The Ignition System of the 1500 consist of the battery, coil, starter, 5DE4 distributor, spark plugs along with obviously the fuel system which is necessary to make the engine run.
The 1500 European and US version had the 45DE4 distributor. The UK continued with a points/condensor version called the 45D4 model. The 45D4 distributor models were introduced with the 1500, replacing the 25D4 model on the 1275.
The 45DE4 was another milestone in attempting to improve
emissions and performance in an ever growing stricter emission
environment. Two electronic versions existed. The original Lucas
model, called the "Opus" was used through 1979. Its main feature
was that it had the amplifier module mounted on the distributor
body. This model proved to be notorious for problems and
unreliability. In 1980 a model called the "C.E.I", standing for
"Constant Energy Ignition" was introduced . It replaced the Opus
and can be quickly identified by its having the amplifier located
remotely. Today Opus parts can not be found and even the CEI
version is difficult to find parts for however interestingly the
C.E.I. electronic subcomponent was a GMC part and can be replaced
easily. See below:
Here are several modern electronic distributor makers for the 45D4E: Pertronix II Ignitor
Ignition Date:
| Model | 1500 1975 UK only | 1500 1975-77 All other markets | 1500 1978 on Fed. US/Canada |
|---|---|---|---|
| Firing Order | 1342 | 1342 | 1342 |
| Spark Plugs | Champion N9Y | Champion N12Y | Champion N12Y |
| Plug Gap | 0.24" to 0.26" | 0.24" to 0.26" | 0.24" to 0.26" |
| Lucas Coil type | 15C6 | 15C6 | 15C6 |
| Lucas Distributor | 45D4 | 45DE4 | 45DE4 |
| Point Gap | 0.014" to 0.016" | 0.014" to 0.016" | 0.014" to 0.016" |
| Static Timing | - | N/A | N/A |
| Strobe Timing | 2 ATDC at 800 rpm | 2 ATDC at 800 rpm | 10 ATDC at 800 rpm |
Ignition Circuit: Below are the 2 core Ignition circuit layouts for the 1500.
Static Timing: Remove rocker cover and spark plugs. Adjust and set the points. Rotate the engine until piston 1 (closet the pulley wheel) is at the top of its stroke. The exhaust valve of piston 4 will be just closing and the inlet valve just opening. Turn the crankshaft until the timing mark on the crankshaft pulley is in line with the TDC pointer on the timing cover case. Slacken the distributor pinch bolts and rotate the body anti-clockwise until the points are closed. With the LT lead connected to the distributor, turn on the ignition. Connect a 12-volt lamp in parallel with the points. While the points are closed, the lamp remains off. Rotate the distributor clockwise until the lamp lights, whereupon the points will have just opened. Secure the clamp and pinch the bolt. Check that rotor arm is opposite the terminal in the distributor cap which goes to the spark plug #1. Reconnect the advance pipe, refit the distributor cap, rocker cover and spark plugs.
Strobe Timing: Follow the strobe gun instructions, Disconnect the vacume advance pipe where fitted. Set engine revs as required by adjusting the idle speed screw on the carbs and alter the timing by twisting the distributor while in position.
Using Vacum Gauge: This is a useful guide in learning what a vacum gauge can help you determine about your engine. Make Sure to go to the original site as it has important additional information.
Older distributors with breaker points have another section in the bottom half of the distributor -- this section does the job of breaking the current to the coil. The ground side of the coil is connected to the breaker points.
A cam in the center of the distributor pushes a lever connected to one of the points. Whenever the cam pushes the lever, it opens the points. This causes the coil to suddenly lose its ground, generating a high-voltage pulse.
The points also control the timing of the spark. They may have a vacuum advance or a centrifugal advance. These mechanisms advance the timing in proportion to engine load or engine speed.
Spark timing is so critical to an engine's performance that most cars don't use points. Instead, they use a sensor that tells the engine control unit (ECU) the exact position of the pistons. The engine computer then controls a transistor that opens and closes the current to the coil.
Older distributors with breaker points have another section in the bottom half of the distributor -- this section does the job of breaking the current to the coil. The ground side of the coil is connected to the breaker points.
A cam in the center of the distributor pushes a lever connected to one of the points. Whenever the cam pushes the lever, it opens the points. This causes the coil to suddenly lose its ground, generating a high-voltage pulse.
The points also control the timing of the spark. They may have a vacuum advance or a centrifugal advance. These mechanisms advance the timing in proportion to engine load or engine speed.
Spark timing is so critical to an engine's performance that most cars don't use points. Instead, they use a sensor that tells the engine control unit (ECU) the exact position of the pistons. The engine computer then controls a transistor that opens and closes the current to the coil.
The Alternator: Cick here to learn about converting your alternator to a better unit
The SU fuel pump is an impulse type of pump. That is, when power is supplied to the pump, current flows through the points and the solenoid coil. The energized coil acts on the iron disk attached to the diaphragm, pulling it and the diaphragm toward the coil. This movement of the diaphragm develops a vacuum in the pump body, which pulls fuel from the tank, through a check valve and into the body. The movement of the diaphragm also causes a shaft that is attached between it and the lower points bridge or carrier to push the carrier up, making the carrier to `throw over' and open the points. Once the points open, the flow of current through the coil is interrupted, allowing the diaphragm to be pushed back to it's original position by the volute spring, which in turn pushes the fuel in the pump body out through another check valve to the carburetors. Once the diaphragm reaches it's original position, the points carrier `throws over' to the points closed position and the whole action is repeated ñ thus the familiar tic, tic, tic sound of the pump. The pump pressure is established by the strength of the volute spring which resides between the iron disk on top of the diaphragm and the bottom of the coil. The check valves can be either a simple brass disk that held against the valve seat by combination of gravity and back pressure in the system in the case of the L, HP and LCS pumps or a plastic sheet in a valve assembly that closes against the assembly's valve seat and is held against the seat by system pressure in the case of the later AUF 300 and AZX 1300 series pumps. In both cases, the system pressure is developed on the carburetor or outlet side of the pump, so the valves act as check valves to keep fuel from flowing back to the tank.
