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Petrol injection misfire


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I recently bought another TR. It has done very little mileage in the past 6 years as it has been mostely stud. It was running reasonably well but the tickover was 1200rpm. I did a couple of 40 mile runs but on thalast one it started misfiring badly. It has excellent compressions, new plugs and electronic ignition, so I assume the problem is with the lucas injection system, I know the previouse owner had problems with it. I do not want to play about with it myself so was wondering if any one could recommend an experienced Lucas PI tuner near me. I live near Skipton in North yorkshire.

 

 

 

 

 

 

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I take it youve put fresh fuel in it for a start, it may well need the fuel filter changing too if its not done much for years. Start there and see how it goes then, probably could do with an "Italian" service as well.

Stuart.

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4 minutes ago, openroad said:

At a guess that Italian Sevice , means give it a good thrashing u til it starts behaving   !!!

Got it in one!

Stuart.

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Phil last year I returned back to UK after working abroad for several years. I kept my TR6 and only occasionally started it up when I returned for Xmas or some hols. So the car was probably only started 5 times in seven or eight years. I even had the original fuel in the tank. Anyway once back home I set about getting the car onto the road. Incredibly it did start but it did run rough. Trying to keep this short, but in process of getting car back on road the car (I) ran out of fuel. I changed the fuel filter and checked the inline filter. The filter was very over due a replacement. I then put new E5 petrol into the car. It still ran rough and intermittently started to mis fire even more. I cleared lines with new fuel. I eventually thought injectors were the problem. I was fortunate to speak with a very knowledgeable TR person and went thru a step by step diagnostic. In doing this the MU started to leak fuel - suspect it was very small leak to start but it developed into clear leak with visible fuel dropping out. It was clear I needed to refurb the MU and the injectors. I did get the MU overhauled and the injectors. Installed the new bits and it fired up first time and ran smooth - better than I remember when I first got the car.

So I have got the TR6 running well now. I think the car sitting for several years did cause problem for MU and injectors. Running the tank to near empty was in excusable but was a mistake. But filters did do their job. The E5 I think killed the MU internal seals / diaphragm. The MU and injectors were overhauled by person located just south of Manchester - very good (I would say excellent) and it was so easy to swap unit and get it back working. The folks on this TR forum are a wealth of knowledge and highly recommend finding one who is local to go thru a diagnostic step approach with you.

P.s. The Italian service needs a long steep hill to run up - this was the other advice I had.

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Even with electronic ignition the first place to look is ignition - coil, cap, leads and plugs plus all the connections. My TR6 had similar missing problems and it was a corroded connection on the electronic ignition. Previously it was been the coil and (on the TR2) condensor (the latter not relevant in your case).

Replace the coil first as a likely culprit.

 

Edited by John McCormack
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3 hours ago, John McCormack said:

Even with electronic ignition the first place to look is ignition - coil, cap, leads and plugs plus all the connections. My TR6 had similar missing problems and it was a corroded connection on the electronic ignition. Previously it was been the coil and (on the TR2) condensor (the latter not relevant in your case).

Replace the coil first as a likely culprit.

 

Yep, 75% or more of misfire problems are caused by ignition.  Check if the plugs were wet after the misfire episode. Generally if they're wet they're not firing, if they're sooty the mixtures too rich. Your enrichment lever is releasing fully?

Edited by Mike C
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Thanks for the advice. I will change the filters and plugs, Its obviouse the previouse owner has been playing around with it (I found the injector clamping plates in the boot). I have checked the injectors and found at least 1 is just dribbling and another has half a spray so I will replace all the injectors. Which is the best firm to buy refurb injectors from? The other thing I notice is the metering air valve was nearly screwed right in, what effect does this have?

Phil

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not a good idea to drive with injectors  not clamped, a backfire in the inlet manifold could blow an injector out while spraying fuel....

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3 hours ago, Phil Read said:

Thanks for the advice. I will change the filters and plugs, Its obviouse the previouse owner has been playing around with it (I found the injector clamping plates in the boot). I have checked the injectors and found at least 1 is just dribbling and another has half a spray so I will replace all the injectors. Which is the best firm to buy refurb injectors from? The other thing I notice is the metering air valve was nearly screwed right in, what effect does this have?

Phil

The idle metering valve doesn't open much- I open mine until I get an idle speed of around 900 rpm-  I believe that any speed lower than this can cause pressure pulses that  damage the MU and throttle butterflies.

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Phil,

Besides the above good suggestions:

if the MU has not been converted for E5/E10, I would send it with injectors and prv to Neil Ferguson (or another specialist). Also ask the nylon lines to be renewed. And renew all rubber hoses in feed and return- pipes.

Not worth the risk, and this will vastly improve reliability.

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6 hours ago, Waldi said:

Phil,

Besides the above good suggestions:

if the MU has not been converted for E5/E10, I would send it with injectors and prv to Neil Ferguson (or another specialist). Also ask the nylon lines to be renewed. And renew all rubber hoses in feed and return- pipes.

Not worth the risk, and this will vastly improve reliability.

You might have to replace (or service) the fuel pump while you're at it. I've just had to replace everything between the tank and the fuel injectors after leaving my car for 4 years with fuel in it.

Another part worth checking is the MU drive shaft fuel and oil seals in the pedestal. Mine started leaking petrol into directly into the sump - I only noticed because the oil level was above the 'max' line on the dipstick. When I took the old seals out they were so rigid that they literally shattered. 

Cheers, Robert

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  • 2 weeks later...

Just an update. drained the tank, new fuel, new filter, reconditioned injectors, the previouse owner replaced the pump and metering device. I notice the choke is not working, it looks as though the cam has been put on wrong, however the engine starts but hunts like hell., any thing between 800 and 1200 rpm, any one any thoughts on what would cause this?

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too rich ? soot particles in exhaust? check dodgy choke lever. PRV not working ( give it a thump or two), butterflies not closing equally (  it will drive OK but tickover poor)

 

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  • 3 weeks later...

I fit new injectors and spark plugs, no improvement. In the end I took the car to TR BITZ which is my nearset specialist. It came out a different car, no misfire, good tickover, and it drives smoothly. Evidently the main problem was the throttle linkages between the throttle bodies etc.

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Great to hear you had a positive result Phil!

now its set up right you should hopefully have many years of reliable operation, i renovated my car’s PI system in 2013 and it’s been perfect ever since.

steve

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