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TR6 Fuel Injection problem


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I have a 1971 TR6 CP fitted with the later CR fuel injection system and a Bosch pump.  I recently removed the engine and gearbox to restore the engine bay and repair several fluid leaks.  The fuel injection system was dismantled and the inlet manifolds soda cleaned.  Before dismantling the car ran perfectly.  The Bosch unit in the boot was not disturbed.  Dismantling and reassembly was done by a very skilled mechanic. 

The car now starts on the button, but runs all the time at 3,000 rpm.  If all 6 inlets are covered it ticks over perfectly!  There is clearly an air leak, but we cannot find it.  It is likely to be something really obvious that we have missed.

Has anyone else experienced the same problem?  Any suggestions as to where to look?

Thanks, Colin Caborn

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Hi Colin,

its common after cleaning the deposits out from around the butterflies on the pi system for this to happen.

3000 rpm does sound high though - but as you are able to get engine speed down by covering the inlets I think you need to measure the clearance on the butterflies.

Bob

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The fact that you are able to get the idle to normal levels by covering the inlets means the leak can only be through the throttle plates not sealing fully after the clean up. It could it be they are not fully closed when at idle. 

Gareth

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You've probably checked this, but do you still have the CP manifold?  Is there a tube with large screw connected to the manifold at the front of the engine?

If so tighten the screw and the idle speed should  drop.

If you don't have the idle air tube I'd agree with the above- you have air leakage through the throttle butterflies or throttle spindles.

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Hi Colin

it does sound like air is getting past the throttles when they should be closed

as above, this could be just from the cleaning, they are old and now don’t seal ( the dirt sealed them previously)

or it could be that the throttle mechanism isnt allowing the throttle plates to close fully

or it could be that the ‘choke’ fast idle ( if still fitted) isnt set correctly

or it could be a combination!

i’d be checking the mechanisms first as that’s easy to fix, then move on to the throttle plates and alignment of the three bodies

good luck!

steve

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5 hours ago, Mike C said:

You've probably checked this, but do you still have the CP manifold?  Is there a tube with large screw connected to the manifold at the front of the engine?

If so tighten the screw and the idle speed should  drop.

If you don't have the idle air tube I'd agree with the above- you have air leakage through the throttle butterflies or throttle spindles.

If the butterflies are open at idle this can be checked using feeler gauges under each butterfly. If fully closed at idle they should trap a .0002" gauge. But make sure that the air valve is not open too far, for correct idle speed. The butterflies must be adjusted using a air flow meter  for sync in my experience.

Bruce.

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2 hours ago, astontr6 said:

If the butterflies are open at idle this can be checked using feeler gauges under each butterfly. If fully closed at idle they should trap a .0002" gauge. But make sure that the air valve is not open too far, for correct idle speed. The butterflies must be adjusted using a air flow meter  for sync in my experience.

Bruce.

Good point Bruce, the first thing i’d do is put a flow meter on the throttle to see which are letting air past

then adjust the linkages to hopefully get them all closed/very close to closed

Colin, whereabouts are you?

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Colin,

You suggest everything is OK when all inlets are covered. Do you mean you have covered all 6 'trumpets' thereby ruling out the butterflies not closing sufficiently? That's how I understand it anyway. If so, have you lost or damaged an air tube/balance pipe plug in one of the manifolds? Have you got excessive movement in the spindle holes allowing air in? One of the 3 top connectors are letting in air (think they are 1/2" BSP ports)? Won't take much to realise 3,000 rpm.

Colin

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Thank you everybody for your valuable help. I need now to get my much more knowledgeable friend to take another look at it with your advise to help him. 

In reply to Steve, I live just outside Bedford.

I will report back when we have put your advise to the test .more to follow!

                                                             Thanks, colin.

                                                     

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If your friend has a vacuum gauge, plug it into the brake booster connection and measure the idle vacuum. My engine must get to  10 inches Hg, some engines need more.

Any less and you definitely have a leak. 

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Er... if it idles ok with all 6 inlets covered/ blanked the air leak is down stream of the throttle butterflies!

Check the injectors have o rings fitted

Disconnect and blank the vac hose to the servo

Check the condition of the hose to the MU

 

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  • 3 weeks later...

Thanks again for all the advice. my mechanic friend thinks that he has now checked all the points raised, but the problem still persists. He thinks that cylinders 3 and 5 are now the ones causing the engine to race. He has completely run out of ideas and given up for the moment after spending hours trying to help me. I think I need a knowledgeable person in the Bedford area who is able to come (safely) and take a look. I am happy to pay for the time and expertise. Does anyone know such a genius?

                                   Thanks again, colin.

