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Hi All,

A Happy New Year to you!

I suspect that my TR5 is running rich. This was somewhat anecdotal at first as a friend following me on a run out told me that there was a smell of petrol from the car. However, at a recent MOT test my local garage tested the CO and it was 7.012. They thought that it should be near to 3. The Lambda was 0.807. I have searched this forum for help but can't find anything specific enough. Carl of Prestige Injection has been most helpful in advising me and I have picked up some suggestions from the forum. This is what I have done to date:

  1. Checked the injector spray pattern with the engine running. I get a nice conical spray from each one.  
  2. Checked the vacuum level in the inlet manifold, which is fine.
  3. Done the "suck and hold" test on the Metering Unit (MU) to check the diaphragm. After holding the diaphragm can be heard to drop back into place.
  4. Checked the MU over rich setting and that it returns properly once the choke knob is pushed in.
  5. Replaced the air filter.
  6. Checked that all of the inlet butterflies are closed and balanced at idle, confirmed with an air flow meter, and that they all open fully. The car has the slow running air valve.
  7. Checked that fuel is returning freely to the tank from the MU both with the engine idling and with just the pump running.
  8. I haven't checked the pressure relief valve setting but it is returning fuel back to the petrol tank as I found a leak. The car has the TR6 type of tank and a Bosch fuel pump.

The history file shows that the MU is a Prestige reconditioned unit fitted when the car was restored in 2000. The car has travelled 14k miles since. The car runs very well but is prone to pink under load. I use Shell V-Power petrol. I have checked the static ignition timing and it seems to be be spot on. The engine is in excellent condition, with an unleaded head fitted and the standard ignition set up.

Prestige Injection has offered to test the calibration of the MU and to confirm that all of the injectors are working correctly. They have suggested that I send the MU, hoses and injectors still connected together for this test. Before I do this I have three questions to ask:

  1. Is the apparent rich running unusual or is it typical of a TR5? Some forum posts (TR5 & TR6) suggest that it is typical. 
  2. Are there any other check I could carry out?
  3. Any other thoughts?

Many thanks,

Denis

Edited by DenisMc
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Hi Denis,

I TRy not to follow anything with PI fitted.  They do run rich.

Excess oil being sucked into the compression chamber can cause pinking. 

You shouldn't need the CO2 checking during an MOT but no harm caused to see whats going on.

Going up mountains with PI can be fun - it gets richer.

I understand that some MU's were fitted for high altitude driving

 

Roger

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Hi Denis,

As a reference for you I had my fresh rebuild, standard engine TR5 PI checked at last MOT in August and CO was measured 4.5%. I thought this might be too high and checked with Neil Ferguson who advised it was OK, but maybe top of the range.  I also have a CP TR6 , checked at last MOT in November - it was 3.5%. Both run fine. I decided on an "if it ain't broke don't fix it" approach.

Ian

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Simplest solution is just to send it all off and get it recalibrated. They always get richer with mileage due to wear on the shuttle and end stops in the rotor.

The metering unit has to be removed before you can check the max and min shuttle travel which is actually a DIY job. The rectangular black plastic cover held on by 4 screws conceals the metering track.

With the linkage at the bottom of its travel (no vacuum full throttle) there should be about 56-57 thou gap between the rollers and the centre part of the rotor. This is adjusted with the little threaded widget with a locknut at the bottom of the unit.

The minimum fuel setting needs the lid of the vacuum chamber (where the hose attaches) taking off (4 screws) The springs are then removed and the lid replaced. Suck on the hose and see the linkage pulled to the upper setting. The gap between the rollers and the centre of the rotor should be about 2-3 thou. Adjustment is with the screw on the slotted hole on the linkage, just like setting points.

Don't touch the locking rings which alter the vacuum spring adjustment, they are often painted as an anti tamper deterent

When I had a PI saloon as my daily driver (12,000 miles/year), this was an annual check and adjustment which could be done without removing the metering unit. When I bought it the fuel consumption was dreadful and I think there was about 7-8 thou too much clearance top and bottom which is about 10-15% too much fuel at full throttle, but about 300% too much at the opposite end on over run.

It would be worth checking the valve clearances as well. Anything that reduces inlet manifold vaccuum will richen the mixture

Neil

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Thank you Roger, Ian and Neil for your prompt and most helpful replies. Roger, my local garage checked the CO at my request. Pleasingly, the car sailed through the MOT test. Neil Ferguson has been in touch by email and following a discussion has suggested that I send the MU to him for a calibration check along with the injectors for a functional test. I have not removed the MU before but having looked at the workshop manual it seems to be straightforward. A concern I do have is whether I am going to have a flood of petrol when I release the fuel line due to the "head" difference between the petrol tank level and the MU. The tank is half full. Is this likely to be a problem?

Thanks,

Denis

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Thanks Roy and Harry for your tips. I am going to have a go at it in the next couple of days and will try clamping one of the pipes in the boot.

Regards,

Denis

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I haven't checked that. How do I do it please? 

