Slower starting

[John McCormack]

My 1970 TR6 has a Bosch fuel pump and changed filtering done professionally.

Until recently it would start after one or two cranks of a few seconds.

It now needs 2-3 cranks of a few more seconds than previously. The car idles and drives superbly after start.

Reading the manual it appears possible that slower starting could be due to the fuel filter becoming clogged.

Any other ideas please?

[barkerwilliams]

I believe my 6 is typical of many. If i have used the car yesterday it starts first pull, if it has stood a week two or three pulls. If it has stood over a month there is extended cranking. As far as I am aware it is the fuel draining back down the injector lines, the longer it stands the more it drains back and the more cranks it needs to refill the lines.

As the fuel tank is very high in the car a full tank will set a high minimum level in the injector lines, an empty'ish tank will empty the injector lines completely over a period of time.

The fuel can only drain back down the injector lines if air replaces it in the line. So either the injector, or its plumbing is leaking air or there is air dissolved in the fuel which comes out of solution and rises up the injector line. It is possible that an injector line connection on the metering unit is failing and leaking air, most likely candidate are the banjo connectors on the back of the unit but these have o rings which do not like being disturbed.

The injectors do not seal wonderfully to prevent air entering the lines,  certainly not over a period of days or weeks. I do not believe that an original TR6 injection system can be made to start instantly after a few days off as will a modern car which has a pressurised fuel rail feeding each injector directly whereas the TR's injector is a pressure relief valve at the end of two foot of small bore pipe which is drip fed minute quantities of fuel on each cycle by the metering unit which takes a large number of engine cycles to refill the injector lines before the cylinders can get a shot of petrol.

Easy five minute test.

Park car sensibly to access offside engine.

Leave for between two days and a couple of weeks.

Open bonnet

Remove live feed wire from coil.

Remove the three bolts and holddown plates for the injectors

Place carboard sheet (2'x1') over engine and position injectors onto carboard in order.

Get mobile phone camera and film the cardboard.

Have assistant crank the engine until all injectors have injected petrol onto the cardboard.

Stop cranking and review footage.

You may see one injector ejects after a couple of engine rotations (sound track) whereas others may not eject until engine has done a large number rotations. This will give you a clue that particular injectors have drained their fuel lines but others remain full. Filming it allows you to review and determine which, if any, injectors are an issue.  Perhaps one or two injectors are a little sticky and don't open quickly and just dribble fuel, easy to see once out.

A cold engine and cold battery do not make it easy to get a suitable fuel/air mix in the cylinders and a cold dribbling injector is not producing the explosive vapour needed for ignition. 

 

 

 

Edited December 25, 2023 by barkerwilliams

[Mike C]

I'd believe most TR6 owners would accept starting after 2-3 cranks to be pretty a good result.

I don't believe the slightly longer cranking duration would be caused by a clogged fuel filter. The fuel demand when cranking is fairly low- clogged filters normally cause problems at high speed/high fuel demand.

Have you checked the adjustment of the enrichment lever on the MU?

 

 

[Waldi]

Mine is not a quick starter.
All components are reconditioned in 2018. I never investigated, I like the “card board test”, maybe I will try that, one day…

I have an AFR meter in my car so can see how lean the mixture is when cold, likely from condensation or agglomeration of the fine droplets (mist) on the inlet system.
This does not help starting either.

Waldi

[BlueTR3A-5EKT]

16 hours ago, John McCormack said:

My 1970 TR6 has a Bosch fuel pump and changed filtering done professionally.

Until recently it would start after one or two cranks of a few seconds.

It now needs 2-3 cranks of a few more seconds than previously. The car idles and drives superbly after start.

Reading the manual it appears possible that slower starting could be due to the fuel filter becoming clogged.

Any other ideas please?

Have you cleaned the plugs?   That simple task fixes my poor starting 

[Neil Ferguson]

Check the voltage at the fuel pump while cranking the engine. If it drops below 11volts rewire the pump via a relay (this is a very common problem)

[John McCormack]

Thank you all.

I have filled the tank as it was a bit low and it immediately seems to be starter better. Back to a couple of short cranks.

I thought it might be possible that the fuel level in the injection pipes dropped a bit with a low tank level. I am not sure how this might happen but in my mind it was a possibility. I am chasing an old metering unit to dismantle and see exactly how they work.

I will check the plugs, haven't done it for a long while. I should do a tappet check as well. I believe in 'if it ain't broke don't fix it'. But they might need a bit of a clean and adjustment.

Edited December 29, 2023 by John McCormack

[TR NIALL]

15 minutes ago, John McCormack said:

Thank you all.

I have filled the tank as it was a bit low and it immediately seems to be starter better. Back to a couple of short cranks.

I thought it might be possible that the fuel level in the injection pipes dropped a bit with a low tank level. I am not sure how this might happen but in my mind it was a possibility. I am chasing an old metering unit to dismantle and see exactly how they work.

