My Bedford TK is acting up
 

I have a -71 Bedford TK with the 330 diesel (MP044) naturally aspirated with the hydraulically governed CAV injector pump. I've had it some years, and even though the engine is definitly "worn" (some smoke, turns easily), it's always been very easy to start - even in -20 C.

This winter however, it suddenly wouldn't start one day. After a lot of glowing and grinding I finally managed to get it to "start" on one cylinder. That's not uncommon in the cold (was about -10 C then), so I tried to keep it alive on this one cylinder until the others would heat up enough to start firing. But it never happened, and in the end I gave up. I figured it could wait until the weather got warmer to save the battery and starter. Since that I've had a couple of tries where I haven't been able to start it at all, just some random ignites a very few times.Now it's spring and my plan was to get it ready for MOT.

Some years back my feed pump died, and I made an "emergency repair" by replacing the valves with some I found from an old Massey Ferguson feed pump that were, as far as I could tell, identical. However, I didn't really trust that the valves would stay in place since you have to "stake" the housing to secure the valves, which doesn't work as well the second time. In addition to that the threads for the incoming connection had seen their best days. So, I ordered a NOS pump from the UK - which I've never come around to actually install.

Everything points to lack of fuel, both that it would fire on one cylinder only and the fact that it will temporary start when spraying starting spray into the air filter. I therefore figured that the feed pump must have died, so I replaced it with the brand new one I had. I also changed the fuel filter since I can't really remember when I did that last, and it was definitly due.

My problem now is that I can't seem to get the bleeding/venting "right" for some unknown reason. Btw, I'd like to congratulate whoever figured that it was a bright idea to install the feed pump and the injector pump on opposite sides of the engine - it really makes bleeding easy for one person..! Anyway, I've bled this engine, and many others for that sake, many times before and this Bedford has always been very easy to bleed. This time around though, I keep getting small air bubbles no matter how long I bleed. I also experience a strage phenomena where the feed pump handle is really slow to return even though the bleeding plug is open. It feels just like it does when you have a pressurised system when I pump. It does come diesel and air of the bleeding plug hole though, but I think it flow is a bit small.

Normally when I see small air bubbles like this, I assume it's a leak on the vacuum side of the pump, so I've unscrewed the input connection again, cleaned and reinstalled it with thread tape to make extra sure there's no leak there. Still the result is the same. I've looked over the fuel line from the tank to the feed pump, and it's completely dry as far as I can see, except close to the pump where I've made a mess each time I've disconnected it.

So, in short, I've really got no idea what could be causing this at the moment. The most logical explanation would be that the "input fuel line" would be partially blocked somewhere so that the vacuum manages to pull some air in at joints that would otherwise be "sealed". That would also possibly explain the slow return of the feed pump handle, but I'm not sure simply if a vacuum is strong enough to cause this. A blockage after the feed pump would better explain the slow return, but that wouldn't explain the small bubbles at all. I'm stuck.

I haven't yet pulled the fuel intake out of the tank since I'm a bit scared about how many of the bolts that will break when I try to disconnect it, but I've tried to look inside with a optical scope camera, but they aren't as easy to control as one would imagine. I can't really see that much except that it seems to be a plastic cylinder in there probably containing the fuel indicator float. Does anybody here have any experience with those, often there is a small filter in the bottom which could possibly be blocked. I've also considered it a leak could have arisen inside the fuel tank above the fuel level sucking in air. Is this likely at all, or am I focusing on the wrong part of the fuel system here?

Any ideas/experience appreciated.

You seem to have all the right ideas, but is the vent hole in the fuel tank filler cap blocked?
It sounds like you are trying to suck against a vacuum . . .

Maybe, as you suspect, the suction pipe is blocked - you could fix some clear plastic tubing and see how easily you can suck fuel (stop when it reaches the clear tubing!).

I think that the plastic cylinder is the float for the gauge.

I'll check my manual and see what else I can find.

There's no vacuum in the tank itself, I've even tried with the cap off. I could try to suck myself, but I'm not really sure how to judge how hard it should be, and I suspect getting a good seal against the existing connector would be somewhat difficult.

I guess I'll just have to pull the whole suction/float module and see - even though I really don't want to ;)

My manual is for the military MK model. The MK engine was a multi-fuel version of the 330cu in diesel engine with an injection pump that could be set to suit aviation fuels as well as diesel.

The transfer pump (on the MK) is an electric pump.

You describe a hand lever, suggesting that yours is a mechanical (engine-driven) lift pump.

