Diagnostics
An E-Type that will not start
Starting faults divide cleanly at the first question, and most of the wasted effort comes from skipping it. Whether the engine turns over decides which half of the car you are working on.
All series, six-cylinder and V12. Nodes that apply only to the Series 3 V12 say so. If the car starts when cold and not when hot, use the hot starting diagnosis instead.
Question
What happens when you turn the key?
Everything downstream depends on this. A car that does not turn over has an electrical or mechanical problem at the starter end. A car that turns over normally and will not fire has a spark or fuel problem. They share almost nothing, and working on the wrong half is the commonest way to waste a weekend.
Answer this
- Nothing at all, no soundGoes to: Nothing at all. What do the lights do?
- One loud click or clunk, then nothingGoes to: The solenoid is engaging, the motor is not turning
- It turns over, but slowlyGoes to: It turns over slowly. When?
- It turns over normally but does not fireGoes to: It turns over properly. Spark or fuel?
- It fires, runs for a second or two, then diesGoes to: It fires and then dies
- It starts perfectly cold, and only misbehaves when hotThat is a different fault family with its own diagnosis.
Question
Nothing at all. What do the lights do?
The question is whether the battery and its connections can deliver current, or whether current is not being asked for.
Answer this
Finding
The solenoid is engaging, the motor is not turning
Why this follows. A single loud clunk is the solenoid throwing the pinion forward. If the engine does not then turn, the solenoid has done its job and the motor has not.
What to do
- Distinguish this from rapid repeated clicking, which is a flat battery or a poor connection rather than this fault.
- Check the battery under load. A cell that collapses only under starter current gives exactly this symptom while lights stay bright.
- Check the heavy cable from battery to solenoid and from solenoid to starter, and the voltage drop across each while cranking.
- Consider a jammed pinion. On a car that has sat, the pinion can stick on its shaft.
- Consider a seized starter motor, or worn brushes and bushes.
- Rule out a seized engine before condemning the starter, by turning the engine by hand at the crankshaft pulley.
Read further: Earths, wiring and the loom
Question
It turns over slowly. When?
Answer this
Question
It turns over properly. Spark or fuel?
Petrol and sparks. Keep the plug well away from the fuel system and do not do this with fuel spilled anywhere near.
There is no point guessing between them when the test is quick. Pull a plug lead, fit a spare plug into it, rest the plug's body firmly against clean bare metal on the engine, and have somebody crank while you watch for a spark.
Do this away from the carburettors and away from any smell of petrol, and hold the lead by its insulation.
Answer this
Finding
It fires and then dies
Why this follows. Something is good enough to light the engine once and not good enough to keep it running, which usually means supply rather than absence.
What to do
- Check the fuel supply can keep up. A pump that primes the float chambers but cannot sustain flow gives exactly this.
- Check the filter and the hoses as in the delivery branch.
- Check whether the car runs on starting fluid or a primed throttle and then dies, which confirms fuel supply rather than ignition.
- Check the ballast resistor arrangement if fitted. A coil fed at the starting voltage and not at the running voltage will fire and then stop.
- Check the ignition switch itself. A worn switch can supply the start position and not the run position.
- Check for a fuel cut-off, inertia switch or aftermarket immobiliser that is cutting in.
Read further: The ignition system, Triple SU carburettors
Finding
The supply or the earth, not the starter
Confirm your car's polarity before connecting a battery, a charger or a meter. It changed during the E-Type's life and the archive has not established the exact change point, so check the car in front of you rather than assuming.
Why this follows. Lights that are dim before the starter is even asked to turn mean the current is not getting out of the battery, or not getting back to it.
What to do
- Battery condition and state of charge, tested under load rather than by resting voltage alone.
- Both battery terminals, cleaned to bright metal. Corrosion under a clamp that looks sound is common.
- The earth strap from the battery to the body.
- The separate engine to body earth strap. This is the one most often missing, corroded or painted over after a restoration, and the starter draws its return through it.
- Voltage drop across each connection while cranking is attempted, which finds a bad joint that looks perfect.
Read further: Earths, wiring and the loom, The charging system
Finding
The starter is not being asked to turn
Why this follows. Bright lights that do not dim mean the battery is capable and nothing is drawing on it, so the command is not reaching the starter.
What to do
- Check for voltage at the solenoid's small trigger terminal while somebody turns the key. If it is absent, the fault is upstream of the solenoid.
- If voltage is absent, work back through the ignition switch, the wiring to it, and any relay or immobiliser fitted later. Aftermarket immobilisers are a frequent and undocumented cause.
- If voltage is present at the trigger terminal and nothing happens, the solenoid or the starter is at fault.
- Check the solenoid's own earth and mounting.
Read further: Earths, wiring and the loom, Instruments and switches
Finding
Slow cranking in all conditions
Why this follows. Slow cranking is either too little current arriving, too much resistance in the path, or more drag in the engine than the starter was designed to overcome.
