I’d like to try and make sure I have the timing right on the AV590 engine in RM471 which was rebuilt with new cylinder block heads, bearings and piston rings 3 years and about 8,000 miles ago. The fuel injector pump and injectors were checked at the same time. The engine takes a lot of cranking to start in very cold weather and smokes a bit until it is warm. Performance is sluggish, being slow to pick up speed. Pulling power is poor at low revs on hills or with a full load on.

When the fluid flywheel is turned so that TDC is at the top (first photo) the injector pump is at the position shown in the second photo. I think this is wrong and seem to remember that it was lined up with INJ when we rebuilt it.





I’d like to put it right and would also be grateful for advice on how to make further adjustments to tune the engine for better performance.

My bus number (if any): RM238, RM471 and RM2213

The mark on the second pic should line up with the tdc mark. It seems your timing is a tad out. To improve performance I found it pays to advance the timing slightly - this really is a trial and error task.

My bus number (if any): RM1001

Allowing for the difficulty in lining up the camera with the timing marks, the pictures appear to show that the timing is correct. Even though a small adjustment to the timing is a relatively simple and quick operation, you should really be looking elsewhere first.
Time and again vehicles are defected for lack of power, when all that is wrong is that full throttle at the pedal, is not full throttle at the pump; check this carefully. Also is the engine stop control fully off at the pump end?
The injector pump rack can stick if it is not getting enough lubrication; particularly if the vehicle is left standing for long periods - top up the oils in the pump and governor.
When was the fuel filter last changed or cleaned?
Has the sediment in the bottom of the fuel tank been drained off recently? Have a look into the tank with a torch what can you see at the bottom of the tank? it ought to be shiny clean. If it is plainly contaminated it will have to come off and be properly cleaned out.
There should be a small thimble shaped brass gauze in the inlet connection of the lift pump, this blocks up very easily. While this is apart examine the connections to it very carefully, is there any evidence of foreign bodies? if so then all the fuel lines will have to be cleaned out. Again while this is apart remove the rubber flexible hoses that are part of the fuel pipework, these deteriorate with age and the walls collapse internally. There should also be another gauze in the inlet to the FIP as well.
Are there any small fuel leaks anywhere? if fuel can get out then air can get in; not enough to stop the engine, but just enough cut down on power.
Finally and very important,unless the valve clearances are correct the true valve timing will be wrong.
As for the smoke on start up and long cranking time, don't forget that these engines have no starting aid and rely entirely on the heat generated during compression to start. There is some 3/4 of a ton of cast iron and there are some 11 gallons of coolant and oil- all at about zero degrees centigrade that act as a very reliable heat sink. This combined with the decreased ability of the batteries at low temperatures to provide an adequate cranking speed, lead to poor starting. On tired engines, this is aggravated by a lack of compression and a fuel system that does not deliver adequately atomised fuel, in sufficient quantity, at the right time. The smoke is simply unburnt fuel, which as you say disappears as things warm up.
It may well be that a small adjustment to the timing will show an improvement, but any of the above defects will certainly have significant effects.

One final point regarding perceived lack of power. A full RM load of men does not weigh 11 1/2 tons any more; it is more likely to come out at 13 tonnes plus and an RML at over 14 tonnes. How many 10 stone men do you know?

Hello to all on here. I have been following this post with interest.

As an ex LT bus mechanic who worked at poplar garage, a routemaster engine with no power; or pulling bad as the old boys would have called it was a common problem.

I think roy's post gives some excellent pointers.

The engine stop cable, ( airons cable i think it was called) would stick if not lubricated. Its well worth having an assistant in the cab to work this on and off, to check if it is indeed coming off and allowing the engine to start. ( many a starter motor was burnt out because a driver hung on the starter when the bus was not firing up.)

I would go back to basics again as roy mentioned. Check all the throttle clevis pins and fork arms for wear. A small amount of wear on each of those will prevent full throttle.

Please dont mind me asking this Question. When the engine and fuel pump was set up, was the engine turned over in the direction of rotation. If viewed from the flywheel end, turn the engine anti-clockwise to set up to TDC, not the other way.

Many years ago a bus mechanic by the name of Bill Nellis ( he saw the RMs new into poplar in 1959) showed me how to do a simple test for checking full throttle just using a bus ticket.( anyone ever heard of that dodge?) Bill would try this trick when an Rm had been on 16 rota and had its fuel pump changed.

I hope you guys will excuse my post on here, reading all this brings back some happy memories for me.

Regards to all.

John H

Hi John

I've just emailed you, likewise happy memories.

Regards

Claire

My bus number (if any): 2330 etc.

