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Gardner 6LXB engine problem...


Asciidv

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6lxb.jpg

 

A sad tale.....

I started up my Gardner 6LXB and the engine began to race. I thought it was probably due to a sticky air operated accelerator cylinder, so I pressed the engine stop button and nothing happened. So I lifted the engine lid and pushed back on the engine stop lever on the injector pump and after about 10 or 15 seconds the engine slowly came to a halt. The next time I tried to start it, it just wouldn't start. It seemed as if the engine stop mechanism had stuck in the stop position. I am not familiar with the Gardner injector pump so all the rest I did by instinct.

 

Taking off the pump covers reveals the stop lever which pulls on a thin connecting rod which I assume moves a rod through the length of the injector pump. At the other end of this rod is a spring plunger which I assume keeps the rod in the 'open' position until the engine stop lever moves it to the 'closed' position. However this rod appears to be jammed. There is a slight amount of push-pull movement (perhaps about 15 thou) but that is all. Does anyone have any ideas?

 

I have just bought a 6LXB manual on ebay but it will not be here until next week. I would love to have it running again this weekend. Any suggestions would be gratefully received. I hope I do not have to go to a bus forum for my answer!!!

 

Best wishes,

 

Barry.

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There's probably enough "Bus Menders" on here to get you the info you need without doing anything silly like going onto a bus forum.

 

The rod shown in your diagram does travel the length of the pump, and it operates the plungers that actually control the amount of diesel injected into the cylinders and subsequently the speed of the motor.

 

On the other end of that rod is a spring set up that holds it in the run/idle position, so that it can tickover. The whole rack should slide up and down with no more than finger pressure when that rod is disconnected from the govenor.

 

I have access to a 6LXB manual at work and (with luck) will copy the necessary pages for you. If you PM me an Email address I can send them through

 

Best regards

 

Rob

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I have access to a 6LXB manual at work and (with luck) will copy the necessary pages for you. If you PM me an Email address I can send them through Best regardsRob
Rob,Thanks for this, I will look forward to the relevant pages from the manual (DrBAH999@aol.com). It is a mystery why and how this rod is jammed. I thought a little tap with a hammer might free it, but even with your biggest hammer I don't think it will spring free. There is more to this than meets the eye.
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Pages sent, they should help you I have known the rack to partially seize in between the two halves of the pump, there should be a convoluted gaiter in the gap, but they tend to go brittle and break up allowing dirt in to cause a seizure.

 

It is possible to split the link in the middle which would allow you to isolate each half, could save a bit of extra work..

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Boat driver indeed! Don't worry it has wheels, but it is in fact a Dennis Fire Engine Control unit. It was built in the cold war years. The idea behind it was that it could head for the hills if the bombs started dropping and command the fire brigades in the North of England from somewhere safe. Although it was (is) fitted with an extensive array of VHF and UHF Storno radio equipment it was pre-mobile phone days, so there is an external panel for connection to your nearest telegraph pole to link in conventional land lines.

 

It was actually built on a Dennis Dominator bus chassis, but no-one better call it a bus.

 

cm2lr.jpg

 

 

Barry.

Edited by Asciidv
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It's not uncommon for the rack to become sticky over time, it's worth squirting some engine oil over it while you have the covers off. I used to do this about every 3 months on Gardener engined buses that were in use every day. From memory ther is a little screw in the rack cover plates for this purpose.

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....and this weekend some progress. Following advice from Rob on this forum I split the link joining the two racks together. The right side rack was completely free but the left side rack was completely solid. I therefore removed the top section of the left bank of the pump. 2 of the pistons are correctly sprung, but the central piston has no springing at all. I suspect that the spring has broken and has jammed rack, but this has to be explored another day. This video shows all;

 

Barry.

 

[video=youtube_share;5zW8Hha1QoU]

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  • 2 weeks later...

The left bank of injector pump was removed.

 

ip1.JPG

 

ip2.JPG

 

The pin has a spiral slot cut into the end of it. A it is pushed up by the injector pump cam it carries diesel into the injector pump pipe. The rotation of the pin determines how much fuel is transferred. The pinion gear shown in the picture which rotates when the longitudinal rack is moved in turns rotates the pin. In my case the pin had stuck in the fully up position which prevented the pin from rotating, which prevented the rack from moving. Gently tapping the pin out and then cleaning it with no more than a few squirts of WD40 made everything move smoothly again.

 

After talking to an old sage on Gardner engines, I learnt that pin sticking is not uncommon and there is a very easy 'fix' without removing the injector bank. Quite simply you can disconnect the injector pipe, remove the pipe coupler and lift out the one way valve. The top of the stuck pin is now visible and this can be tapped back down with a piece of 1/8th diameter rod.

 

HOWEVER I STILL HAVE AN UNKNOWN.

 

All of this began when I started the engine and it began to race away. Now with the pump all assembled again with everything moving freely the rack is in the full throttle position. I would have imagined that the governor should be pushing the rack over to the left to be starting with minimal fuel. Starting on full fuel delivery just doesn't seen right!

 

I had thought that the governor spring might be broken but this is a huge valve spring type spring and when I took it out it was perfect. So the question to ask you all is....with the engine stationary should the rack be sprung in the full fuel delivery position over to the right, which means it starts up like this until the governor acts?

 

001.jpg

 

Any suggestion would be gratefully received.

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Barry,

 

In my opinion the pump at engine at rest should have max fuel delivery. As soon as engine starts the governor will move the rack and control the revs. Many engines, I think inc a Gradner, have an excess fuel device which allowed the rack to move even further than the normal full power position. Normally these devices are arranged so that they cannot be used when being driven along the road. Usually the device is operated on the pump itself and not from the cab. It resets to normal on the first time the rack is moved to reduce max fuel after starting.

 

If the rack was at min fuel position at rest, it could never start from cold!

 

Out of interest, in the TA with Bedford TM 8 tonnes, we found that we could operate the excess fuel device from inside the cab when on the road. It was arranged so that the handbrake valve lever was in the way. Unfortunately, it was still possible to obtain excess fuel! I can tell you it was like another 50 % of power! Very naughty!!

 

John

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Today, I bolted everything back together again. I was still a little doubtful whether it was correct to be starting on full fuel delivery, but as you will see from the video it is absolutely correct. The governor acts instantaneously pushing the rack to the left to reduce fuel delivery to give the tickover speed. The engine stop lever pushes the rack even further to the left to shut off fuel delivery altogether. So back on the road again! Thanks to all who have been so helpful with their advice and comments.

 

[video=youtube;TFlPGu0L-qg]

 

 

Best wishes,

 

 

Barry.

 

(P.S. The heavy breathing you can hear between the first engine start and the second isn't me, but 'Leo' my dog who keeps me company and passes the spanners when I am down at the shed).

 

leo.jpg

Edited by Asciidv
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That's ok, I still have trouble telling the difference between Whitworth and AF spanners too. I get that adopting the Metric system was too difficult and, more importantly, too French, but why oh why couldn't they have used decimal measurements rather than fractions of an inch!?

 

That said, I also struggle with analogue clocks, so I guess that I'm a product of my generation :P

 

(I can work out fractions and analogue clocks, but to do so, I have to do some calculations; I can't just look at them and "see" their values. I'm getting better at AF, but I've only owned AF tools for the last year or so, with everything prior to that being metric)

 

Cheers,

Terry

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