'73 Europa TC - backfiring? - LotusTalk - The Lotus Cars Community
 
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post #1 of 16 (permalink) Old 04-27-2010, 05:53 AM Thread Starter
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'73 Europa TC - backfiring?

Just replaced breaker points in my '73 Europa with a Pertronic Electronic Ignition module and immediately started experiencing excessive backfiring on decelleration. I have tried to make sure of correct ignition timing but am still experiencing this issue. Any suggestions how to troubleshoot this would be appreciated. Wasn't sure if ballast resistor was needed with this unit on the Lotus.

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Jim
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post #2 of 16 (permalink) Old 04-27-2010, 06:06 AM
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Very interesting because mine has had a backfiring problem since adding the Pertronix ignition module too. I hadn't related the two events until I saw this post. I have minimized it by advancing the timing but it is stil abit disconcerting. You should not need the ballast resistor with this system as the resistors purpose is to decrease "burning" of the points which are no longer present. Might be worth going back to the points and condenser and seeing if it makes a difference. I thought it was due to the Strombergs and rebuilt them several times to no effect....Dave
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post #3 of 16 (permalink) Old 04-28-2010, 12:03 PM
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Didn't the Pertronix directions (you DID read the directions, correct? ) specify a certain resistance for the coil to be used with the ignition unit?

I never had a TC but I did install them on two Ford Kent engines in cars I owned. No backfiring.


You may also want to pull the dizzy (I know, easier said than done) and inspect the relationship between the rotor and distributor cap. On one Pertronix unit I had, the ring forced the rotor into the cap and I had to grind the mounting plate a bit. (That was an early 70s Ford crossflow with Ford ignition, though)

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post #4 of 16 (permalink) Old 04-28-2010, 12:51 PM
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I experienced back firing on a Lotus Twin Cam Engine which turned out to be a burnt exhaust valve.
Michael
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post #5 of 16 (permalink) Old 04-29-2010, 10:03 AM Thread Starter
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Tried both my original coil and a coil for that application from Pertronix with the same result.

dwkoski, It sounds like we are experiecing the same problem. I too have played with advancing and retarding the ignition timing which affects idle and performance but even with correct timing the problem persists.

A burned valve could be a possibility however, the condition began immediately following the installation of the electronic ignition system. I am going to re-install the points and see if the condition disappears. Will let you know what I find out.

Jim
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post #6 of 16 (permalink) Old 04-29-2010, 12:17 PM
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is the backfiring thru the carbs or thru the exhaust?

There is a rule of thumb for either....not that I can remember it.

As I don't believe in mechanical coincidences, it's gotta be the ign.

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post #7 of 16 (permalink) Old 04-29-2010, 01:22 PM
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Quote:
Originally Posted by Jim Bittel View Post

A burned valve could be a possibility however, the condition began immediately following the installation of the electronic ignition system. I am going to re-install the points and see if the condition disappears. Will let you know what I find out.

Jim
I bet it goes away. That could mean that the ignitor ring is producing the wrong "dwell" or something. Or it's not quite compatible with the advance curve.

Have you tried calling the Pertronix tech line? That's what I did with the one I had to modify. They will probably ask you the dizzy mfr and ID number of the Dizzy.


Good Luck

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post #8 of 16 (permalink) Old 04-29-2010, 05:11 PM
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Read the plugs yet?

Does it only do it when you back off the throttle?
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post #9 of 16 (permalink) Old 05-10-2014, 05:39 PM
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backfire/popping exhaust on deceleration answer?

Picking up an old thread here seeking resolution to my issue of popping / back firing in exhaust on deceleration, however I don't have Petronix, but equipped with original points, condenser. Twin Cam. I've given it a complete tune-up, carb rebuild, timing check, etc., but it still pops through exhaust while decelerating in gear on the upper rev end. Did this before tune up as well. Can't imagine all of us having burnt valves?
what was the resolution to this seemingly "common" problem????
thanks!

