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Driving a DMU


Fault Finding

(Compiled by Stan Acaster (Dean Forest DMU Group))

As well as the faults listed below, there are some reasons why an engine must be stopped and its corresponding final drive isolated, these are:

  1. Continuous excessive smoke from the exhaust.
  2. Cylinder head gasket blowing.
  3. Any unusual knocking or other noise in an engine or a transmission.
  4. Overheated fluid coupling.
  5. Overheated or otherwise defective gearbox or final drive.
  6. Water or fuel oil in an engine sump.
  7. Fuel oil line leaks.
  8. Radiator fan belts missing.
  9. No. 7 fuse blown or a flat battery on a power car.

It is important that the final drive to an engine, which has had to be stopped, or for any reason has failed to start, is isolated as quickly as possible. If it is not isolated, the final drive is 'driving back' through the gearbox gear trains, overspeeding them and causing excessive wear.

REMEMBER... On diesel trains, passengers are riding over the power equipment, so do not take any unnecessary risks when faults exist. The only proof that a final drive is isolated is that the cardan shaft can be rotated freely by hand.

DO... read carefully the sections in the official DRIVING INSTRUCTIONS regarding:-

  • changing ends
  • reversing the train
  • stabling the train

DO... 'toggle up' the gearbox brake bands as detailed on the official DRIVING INSTRUCTIONS.

DO... throttle back when maximum 'revs' are indicated when in 4th gear.

DO NOT... check the level of lubricating oil in the engine sump whilst the engine is running.

REMEMBER to ALWAYS... book all known defects and to pass on to any relief driver any such information that may affect the proper working of the train.

