LUCAS INJECTION

Lucas MK1 and MK2 fuel / petrol injection

 

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Lucas Service Training Centre
Petrol Injection Mk II


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Faults, Possible Causes and Action

1. Misfiring

(a) After cold start
(i) One or more sparking plugs may be fouled by too rich a mixture due to excessive use of over- fuel lever. Remove plugs, clean and dry or replace as necessary. When starting, return over- fuel lever to normal running position as soon as possible.

(ii) Check that overfuel lever is responsive to manual control over its full range, and that when in the “off” position there is a clearance of 0.004”-0~008” (0.10 mm-0.20 mm) between the lever and the adjustment screw.

(iii) Throttle butterflies incorrectly set.

(iv) Check for air leaks at injector insulating blocks.

(v) Injector stuck open, remove and blow through with air line.

(b) After hot soak

(i) Check engine compressions.

(ii) If cylinder compressions are correct, locate cylinders which are misfiring and “crack” open union on injectors concerned to allow a small quantity of fuel to escape. Retighten unions and increase engine rev/mm. If misfiring has now ceased, fault was due to partially empty injector lines and could have been caused by leakage of fuel or faulty non-return valves in outlet connections concerned. If the latter, renew faulty outlet connections; remembering to renew every seal which has been disturbed.

4. Under-fuelling on one or more cylinders

(i) Leaking connections on injector pipes or damaged pipes. Leaking “Dowty” washers. Tighten connections or replace pipes or washers.

5. Lack of response

(I) Throttle butterflies are incorrectly set. Synchronize butterflies.

(ii) Injector pipes are connected to the wrong injectors, giving an incorrect injection sequence. Rectify, as necessary.

(iii) Line pressure is low. Check line fuel pressure by inserting a pressure gauge in main petrol line, switching on the ignition. Gauge should read 100-110 lbf/in2 (689.50-758.50 kN/m2). Adjust relief valve, if necessary.

(iv) Obstruction in the return to tank drain pipe. In extreme cases the cam follower diaphragm will be displaced.

(v) Metering unit timed to engine, is 180 degrees out.

6. Engine cutting out on bends or on straight

(i) Installation is not modified as per Standard Triumph instructions. Correct as necessary.

(ii) Dirt in petrol tank momentarily obstructing the outlet pipe.

(iii) Transient failure in supply of electrical power to pump motor. Check all supply lines and connections in motor circuit.

7. Vapor locking

(i) Overheating of pump and motor, which in turn vaporizes fuel in pump element. Check fuel line pressure. If line pressure is high, this will overload motor and cause overheating. Check current consumption of motor does not exceed 5.5 amps at 13.5 volts. If current is above this figure, but line pressure is correct, remove motor for electrical and mechanical examination.

2. Rough Idling

(1) Throttle butterflies incorrectly set. Synchronize butterflies.

(ii) Injector pipes connected to the wrong injectors giving an incorrect injection sequence.

(iii) Check for air leaks which could lead to uneven air distribution.

3. Overfuelling on one or more cylinders

(i) Damaged grommet seals between nose of outlet connection and sleeve, allowing unmetered fuel to enter the injector line or lines giving continuous injection. On “Banjo” type outlets this can also occur if the inner ‘0’ ring on the “Banjo” is damaged.

(ii) Renew the seal on any line which is over-fuelling. (Remember: Renew any seal which has been removed, it must not be re-used.)

8. Excessive fuel consumption

(i) Check for (obvious) leaks at all petrol connections. Check operation of overfuel lever and clearance when in “off” position. Check for obstruction in return to tank drain pipe. Line pressure may be high. Check pipe and relief valve setting.

If a variable vacuum supply and accurate vacuum gauge is available, check gap between cam follower and rollers in control unit as detailed in workshop instructions. Check inlet manifold depression.

Note: High vacuum gives minimum fuel condition. Low vacuum gives maximum fuel condition.

9. Engine fails to start

                          Check line pressure. Check that fuel pump is operating.

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