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PI engine misfire


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Greetings gentlemen,

I am a US residence with a 1970 TR6 PI. Yesterday (by two different mechanics) I was told that I have a misfire in one of the cylinders, and could be running on 5. I personally couldnt tell, my car pulls, and accelerates without any hesitation, even when it is in overdrive. I have the same strong pull going up the hills around where I live. Additionally, my TR6 is equipped With Fast Road 83 cam

 

Inlet Timing: 37-63

Exhaust Timing: 74-28

Camshaft Duration: 280°

Lift: 0.288"

Install Figure: 103°

Inlet Valve Clearance: 0.022"

Exhaust Valve Clearance: 0.024

 

Replaced (two days ago):

1. Bosch fuel pump (pressure reads 105 psi)

2. Replaced fuel filter (Mann)

 

I have performed the following (Yesterday):

1. Checked plugs. All were in great shape. None were dark, wet, or fouled-up

2. Compression test. All 6 were at exactly 150 PSI

 

I will check:

1. my valve clearances

 

Dont know how to check:

1. MU

2. Injectors (Thinking of buying a new set)

 

Do you have any other suggestion?

 

Also, has anyone heard of Mr. Malcolm G Jones of PRESTIGE

DEVELOPMENTS & INJECTION?

 

Thank you all for your help,

 

Cheers,

 

Sam

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Hi Sam, I would suggest checking the injectors. A member on here suggested this. I am by no means an expert, in fact I am very much starting out with doing bits on older cars.

 

Really straight forward to do. remove the metal plate holding each pair of injectors in, then pull one out and turn the car on. Make sure you spray it into a jar and you should see the cone shape spray into the jar. Turn the car off put the injector back in and try the next one.

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Sam,

As you have recently disturbed the PI I by fittng the new pump it may merely need a good hard drive to get air out of the system. Try a full throttle, high rpm, 'Italian tune up' up those hills.

Malcolm Jones is very well known PI expert and an active member of the North Wales TRR Group.

Peter

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+1 for Italian Tune up.

 

You might also try a fuel,system cleaner, eg redex, as with little use these systems get gunged up

 

In the long term be sure to use the car regularly, including a good blast as the PI system is very reliable if used but doesnt like standing.

 

Steve

Edited by SDerbyshire
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Can I drive the car for 30+ mins or does it have to be at idel for 30 mons?

Dont forget to disconnect the coil while your letting the pump run or you will burn it out. Reconnect afterwards before starting.

Stuart.

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Stuart,

 

Please forgive me, When you say to disconnect the coil, do you mean the coil that sends powe to the spark plugs? Just want to be sure.

 

In fact I was thinking, just leting the pump run for 30 mins probably not good for it and wasnt sure how to avoid damaging it. How will removing the coil (spark plugs) will prevent the pump from burning?

 

Thank you

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The fuel pump runs full time when engine running, itll be fine!

 

Excess fuel is returned to the tank, when idling this is 90%+ of the fuel, at full load there is still some returned.

 

Its a tough life being a fuel pump!

 

30 mins wont bother it at all, if its healthy.

 

Steve

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Stuart,

 

Please forgive me, When you say to disconnect the coil, do you mean the coil that sends powe to the spark plugs? Just want to be sure.

 

In fact I was thinking, just leting the pump run for 30 mins probably not good for it and wasnt sure how to avoid damaging it. How will removing the coil (spark plugs) will prevent the pump from burning?

 

Thank you

Yes disconnect ignition coil to stop it burning out. The pump will be fine to run for 30 mins.

Stuart.

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With regards to Redex upper cylinder lubricant. Back in the 1970s some of my production engineering colleagues

who worked for British Leyland recommended its use in 2.5 pi saloons & TRs as a lubricant for the Lucas injection

system.

 

Harvey S. Maitland

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Done this many times,different cars,no problems and works well to purge air etc. Ensure you're battery is up to it so it's getting full power to drive the pump at full pressure.

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Friend used to put a small dollop of 2 stroke oil in the tank at each fill up, to lubricate the Pi system, but I've never bothered. RedEx difficult to get now (?) But several brands of injector cleaner available.

 

Air bubbles a big no-no for Pi, or any injector system. They are excluded automatically by the float chamber of a carb, but end up in the injector, which stops delivering fuel until the bubble clears. See the Lucus Manual for the various pots and ways they tried to prevent air being drawn in on a low tank. Best is a proper swirl pot, but that needs a lifter pump as well.

 

John

Edited by john.r.davies
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With the coil disconnected, engine not running, MU not functioning, and injectors not firing, where do the air bubbles go? I am imagining the fuel circulating between the pump and the MU.

 

Thanks,

 

Sam

The return pipe,save us all :lol:

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Just for the avoidance of doubt, when purging the system disconnect the low tension (white) lead from the distributor to the coil. Don't disconnect the thick HT lead, that won't help.

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