My manual shows a shut-off tap between the fuel tank and the primary fuel filter (there are two filters on the MK model). The primary filter is between the tank and the delivery pump (not the injection pump).

Maybe your tap (if yours has one) is partially blocked?

Otherwise, your lift pump should be capable of freely-delivering fuel (if you disconnect the outlet pipe). If the fuel doesn't flow freely then that is your problem.

There is no filter (or anything similar) inside the tank (of the MK) so fuel should be able to be drawn easily from the tank by the lift pump.

If you cannot easily suck fuel from the tank, there might be an obstruction on (or in) the pipe.
You might have a crack somewhere in the fuel pipe between the tank and the lift pump allowing air in.

Reading your description of the sluggish return of the fuel pump lever it sounds that there is something wrong (as if the diaphragm has hardened or a spring has broken). I would think it should return easily.

Do not suck directly on the metal pipe - use a good long length of clear plastic 'hose' (at least a couple of metres) with enough to allow a dip down between you and the tank. You should be able to easily suck fuel from the tank until it runs down into the hose where you can see it before it gets anywhere near your mouth.

I haven't found a tap anywhere on the fuel line, but it's a bit hard to access parts of the fuel line (inside the frame) without raising the tip, which again is difficult when the engine won't start - so I can't bee 100% sure there isn't one. Anyway, my lift pump is mechanical and of this type. I only have one fuel filter, and that's placed between the lift pump and the injector pump (that's the one I just changed). There is however a very "simple filter" inside the lift pump itself, which is just a brass mesh if I remember correctly. That one is probably instead of anything at the intake in the tank, which would make it possible for something to get sucked into the pipe in the tank and partially block it.

The slow return of the lift pump lever isn't a defect of the lift pump itself, since both the old and the new pump does this, and this is not the case the first couple of pumps. It's obvious that either a pressure builds up after the pump or a vacuum builds up before the pump causing the slow return. I guess the only way to find out where this is is to loosen connectors different places on the fuel line and see when or if the resistance goes away.

My worst fear is that something's gone wrong with the injector pump itself, and that it won't let the fuel pass freely thus building up pressure. I don't know about enough about the inner working of the injector pump, but maybe for example a stuck "engine stop" valve could cause this? At this point though, I'm still trying to find faults anywhere else but the injector pump...

I understood what you meant by the plastic hose, I would never get my head down to the pipe anyway. I'm worried about the seal between the plastic hose and the pipe, since the connector threads seems like something in the range of 3/8" and I don't have any clear hose larger than around 1/4" inside diameter.

Softening the plastic hose by immersing the end in hot (boiling?) water might allow you to stretch it over the connector.

Concentrate first on getting the lift pump to work (disconnected from the injection pump). If that doesn't deliver fuel freely then you have a basic problem.

As I've mentioned, the low-pressure side of the fuel delivery system (from the tank to the lift pump) is simple and should operate freely without obstruction.

From the lift pump to the injection pump (via the filter) there will be more restriction, but it should flow relatively easily. Loosen the connector before the filter and you should be able to pump fuel easily (and without air - unless there is insufficient fuel in the tank of course!) - or a blockage or split in the supply pipe.

Was the fuel pump that you changed the lift pump or the injection pump?
You mention thread tape - is there a chance that there is some blocking the pipe?

Loosen the connection between the filter and the injection pump and you should be able to pump fuel easily. If this isn't possible there may be a blockage in the filter.

It's only when the fuel leaves the injection pump that it is at (very) high pressure.
The injection pump shouldn't pass fuel until it reaches very high pressure (apart from the relief valve which might return the fuel to the tank).

Unless you can supply adequate air-free fuel to the injection pump it stands no chance of working.

I replaced the lift pump. I was carefult with the thread tape, and the symphtoms where the same before I added thread tape.

When I'm talking about the strange buildup of pressure or vacuum, the bleed/vent plugs are open. If they were closed, it would be normal and expected for å pressure to build up in the injection pump.

Are all the fuel lines clear of dirt, it might be a good idea to give them a good blast out with an air line. Also I'm sure those old Bedfords had a glass water trap in the line, if they were over tightened they used to crack.

Yesterday I pulled the inlet pipe/float from the tank. The bottom 4-5" of the inlet pipe was covered in something that reminded me of a mixture of tar and bitumen. The only thing I had that was able to remove it was xylene, and I think I got most of it. I don't think it were enough of it inside the pipe for that to cause the problem though. It did nothing to reslove the buildup of "pressure" when I pump, so I opened the fuel line at different places and found that it cause is indeed pressure (not vacuum), and the pressure/blockage is within the injector pump itself (if flows freely after the filter).

