TR6 PI : from idle, very reluctant to respond to the accelerator.

[Jules TR6]

This question is following on from an issue I started in another thread - though that is now getting rather long. Summery, TR6 PI, was running smooth, but with occasional misfire.

To try and resolve the occasional misfire, new coil (newfangled resin filled), dizzy cap, electronic ignition (was points before), rotor arm, HT leads, ran ok though rather 'flat'. Then it started misfiring again, and now it's just generally bad. The fact is was 'ok', now bad, something fairly suddenly (and maybe progressively rapidly) went wrong.

Cleaned the BP6ES plugs (some sooty), checked timing (was ok), injectors - and bled one. No better, maybe worse - though not sure as I haven't had the courage to take it on the road to see if the misfire is any better.

This is the issue :

1. hard to start, a lot of cranking (even after giving the fuel pump 20 secs to build pressure).

2. when the engine is running, from idle pushing the accelerator, the engine is very hesitant to raise the revs, instead it sounds like it breathes heavy, and the engine turns / rotating titling the vehicle - until the revs rise (eg to 4000rpm) then the engine settles, jabbing the accelerator then can result in backfire. But noticeably, from idle (800rpm) it really doesn't want to respond to the accelerator (and when driving results in stalling).

3. With the engine warm, i.e even after 5mins of running, turning off (or stalling), it wont start (needs longer than 1/2hr to cool/settle down).

Do all of these point to one issue to you? - mainly point 2. the strange reluctance to respond to the accelerator (feels like the engine is almost flooding/choking on itself, not burning through the delivered fuel).

I can try new plugs tomorrow (multi-electrode BP6RT), ...and maybe try the old coil if you think that might be the overall cause?

[Phil Kirk]

Hi, Jules, Have you checked /cleaned the fuel filter?

Phil

[Kevo_6]

16 minutes ago, Jules TR6 said:

This question is following on from an issue I started in another thread - though that is now getting rather long. Summery, TR6 PI, was running smooth, but with occasional misfire.

To try and resolve the occasional misfire, new coil (newfangled resin filled), dizzy cap, electronic ignition (was points before), rotor arm, HT leads, ran ok though rather 'flat'. Then it started misfiring again, and now it's just generally bad. The fact is was 'ok', now bad, something fairly suddenly (and maybe progressively rapidly) went wrong.

Cleaned the BP6ES plugs (some sooty), checked timing (was ok), injectors - and bled one. No better, maybe worse - though not sure as I haven't had the courage to take it on the road to see if the misfire is any better.

This is the issue :

1. hard to start, a lot of cranking (even after giving the fuel pump 20 secs to build pressure).

2. when the engine is running, from idle pushing the accelerator, the engine is very hesitant to raise the revs, instead it sounds like it breathes heavy, and the engine turns / rotating titling the vehicle - until the revs rise (eg to 4000rpm) then the engine settles, jabbing the accelerator then can result in backfire. But noticeably, from idle (800rpm) it really doesn't want to respond to the accelerator (and when driving results in stalling).

3. With the engine warm, i.e even after 5mins of running, turning off (or stalling), it wont start (needs longer than 1/2hr to cool/settle down).

Do all of these point to one issue to you? - mainly point 2. the strange reluctance to respond to the accelerator (feels like the engine is almost flooding/choking on itself, not burning through the delivered fuel).

I can try new plugs tomorrow (multi-electrode BP6RT), ...and maybe try the old coil if you think that might be the overall cause?

Hi, I had a similar issue as to your point 2. It turned out to be a blown head gasket. Have you done a compression test as that might give a clue!

[Jules TR6]

43 minutes ago, Kevo_6 said:

Hi, I had a similar issue as to your point 2. It turned out to be a blown head gasket. Have you done a compression test as that might give a clue!

...that's sounds serious.

I haven't got a compression tester, but am hearing a slight chuffing from the front of the engine - which maybe just the fan-belt / alternator / coolant pump, ...or the head gasket? If it's the head gasket I suppose it would also explain the reluctance to start - lack of compression (or it's the plugs).