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8 minutes ago, Colin Caborn said:

Thanks again for all the advice. my mechanic friend thinks that he has now checked all the points raised, but the problem still persists. He thinks that cylinders 3 and 5 are now the ones causing the engine to race. He has completely run out of ideas and given up for the moment after spending hours trying to help me. I think I need a knowledgeable person in the Bedford area who is able to come (safely) and take a look. I am happy to pay for the time and expertise. Does anyone know such a genius?

                                   Thanks again, colin.

Hi Colin, I’m in St Neots. Where are you? Happy to come and have a look or I can check your throttle bodies on my test engine. 

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  • 3 weeks later...

Thank you very much to everyone who helped me to solve this very difficult problem. The unanimous view was that the fast running was caused by air being sucked into the throttle bodies due to wear in the spindles and/or misalignment of the butterflies. You were all correct. The complication was that my usually brilliant mechanic, who is not an expert on the foibles of temperamental TR injection systems, was adamant that he had checked, and eliminated, wear as the cause. Slight diplomatic problem!!

To my rescue came Marting, a member of this forum, from St Neots, not far from where I live. He runs a business specialising in restoring TR fuel injection systems, supplying parts, and remanufacturing some of the rare parts not available from big parts suppliers. He collected the throttle bodies, sent me a detailed photographic condition report showing all the wear, offered me a choice of three levels of reconditioning, carried out the work, and returned and refitted them, all for a very reasonable price.  All this was completed in less than a week, and the car started and ran correctly at the first touch of the button.

Thanks Marting. I recommend your brilliant sevice to everyone!

                                                                           Colin.  

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Glad you found the solution there Colin. Good to know there is a member who can sort out issues like this too.

Gareth

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Hurrah!

now the car needs a lot of ‘testing’ to make sure it’s consistently good ;-)

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12 hours ago, Colin Caborn said:

........To my rescue came Marting, a member of this forum, from St Neots, not far from where I live. He runs a business specialising in restoring TR fuel injection systems, supplying parts, and remanufacturing some of the rare parts not available from big parts suppliers.

Glad you got the problem sorted Colin - would that be Martin of 'Martin's Fuel Injection'?  If I remember correctly he worked out of his home garage in Essex in the 80's and really knew his stuff on Bosch and Lucas systems. 

I thought Martin had retired many years ago - it would be good to know if he's back on business and how to contact him.

Cheers, Andrew   

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46 minutes ago, Andrew Smith said:

Glad you got the problem sorted Colin - would that be Martin of 'Martin's Fuel Injection'?  If I remember correctly he worked out of his home garage in Essex in the 80's and really knew his stuff on Bosch and Lucas systems. 

I thought Martin had retired many years ago - it would be good to know if he's back on business and how to contact him.

Cheers, Andrew   

Yes I remember him! He supplied me with my Bosch pump conversion kit in the very early 1980's which KMI manufactured. Pump lasted over 40 years and was only replaced because of its age and I was going on a 3000 miles trip.

Bruce.

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On 4/3/2021 at 9:39 AM, Andrew Smith said:

Glad you got the problem sorted Colin - would that be Martin of 'Martin's Fuel Injection'?  If I remember correctly he worked out of his home garage in Essex in the 80's and really knew his stuff on Bosch and Lucas systems. 

I thought Martin had retired many years ago - it would be good to know if he's back on business and how to contact him.

Cheers, Andrew   

 

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Hi all.  
My name is Martin Giles. Long time TR owner and member of the TR Register. I am on a bit of a mission to remake all of the the original spec throttle linkage and mechanical PI parts that the big suppliers list as no longer available.
I currently can supply just about everything for CP cars. I have just finished making a twin to single choke cable conversion kit that TRGB will be launching 

I’m trying to build up the services and products that I can provide with a view to make it cover its own costs / or even make a return by the time I retire in a year or two. More details are on the website https://fredmillturnparts.com/

I have just finished making throttle and choke assembly for CR cars which are not listed on the website yet. Next on the list is throttle spindles for CR throttle bodies with removable arms that enable the fitment of sealed bearings.

Get in touch if you need any assistance with CP CR or 2.5pi linkage parts or throttle body reconditioning or EFI mods. 
 

kind regards 

The other Martin!

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On 4/3/2021 at 9:39 AM, Andrew Smith said:

Glad you got the problem sorted Colin - would that be Martin of 'Martin's Fuel Injection'?  If I remember correctly he worked out of his home garage in Essex in the 80's and really knew his stuff on Bosch and Lucas systems. 

I thought Martin had retired many years ago - it would be good to know if he's back on business and how to contact him.

Cheers, Andrew   

Hi Andrew 

thats a familiar looking picture 

70C1AA71-5DA6-410C-9E41-E9A8025F1940.jpeg

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