It's hard to remember just how freely the fuel is supposed to flow through the injector pump with both bleeding screws open, so maybe this isn't a part of the problem at all. Some fuel manages to get through, and after a lot of bleeding I can't see any more of those tiny air bubbles, so I'm guessing those came from me replacing the feed pump and filter and somehow got "trapped" somewhere and only released in very small amounts.

However, I still haven't gotten any response bleeding on the injector lines themselves. I get some very few droplets coming out, but no high pressure "burst" as it's supposed to, so it seems like the high pressure pump doesn't do it's job.

At this stage it looks like my injector pump might have died, or that I still have some air in the system - I'm not sure which. It's very strange in any case, as I've bleed the Bedford several times before and it's always went very fast without any trouble.

It's sad though, since I don't really think this engine is in good enough condition (smoke, low compression) to justify a replacement injector pump so if that's the case it a engine replacement would be the right thing to do. There are very few TK's left here in Norway though, so I don't think sourcing a good engine will be very easy. It's also quite a big job since I have to remove the cab to replace it, so I'm not sure it's worth the effort even if I could find one. This just may be end-of-life for my beloved Bedford, and it's a real shame since the rest of the car is working just fine.

I'm going to give it one more try later today to see if I can somehow manage to get some pressure on the injectors.

If you can connect a clear length of plastic pipe to the inlet side if the lift pump and put the other end in a can of clean diesel. Then bleed as per normal, this will bypass all the rest of the fuel supply lines and filters. If this is successful and you are able to get fuel up to the injectors then the fault is in the fuel supply from the tank.

As stated in the previous post, "sadly" it seems that the rest of the fuel line is fine. The filter is placed after the lift pump, and when I loosen the connection from the filter to the injection pumpm the fuel flows freely. This includes the whole fuel line including the filter unit, so the resistance has to come from within the injector pump itself.

The thing I find very strange it the fact that it ran normally when I parked it, and then I've had no luck starting it since. If there were some kind of mechanical malfunction inside the injector pump it would be very unlikely that this would occur while it was not in use, but even though unlikely the fault could've occured just as I stopped it the last time or when I tried to start it the next time. That's why I've had a slight suspicion to the stop valve on the injector pump, could that for some reason be stuck in the "stop" position internally even though the external lever returns to it's normal position? I don't know the internal workings of the injection pump so it's not clear to me if that would block fuel also when trying to bleed, but I do know that what the stop valve does is to somehow cut of the fuel supply.

According to the Bedford manual that I have (for the MK model which has the same 330 cu in diesel engine - though with an additional setting for the injection pump to allow the use of aviation fuel) it sounds as if the stop control is binding. It should 'snap' to the full-fuel position with a distinct click. If this does not occur, indicating that the control rod is binding, slacken and retighten thevalve-holder

The part of the injection pump where the stop lever is connected is quite hard to access because the lack of a tilt-cab so I'm not sure if I know exactly where the stop-valve is located, but there's definitly no click when I move the stop lever.

Is your injection pump an in-line one or a rotary one?

Can you reach the pump (I'm small, so I could crawl inside the side flap behind the front mudgard).

Whereabouts is the bleed screw that you are talking about?

Can you reach the injector pipes?

Loosening some of them then cranking the engine should bleed the system.

Do not overtighten them afterwards - they are easy to crack.

As far as I can tell, this pump is identical to mine: http://shop.startermotorsalternators...p#.UXwGQMp1mb4

I guess that's rotary type. I have a manual showing the pump, mine is the first type in this document, the CAV hydralically Governed DPA starting on page 11. The PDF file is too big to upload as an attachment, so I've uploaded it to a webserver at this address: http://superbum.org/Bedford_330_Fuel_and_exhaust.PDF

This pump has two bleeding screws, see page 11, one on the pump body and one on the top of the governor. As usual, one bleeds the lower one first and then finishes with the one on the top/governor. I can reach and see the pump on the left side, but can't see the right side. I can only reach the pump with my left arm, so in-depth inspection is difficult.

I can reach the 3 or 4 injector pipes from the rear, the front ones are out of range. I have tried to open them and crank, and as mentioned above, I don't get the proper "burst" of fuel I'm used to seeing when venting injection pipes, it's more of a weak trickle.

It is, indeed, a rotary pump. The MK was fitted with an inline pump, so my instructions about that don't apply. Sorry if that confused you.

My engine knowledge is limited, we need someone more familiar to join in.