FAULT INDICATION TO DRIVER POSSIBLE CAUSE ACTION TO BE TAKEN
1. Control Circuit light is OUT when the CIS key turned on Control circuit light OUT a) Defective bulb a) Press buzzer button. If the buzzer sounds the bulb is defective. If the buzzer does not sound b) c) and a)
b) Battery switch at OFF b) Place Switch to ON
c) Battery is 'flat' c) If on a depot, request assistance. If away from a depot and there is only one power car in the train, assistance is required.
If the 'flat' battery is on a leading car or on a car which becomes the leading car in the train, take the C.I.S. key to another Control Switch in any other driving cab and turn it to ON.
The train can now be driven from the leading car.
d) No. 6 fuse (blown) on this car d) Take the C.I.S. Key to another Control Switch in any other driving cab and turn it to ON.
The train can now be driven from the leading car.
2. Engine will not start when the local start button is pressed No Response from the starter motor a) Engine Isolation switch at OFF a) Check if the corresponding final drive is isolated. If the final drive is isolated do not attempt to start this engine. If the final drive is NOT isolated examine the engine for any possible defects before turning the engine isolation switch ON.
b) Double pole switch on FIRE ALARM panel at OFF b) Determine whey the switch is at OFF and check the Graviner fire bottle. If the fire bottle has been discharged DO NOT attempt to start the engine. Isolate the engine and the corresponding final drive.
c) Battery switch at OFF 'flat' battery or No. 6 has blown. c) See fault 1.
3. Engine will not respond from start button, in the cab. a) Direction not selected. a) Select Direction providing air pressure is above 75 p.s.i.
b) Test button stuck in. b) Release test button.
3A. Engine will not turn when local start button is pressed i) No response from starter motor a) No. 7 positive fuse blown a) Isolate the engine/s and final drive/s also the D.S.D. Valve when air pressure is available on affected car. See failure of Nos. 6 and 7 fuses.
ii) Starter motor responds but fails to turn engine b) Battery flat. b) See failure of Nos. 6 and 7 fuses.
c) Start button defective. c) Try and start from the driving compartment when sufficient air pressure is available. If engine still does not start isolate the engine and corresponding final drive.
d) Starter pinion sticking or not engaging with starter ring. d) Do not keep start button depressed or persist in attempting to start this engine. Isolate the engine and corresponding final drive.
e) Engine seized e) As above.
f) Water in cylinder (a loud knock will be heard). f) As above.
3B. Engine turns but will not fire when local start button is pressed As in Fault Column a) Fuel oil supply cock closed. a) Open cock and bleed system if necessary.
b) No fuel in tank. b) Isolate engine/s and final drive/s on this car.
c) Air lock in fuel oil system c) Bleed the system
3C. Engine turns and fires but stops when local start button is released As in Fault Column a) Low lubricating oil pressure. a) Check oil level in engine sump. If level is ABOVE MINIMUM ATTEMPT ANOTHER TWO starts.
b) Low cooling water level. b) Where permissible top up radiator tank. If topping up is not allowed or possible, isolate the engine and the corresponding final drive.
4. An engine light goes out whilst running with he throttle OPEN Engine light on panel OUT At the first point check if the engine has in fact topped.
a) Bulb defective a) If the engine is running, check this light from another driving compartment.
If light illuminates proceed, if not, isolate this engine and corresponding final drive.
b) Low lubricating oil pressure. b) Engine is not running ... check oil level in engine sump. If level is above minimum try no more than three attempts to restart the engine.
c) Low cooling water level. c) If topping up is permissible, top up. If not, isolate the engine and corresponding final drive.
b) and c) If the engine still does not start when these items are in order, isolate the engine and the corresponding final drive.
5. An Air/Axle light Air/Axle Light is OUT a) Air pressure below 75 p.s.i. a) (i) Engine stopped (i.e. when taking to a train or changing ends). Remove reversing lever - start engines locally to build up air pressure.
a) (ii) Engines running (i.e. when reversing without changing ends) DO NOT speed up engines from the Cab. Remove reversing level and air pressure to build up.
b) Air pressure above 75 p.s.i. b) (i) Engine stopped ('taking to' or changing ends). Watch for Air/Axle light when engines are started. DO NOT 'race' the engines under this condition.
b)(ii) Engines running. (Reversing without changing ends). With engines IDLING, select opposite direction - pause- re-select required direction and check if light illuminates. If light remains out, stop all engines - pause 30 secs. - restart engines and check light.
NOTE: If the engines of the car for which the air/axle light is OUT do not stop when the STOP button is pressed, this means that the No. 7 fuse on that car has probably failed. If light still remains out, proceed to car indicated and check if either prop' shaft is rotating. If so, stop the corresponding engine at once and isolate engine and final driver.
If shafts are stationary, check air/axle light in cab of THIS car by pressing TEST button. If this light illuminates, proceed normally but recheck each time the train is reversed. If the light does NOT illuminate when TEST button is pressed, check air pressure and final drive indicators for this car. If these are correct proceed normally but recheck each time the train is reversed. If air pressure is below 75 p.s.i. or if either final drive indicator is in the wrong direction isolate the corresponding engine and final drive.
6. An Air/Axle light goes out whilst running. Air/Axle light on panel out. REDUCE SPEED to 25 m.p.h. to a suitable point where a check can be made.
a) Air pressure below 75 p.s.i a) As for a) Fault 5
b) Air pressure above 75 p.s.i. b) As for b) Fault 5
c) Vacuum destroyed c) No. 7 fuse 'blown' on the car indicated (see notes concerning this fuse)
7. Loss of air pressure SINGLE UNIT a) Unloader valve sticking a) Blank of f valve with cap provided. Check that safety valve blows at approximately 95 p.s.i. Report blanking off valve.
b) Air leak that cannot be rectified. b) Stop the engine/s and isolate the final drive/s as quickly as possible, request assistance.
8. Loss of air pressure ONE POWER CAR ONE TRAILER a) Unloader valve sticking a) As for 7a)
b) Leak on power car that cannot be rectified. b) As for 7b)
c) Leak on trailer car air system. c) Isolate the air system of the power car from that of the trailer car by closing the air cocks between the vehicles. If the trailer car is leading, the guard must ride in driving cab (see Regulations).