What to do
- Battery capacity and condition under load. An old battery that holds a good resting voltage can still be incapable of starter current.
- Voltage drop along the whole starter circuit while cranking, including the earth return, which is half the circuit and is usually the half that is ignored.
- Starter brushes, bushes and armature. A tired starter draws more current and turns more slowly.
- Engine oil grade. Oil far heavier than the engine wants makes cranking hard when cold.
- Ignition timing. Timing advanced too far makes the engine fight the starter and can produce a kickback rather than simple slow cranking.
Read further: The ignition system, The charging system
Question
No spark. Which engine?
The six-cylinder cars and the V12 fail in different places, so the tree divides here.
Answer this
Question
Good spark. Where does the fuel stop?
Work forwards from the tank rather than backwards from the carburettors, because the cheap checks are at the back.
Answer this
Finding
No spark, six-cylinder
Why this follows. On a points system the failure is nearly always in the low tension side, the distributor, or the path to earth, and all of it is checkable without buying anything.
What to do
- Confirm there is voltage at the coil's low tension feed with the ignition on.
- Check the points are opening and closing, and that the faces are not burnt or closed up. A points gap that has closed to nothing gives no spark at all.
- Check the condenser. A failed condenser gives no spark or a very weak one, and it is the cheapest part in the chain.
- Check the distributor cap and rotor arm for tracking. Hold the cap up to the light and look for a hairline carbon track inside it.
- Check the distributor baseplate earth, which is easy to overlook and disables the whole system when it fails.
- Check the coil, and whether the car has a ballast resistor arrangement, because a bypassed or wrongly wired ballast changes what voltage the coil should be seeing.
- Check the high tension leads and their condition. Old leads break down internally and often only when hot.
Read further: The ignition system, Earths, wiring and the loom
Finding
No spark, Series 3 V12
Why this follows. The V12 uses Lucas OPUS, which is a transistorised system with a known weak point, so the diagnosis is not the same as on a points car.
This node applies only to the Series 3 V12.
What to do
- Check the OPUS amplifier. It is the component with the reputation, and it commonly fails with heat, which means a car that will not restart warm and will start cold points here strongly.
- Check the pick-up module and its air gap inside the distributor.
- Check the wiring and connectors to the amplifier, which sit in a hot part of the engine bay.
- Check the coil and the ballast arrangement.
- Before condemning anything, confirm the fault is genuinely in the ignition rather than in a common supply feeding it.
Read further: Lucas OPUS ignition on the V12
Finding
The pump is not running
Why this follows. An SU electric pump should be audible when the ignition is first switched on, ticking rapidly and then slowing as the float chambers fill. Silence means it is not being fed, not earthed, or not working.
What to do
- Check for voltage at the pump with the ignition on.
- Check the pump's earth. On a rear-mounted pump this is a classic failure and it costs nothing to inspect.
- Check the points inside the pump if it is the original type. They corrode and stick.
- A firm tap on the pump body that produces a burst of ticking is diagnostic of sticking internal points, and is a way to confirm the fault rather than a repair.
- On a car with a replacement solid state pump, check it is wired for the car's polarity.
Read further: Earths, wiring and the loom
Finding
The pump runs but nothing arrives
Why this follows. The pump is working, so the obstruction is between it and the float chambers, or the pump is running dry because it cannot draw from the tank.
What to do
- Check the fuel filter. On a car that has stood, sediment and rust from the tank block it first.
- Check the tank itself for sediment and for a blocked pick-up.
- Check the flexible hoses. Hoses degraded by ethanol collapse internally and can close under suction while looking perfectly sound outside.
- Check for an air leak on the suction side of the pump, which makes the pump tick continuously without moving fuel.
- Check the float chamber needle valves are not stuck shut.
Read further: Modern fuel and E10, Triple SU carburettors
Finding
Fuel is arriving and it still will not fire
Why this follows. If both spark and fuel are present, the fault is usually the quantity of fuel rather than its absence, or the fuel itself.
What to do
- Check whether it is flooded. Plugs wet with petrol, a strong smell, and a car that has been repeatedly cranked on full choke all point that way. Remove the plugs, dry them, and crank with the throttle fully open to clear it.
- Check the float chamber needle valves are not stuck open, which floods the engine continuously.
- Check the fuel is not stale. Modern petrol deteriorates within months rather than years, and a car that has stood a season may simply have fuel that will no longer light.
- Check the plugs themselves. Plugs fouled by repeated failed starts will not fire even once the original fault is fixed.
- Check the ignition timing has not slipped, since a spark at the wrong moment is as useless as no spark.
Read further: Triple SU carburettors, Modern fuel and E10, The ignition system
Sources
- General engineering practice, and published owner, club and specialist accounts. The archive has not worked from the factory workshop manual directly, and says so rather than implying otherwise.
- This archive's own articles on the ignition system, the charging system, earths and wiring, the triple SU carburettors, Lucas OPUS ignition and modern fuel, which carry their own sources.
Last reviewed .