If you are quite certain that you have a good supply of fuel to the injector pump but nothing or very little fuel coming out of the injectors, then it must be the injector pump at fault. Does it only have a mechanical stop lever or is there a stop solenoid as well ? Solenoids can burn out or lose there feeds, if it has one it will get its feed from the ignition, to test it turn this on and then pull the wire off and then re-connect it you will hear a click if it's working. If it only has a mechanical stop make sure the lever arm is not lose on the spindle and it's not just the arm that's moving. I also seem to recall that DPA pumps had a filter screen in the union on the top of the pump where the fuel feed connects. This was a last ditch defence against bits of rubbish going into to it, you should be able to check this by taking the feed pipe off and looking into the top of the pump. Going back to the procedure for bleeding the system, the instructions were at one time to first bleed from the lower bleed screw - close this off then bleed from the top one, turn the engine 180 degrees and repeat the process.
Finally if all else fails then there is always every diesel fitters favourite tool, the can of ' Easy Start ' but not too much or you can cause damage. The best way is straight into the Venturi with the air filter trunking off and the engine spinning over, but again not too much. Good luck and let me know how you get on.

The stop is mechanical and it moves freely and returns all the way, but it could in theory still be stuck inside the injection pump I guess, depending on the internal design which is unknown to me.

The filter screen on the fuel inlet however was unknown to me, but when I think about it the connection is "unnecessary" big so it makes sense that there's something there. Definitly worth a check.

Turning the engine 180 degrees and rebleeding was also new to me, it doesn't say in the bleed procedure from Bedford, but I guess it could still be worth a try to hopefully release some potentially trapped air inside the injection pump.

Keeping my fingers crossed that the filter screen is blocked... ;)

PS! Regarding starting spray I've already tried that, and I know how to apply it and that's it really not healty for diesels, and that one must under no circumstances glow when using it. However, since the engine is worn/has a reduced compression the risk is less. The problem is, that the engine starts on the starting spray, but stops as soon as we stop supplying. Strong evidence for the lack of injected fuel.

One last thing I have just thought of it to make sure the lever on the lift pump is at the lowest point on the engine camshaft when you use the hand primer.
This is so that you get a full stroke on the diaphragm to deliver the maximum amount of fuel. You can tell what position it is in by the resistance on the hand primer.

Yes, I'm aware of that, but as mentioned before after a couple of "pumps" the pressure builds up and the diaphragm/membrane doesn't return with the lever so that you can feel it's not actually pumping much. Opening the pipe connection into the injector pump releases the pressure and the diaphragm/membrane returns. That's why I suspect some kind of blockage, and the filter screen is a great candidate.

I don't think that you should be able to pump fuel through the injection pump (other than through the pressure-relief valve which might vent back to the fuel tank). The injection pump controls the squirts to the injectors.

The MK relief valve is set to 20 psi (the electric supply pump keeps the supply system at this pressure - the pump delivers fuel up to 25 psi, and the excess 'spills' back into the fuel tank, together with the leakage from the (in-line) injection pump gallery).

As I see it, I shouldn't be able to pump through the injection pump with the venting screws closed, but I'm talking about when they are open. Pressure still builds up when they are open, and only very small amounts of fuel comes out when bleeding. That, combined with the fact that the lift pump stops "gripping" after a couple of pumps (if I wait a while, pressure is reduced enough to let me do another pump) indicates to me that somewhere the fuel has a hard time getting through. Since loosening the incoming pipe to the injector pump releases this pressure, it's now narrowed down to either being the filter screen (hopefully) mounted on the inlet to the injection pump, or somewhere inside the injection pump.

Unfortunately the weather gods have decided to make it rain here today, so I'm not going to check this until tomorrow at the earliest (depending on the weather).

Just to add to your comments above, a stuck stop control (in the closed position) would stop any fuel from passing through.

Check the control cable or the solenoid wiring if the stop control is electrically operated.
(I think that this has already been mentioned above)

Yes, it's already been mentioned, and I as I've stated it moves freely outside the injection pump. What happens internally however is unknown, and I consider that as an alternative explanation, but I'm not sure it helps me if that is the case since it doesn't seem to be much I can do about that without opening the injection pump, and that isn't really an alternative. I can't even understand how I could get enough space to manage to remove the injection pump, and opening them without detailed drawings/procedures has little chance of success. I did manage to unstick a stuck stop valve in a Ford D-series "Minimec" injection pump once, but I promised myself to never open one again - I wasn't at all sure that pump would ever work again (but it did actually). But this truck hadn't been used for several years, this is not the case with my Bedford and I can't really believe that the stop valve would have the time to just "get stuck" from corrotion, so it would probably mean some kind of internal mechanical failure.