As with anything that uses a set of points opening and closing, there is point wear, both mechanical (slight) and electrical arching (major) that eventually causes operation to deteriorate and eventually stop all together. Over the years, various methods were employed to suppress the electrical arching at the points. Originally, on the L type pumps, the only suppressor used was a swamping resistor, in the form of resistance wire wrapped around the coil and attached in parallel with it. As stronger coils that draw more current were employed, a 0.47 microfarad capacitor was added to assist the swamping resistor suppress the arching (by the way, even though it looks like an electrolytic capacitor, it is not and therefore is not polarity sensitive). With the introduction of the AUF 300 and AZX series pumps, the capacitor was replaced with a diode to work in conjunction the swamping resistor. This arrangement made the pumps polarity sensitive. All of the systems of arch suppression worked fairly well with the series of pumps they were designed for, giving the pumps a reasonable life expectancy (except the expectancy of the owners). Finally, the all electronic pumps were introduced, which replaced the points with a Hall effect circuit to control the current flow in the coil. These pumps look and operate the same as the points style pumps, complete with the familiar tic, tic, tic sound, but there is no longer any problem with point wear and the life expectancy of the pumps is now established by the life of the diaphragm and check valves.
The following are some of the more common problems with SU fuel pumps:
Instructions on repair, reassembly and adjustments of the pumps can be found in the shop manual or the Haynes manual for all of the cars. The information on the fuel pumps for the TD is in Section B.2 of the shop manual and section D.3 of the shop manual for the MGB (pre 74). In the Haynes manual for the MGBs it is in Chapter 3 sections 4 through 11. For all the other models, you will have to search your manuals for the information since I don't have the manuals for them. Repair parts for the pumps can be purchased through Moss Motors, Victoria British, or directly from Burlen Fuel.
Article written by Dave DuBois.
The starter on 1500 is the standard Lucas starter (Lucas number 25149 [s3512] starter). You can find starters looking like the Lucas starter but quality may be less then ideal. I have gone through several over the years and am now rethinking that I may go for a reduction starter. Victoria British carries a Lucas like starter for around $80, Moss carries one for $140 or a rebuilt Lucas for $210 or a reduction starter for $272.
Lucas Starter
verses Reduction starter
The typical reduction starter being used is a 1.2 HP nippondenso starter. This reduction starter replaces the Lucas number 25149 [s3512] starter, used in numerous British cars from the 1950's till 1980. It offers several clocking positions for different applications. Most are quite easy installations requiring no modification of the vehicle other than small wiring changes. However for the 1500 midget it will require a 'blind bolt installation' which is not quite as easy, but still not a problem. The same is true of the early MGB. It may also require a very slightly shorter bolt, to ensure the threads do not bottom out in the blind threaded hole.
The www.BritishStarters.com advertises their 1.2 HP nippondenso starter as "an expertly machined and modified unit that will work in the Austin Healey Sprite and MG Midget". Quote "This works in all year vehicles and in all engine sizes/configurations. This is a great starter at a fantastic price. Stronger and lighter than the original starter with no permanent modification needed to you vehicle. Bolt it on and go! We sell a bunch of these and they are always in stock"! Price is quoted at $190. This is probably the one I will end up getting.
Electrical Hook-up: The nippondenso starter has one large bolted terminal for the positive battery cable from your vehicle. There is also a second small solenoid terminal (1/4" male spade connector) which connects to the wire from your vehicle's ignition switch. You have the option to bypass this starter's solenoid for simplicity and to retain the use of your car's original external solenoid.
I purchased this and installed it during a warm spell in March. The car started up when in the past it took "ether spray" and a ton of turning the lucas starter repeatedly over and over. I am totally impressed with the advantage of the reduction starter except once I got the car started I noted that the starter didn't appear to disengage. So I pulled it and that began the problem solving story.I had noted also that there appeared to be a gap in the bell housing with the new starter inserted. I asked the person I had purchased this from and was told it was acceptable and ok to leave.
Not knowing where to get shims I contacted the actual person who creates the starter and mounting plate. He was very helpful and assisted me. First he asked if there was a shim on the old system. I replied not that I was aware of. It turned out that actually there was but it was so tight on the old lucas I thought it was part of that system.
He said that with the reduction starter the clearance distance is more critical. In checking the length that the engagement head extends I noted a fairly large difference. I was informed that the distance between the mounting surface on the bell housing and the teeth on the flywheel, meansuring from the surface area closes to the opening should be just over 1 inch. Mine was just under 3/4 of an inch and would require shims to correct.
He sent me a new head plus shim that would make up this distance so I replaced the starter head, added the shim and installed and no more disengagement problem BUT now I heard metal on metal and had to pull the started a 2nd time. The hex bolt that held the mounting plate to the starter protuded enough to be hitting the flywheel so thought if I removed shim that might have enough distance to stop hitting of flywheel against that bolt. Reinstalled and metal on metal once again but only when I engaged clutch and than afterwards it would start. Pulled starter 3rd time and was thinking that old lucas shim plus new old head of starter might do the trick and tried that. Now everything worked great.
It is so nice to jump in car, turn starter a few times and have mg fireup and away I can drive verses the old system of pop hood, spray either, start car and hope battery is charged enough to turn over and over again until fires, get out of car, close hood, get back into car.