John, from my point of view I welcome constructive and informative input from you and anyone else who worked in the Works or the garages. Unfortunately a lot of the garage and Works staff had no interest in buses as such and much valuable experience and knowledge left when they did. The other problem is anno domini. When I ask my brother, who like you was in the garages, he always says you do realise its 30 years since I got under an RM RT etc? Most of it come back to him though......... eventually!! I would be interested to hear about the bus ticket trick for a start, was this like a poor man's feeler gauge?

My bus number (if any): RMC 1458, RM 1585, RTL 960 and 15 RTs

Claire, Many thanks i will send you an email.



Brian,

many thanks for your post.

Its certainly been a few years since i worked on routemasters. I certainly thought this was the easiest vehicle to work on. We only ran AEC engined Rms from Poplar during my days there. 1971-1985.some of these had the rear air suspension too. Gave very little trouble.

The full throttle bus ticket dodge was something clever that i'm sure was devised by one of the men on the shop floor. Bill Nellis the bus mechanic i spoke about was a gold mine of infomation during my time there. This man would have day foremen from other garages in our district phoning him up and asking his advice.

I send my apologies if im vague on this point but if i can remember, bill would have an assistant in the drivers cab pressing down the throttle.
( engine switched off) Bill would then take his bus ticket when the throttle was opened and place this ticket at the rear part of the inline fuel pump lever. Bill would then ask the assistant to remove his foot from the pedal. The fuel pump lever should.....nip the ticket and the ticket would tear if you tryed to remove it. ( full throttle) If the ticket did not tear it indicated that the vehicle was not getting full throttle,and the fuel pump arm/s were out of adjustment.

I understand this may sound unbelievable, however it did work. It was just one of the many little tricks that inside staff found out about their new routemasters, after tinkering with them on a quiet sunday afternoon, as old bill, and his mates did.

I send my best wishes to all folk who are working hard to preserve their vehicles.

Regards John H

Thanks to everybody above for their helpful suggestions. I've devised a checklist and will be working throughout carefully this week. I'll post progress reports and results in due course. Thanks again and please add any other items you fell should be on the checklist.


Check list for loss of power

1. Check full throttle at the pedal is not full throttle at the pump; check linkage.

2. Check engine stop control fully off at the pump end.

3. Top up the oils in the pump and governor.

4. When was fuel filter last changed or cleaned?

5. Drain off sediment in the bottom of the fuel tank.

6. Have a look into the tank with a torch what can you see at the bottom of the tank. It ought to be shiny clean. If it is plainly contaminated it will have to come off and be properly cleaned out.

7. Check small thimble shaped brass gauze in the inlet connection of the lift pump, this blocks up very easily. While this is apart examine the connections to it very carefully, is there any evidence of foreign bodies? If so then all the fuel lines will have to be cleaned out.

8. While this is apart remove the rubber flexible hoses that are part of the fuel pipe work, these deteriorate with age and the walls collapse internally.

9. Check the gauze in the inlet to the FIP as well.

10. Check for any small fuel leaks anywhere. If fuel can get out then air can get in; not enough to stop the engine, but just enough cut down on power.

11. Check the valve clearances. Unless the valve clearances are correct the true valve timing will be wrong.

12. Get injectors cleaned, checked and adjusted.

My bus number (if any): RM238, RM471 and RM2213

Hello all,

I've been trying to rack my brains and think of anything else to add to the list.

Forgive me mentioning this but if you've ever had your fuel pump bolts disconnected were you able to check the fuel pump coupling for wear.( I think there were two of those?) I know they were funny shaped round looking things, but i do recall we had a few that had worn, and thrown the fuel pump/ engine timing out.

Some fuel pump bolts had been found on the coupling bottoming out, ie the head of the bolt was not tight up against the coupling, you could move the washer on the bolt head with your finger.

May i also advise caution if you do decide to remove your injectors for cleaning and testing. I did witness one of my old colleages trying to extract an injector from an AEC engine, only to pull out the injector sleeve as well.( had to have the heads changed after the dock foreman saw it, he was not happy.)

Regards to all.

John H

This will be from memory and without reference to any list, so something vital is bound to be missing.
As with any fault finding operation, the vehicle needs to be considered as a ‘patient’, your GP will refer to your recorded ‘history’ and will take a fresh verbal one from you before attempting a diagnosis. Vehicles should be treated in exactly the same way. Ask yourself questions about when the fault occurred? How frequently? after what period of operation? Weather and temperature conditions? Load carried? What previous work has been recently carried out? The answers to these questions should be provided to any third party investigating the fault.
The Fleet mechanic may well pick items seemingly at random from any list based on knowledge of the particular vehicle involved. This is exactly why your GP took that history about you and your painful big toe.