Maybe instead of trying new plugs, I should just get it straight into a garage ...possibly even picked-up, as if it might the head gasket I'm very relucent to try an drive it.

Could installing electronic ignition have caused this?

[DRD]

Have you checked all the injectors are spraying fuel correctly into a jar.

[Topoff]

Have you checked the firing order is correct, ie are the leads on the right plugs in the right order in the right direction ?

[Mike C]

3 hours ago, Jules TR6 said:

...that's sounds serious.

I haven't got a compression tester, but am hearing a slight chuffing from the front of the engine - which maybe just the fan-belt / alternator / coolant pump, ...or the head gasket? If it's the head gasket I suppose it would also explain the reluctance to start - lack of compression (or it's the plugs).

Maybe instead of trying new plugs, I should just get it straight into a garage ...possibly even picked-up, as if it might the head gasket I'm very relucent to try an drive it.

Could installing electronic ignition have caused this?

A blown head gasket will generally produce bubbles in the coolant when you blip the throttle or sometimes water/steam in the exhaust.

I'd look at the plug leads,distributor rotor button/cap and throttle linkages for starters  .

I'd also be reluctant to drive the vehicle on public roads while it's running in that condition.

 

[Mk2 Chopper]

Did you do the tongue test to check the diaphragm can hold vacuum? If it can't the engine will run super rich and will find the symptoms you have. 

Have you checked the 'choke' lever on the MU is fully closed when off, again if out of adjustment it'll be very rich. 

You said timing is okay, have you tried ignoring the pulley marks and slowly turning the distributor clock wise/ anti clock wise to get it at the fastest idle speed? 

You may find the plugs are ruined now they've been so sooted up, and a new set may help. It sounds like it's done a lot of cold starting which won't help them. 

Gareth

[Jules TR6]

3 hours ago, Mk2 Chopper said:

Did you do the tongue test to check the diaphragm can hold vacuum? If it can't the engine will run super rich and will find the symptoms you have. 

Have you checked the 'choke' lever on the MU is fully closed when off, again if out of adjustment it'll be very rich. 

You said timing is okay, have you tried ignoring the pulley marks and slowly turning the distributor clock wise/ anti clock wise to get it at the fastest idle speed? 

You may find the plugs are ruined now they've been so sooted up, and a new set may help. It sounds like it's done a lot of cold starting which won't help them. 

Gareth

Today...

1. MU diaphragm suck test : passed.

2. Choke lever on MU is fully off (with a gap before starting to pull on).

3. New spark plugs.

4. HT lead order correct, injector order correct.

No change, still hard to start and very reluctant to respond to the accelerator, 'chokes' when dabbing accelerator, on release of the pedal revs drop quickly dipping below idle speed. I increasingly fear a blown head gasket - but why it blew I've no idea.

I could try the old coil.

[Mike C]

Try the old coil, especially if it has a name on it like "Bosch".

[RobH]

Don't panic. Apply Occam's razor.

In trying to cure a slight misfire you replaced all the ignition components and fitted electronic ignition. It didn't cure the misfire and then things got worse.  Quite possibly then, the cause of the new problem is something you did. 

Before jumping to dire conclusions, the first thing to do is put the old ignition bits back, starting with the points.  

[Jules TR6]

1 hour ago, RobH said:

Don't panic. Apply Occam's razor.

In trying to cure a slight misfire you replaced all the ignition components and fitted electronic ignition. It didn't cure the misfire and then things got worse.  Quite possibly then, the cause of the new problem is something you did. 

Before jumping to dire conclusions, the first thing to do is put the old ignition bits back, starting with the points.  

Finally a good result :

Electronic ignition still in, didn't want to swap everything again, started with the coil, and put the old coil back (Lucas, looks very old).

Starts much better, immediate improvement noticed. The throttle was a little reluctant, but now warmed up, timing checked again, and idle, the accelerator responds as it should - as far as I can tell. My worst fears (blown head gasket) are now passing quickly.

