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Lost Both Front Cylinders :-(


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Hi All.

 

Now that the new exhaust manifold is in place I've refitted the throttle bodies and tweaked the throttle linkage by adding a brass roller where there was previously just a pin for the cam to run on. This annoyed me immensely - I presume there was originally a roller of some type on that pin?

 

Anyway, with everything bolted back in place I fired the engine up (after first bringing oil pressure up with the ignition coil low tension feed disconnected) and much to my bemusement it's misfiring badly, at idle and with throttle. Bemused, because it was running perfectly before I removed all the bits to fit the new manifold!

 

Using an infra-red thermometer I was able to pinpoint the two front cylinders as the culprits - both cold. Fitted new plugs, no change even though my timing light told me they were both firing. Removed and placed them on the valve cover to check and yes I've got spark. Pulled the two injectors and checked them in a clear container. Both discharging fuel in a nice spray pattern so I figure its getting fuel.

 

Back to the distributor. Checked and double checked the leads, all in correct positions and the cap is like new. It has a Pertronix module - could this be playing up perhaps as I also noticed the odd spitback from #6 cylinder?

 

There are no stray rags in the front throttle body, the new gasket had holes in the right places and the butterflies are close to balanced (can't really get this right again until the bloody thing is running properly). There was quite a bit of synthetic spray grease in the TB bores as I lubed the hell out of the shafts whilst they were on the bench.

 

I'm stumped gents. What am I missing here?

 

Gavin

NZ

 

post-14246-0-54161600-1503815926_thumb.jpgpost-14246-0-21484800-1503815937_thumb.jpg

 

 

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Bummer, after all tour work.

If you have a spark and fuel, I suspect the air to fuel ratio?

Can you open no 1&2 up just a little and see what it does?

Waldi

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Hi Gavin

 

You mentioned all the leads are in the correct place on the distributor. Stupid question maybe, but have you got the firing order correct or is this what you meant? I think it's 1-5-3-6-2-4. So easy to overlook something very simple, been there and done it!

 

Also check for a crack in the plug ceramic or check the plug as when you're undoing things it's easy to tap the plug with something and crack it. Other than that, are the throttle bodies seating correctly maybe?

 

Regards

 

Kevin

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Bummer, after all tour work.

If you have a spark and fuel, I suspect the air to fuel ratio?

Can you open no 1&2 up just a little and see what it does?

Waldi

 

Hi Waldi.

 

Even with the air bleed screw open they don't run, neither when the butterflies are partially open and running at 2,500 rpm. I have spark out of the engine, but that may well disappear under compression which makes me wonder about the Pertronix module.

 

Gavin

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Hi Gavin

I dont have a PI car so may be asking a dumb question, but is it possible to have the injector lines swaped between 1 and 2?

 

George

Hi George.

 

No, not a dumb question but I haven't changed the location of the lines which are well marked. Even if they were I would still expect the cylinders to fire.

 

Gavin

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Hi Gavin

 

You mentioned all the leads are in the correct place on the distributor. Stupid question maybe, but have you got the firing order correct or is this what you meant? I think it's 1-5-3-6-2-4. So easy to overlook something very simple, been there and done it!

 

Also check for a crack in the plug ceramic or check the plug as when you're undoing things it's easy to tap the plug with something and crack it. Other than that, are the throttle bodies seating correctly maybe?

 

Regards

 

Kevin

Hi Kevin.

 

Checked and rechecked location of the leads on the distributor. Plugs are new and I'm quite particular about fitting them so virtually no chance of cracked ceramics (2?).

 

Butterflies are very close, but I need the engine running to do the final balance with my airflow meter.

 

Gavin

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I'd check for air leaks/ loose bolts on the inlet manifold, although if these are present the engine would be very hard to start.

 

Note that Pertronix state that their module is not to be left energized for more than a short time without the engine running. I've never had a problem with this as I remove the LT lead from the ballast resistor whenever I work on the car with the ignition on, but maybe you did this some time in the recent past.

 

Are you sure your injector spray patterns are good enough ? I've developed a similar problem since I last ran my engine , but I can feel a weak " pulse " in No 1 injector which I'll remove and clean tomorrow.

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Gavin,

 

have you run the airflow meter over all six with the engine running? Are all six sucking with a similar reading?

 

mark crank pulley with a dot of white paint at approx. (no need to be accurate) 120' and 240' and work down through all six plug leads with a timing light. 1 & 6 should fire on the timing mark, 5 & 2 near to one of the dots you painted and 3 & 4 near the other dot. Fast & easy with a clip-on timing light.

 

After that there is only fuel. Remove injector retaining plate on 1 & 2 and with the engine running withdraw injector 1 until about 2" clear of its fitting and pointing at the hole, is there a good spray that is being sucked into the manifold? On a working engine it should still run on all six. Similarly with no 2 injector.

 

Alan

Edited by barkerwilliams
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If its got fuel and spark it only needs air- are the front pair of butterflies opening with the others?

If they are, swap the electrickery for points. It must be a really feeble spark as there is little compression at tickover.

Peter

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With it being a pair of cylinders not working look at things that affect only that pair , which is the throttle body.