d) Burst air pipes between vehicles. d) As for c).
9. Loss of air pressure. MORE THAN ONE POWER CAR IN FORMATION a) Unloader valve sticking a) Blank off with cap provided. Check that the safety valve b;lows off at approx. 98 p.s.i. Report blanking off valve.
b) Leak on power car air system that cannot be rectified. b) Isolate the engine/s and final drive/s as quickly as possible. Isolate the air system of this car from the remainder of the train. If this car is or becomes the leading car in the train, the guard must ride in the driving cab of any other car (see Regulations). Have guard to check and report the state of the air pressure in the remainder of the train.
c) Leak on trailing car air system c) Isolate the air system of this car from he remainder of the train. If this car is the leading car of the train act as instructed regarding the guard in b).
10. Unable to create train pipe vacuum SINGLE UNIT No train pipe or high vacuum when brake valve is in the OFF position. a) Hand brake ON. Buzzer sounds. a) Take off the hand brake.
High vacuum normal when brake valve is in the LAP position. b) D.S.D. Valve defective. b) Isolate the D.S.D. Valve. Guard or second man to ride with driver.
c) Passenger communication valve open c) Close the valve.
d) Emergency valve open d) Close the valve.
e) Leak on train pipe cannot be rectified. e) Release vacuum from the top side of the brake cylinders. Proceed at reduced speed and with caution. Guard to ride with driver to operate hand brake. Withdraw the unit from service as quickly as possible.
11. Unable to create high vacuum SINGLE UNIT As above Fault 10. High vacuum does not build up in the LAP position. As above Fault 10. Leak in high vacuum pipe. As above Fault 10. If leak cannot be rectified act as in Fault 10c
Unable to create train pipe vacuum ONE POWER CAR ONE TRAILER CAR As in Fault 10. As in Fault 10 a), b), c) and d) As in Fault 10 a), b), c) and d)
e) Leak in power car that cannot be rectified. e) Isolate train pipe between power car and trailer, release vacuum from top side of brake pistons on power car. Drive from rear at reduced speed and with caution. Brake operative on trailing car only. Guard to ride in the loading cab (see Regulations).
f) Leak in trailer car that cannot be rectified. f) Isolate train pipes between power car and trailer. Release vacuum from top side of brake pistons on trailer car. Drive from leading cab at a reduced speed and with caution. Brake operative on leading car only.
12. Unable to create high vacuum on power car. ONE POWER CAR ONE TRAILER CAR As for Fault 10. Brake valve at OFF As for Fault 10 a), b) c) and d).
High vacuum does not build up in LAP POSITION Isolate high vacuum pipe between power car and trailer. If high vacuum can be obtained on power car, defect on trailer car.
a) Leak that cannot be rectified on trailer car. a) If this car is trailing, leave high vacuum pipes isolated and drive normally from power car. Brake will be slower in releasing. If trailer car is leading, leave high vacuum pipes isolated. Drive from power car at reduced speed and with caution. Guard to ride in the leading cab (see Regulations).
b) Leak in high power vacuum pipe of POWER CAR THAT CANNOT BE RECTIFIED b) It will be impossible to create train pipe vacuum on the power or trailer cars. Release vacuum from he top side of all brake cylinders. Proceed at reduced speed and with caution (see Regulations). Guard must ride with driver to operate the hand brake.
13. Unable to create train pipe vacuum TWO OR MORE POWER CARS IN THE FORMATION No train pipe or high vacuum when the brake valve is OFF. High vacuum builds up in LAP position. a) Hand brake ON. Buzzer sounds. a) Take off the hand brake.
b) D.S.D. Valve defective. b) Isolate the defective D.M. Valve. If the D.M. Valve is isolated on the power car which is, or becomes the leading power car of the train, a second man is not necessary because the D.M. Valves on the other cars will be operative. This should however be tested.
c) Passenger communication valve open. c) Close the valve.
d) Emergency valve open. d) Close the valve;
If a), b), c) and d) are not at fault then in order to locate quickly which car is defective, isolate the train pipes between each car in turn. If the train consists of two or more sets, isolate the train pipes at a point half way in the formation to check which is the defective portion, then check as before.
e) If the defect is on the leading car of the train. e) Isolate the train pipes between this car and the next. Release vacuum from the top side of the leading cars brake cylinders. Drive from the next convenient cab. (see Regulations).
If the defect is on a car beyond the first car, isolate the train pipes between the two portions. The driver must now use his own judgement as from part of train he will drive from, according to the brake power available. The vacuum must be release from the top side of the brake cylinders of the unbraked portion.
If he decides to drive a cab other than the leading one he must proceed at a reduced speed and with caution. The guard must ride in the leading cab. (See Regulations).
14. Unable to create high vacuum TWO OR MORE POWER CARS IN THE FORMATION No train pipe or high vacuum when the valve is at OFF. As for Fault 13 a), b), c), d) and e). As for Fault 13 a), b), c), d) and e).
HIGH vacuum builds up in the LAP position. f) Leak in high vacuum pipe. f) To locate quickly which car is defective proceed in a similar manner as for a train pipe defect, isolating the high vacuum pipes instead of the train pipes. If the defect which cannot be rectified is in the rear portion of the train, isolate the high vacuum pipes between he defective car and the front portion. The train can be driven normally from the leading driving compartment, but the brake will be slow in releasing. If the defect is on he leading car, isolate the high vacuum pipes between this car and the remainder of the train.
Drive from the next convenient cab (see Regulations).
15. Train pipe vacuum too high Train pipe vacuum rises to 22/23. a) Auto feed valve requires adjusting. a) Proceed normally to destination. When changing ends, apply the hand brake and release the vacuum from the top side of all vacuum brake cylinders, recreate vacuum pause, two minutes, then fully destroy the vacuum, release the hand brake.
Train pipe vacuum equals the high vacuum. b) Punctured diaphragm on auto feed valve. b) At the convenient point, fully destroy the vacuum, apply the hand brake, release the vacuum from the top side of all brake cylinders, recreate vacuum and when the train pipe reaches 21" place the brake handle to LAP. Then by careful observation maintain 21" by operating the brake valve LAP and OFF. Release hand brake before moving. Alternatively, drive from another cab. (See Regulations).

