distributor, disconnect the white/black wire going to the coil. Turn
on the ignition and use a volt meter to check the voltage between the coil’s (+)
(white wire) terminal and chassis ground. 0 v
Check wiring to and from ignition switch, check the switch.
If 12 v

Test 4: Turn on the ignition and repeatedly tap the white/black wire disconnected
in Test 3 to chassis ground while watching test plug.
Spark

Test 5: Check points. File/burnish and re-gap as necessary. Repeat Test 2 Spark
Turn off ignition, mark and remove all wires from the coil.
Use a volt ohm meter to measure the resistance of the coil’s
primary and secondary windings. Primary should be apx. 3 ohms, secondary should
be several thousand ohms.
Replace coil if measurements are not correct. (See Figures 3 & 4)
If No Spark
Reconnect all wires and see if
engine will run.
Won’t Run


Test 6: Remove condenser. Repeat Test 2
No Spark
Examine ground connections inside distributor. See notes in following section.
Spark
Replace condenser and repeat Test 2
No Spark



Test 7: Check/set ignition
timing. Check and/or replace
cap, rotor, spark plugs & plug
wires. Check fuel system.
Test 6: Remove condenser. Repeat Test 2
No Spark
Examine ground connections inside distributor. See notes in following section.
Spark
Replace condenser and repeat Test 2"

[Charlie Tolman]

Glad to hear that you found the short to ground, and that the engine is running.

SU carbs have a built-in choke, by lowering the jet assembly, which is at the bottom of the carbs. There should be some mechanical linkage that runs between the bottom of the jets, which moves the jets up and down with the aid of a choke cable.

A large nut/screw surrounding the jet is used to adjust the fuel/air mixture.

Charlie T.

[Lrob143]

Thanks for the info.
I removed the radiator for restoring and there is no fan. Since it's a race car do you think I should install one?
I picked up an electric fan, but not sure if needed.

[Charlie Tolman]

Installing a fan depends on the temperature of the weather in your location.
Hot; Yes. Warm; Perhaps. Cold; Probably not.

If you live in an area with moderate temperatures, install one of the two fan blades that are normally bolted to the water pump flange. If you do a considerable amount of slow driving in traffic, then install both fan blades (each blade has two "scoops").

Usually, an electric fan is not required. However, it has the feature that it can be turned off when cruising down the road, thereby saving a little bit of gasoline.

Charlie T.