My Bedford TK is acting up

[Nadar]

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.

[coachman]

Originally Posted by Nadar

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.

[Nadar]

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.

[G-CPTN]

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

[Nadar]

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.

[G-CPTN]

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.

[Nadar]

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.

[G-CPTN]

Originally Posted by Nadar

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

I guess that's rotary type.

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.

[coachman]

Originally Posted by Nadar

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.

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.

[Nadar]

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.