FAILURE OF NO. 6 FUSE

INDICATIONS... All D.S.D Valves operate and the train brakes are fully applied. All indication lights out. ALL gearboxes and torque converters return to neutral. All engines return to IDLING.

ACTION TO BE TAKEN... Take the C.I.S. key to any other cab Control Switch and turn to ON. Return to the leading cab and proceed normally. If however on returning to the leading cab it is found that vacuum cannot be obtained, the Air/Axle light is OUT and the engines do not respond to the throttle on this car it can be assumed that the battery is 'flat'. In this case see instructions for this item.

FAILURE OF NO. 7 FUSE

(Multiple Working). The failure of this fuse ONLY affects control of the power car on which the fuse has 'blown'.

INDICATIONS... (Gearbox and Torque Converter Cars). The train brake will be fully applied by the D.D.S.D.. Valve on the car on which the fuse has 'blown'.

Gearbox Cars Only... The Air/Axle light for the affected car will go OUT. If the engine stop button is pressed the engine lights for the car on which the No. 7 fuse is good will go OUT, but the engine lights for the affected car will remain IN. There is now a power car showing the following indications:

Air/Axle lights OUT
Engine lights IN

Torque Converter Cars ONLY... The Air/Axle light and the engine lights go OUT (although the engine will still be running) for the affected car.

All Cars... The indications given above show on the leading car panel on which car No. 7 fuse has blown. Isolate the engine/s and final drive/s. The Forward and Reverse E.P. Valves on this car will have to be operated manually to enable this to be done. Isolate the D.S.D. Valve.

The remainder of the train can now be operated normally. A second man is NOT necessary should the affected car be the leading one if there is more than one power car in the train, the D.S.D. Valves should function normally on these cars, but the should be tested in the usual manner. If No. 7 fuse 'blows' on a car which is or becomes the leading car, the train can be driven from THIS car.

