Fault Finding -

Note: Whilst most of these procedures can be tackled satisfactorily by the average d-i-y owner,
several procedures are only suitable for a qualified engineer to undertake.
Please ensure you are capable of correctly following a procedure before embarking upon it.

Details follow for the Thornycroft T154 and Perkins 4108 Etc

Members' Questions (General)

Thornycroft T154  
Is the cranking speed low, or does the engine not turn over at all?

Yes: Go to Check 2.
No: Go to Check 6

Is the battery fully charged and in good condition? Yes: Go to Check 3.
No: Change or re-charge the battery as necessary
Are the connections in the starter circuit satisfactory? Yes: Go to check 4.
No: Make all the starter connections satisfactory.
Is the engine oil of the correct grade? Yes: Go to Check 5.
No: Change to the correct grade of engine oil.
Is the starter motor faulty? No: Investigate the engine for tightness.
Yes: Overhaul or replace the starter motor.
Is fuel reaching the injectors? Yes: Go to Check 13.
No: Go to Check 7.
Is the stop control correctly set and is its linkage free? Yes: Go to Check 8.
No: Reset the control position or linkage as necessary.
Is there a supply of clean fuel in the tank? Yes: Go to Check 9.
No: Refill the fuel tank and bleed the fuel system.
Are there leaks at fuel pipes or connections? Is there a fractured fuel pipe? No: Go to Check 10.
Yes: Cure the leaks / replace the broken pipe, bleed the fuel system.
Is there a blockage in the fuel system? No: Go to Check 11.
Yes: Clear the blockage or renew the filter element as necessary, then bleed the fuel system.
Is the lift pump delivering fuel? Yes: Go to Check 12.
No: Overhaul or replace the lift pump and bleed the fuel system.
Does the fuel system require bleeding? No: Have the injection pump overhauled (a specialist job).
Yes: Bleed all air from the fuel system.
Are the injector pipes connected in their correct order? Yes: Go to Check 14.
No: Correct the firing order and bleed the fuel system.
Are the correct injectors correctly fitted? Yes: Go to Check 15.
No: Correct the error and bleed the fuel system.
Are the injector pump timing marks correctly aligned? Yes: Go to Check 16.
No: Re-set the injection pump timing.
Is the air cleaner or induction system blocked? No: Go to Check 17.
Yes: Clear the blockage or clean and re-oil the air filter.
Is the exhaust system restricted? No: Remove the injectors and go to Check 18.
Yes: Clear the restriction.
Is the injector opening pressure and performance satisfactory? Yes: Remove the injection pump and go to Check 19.
No: Have the injection pump overhauled (a specialist job) or renew the injectors.
Is the injection timing pointer correctly positioned when checked with tool MS67A? (a specialist job) Yes: Go to Check 20.
No: Re-set the injection timing pointer (a specialist job).
Is the injection pump performance satisfactory on a test bench (a specialist job) Yes: Go to Check 21.
No: Have the injection pump overhauled or renew the injection pump (a specialist job)
Is the valve / rocker clearance and valve timing correct?

Yes: Investigate the engine for wear or damage causing lack of compression.
No: Correct the valve / rocker clearance and / or valve timing.

Does the throttle linkage interfaere with the idling speed setting?
No: Go to Check 23.
Yes: Correct the throttle linkage adjustment.
Does the stop control linkage interfere with the position of the stop lever?
No: Go to Check 24.
Yes: Set the stop control linkage correctly.
Is the idling stop screw setting correct?
Yes: Go to Check 25.
No: Adjust the engine idling speed.
Is the fuel tank air vent restricted?
No: Go to Check 26.
Yes: Clear the fuel tank air vent.
Are there leaks at the fuel pipes or connections?
No: Go to Check 27.
Yes: Cure the leaks then bleed the fuel system.
Is there a blockage in the fuel system?
No: Go to Check 28.
Yes: Clear the blockage or renew the filter element as necessary, then bleed the fuel system.
Does the fuel system require bleeding?
No: Go to Check 29.
Yes: Bleed all air from the fuel system.
Is the lift pump delivering correct pressure (a specialist job)

Yes: Go to Check 13.
No: Overhaul or renew the lift pump.

Is there an external factor holding the boat back, e.g. something wrapped around the propellor, an anchor dragging, etc?
No: Go to Check 31.
Yes: Cure accordingly, and blush queitly as appropriate!
Is the throttle linkage transmitting full travel to the throttle lever?
Yes: Go to Check 32.
No: Adjust or renew the throttle linkage as necessary.
Is the maximum speed stop screw setting correct? Yes: Go to check 25.
No: Adjust the engine maximum speed (a specialist job)

Note: The information reproduced in this table is very largely based upon that provided in the Repair Operation Manual available from ASAP Supplies.