After consideration of what is known a decision about the order and relevance of investigations must be made. The simplest and most obvious items must be checked first before any serious or expensive dismantling is attempted. Follow this with a check on any known type specific defects providing they fall into roughly the same category. After this relevance, ease of operation and expense are the main goals using any necessary test equipment. Do not stop investigating simply because you have found one fault; there may be others.

This is a chart intended for lack of power, however it can be adapted for poor starting, engine will not start and engine has stopped in service; although for these intentions it is incomplete.


1. Start engine run up until hot or better road test. Floor the throttle, do revs pick up quickly? Does it rattle at the top end i.e. does it sound as if the rocker gear is making a lot of noise? Does sound as if it is misfiring? Is there excessive exhaust smoke with a hot engine? Can you hear a spitting noise as the engine is revved indicating a blown head gasket? Are the brakes binding? Continue with list before returning to this one. Let engine cool down enough to avoid burning yourself.

2. Check full throttle at the pedal is really full throttle at the pump; check linkage. (May require assistance)

**3. Check engine stop control fully off at the pump end, check several times.

4. Have a very careful look into the tank with a torch, what can you see at the bottom of the tank? It ought to be shiny clean, but it probably won’t be. It may well have something floating in it that can block the pick up pipe. Stop. Continue with list before proceeding. If it is plainly contaminated it will have to come off and be properly cleaned out. Practically all fuel troubles originate in the tank. Removing it will not necessarily be easy and repairs if possible could prove expensive.

5. Drain off sediment or water in the bottom of the fuel tank into a clean container for examination and identification. Be prepared this will make a mess; it will go up your sleeve and may cause you to drop the bung. Make sure you can see properly and keep your lead light out of the way. If a drop of fuel or water touches the bulb it will explode and glass could get in your eye or ear.

6. Check injection timing marks align. Stop. Continue with list before returning for rectification. If incorrect recheck several times and then start with pump coupling and condition of flywheel pointer.

7**. Check for any small fuel leaks anywhere. If fuel can get out then air can get in; not necessarily enough to stop the engine, but just enough cut down on power

8. Check that the fuel return pipework is not blocked

9. Check the output from the lift pump. Open a bleed screw and operate the hand primer. Make sure that the injector pump camshaft is on the back of the cam, otherwise the primer will not have a full stroke. Turn the engine if necessary. There should be clearly defined spurts of fuel. If not disconnect the outlet pipe and repeat. Now block off this outlet with you finger on the lift pump side can you feel any pressure? Do not assume that the lift pump is at fault. Continue testing

10. When was fuel filter last changed or cleaned? AEC and Leyland fuel systems have no sediment trap between the tank and the lift pump so the first filter is in the lift pump inlet connection. This will be the first clear indication that the fuel is contaminated. There is bound to be some dirt in the main filter, after all that is what it is there for. Tip the contents into a clean container for examination. After not getting full throttle and a sticking stop control this is the no1 favourite. Depending on what is found determines what to do next. Absolutely filthy, thick sediment, water and floaters mean a thorough clean out of pipes, tank and possibly a new lift pump. Go to no11.
Light fouling means go on to no 12.

11. Check small thimble shaped brass gauze in the inlet connection of the lift pump, this blocks up very easily. While this is apart examine the connections to it very carefully, is there any evidence of foreign bodies? If so then all the fuel lines will have to be cleaned out. This is a fovourite. It can be done without removing the wing, but is awkward. If you have come to a halt beside the road check this before calling for a tow.

12. Check the gauze in the inlet to the FIP.

From this point on dismantling is required and it will be a lot easier with the nearside wing removed, this is heavy and you will require assistance. Make sure that you have released all the fixings before your assistant arrives – he, or particularly she, is going to get very, very fed-up and cold waiting while you free off seized bolts.
Wear gloves. You are also likely to require parts eg. rocker cover gaskets, which may lead to a long delay, so work methodically and lay parts out so that you can tell easily where they came from.

13. Check whether the rack is sticking in the fuel injection pump. Carefully remove the side plate without tearing the gasket, operate the stop control and observe whether the rack moves back when the stop is pushed back in. Then move the rack to and fro with you fingers it should move freely. Replace sideplate and top up oil in pump and governor housing.

