Mis fire

[alfadave]

My tank is ventilated by 2 pipes that cross over at the rear, and exit through the rear of the cills.

Standard on a Plus 2 I thought?

I can usually get a whiff of fumes when near the rear of the car.

And I've never had this mis firing in the last 5-6 years since I restored the car.

[alan.barker]

+1 you'll have a problem to pull a vacuum on a +2 with the 2 big breathers
Alan

[alfadave]

Took the plugs out when it began mis firing, right at home.
No3 wet with fuel. Others ok.

As a precaution, did a comp test whilst it was warm. Throttles full open. 215,210,220,230.

I fitted a link from the battery side of the solenoid to the coil positive.

I started, but wouldn't tick over!

[h20hamelan]

Blue Label Bosch
0221119027
906 859
K12V
Brazil

Blue coil 9 220081083
K12V
957 08
(0221119027)
Germany (though I see on-line, some being made in Brazil now!)

Highest output I found is
Mallory Promaster Classic Series Coils 29440
49k

Bosch makes its caps in Italy, and rotor arms in France. Or at least the couple I purchased last year are stamped, or labeled on box. And from what I recall, the Bosch Porsche 911S points are quality (though its been a few years since I stocked up) they were German.

I think you are running optical, can't recall.

I am not sure where the spark plug debate goes. If Copper or Nickel etc

[alfadave]

Fitted the Lucas dizzy cap today.
At first, the car seemed to run better.......

But after 3 miles the mis fire, and popping from the exhaust returned, and I struggled home.

The Lumenition module is next on my list!

[SENC]

Could it be a carb mounting issue? O-ring/rings bad, or a hard mount causing fuel frothing and starving the engine? Seems a long shot, but didn't see that asked before.

How are you on the rpms until it warms up - are you using higher rpms while cool, or waiting until warm. Trying to think through whether there could be a blockage in one of the main circuits that just isn't having an impact until warm because you're not really engaging them until warm? Also think about the choke/cold start system if you have them still on those carbs - are they sealed/locked shut, or could heat and vibration be causing one or both of them to engage a bit?

Do you have a mechanical fuel pump or electric? Tried running either into a bowl/cup rather than the carbs to ensure the pump is pushing fuel at expected rate and pressure?

[alfadave]

I thought about the O rings. Sprayed Easy Start on them, but no effect.

After I changed the cap, I sat at 3000rpm on my drive. Ran ok ....but I noticed popping from the exhaust.

Drove ok for 2 miles.....then struggled back home.

I don't have a choke control. Levers are in off position.

Mech fuel pump. I opened up a fuel line and it spurted out on operating the starter. Also I have a plastic filter before the carbs....I can see this filling with fuel.
But maybe the pump diaphragm is faulty?
I've asked Sue Miller for a new pump

[Craven]

Is there a fuel pressure regulator in the supply line ? there are reports of very odd faults attributed to regulator failures.

[alfadave]

I've had Filter Kings in the past......but no regulator in this case.

[sprintsoft]

Hi Dave,

Next time its playing up remove the carb tops and check the fuel levels before it cools down, check are levels the same in both carbs or is one being starved - it could be a sticking needle valve.

Iain

[vxah]

How about getting a set of those neons that you put between the plugs and plug leads?
Cheap enough and you can instantly see if any of the cylinders are losing a spark!
I’ve had good diagnostic results with these over the years.
Might also be helpful with a little more elaboration on “struggled” back? 3 cylinders? Less?

[alfadave]

I bypassed the ignition switch, and still had the problem, but worse. Would hardly run in first gear.

Took the carb lids off.....hardly any fuel in either chamber, over 60 mm below the gasket level.

Needle valves and seats clean and operating ok. Idle jets clear. Progression holes clear. Very little sediment in the bottom.

So looks like a fuel delivery issue.

On turning over on the starter, fuel gushed out of the pipe. Maybe the pump has an intermittent fault.

[alan.barker]

Be very careful with the Fuel we don"t want another Elan going up in smoke.
Alan

[Bigbaldybloke]

Looks like you are homing in on the problem, did you try holding your thumb over the fuel pipe to see if there was much pressure, obviously a gauge would be better if you have a suitable one but even the crude thumb test should give you an idea. If it was the pump diaphragm you might get fuel in the oil, have you checked the dipstick, does it smell of fuel? I suspect the valve in the pump is more likely to be the culprit? I’m assuming you checked at the carb banjo fitting, if you checked at the pump outlet, give the flexible fuel line a good check, they can deteriorate inside the outer braiding causing a restriction.
Good luck!

[Donels]

At the rate you're going it will soon fail completely and be easier to fix!

Seriously though I think it's the pump. If both carbs are empty then its not a carb issue. When webers are running dry they do spit back, I burnt a Westfield out with that ignition source. I would replace the pump.