I'm still hoping for a "simple fix" like a blocked filter screen.

The cab tunnel might have a removable panel (some TKs did have) which might allow you better access without removing the cab.

Alternatively, access from an inspection pit (assuming you can move the vehicle!) might be possible. My memory is vague (more than 30 years since I was last 'under' a TK).

The major drawback when removing the cab is whether the mounting bolts (which are through-bolts with nuts - ie they don't screw into the mountings) are seized (despite being copper-plated).

If you do decide to remove the cab I can provide details of what needs to be disconnected. The major thing is that to lift the cab you must use a beam through the door apertures (not the window apertures), otherwise the cab will distort.

There are nothing more to remove I'm afraid, I've welded quite a bit on the cab (most of the floor was gone), so I have a pretty good idea about what's what there. IF I at some stage have to remove the cab, I will definitly need all the tips I can get about disconnecting everything, but I'm a bit worried because of rust around the edges of the roof, especially in the rear. If the cab would "bend" enough to break the windshield, it would be a catastrophe.

One thing is sure: If I ever do remove the cab, I will replace the whole engine and not just the injector pump! The engine is as mentioned before, quite worn even though it's been running fine until now. It's oil consumption however isn't what you would call environmently-friendly ;)

The weather allowed me check the filter screen today, and there was one. It was however relativley clean. I did find some kind of a valve under it though, with a small pison itside that was stuck in some "brown stuff" - not rust as far as I can tell, but some really sticky brown stuff. I got the piston out and cleaned it so it now moves freely again, and put it all back together. I had some hopes after that, but the result is the same. Bad flow when bleeding, and no pressure out on the injector pipes.

I don't know what that "brown" stuff I keep finding is, but it's from 1971 and I guess it's had it's share of bad/dirty fuel along the line. Since this can pass through diesel filters and the filter screen, I'm guessing it's something that's solvable in diesel. There's no telling though which other parts inside the injector pump that could've gotten stuck by the same stuff - so at this point I consider that the most likely culprit. However I see it, I must conclude that the problem is inside the injection pump.

Can any of you tell me where the timing adjustment for the injector pump is? It seems to be 3 bolts that hold the injection pump, and what I'm wondering is: If I remove these (and the injector pipes), will I also loose my timing setting? I'd hate to disturb the timing, since I have no proper means of readjusting it. If I could get the injection pump off without loosing the timing, I guess it could be worth a try to sit down and remove any inspection covers and plugs that I can find and clean and "unstick" anything I can access without pulling the pump completely apart.

The following information is offered without guarantee (my knowledge is chassis, not engine).

According to the MK manual (which is for an inline Minimec pump, not a CAV rotary pump), there is a 'coupling' (like a dog-clutch), probably with a rubber insert.

Provided that you do not disturb the pinch-bolts that secure the halves of the coupling, you should be able to remove the injection pump and replace it without disturbing the timing.

That is how I read the manual which describes how to adjust the timing:-

So, don't disturb the timing and you should be OK.

Edited to add:- read the next post before proceeding to remove the pump.

The following instructions apply specifically to the inline injection pump and may not be relevant for your rotary pump.
Read them carefully and work out your own sequence:-

Removal:-
Installation:-

Who needs "Haynes" eh?:D:D

Thank you for the information. From what I understand from those intructions is sounds difficult not to disturb the timing, especially considered how hard to reach this is. I can see the timing cover, but I can't really understand that it's possible to see anything down the hole if I remove it, since I can under no circumstances get my head directly above the hole. I've tried doing such things with mirrors before, but that tends to be a much better idea in theory than reality.

Even though it's not much to think about because I'd probably need both a different "adapter" connecting the pump to the compressor and different injector pipes, I happen to have several Minimec pumps from Ford D-series 330 cu's. It's a bit annoying having those around when I know that they too have been used for this engine while my pump is currently "dead".

I think I'll have to consider carefully what to do next.. :confused:

Time to enlist the help (or at least the advice) of a vehicle mechanic familiar with Bedford TK engine repairs.

Hehe, sure, but where do I find him/her? There aren't many Bedfords left here in Norway, and I'm pretty sure I couldn't find a garage that would fix it even if I could afford their ridiculous fees. Those that once worked on them are retired a long time ago. I even asked at the local GM dealer where they once sold my Bedford new, and the last one that knew those retired many years ago. They have absolutely no idea Bedford at all.

That's the reason I'm writing here, in the hope that someone who knows could answer.