 

Are the throttles for 1&2 actually opening ?

I'd also swap the injectors from working cylinders to 1&2, just to be sure.

 

Steve

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With it being a pair of cylinders not working look at things that affect only that pair , which is the throttle body.

 

Are the throttles for 1&2 actually opening ?

I'd also swap the injectors from working cylinders to 1&2, just to be sure.

 

Steve

 

Thanks Steve, but whilst the butterflies may not be balanced to perfection they open with all of the others and all open fully.

 

I have made some progress tonight though. By the process of elimination (which, in hindsight, I should have completed earlier) I've determined with the help of a can of brake clean that this is a fueling issue - both cylinders burst into life when they received a dose from the aerosol can.

 

Quite why they are both on the front throttle body assembly is beyond me at this point. I did take all of the injectors out to remove the TB's, but protected them with silicon tube sleeves so I know they're not damaged in any way.

 

Is it possible there has been some leak-down on those two injectors whilst they were sitting on the valve cover? They were there for a few weeks.

 

Gavin

NZ

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Thanks Steve, but whilst the butterflies may not be balanced to perfection they open with all of the others and all open fully.

 

I have made some progress tonight though. By the process of elimination (which, in hindsight, I should have completed earlier) I've determined with the help of a can of brake clean that this is a fueling issue - both cylinders burst into life when they received a dose from the aerosol can.

 

Quite why they are both on the front throttle body assembly is beyond me at this point. I did take all of the injectors out to remove the TB's, but protected them with silicon tube sleeves so I know they're not damaged in any way.

 

Is it possible there has been some leak-down on those two injectors whilst they were sitting on the valve cover? They were there for a few weeks.

 

Gavin

NZ

Hi Gavin,

I would check the poppet valve 'O' rings on 1 & 2 injectors for leaking. Current petrol has a habit of attacking them and they leak down when the engine is switched off. Then the engine does not fire up on all cylinders? I check them by using my son's high pressure cycle pump, can go up to 150 psi and watch the pressure gauge needle as the air escapes, a very quick fall off in pressure shows it to be faulty! I was shown this method years ago by a Lucas/CAV dealer and it never fails. The adaptor from injector to pump is made from using an original spare injector pipe termination.

 

Bruce.

 

Bruce.

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I check them by using my son's high pressure cycle pump, can go up to 150 psi and watch the pressure gauge needle as the air escapes, a very quick fall off in pressure shows it to be faulty! I was shown this method years ago by a Lucas/CAV dealer and it never fails. The adaptor from injector to pump is made from using an original spare injector pipe termination.

 

Bruce.

 

 

I like that idea Bruce, i have one of those pumps too.

 

Gavin , The injectors could easily have drained back/leaked enough to cause 1&2 not to fire FOR A WHILE but i'd expect them to self bleed in a minute or so. Has the engine run for this long?, also tickover is the worst way to bleed the injectors as so little fuel is metered, best to gently drive the car and see if it clears.

 

Steve

Edited by SDerbyshire
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My injectors won't clear air from all of the the lines easily with the just engine idling. I have to blip the throttle to over 3000 rpm a few times.

 

I'm told this is because there's a column of air in the injector line that just "bounces" at low throttle without opening the injector and bleeding off.

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One other thought is that perhaps there is an air leak between the throttle bodies and the head. This could give the symptoms you have outlined with the airleak making the front two TBs too weak to run. Adding spray to these would get them running as it would richen the mixture enough for it to fire..

Cheers

Tim

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With the engine running pull out injectors 1 and 2 and check they are spraying. (Number 2 injector pipe is connected to the metering unit by the banjo connector at the back of the metering unit)

If they are not injecting - remove the injector and blow out with an airline then re-attach and bleed out.

 

If they are injecting check the spark at one and 2 and that they are in the right order. Unlike the injectors the cylinders won't fire if the plug leads are out of sync.

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Thanks all for the advice. Checked both injectors were working with a Heath-Robinson setup hanging from the bonnet to allow any air in the lines to work its way out. Then balanced the throttle butterflies with a feeler gauge for starters, got the engine running and kept the revs up for several minutes until the engine started to warm, then all came good eventually running on six.

 

post-14246-0-10668700-1504422338_thumb.jpg

 

Balanced the T/Bs with my air-flow meter and set the final idle speed with the air-bleed screw.

 

Now starts and runs a treat :):) .

 

Gavin

NZ

 

 

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Hi Gavin,

Very good.

Being a non-english person, I had to look up your Heath-Robinson-set-up????????.

Your set-up, with the injector also pointing upwards, ensures all air is vented, not only in the nylon line, but also in the injector.

Regards,

Waldi

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Hi Gavin,

Very good.

Being a non-english person, I had to look up your Heath-Robinson-set-up.

Your set-up, with the injector also pointing upwards, ensures all air is vented, not only in the nylon line, but also in the injector.

Regards,

Waldi

 

Hi Waldi.

Yes, the plan was to allow the air to rise and escape so this set-up worked well. Heath-Robinson is a term my Dad used, it stumps (confuses) a lot of people. :)

 

Regards

Gavin

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