Jump to content

Spill timing


linnit

Featured Posts

14 hours ago, Mike the Boilerman said:

Bump...

Can anyone explain what spill timing is, please??

It is the art of getting the start of injection at the right point in relationship to the crankshaft.  It involves finding the point at which the spiral groove in the fuel pump element stops letting disel go back to the Inlet. This is known as the spill point hence the name of the job.  I have piosted somewhere on the site instructions for doing it with an integral camshaft pump. On an RN the pump has no integral camshaft so it involves tweaking the fuel pump tappets IIRC.

N

Link to comment
Share on other sites

Spill timing is the equivalent of ignition timing on an older petrol engined car when done on inline injector pumps. Typically this is done by slotted bolt holes in the pump drive so you can alter the pump's camshaft position relative to the engine crankshaft/camshaft position (similar to twisting a distributor). More modern rotary  DPA pumps have slotted mounting holes that allow you to do the same by twisting the pump body.

The shims under a Lister actually alter the phasing to ensure each pump starts injecting at the same time. As the cams that work the pump elements are on the main camshaft if the camshaft timing is correct so is the spill timing. Anyway I doubt "spot on" injection timing is so vitele on older industrial type engines.

Phasing on most inline pumps is done by adjusting the tappets clearance below the pumping elements.

Now for the RN. I was going to reply earlier querying if the OP really wanted to do the spill timing or the phasing but as I do not know the RN very well I desisted. It has an inline pump so I would expect the phasing to be done by the adjustment that the OP referred to and for there to be some king of pump drive adjustment where the pump drive shaft mounts into the drive gear BUT being an old design maybe RN assume that once you correctly fit the pump drive the timing will be correct. If that is the case the OP is asking about how to phase the pumping elements, not spill time it.

For completeness the pumps also have to be calibrated so each element delivers the same amount of fuel. This is done my altering the degree of twist on the pumping element relative to the control rod. On inline pumps it is usually done by clamp bolts on the mechanism that wists the pump element but on the LIsters it is done by the length adjusters on the pump rack/control rod between each pump.

Edited to add: if the OP makes the gap below an element smaller the cam will push the element up sooner and close the spill port in the element case sooner thereby advancing the start of injection.

Edited by Tony Brooks
  • Greenie 2
Link to comment
Share on other sites

48 minutes ago, Tony Brooks said:

Edited to add: if the OP makes the gap below an element smaller the cam will push the element up sooner and close the spill port in the element case sooner thereby advancing the start of injection.

Thank you Tony..that is the answer I was after

Link to comment
Share on other sites

It seems from posts in the other place that a RN's spill timing is indeed carried out at the pump camshaft drive gear with a clamp on the shaft. I may have misunderstood the last bit.

It also occurs to me that messing with the phasing, especially causing the pumping element to lift sooner and thus higher could all too easily result tin the top of the element hitting the delivery valve/pump head. Indeed one of the things one checks during pump overhaul is the bump clearance.

The OP needs to be very careful. I think the safest advice would be to get the pump to a specialist of checking and adjusting so the phasing & calibration is correct and then do the spill/pump timing properly, making marks on the flywheel if required.

Its seems the OP has given the other place more information in that he messed with the phasing some time ago in an attempt to stop diesel knock and indicated that he counted flats on the adjustment so if he is only returning the phasing to what it was before hopefully there will be not problem.

That raises a question about why it was knocking apart from the fact all diesels knock. It could be a timing problem but it could just as well be low cetane fuel or injectors that are not atomising properly. It certainly should not have bee cured by adjusting the phasing.

Link to comment
Share on other sites

1 minute ago, zenataomm said:

I'm not sure of my own name.

However I have been adjusting my timing to this rule for a whole month now.

Please retard my lack of self confidence by advancing what I've got wrong.

The pump piston is attached to the cam and is therefore fixed. Timing is done by shimming the body up or down.

Adding shims moves the pump body up, moving the cut off point in the body further away from the piston, which is later in time. So adding shims retards the timing

I just checked the manual too

Richard

Link to comment
Share on other sites

I would suggest that shimming the Lister is not spill timing but does alter it. It is getting each pump to start injecting at the correct time relative to each other which is phasing although the procedure does alter the pump timing. The timing is done when the camshaft is fitted. However I accept in the case of individual pump engines its arguable.

Link to comment
Share on other sites

  • 2 weeks later...

You can adjust all the pump adjustments internally, ive rebuild my pump due to a fuel issue i was having. It took for ever to find the right spot for the fuel pump.

To advance the start point for the fuel you have 3 ways of doing this.

1. Adjust the cam for the pump arms lifters.

2. You can adjust the pump lifters mine are set so they just tuch the bottom of the pump when the lifters are down means as soon as it starts to push up its pushing fuel. You can adjust it further up so the pump it very slightly pushed in gives you a shorter stroke of fuel. Or adjust it down buth this means it will have to hit the bottom of the pump before it starts pushing.

3 you can adjust it all internally in the pump there are 2 brass parts with teeth on you can move this either a tooth at a time will give more or less fuel or you can undo the to brass parts and move round, this i wouldnt suggest it take hours to get this set in the right place.

Link to comment
Share on other sites

3 above sounds horribly like the calibrating adjustment on the rack/control rod. Unless you have the pump on a test bench an owner should not mess with this. It is used to ensure each pumping element delivers the same amount of fuel and has nothing to do with spill timing.  If you do mess with it you will end up with cylinders delivering different powers so may well induce vibration and in extreme condition just might cause crankshaft failure if the vibration frequency happened to match the natural frequency of the shaft. However on a RN I expect the shaft is so over engineered this is highly unlikely.

On a pump test bench it does not take hours because the volume of fuel injected is delivered into calibrated "test tubes" so you can instantly see which elements need adjusting, which way (more or less fuel) and by how much.

As has been pointed out elsewhere messing with the lift on the elements can cause one to strike the top of the pump/delivery valve so is not the way to do the spill timing although on a RN you would do that to phase the pump (getting all elements to start injection at the correct number of crank degrees apart).

Really unless the owner really knows about setting up injector pumps they should not mess with either adjustment mentioned here. The only exception is on simple separate injector pump designs like the Listers where shimming the pump does the phasing.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.