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JJohn

PI & IGNITION PROBLEMS

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Yet another problem on which I would be grateful for advice!  Following a rebuild of my competition TR6, necessitated as the result of an "incident" at Blyton Park last year, a series of teething problems arose which were worked through and fixed.  However, at the recent Shelsley Walsh round of the TR/Revington Championship round a new problem appeared.  On attempting to start, the engine fired immediately but died within a few seconds and then could not be started.  Eventually and after leaving the fuel pump running for several minutes, it reluctantly fired, running very unevenly .  It eventually cleared and  but never felt right all day.  To try to ensure it would continue to start, I started it every 15 mins throughout the day.  It usually fired up OK but occasionally the same difficulty occurred.  On the competitive runs,  smoke was emitted from the exhaust.  The opinion was that this was unburnt fuel.  Investigation back home revealed that the Bosch pump was dying.  The pressure was found to be way too low.  It was the one which was fitted when I bought the car 5 years ago and was part of the conversion kit sold by TR suppliers.  We replaced it with a Motorsport version with a greater flow rate and the pressure is now as specified.  The fuel filter was also replaced and the opportunity was taken to fit a newly overhauled Lucas metering unit.  On a road test (the car is road legal) of approx 10 miles using bursts of maximum rpm,  the engine ran really well and sounded and felt better than I and Jon Wood  can remember during my ownership.  Jon 's knowledge of TR's,  his practical skills and enthusiasm during the rebuild were invaluable. We concluded that the problem was solved.  We were wrong.  In preparation for this weekend's Harewood events, I went to start the engine and the symptoms exhibited at Shelsley Walsh had returned.  Attention yesterday then turned to the ignition and electrics.  The battery is fine at 13.65V but that fell to 11.5V while cranking.  The reading at the positive feed to the coil was OK static but low when cranking the engine.  The next check was for a spark at the plugs.  Initially, on cranking, there was a reasonably strong spark but it gradually weakened until it faded away completely.  Apart from the obvious wisdom of ensuring all cable connections are good, we are stumped.  Any suggestions for finding and fixing this irritating problem will be gratefully received!

Jim

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Initially, on cranking, there was a reasonably strong spark but it gradually weakened until it faded away completely. 

Do you have electronic ignition?  If not those symptoms could be the points gap closing up or the condenser failing.

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Hi Rob,

 

Thank you for your posting.

Yes the car has electronic ignition.  It is of unknown origin but, when asking for the full spec of the engine, I was told it was fitted with an H & H distributor and had some Mitsubishi components "for reliability".  It is all within the distributor. I have printed confirmation that it is by H & H but no detailed spec.   Jon Wood cannot identify it and he has never trusted it.  This car was driven in  hill climbs extensively by me for four seasons without problems before the "incident" referred to in my plea for advice.  

Jim

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I would swap out the whole distributor for a known good one, preferably standard, from somebody else's working car and give the car a thorough testing. This will eliminate a number of possibilities in one go. Do the same thing with the coil.

Good luck, Mick

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Thanks very much Mick.  As it is, for me, the simplest and quickest of your suggested fixes, I will change the coil first.  If that is ineffective, I will try the distributor swap.  I have a spare, unused coil and a complete, standard distributor.

Jim

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I would be inclined to get Martin (Distributor Doctor) to build you a distributor to suit your engine.

Stuart.

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As you started with a fuelling problem you might want to check that the PRV is working correctly, all the time ... (ie. check the fuel pressure when the engine wont start) 

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What is the voltage at the positive side of the coil with the ignition "on" and NOT cranking? If low the ignition switch could be faulty.

Tim

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Does your ignition system use the normal TR6 ballasted coil  i.e. 12V applied to coil when starting (ignition key turned against the spring), then reduced once the ignition key returns to the run position?

Or has the system been modified by removal of ballast resistor and change of coil?

Ian Cornish

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As usual, the Forum community has come up with possible causes of the problem afflicting my hill climb TR6.  Thank you all very much!  I must now respond to those to whom I have not responded.  The failure to do so to date was the result of concentration on my attempts to establish the reason for the problem. 

Ian, a new loom was included in the rebuild work and the opportunity was taken to include several features found in many competition cars.  It arrived with a different coil and the modified distributor referred to in my earlier reply to a question by Rob asking if electronic ignition was fitted.  A competition style combined IGN/Starter switch was installed so there is no longer a key. 

Tim: Voltage  at the positive coil with IGN "on" & not cranking when checked was 12.95.

Rob: Fuel pressure when failing to start was 100 psi. when checked a few days ago. 

Stuart: my personal experience of DD distributors is not good.

Thank you all for your willingness to help.