Perkins 4107 Etc  
Problem Possible causes (see code list below)
Starter turns engine too slowly 1,2,3,4
Will not start 5,6,7,8,9,10,12,13.14,15, 16,17,18,19,20,22,31,32,33
Difficult to start 5,7,8,9,10,11,12,13,14,15,16,18.19,20,21,22,24,29,31,32,33
Not enough power 8, 9, 10, 11, 12, 13. 14, 18, 19 20, 21,22,23, 24, 25, 26, 27, 31,32,33
Misfire 8, 9, 10, 12, 13. 14, 16, 18, 19. 20, 25, 26, 28, 29, 30, 32
High fuel consumption 11, 13, 14, 16, 18, 19, 20, 22. 23, 24, 25, 27. 28, 29. 31, 32, 33
Black exhaust 11, 13, 14, 16, 18, 19, 20, 22, 24,25, 27,28, 29,31,32,33
Blue/white exhaust 4, 1 6, 1 8, 1 9, 20, 25, 27, 31 , 33, 34, 44, 53
Low lubricating oil pressure 4, 35, 36, 37, 38, 39, 40, 42, 43, 44, 55
Engine knocks 9, 14, 16, 18, 19, 22.26,28,29,31,33, 35,36,45, 56
Runs erratically ,8,9, 10, 11, 12, 13, 14. 16, 20, 21, 23, 26, 28, 29,30,33,44, 56
Vibration 13, 14, 20, 23, 25, 26, 29, 30. 33, 44, 46, 47
High lubricating oil pressure 4. 37, 40
Engine temperature too high 11, 13, 14, 16, 18, 19,24, 25,44,48,49, 50, 51, 52,53, 54
Crankcase pressure 25,31,33,34,44,52
Bad compression 11,19, 25, 28, 29. 31, 32, 33, 34, 45, 56
Starts and stops 10,11,12

Code List of Possible Causes:

1 Battery capacity low.
2 Bad electrical connections.
3 Fault in starter motor.
4 Wrong grade of lubricating oil.
5 Low engine speed from starter motor.
6 Fuel tank empty.
7 Stop control fault.
8 Restriction in fuel pipe.
9 Fault in fuel lift pump.
10 Dirty fuel filter element.
11 Restriction in air filter or induction system.
12 Air in fuel system.
13 Fault in fuel injection pump.
14 Fault in atomisers or not correct type.
15 Cold start equipment not used correctly.
16 Fault in cold start equipment.
17 Broken fuel injection pump drive.
18 Fuel injection pump timing not correct.
19 Valve timing not correct.
20 Bad compression.
21 Restriction in fuel tank vent.
22 Type or grade of fuel not correct.
23 Restriction of engine speed control movement.
24 Restriction in exhaust pipe.
25 Cylinder head gasket leaks.
26 Engine temperature too high.
27 Engine temperature too low.
28 Valve tip clearances not correct.
29 Valves not free.
30 Wrong high pressure pipes.
31 Worn cylinder bores.
32 Valves and seats do not seal correctly.
33 Piston rings not free or are worn or broken.
34 Valve stems and/or guides worn.
35 Crankshaft bearings worn or damaged.
36 Not enough lubricating oil in the sump.
37 Gauge not correct.
38 Lubricating oil pump worn.
39 Relief valve not free to close.
40 Relief valve not free to open.
41 Relief valve spring broken.
42 Fault in suction pipe of lubricating oil pump.
43 Dirty lubricating oil filter element.
44 Piston damage.
45 Piston height not correct.
46 Fault in engine mounting (housing).
47 Flywheel housing or flywheel misaligned.
48 Fault in thermostat or wrong type.
49 Restriction in coolant passages.
50 Water pump drive belt loose.
51 Fault in water pump.
52 Restriction in breather pipe.
53 Damage valve stem oil seals (where used).
54 Not enough coolant in system.
55 Restriction in sump strainer.
56 Valve spring broken.


Members's questions
Engine races then settles back, repeatedly.
The BMC (1974 Diesel)engine on our recently acquired 813 has a habit of suddenly increasing revs every so often and then dropping back (10-15 mins or so) and on two occasions have actually stopped. (dramas almost!). Filters have been replaced and there appears to be no water in the fuel. I can find no trace of any leaks. Suggestions would be very much appreciated.
Answer: Almost definately air in the system, where is another matter.
To prove it, remove the return pipe, place in container and run engine. Put return pipe at the bottom of the container and watch for bubbles with engine running.
To find it, check all compression unions from the tank to the lift pump for tightness. I have come across several ISO 7840 flexi pipes drawing air between the hose and the hose end.
After the lift pump the system is pressurised so it wont be there.
And, a member added: I have just had something like this happen to me. Turned out to be the dip tube inside the fuel tank had cracked at the top so would suck fuel up but also let in a little air that would eventually build up to a bubble and stop the engine. The revs would also be up and down in the meantime. Probably not your trouble but worth keeping in mind.




Seamaster 17 Cub / Seamaster 20 Captain / Seamaster 21 / Seamaster 23 / Seamaster 24 Cadet / Seamaster 25 / Seamaster 26 / Seamaster 27
Seamaster 725 / Seamaster 8 metre / Seamaster 813 / Seamaster 28 / Seamaster 820 / Seamaster 30 / Seamaster 950 / Seamaster 34
Seamaster 23S / Seamaster 29 / Seamaster 815 / Seamaster 28 Sailer / Seamaster 925 / Seamaster 1125

Seamaster Club