I will check the plugs, haven't done it for a long while. I should do a tappet check as well. I believe in 'if it ain't broke don't fix it'. But they might need a bit of a clean and adjustment.

New Plugs and it’ll make one hell of a difference.

[Mike C]

2 hours ago, John McCormack said:

Thank you all.

I have filled the tank as it was a bit low and it immediately seems to be starter better. Back to a couple of short cranks.

I thought it might be possible that the fuel level in the injection pipes dropped a bit with a low tank level. I am not sure how this might happen but in my mind it was a possibility. I am chasing an old metering unit to dismantle and see exactly how they work.

I will check the plugs, haven't done it for a long while. I should do a tappet check as well. I believe in 'if it ain't broke don't fix it'. But they might need a bit of a clean and adjustment.

You might have had stale fuel previously?

[mleadbeater]

The Triumph workshop manual, known as the Brown Book, contains a good description of the metering unit, see link below.

I personally doubt tank fuel levels make a difference, the fuel pressure required is 110 psi, the pressure to open each injector is around 50 psi, the difference in these pressures is what drives the metering shuttle back and forth.

Are your plugs getting sooted up?

 

I’ve just fitted a new dizzy with electronic ignition, she seems to start and run much better, as I’ve always found with previous cars when fitted with e.i.

Mike

https://tecb.eu/onewebmedia/TR6_repair_manual.pdf

[SirHector]

On 12/29/2023 at 2:36 PM, mleadbeater said:

The Triumph workshop manual, known as the Brown Book, contains a good description of the metering unit, see link below.

I personally doubt tank fuel levels make a difference, the fuel pressure required is 110 psi, the pressure to open each injector is around 50 psi, the difference in these pressures is what drives the metering shuttle back and forth.

Are your plugs getting sooted up?

 

I’ve just fitted a new dizzy with electronic ignition, she seems to start and run much better, as I’ve always found with previous cars when fitted with e.i.

Mike

https://tecb.eu/onewebmedia/TR6_repair_manual.pdf

New ownership here…..but my car runs very rich would this point to a faulty MU do you think

[Mike C]

2 hours ago, SirHector said:

New ownership here…..but my car runs very rich would this point to a faulty MU do you think

Check the enrichment lever on the side of the MU is releasing fully.

[barkerwilliams]

How do you know it runs rich?

A Pi runs rich at tickover by design so if you inspect the plugs they will be sooty.

To inspect the plugs you need to take the car for a run and get it hot. When you get home do not let the engine idle, but when you park run the engine at 2-3000 rpm for a minute then kill the engine.

Have a cup of coffee whilst the engine cools then remove and inspect the plugs.

Lots of Pi's also run a hotter plug on cylinders 5 & 6. These cylinders have the worst airflow and a hotter plug keeps them cleaner.

Alan

[SirHector]

4 hours ago, barkerwilliams said:

How do you know it runs rich?

A Pi runs rich at tickover by design so if you inspect the plugs they will be sooty.

To inspect the plugs you need to take the car for a run and get it hot. When you get home do not let the engine idle, but when you park run the engine at 2-3000 rpm for a minute then kill the engine.

Have a cup of coffee whilst the engine cools then remove and inspect the plugs.

Lots of Pi's also run a hotter plug on cylinders 5 & 6. These cylinders have the worst airflow and a hotter plug keeps them cleaner.

Alan

Thanks Alan

will give this a go when the weather looks fine for a run out…..but it really does stink I’m told by the Mrs who was following me on a 60mile run home!

[mleadbeater]

you might try to use a Colortune, its a sort of window spark plug, lets you see the colour of the flame in any cylinder as it runs. 

Ive used one for decades, in many cars, gives an instant indicator of combustion.

Ebay has them listed.

Mike

[cp25616]

John I would pay heed to Neil Fergusons reply above. The standard wiring leading to the Lucas fuel pump was only just  good enough for the standard set up. You now have a Bosch fuel pump which draws more current effectively making the standard wiring overloaded i.e not good enough. When starting,  the fuel pump draws a considerable amount of power and then you have the starter motor trying to start on whats left. If your battery is top notch fully charged then it will do but if not there just isn't enough juice getting to the fuel pump making it harder to start and taking longer too.

I once had a problem with poor starting and Malcolm Jones from Prestige recommended placing a battery in the boot to solely feed the pump and letting the normal battery do the starting, jeez it started quicker than a modern car. He recommended upgrading the wiring to the fuel pump using modern wiring with a Lucas 6ra relay( or equivalent) inline taking the power from the white wire after the inertia switch under the bonnet. Works perfectly and starts very well and quickly too. Worth a try John.

Alan G

[Mk2 Chopper]

16 hours ago, SirHector said:

Thanks Alan

will give this a go when the weather looks fine for a run out…..but it really does stink I’m told by the Mrs who was following me on a 60mile run home!