Just took it up the lane and back, feels ok. But haven't had it on the open road yet.

The new coil (probably faulty) was a resin-filled Viper coil (for ballast), maybe these brands are rather hit or miss. Surprised if it failed so quickly, but why wouldn't it just totally fail? - why the weird ignition behaviour - irregular and sluggish? Anyway for now, I'm leaving everything as is, and am blaming the Viper coil.

/

Having had my head in the engine bay for so long I am noticing a slight high pitch whistle/hiss/wheeze, in time with the engine, somewhere between the 1 and 4th injector. Hard to be sure where! - maybe just the K&N intake filters, or the exhaust manifold, or injector 3 - which is the only injector to leave its collar in the engine when the injector is pulled.

If an injector is 'sucked' into it's seat, can it leak gases/compression - and wheeze? but if it can be pulled out of it's collar surely the seal can't be too good? - seems a rather basic method of gaining a seal - just sliding it out of its collar!

Or are some slight wheezes normal under the bonnet?

 

[RobH]

It may be the electronic ignition didn't like something about that coil so was playing up.  

[Kevo_6]

Glad to hear that you are getting some where with it now.

[Mk2 Chopper]

Great news, double check the lucar connector for the coil, they can corrode, including the wires, and cause cutting out etc. 

Gareth

[RobH]

47 minutes ago, Mk2 Chopper said:

double check the lucar connector for the coil, they can corrode, including the wires, and cause cutting out etc. 

 

Yes that is a known weak point. The lead that goes from the distributor to the  coil is unsupported and waggles about due to vibration. and engine movement. That can lead to fractures in the inner conductor at the stress point where it enters the spade connector.  You can't see that inside the wire insulation.   Swapping the coil involves handling that wire so depending on whether the broken ends get pushed together or pulled apart in the handling,  you can cause or (temporarily) cure a faulty connection and assume that it is due to swapping the coil. 

[Jules TR6]

2 hours ago, RobH said:

Yes that is a known weak point. The lead that goes from the distributor to the  coil is unsupported and waggles about due to vibration. and engine movement. That can lead to fractures in the inner conductor at the stress point where it enters the spade connector.  You can't see that inside the wire insulation.   Swapping the coil involves handling that wire so depending on whether the broken ends get pushed together or pulled apart in the handling,  you can cause or (temporarily) cure a faulty connection and assume that it is due to swapping the coil. 

The HT leads are all new, carbon rather than copper core. But yes even a new cable can fail or be dodgy from the get go.

I'm not keen to swap back to the Viper coil just to check this, but will keep the knowledge in mind. Tonight is for celebration - which I hope lasts.

Thank you for the link to the document about coils that you wrote, kinda what we all need to know!

My only issue now is that while a ballast compatible coil can be used for electronic ignition (with a ballast resistor in the harness), it seems that for electronic ignition the ballast is best bypassed and a 3ohm coil used (not sure why, and if keeping to the ballast system killed the Viper ballast coil). But I have no idea how to bypass the ballast.

At present I just hope the 50 year Lucas 1.5 ohm coil doesn't fail with the electronic ignition, that would be a shame.

 

[RobH]

1 hour ago, Jules TR6 said:

The HT leads are all new, carbon rather than copper core. But yes even a new cable can fail or be dodgy from the get go.

Not the HT leads- it's the thin wire between the dizzy body and the  '-'coil spade terminal.  However if your electronic module is Powerspark that is probably an integral lead. 

1 hour ago, Jules TR6 said:

But I have no idea how to bypass the ballast.

You take the two leads off the + terminal on the coil and insulate the ends.  Then fit a new white wire from that terminal on the coil to the white wire on the fuse holder.  ( you can do it using the existing wires but how that is done depends on the year of your car because there were three different wiring methods, so this is easier )

There really is no need though. Either system, ballasted or un-ballasted, should work.