ALL TRAINS... If No. 7 fuse 'blows' causing the train to be stopped in a tunnel or on a viaduct, near conductor rails, in section or in any other unsuitable place, then to move the train to a more suitable point as quickly as possible where the engine/s and final drive/s can be isolated, the D.S.D. Valve on the affected car should be isolated. It is MOST IMPORTANT that the engine/s and final drive/s should be isolated as quickly as possible after the failure of a No. 7 fuse for the following reasons:- The gearbox/es of the affected car will return to NEUTRAL and would be driven in this condition by the final drive/s. The E.P. Valves controlling the supply of air to the final drive/s operating pistons will be de-energised resulting in the loss of air pressure to the appropriate piston. There is now the possibility of a sliding dog becoming disengaged from the bevel pinions. In both cases severe damage can be caused to the gearbox gear trains and the final drive bevel pinion and sliding dog teeth.

FLAT BATTERY ON A POWER CAR

In the event of this failure, carry out the isolation procedure as for a No. 7 fuse blowing. If the failure occurs on a power car that is, or becomes the leading car of the train, in addition to isolating the engine/s and final drive/s the C.I.S. key must be taken to the control switch in another driving cab and turned to ON. THE TRAIN CAN NOW BE DRIVEN FROM THE LEADING CAB.

ISOLATION OF FINAL DRIVES

  1. Stop the engines.
  2. Turn the starter isolation switch quarter turn anti-clockwise.
  3. Enter guards compartment from this side, obtain the isolating rod and leave the compartment by the opposite door to the one by which the compartment was entered. Proceed to the final drive.
  4. Pull out the isolating plunger, turn it quarter turn, then release it into the deep horizontal slot. (Ensure the plunger enters this slot, but remember at this juncture it will not go fully home).
  5. Enter the driving cab and operate the reversing lever several times, pausing each time a direction is selected.
  6. Return to the final drive and check that the pin has fully inserted and the cardan shaft can be rotated freely.
    NOTE: This is the only proof that the final drive is correctly isolated.
  7. Replace the isolating rod in guards compartment.
  8. Return to the driving cab and restart the remaining engines and check that the engine and Air/Axle light for the car affected remain out. Final drives can be isolated by drivers only when air pressure is available. If after carrying out the above isolation drill it is found that the cardan shaft is still locked the following precautions must be carefully observed:-
    1. the train may proceed to its destination at a speed NOT EXCEEDING 25 m.p.h. (providing the final drive is set for that direction) where the final drive MUST be isolated or the affected car to be taken out of service. If the destination is a considerable distance away the driver should use his own discretion as to whether he proceeds to that point at 25 m.p.h. or puts off the defective vehicle at some intermediate point, whichever would result in the least loss of time.
    2. if it is necessary to move the train int he wrong direction to the final drive IN ORDER TO CLEAR THE MAIN LINE ONLY this may be done at a speed not exceeding 5 m.p.h. and this for the shortest distance only.

SLIPPING GEARBOX BRAKE BANDS

This is indicated by the tachometer showing 'CHANGE UP' when the speedometer indicates a road speed nearer 'CHANGE DOWN' for the respective gear.

At the next convenient point and with air pressure about the maximum proceed as follows:-

  1. STOP ALL ENGINES
  2. 'HOLD IN' the deadmans circuit by means of the throttle handle.
  3. Select the defective gear about 30 times, pausing 5 seconds each time the gear is selected.
  4. Restart the engines, proceed and check the operation of this gear.

If air pressure falls to below 65 p.s.i. during the toggling procedure, restart the engines and allow air pressure to build up sufficiently to complete the operation. If drivers would 'toggle up' the gearbox brake bands one per shift on any train, slipping brake bands would be a rare occurrence. In addition much smoother gear changing would be achieved.

Intro
Prep and Basic Technique
General Info
Do's Dont's and Remembers
What do I do if...?
Fault Finding ->
Jumpers Disconnected

Driving a mechanical transmission DMU meant changing gears, those that had hydraulic transmission didn't (unless they were coupled to a mechanical DMU).

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