Yesterday I removed the distributor cap and found that every plug lead contact was damaged and there was a scratch on the inner surface of the cap.  Marks on the brass tip of the rotor arm confirmed that it had caused the damage.  Perhaps the cap had not been correctly replaced when last removed. The advice then was to check the MU drive dog which could have been broken by the distributor drive jamming momentarily.  With #1 fuel line removed and the poppet valve extracted with #6 cylinder at TDC I turned the engine by hand.  I cannot be certain of seeing the hole in the MU rotor but every small movement of the engine resulted in disturbance of the residual fuel which caused the fuel to spill out of the port.  Does this confirm that the rotor is turning? I am a novice where PI is concerned and am baffled.  This engine ran without missing a beat throughout 4 busy seasons of hill climbing.  The only problem during that spell was a leaking head gasket 2 years ago.  That makes the current situation doubly frustrating

Jim

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4 hours ago, JJohn said:

o. 

Stuart: my personal experience of DD distributors is not good.

 

 

Jim

Care to elaborate as Ive been using him since he set the business up and he has always done a first class job for me.

Stuart.

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Hi Jim,

if a dizzy cap is damaged, even scratched, it can lead to poor sparking, so replace it. Replace the rotor as well, not the black one with a rivet (these are known to short), but best by a red one stamped DD.

I would first do that, then worry about the MU if still not ok.

Waldi

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Apologies for the period of silence.  I have been devoting almost all of my time to attempting to have the TR6 fit & ready for two days of hill climbing at Harewood Hill this weekend.  Thanks to the practical assistance of fellow Cleveland Group members, father and son Peter and Neil Willis the car appears back to its old self.  When I spoke to Neil at about 6 pm yesterday to ask if he could suggest a remedy, he offered to come to my home.  He, and Peter arrived an hour later and, applying their considerable TR knowledge and engineering prowess, they left for their home at approx. 9:15.  They ran a series of tests on the PI system and discovered that the PRV was restricting the fuel flow to the metering unit.  This resulted in there being insufficient pressure to operate the injectors.  By using my unused spare PRV as a test for the fuel pressure, the one installed was found to be the culprit.  The new one was fitted and with engine running and demanding fuel, the pressure was 120 psi. The damaged distributor cap and rotor arm were replaced with items from my spares stock and once the PI system had been bled, the engine sounded healthy again.  When I thanked Peter and Neil for their success, Peter told me I should not thank them until I had tried a cold start!  This morning I used my usual sequence and the engine started instantly I pressed the button.  The car is ready for tomorrow's Harewood event to which I am now really looking forward!  I hope the Willis's deem it acceptable if I say how grateful I am for the generous effort they have made.

Stuart asked if I would elaborate on my comment about the Distributor Doctor.  Some time ago, I am not sure when, I sent a very tired distributor I had acquired for  refurbishment  to replace on the one fitted to my touring TR6, which was probably the original factory unit.  I provided all the details I was asked for, including whether the existing unit was using the vaccuum advance/retard  mechanism.  It was and so it was decided to include it during the rebuild.  I installed it and took the car to be set up at a rolling road.   After approx 30 mins,  the.   operator, who is widely respected, said he could not get a satisfactory result.  The vacuum pipe was disconnected and the then engine ran  well.   Eventually, the rebuilt unit was discarded and the old original one replaced it.  That is how it became an emergency stand by spare. 

Thank you to you all!

Jim

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Jim - did you inform Martin (Distributor Doctor) of the problem with the distributor which he had refurbished for you?

Martin is a very straight fellow with an excellent reputation (as Stuart has said), and I feel sure that he would put right any problem which might occur in a unit which he had refurbished.

Ian Cornish

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I really think you should talk to Martin (Distributor doctor ) about this and give him the opportunity to remedy the situation rather than dissing him on a public forum.

120PSI is too high a pressure so did you turn it down to the recommended 105PSI?

Stuart.

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Jim and everyone,

PLEASE remember our rule against posting derogatory remarks against suppliers,especially where there is no record of the supplier being asked to respond/rectify the issue . Many of these people are small outfit 's and mistakes do happen but give them the chance to rectify/respond.

Brian.

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I apologise for my uncomplimentary postings about the DD.  I have no complaints about the quality of the parts  supplied by Martin Jay; those I have bought have all been excellent.  When I posted my first comments I was really wound up by the difficulties encountered in trying to fix another of the "Teething" problems following the rebuild of my hill climb TR6 and over reacted when  suggestions from members offering me help reminded me of an experience in the past .  That is no excuse for making comments in the manner I did and Martin deserves my sincere apology, which I now offer.  This problem concerned  my other TR6 and was resolved at the time (July 2014) and should have been erased from my memory long ago.

Jim

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Hi Stuart

Thank you for your suggestion that the fuel pressure in the PI system in my TR is too high at 120psi.  It is still set at that value, which is measured at the PRV.  The advice locally is that it will be lower than 120 at the MU. It is now performing at least as well and probably better than in the past.

Jim

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