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34 minutes ago, DenisMc said:

I haven't checked that. How do I do it please? 

It's all in the BL manual and in the Lucas PI handbook. The former is in the Resources section in the Members' Area of the main web site. The latter was posted a week or so ago in the thread "Help on TR Metering Unit Timing" in the TR6 forum.

Having said that, you can be confident it's not MU timing that's causing rich running. You appear to have checked all the typical causes, so you're probably best getting it looked at by Prestige. As Neil says, tweaking the MU is pretty straightforward (if you have the manual), but I'd start by getting it set up properly. Before you reinstall, measure the cam follower/ datum track roller gaps to give to a baseline. A couple of thou makes a big difference at anything below WOT. Again, as Neil says, do. not. touch. the calibration screws under the black cover unless you a) want to send it to Prestige to sort out the mess you will make, or b) have a vacuum calibration rig.

You can check the MU timing when you reinstall.

John

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Thank you for your suggestions. I have looked in the various manuals that came with the car and am now clear about checking the timing of the MU. One question though. All of the manuals mention that once the MU is removed the next step is to remove the pinion from the pedestal. Is it necessary to do this? I am planning to set the engine at TDC with No 1 cylinder on the firing stroke and simply remove and eventually refit the MU, leaving the pinion undisturbed.

Thanks,

Denis

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39 minutes ago, DenisMc said:

Thank you for your suggestions. I have looked in the various manuals that came with the car and am now clear about checking the timing of the MU. One question though. All of the manuals mention that once the MU is removed the next step is to remove the pinion from the pedestal. Is it necessary to do this? I am planning to set the engine at TDC with No 1 cylinder on the firing stroke and simply remove and eventually refit the MU, leaving the pinion undisturbed.

Thanks,

Denis

Denis no there is a plastic key that joins the drive 

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Thanks ntc for your reply. I am aware of the plastic coupling that connects the MU to the pinion but understand that this just lifts out. Sorry, but I still don't see why I can't leave the pinion undisturbed in the pedestal. Sorry to be a pain here...

Thanks,

Denis

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John I do not know what you mean by valves. If you mean the Petrol tap this is the one I have fitted to a mates TR5 and no that does not leak. You will thank me when servicing comes around. This is mine with a different tap which I will change at some point. Mine is EFI and just recently I converted to Jenvey Heritage throttle bodies(look alike webbersIMG_0254.thumb.JPG.edb7ef54de494420f659cd5f14ea871e.JPG

 

 

 

20190327_183028_resized.jpg

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Hi Guys,

Many thanks all for your answers. I am now clear about what to do and shall remove the MU in the next couple of days. I'll post again when Neil Ferguson reports on his findings. 

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Denis

Just make sure you are at tdc number one on fire then just loosen the banjos and remove the mu the bolt at the back is awkward to get at when removed the key should be inline when replacing it just smear it with grease to hold it in place 

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Sorry Harry,

In my language (40 years in major water engineering projects) taps appear in bathrooms or kitchens. I should have been more precise and said "fuel tank isolating valve".

Anyway I am pleased to hear it does not leak and what an impressive installation (!!!), far away from my totally standard TR6

Thanks

John

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Hi ntc,

When I started the job today I set the engine at TDC with No 1 cylinder on the ignition stroke. By this I mean that the rotor arm was pointing at the No 1 cylinder electrode in the distributor. Is that correct? I actually made good progress, but was unable to fully clamp off the fuel pipe in the boot.  Despite trying various methods the petrol just kept dripping out at the connection with the MU. I obviously need a "fuel tank isolating valve"! For now I have ordered some plastic clamps from Amazon that should arrive tomorrow.

Thanks,

Denis

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1 hour ago, DenisMc said:

Hi ntc,

When I started the job today I set the engine at TDC with No 1 cylinder on the ignition stroke. By this I mean that the rotor arm was pointing at the No 1 cylinder electrode in the distributor. Is that correct? I actually made good progress, but was unable to fully clamp off the fuel pipe in the boot.  Despite trying various methods the petrol just kept dripping out at the connection with the MU. I obviously need a "fuel tank isolating valve"! For now I have ordered some plastic clamps from Amazon that should arrive tomorrow.

Thanks,

Denis

Yes that is correct but make sure you are at tdc as that will help you later when Neil has done his magic, you could always use mole grips and protect the pipe 

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Hi ntc,

Thanks for your reply. I tried mole grips with a rag in the jaws to protect the pipe but the petrol just kept on dripping! I suppose it could just have been draining out of the pipes. I'll try the clamps tomorrow.

Regards,

Denis

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8 minutes ago, DenisMc said:

Hi ntc,

Thanks for your reply. I tried mole grips with a rag in the jaws to protect the pipe but the petrol just kept on dripping! I suppose it could just have been draining out of the pipes. I'll try the clamps tomorrow.

Regards,

Denis

If you jack the front of the car up as high as possible will help to stop fuel running out.

Stuart.

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Hi Stuart,

A great suggestion! Now why didn't I think of that...

Regards,

Denis

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