14. Check the valve clearances 10 to 12 thou. AEC Engine hot. 20 thou Leyland engine cold. Turn the engine in the normal direction of rotation. Do not use the fan blades to turn the engine over. Make sure you know which is inlet and which exhaust. Valves can close up as well as widen. Have a look at how much thread is protruding through the rocker locknut, no thread means badly worn valve gear. Later on after all diagnosis completed, If desired, to check, remove the rockers and shaft, then observe the tops of the valve retainers if these aren’t virtually in a straight line then the valves or seats are likely to be worn. Same applies to the tips of the valves. The rocker gear, pushrods etc all wear badly and these are the items not generally replaced when rebuilding an engine to a price.

15.Repeat 9. Remove inlet and outlet connection adaptors from lift pump and operate primer, you should feel suction at the inlet and pressure at the outlet. Do not condemn at this stage. Check adaptors and the ports of the pump for evidence of contamination.

16. Remove the rubber flexible hoses that are part of the fuel pipe work, these deteriorate with age and the walls collapse internally.

17. Get injectors cleaned, checked and adjusted. Run the engine up to temperature, spray the injectors with WD40 or similar around the sleeves and attempt to remove. Release all the pipework and fixings first then free off the easy ones. Liberal spraying and gentle hammering with a brass punch against the fixing bosses in an attempt to rotate the injector each way followed alternately, by levering and knocking back onto its seating, should eventually free off a stuck injector. It will be cheaper to replace a damaged injector than to have a specialist make and fit a new injector sleeve. You will also have to remove the cylinder head.

18. Carry out a compression test with the engine hot and then again when it is cold. If enough difficulty has been experienced removing the injectors for the engine to have not been run for about four hours, then refit the injectors and warm it up again. 400-450psi all cylinders = generally considered to be essential for good health. 300-350 psi all cylinders = tired engine, but not unduly concerned unless there are other cylinders reading 400+ or 300- However, if absolutely certain nothing else is wrong then this is the reason for low power. Below 300 attention is required, as is any variation between adjacent cylinders of more than 25-30 psi. This may only be a head gasket failure or valve fault. It is now your choice whether or not to proceed without checking 19. and 20.

19. Remove lift pump and send for test.

20. Remove fuel injection pump and send for test.


2** Cummins, Iveco (and Scania??) have an electrically operated fuel stop/run solenoid. These can stick.

7** Cummins, Iveco (and Scania??) have a lift pump susceptible to sucking air at the primer plunger.

As I haven’t seen a Dartmaster for some time I can’t remember whether they are turbocharged or not. If as I suspect they are, then at no7 remove inlet pipe and check condition of impeller blades and bearings.

I’ve just got home after working on RM471’s engine and read Roy’s excellent 18 point diagnostic guide. I agree with the similarity of engine fault finding to my previous work as a doctor in relation to history taking, diagnostic skills and familiarity with the individual patient. Unfortunately I have no formal training in diesel engine maintenance though I learnt a lot when I took the engine apart and helped an master craftsman rebuild it just over two years ago.

I’ve tackled the following points.

1. The engine is slow to pick up revs when the throttle is floored, there is no excessive noise, no misfiring, no spitting noise and no excessive smoke when warm.

2 & 3. The throttle and engine stop linkages seem fine.

4. You can see part of the bottom of the tank with a torch and you can see the metal clearly and no foreign bodies.

5. I haven’t drained off any sediment yet as the bung has a square, not hexagonal cap and I am concerned a spanner will slip, rounding it off. I’ll clean off the layers of chassis paint and try again later.

6. There is no play in the coupling to the fuel injector pump and the alignment seems OK, see above picture.

7. There are no fuel leaks.

8. The lift pump output seems OK.

10. We changed the cloth fuel filter six months ago. The old cloth was not badly soiled and the contents of the bowl were unremarkable.

11. There is no thimble shaped brass gauze in the inlet connection to the fuel injector pump. I can’t undo the inlet to the lift pump because access is so difficult. I’ll try and borrow an angled spanner for this. Does anyone know where I might get new thimble filters?

17. I have a spare set of injectors and these have been cleaned, checked and adjusted. I won’t fit them till I’ve done all the other work on the fuel system

18. I’m replacing all the flexible fuel pipe sections under the bonnet and will also do the sections underneath the body of the bus because they look old and brittle. So far they have not been blocked and there doesn’t seem to be any separation of the inner layers.

Thanks again for your help Roy and I’ll update you with further reports on progress.

My bus number (if any): RM238, RM471 and RM2213

Seems to me you've covered just about everything. The only thing left must be the fuel pump - you say it's slow to pick up when throttle is floored. If it was me I'd be back to the pump shop to run further checks.

My bus number (if any): RM1001

Good advice Mike, but it could just be sticky fuel.

Diesel does get gunky after a while in the fuel pump, something LT rarely had to deal with.

My bus number (if any): RMC 1458 RM 1585 RTL 960 and 15 RTs