A look at your tail pipe will no doubt confirm and be very sooty. 

The first things to do are making sure the correct combustion is occurring and is at its most efficient. The following things would be with going through: clean/ new plugs gapped correctly, clean/ new points (and condensor) gapped correctly, timing correct, all throttle plates fully closed and air flow balanced, valve adjustment checked/ corrected, air filter is clean/ new. 

Check 'choke' is set correctly at MU. Check for vacuum leaks in pipe to MU.

These should get you to a base level to see how your system performs. If it's still running rich, you can check the compressions of the cylinders, fuel pressure at the MU and how much vacuum you are getting for the MU.

Beyond that the MU could then need a rebuild and adjustment. 

Gareth

 

[SirHector]

Thanks Gareth very informative and will be following the advice. Thanks buddy 

[Mk2 Chopper]

1 hour ago, SirHector said:

Thanks Gareth very informative and will be following the advice. Thanks buddy 

No worries, let us know how you get on. 

Gareth

[John McCormack]

Thank you for the advice.

I haven't checked the voltage to the fuel pump while cranking yet. The engine cranks very well so while this is a possibility I don't feel it is likely. I didn't install the Bosch pump but it was done by a very competent TR6 PI person and I can see it has newer thicker wiring.

What I have done is set my plugs and tappets.

The plug gaps were well over 25 thou, I may have set them to 32 thou which is the sidescreen setting. It is habit after 48 years of TR2 ownership.

The plugs are BP5HS and have now done 9,000kms. I might benefit from putting new ones in.

I read up on the metering unit and how critical vacuum is to its performance.  I checked the tappets and the gap on three was very loose, maybe three or more thou out, and one was a bit too tight, about a thou.

I expect that this would adversely affect valve timing, engine breathing and vacuum.

After this enjoyable bit of fiddling the engine performs noticeably better, it idles smoother, accelerates harder and spins more freely. It feels like it cruises with a lighter throttle than before. I'm really very pleased with its performance. The brakes also appear to be better, maybe the booster is getter better vacuum.

However, starting the car when it has been sitting for a few days is unchanged. It needs a bit of cranking and I have to be careful with the enrichment setting. Too much and it doesn't like it. Once the engine has been warmed up it starts immediately, within a second of cranking.

I will put up with the slower starting for now as the performance is truly wonderful.

As suggested above, new plugs might be in order. What plugs are preferred? The car has Lumenition ignition with a stock coil.

[Mike C]

I use NGK BUR 6ET's they will fire when wet or carboned up -which is a pretty common operating condition with a TR.

 

On 1/1/2024 at 8:17 PM, SirHector said:

New ownership here…..but my car runs very rich would this point to a faulty MU do you think

Check the enrichment lever on the side of the MU is releasing fully.

[John McCormack]

2 hours ago, Mike C said:

I use NGK BUR 6ET's they will fire when wet or carboned up -which is a pretty common operating condition with a TR.

 

Check the enrichment lever on the side of the MU is releasing fully.

Thanks for that advice. Yes the enrichment lever returns fully. I got caught with that early in my TR6 ownership.

[TR NIALL]

39 minutes ago, John McCormack said:

Thanks for that advice. Yes the enrichment lever returns fully. I got caught with that early in my TR6 ownership.

Have you also got the Choke connected and is it set up right?

[John McCormack]

1 hour ago, TR NIALL said:

Have you also got the Choke connected and is it set up right?

Yep, as far as I can make out. I had to put a new cable in some years ago and set it up to operate the enrichment lever and throttle. 

The issue with the slower starting is quite recent, the last few months. The choke cable has been there for 4-5 years.

I get full enrichment at full extension of the knob.

Is there anything I should be checking with the choke setup?

PS. This made me think about the choke a bit more deeply. I've just been out to the garage (a beautiful balmy summer evening here, not too hot or cold, just nice) and checked the choke operation. On full choke I'm getting full enrichment and about 1/8" to 3/16" lift on the throttle.

However, I did find that there is a resistance in the choke operation before it gets to full choke and I I may not have been getting full choke when I've been starting her. I found previously that if I didn't have full choke the engine would kick but not start and then flood.

I will give it a go over the next few days making sure I actually get full choke, it might solve the starting problem.

Edited January 5 by John McCormack

[TR NIALL]

31 minutes ago, John McCormack said:

Yep, as far as I can make out. I had to put a new cable in some years ago and set it up to operate the enrichment lever and throttle. 

The issue with the slower starting is quite recent, the last few months. The choke cable has been there for 4-5 years.

I get full enrichment at full extension of the knob.

Is there anything I should be checking with the choke setup?

I’ve never have to use full enrichment mine will start by just slightly cracking open the Choke with a bit of enrichment from the MU,I turn the Ignition on for between 30/45 seconds pull the Choke slightly and flick the Starter it normally fires and I push back in Choke back in immediately and then control tickover with the loud pedal.