Last edited by QQROPA; 05-11-2014 at 04:19 AM.
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post #10 of 16 (permalink) Old 05-12-2014, 07:13 AM
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There was a lot of old nonsense written in this thread, so I wouldn't expect to get much help from it.

Popping and banging in the exhaust on overrun is caused by unburnt fuel passing into the hot exhaust, often when there is also a leak in the exhaust letting a little air in. The resultant mixture meets something hot and explodes. Nothing to do with ignition timing.

I had a car which, if I lifted the throttle and turned off the ignition, then turned it back on again, would go off like a small cannon! (Note, it did not have an ignition steering lock).

My Elise pops bangs and gurgles on the overrun too, so does the Elan. There's nothing really wrong with either of them.

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post #11 of 16 (permalink) Old 05-14-2014, 04:04 AM
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I did just rebuild the carbs since with an overhaul kit and it's now running very smooth, peppy, and what a difference it has made.....oh, and it seems to have all but eliminated the popping/backfiring on deceleration issue. So i'm thinking my carbs before rebuild were running rich (extra fuel in exhaust) and even showed some "run-on" or "dieseling" when ignition shut off. Those issues appear to be history now. I'm much more relieved.
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post #12 of 16 (permalink) Old 05-15-2014, 07:52 AM
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Quote:
Originally Posted by QQROPA View Post
I did just rebuild the carbs since with an overhaul kit and it's now running very smooth, peppy, and what a difference it has made.....oh, and it seems to have all but eliminated the popping/backfiring on deceleration issue. So i'm thinking my carbs before rebuild were running rich (extra fuel in exhaust) and even showed some "run-on" or "dieseling" when ignition shut off. Those issues appear to be history now. I'm much more relieved.
thanks
That seems quite likely - glad you resolved your problem!

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post #13 of 16 (permalink) Old 05-15-2014, 08:33 AM
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Glad it is resolved. Those symptoms can be caused by something else that I'm going through right now on my 69 Plus 2 which is too much fuel pressure for the webers after replacing the fuel pump. Same symptoms as running extremely rich. Unfortunately, I rebuilt the carbs before getting a regulator as I replaced with the original mechanical pump and assumed there would not be a pressure problem
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post #14 of 16 (permalink) Old 09-24-2014, 07:13 PM
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74 europa TC vacuum leak?

New to the lotus scene and had a question regarding my TC. I recently installed a new stainless steel exhaust from Dave Bean. Had to remove the 2 crossover tubes and seal the 2 ports where the pipes bolted to the intake manifold. The car runs fine but it takes about 1/4 throttle to hold idle. Thinking it sounds like a vacuum leak. I sprayed around the intake with carb spray trying to detect a leak but found none. The idle screws do not even run far enough down to begin holding the carbs open to stay running. Idles at 800 RPM at 1/4 throttle opening. Any suggestions would be great.

Thanks,
Anthony Migliore
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post #15 of 16 (permalink) Old 10-04-2014, 11:14 AM
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Anthony,

This is a Stromberg engine I assume.

Best way to find a vacuum leak is to use a spark plug cap and a small hose attached to a propane torch head.

This is more accurate, i.e. easier to pinpoint.

And, it does sound like a vacuum leak.

On the TC, Webers are "spring mounted", which can easily lead to leaks, but not sure about Strombergs. Don't forget to use hose near carb mounts too.

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post #16 of 16 (permalink) Old 10-05-2014, 06:45 PM
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It may indeed be an air leak, but I have another question.
When you removed the crossover pipes, what did you do about the secondary throttles? It it usual to disconnect them and fix them in an open position, or better, to remove the butterflies altogether.
If you don't do one or other, then with the crossover pipes removed and the ports blanked, there is little or no air-fuel supply for the initial stages of throttle opening.

Quote:
Originally Posted by migseuropa View Post
New to the lotus scene and had a question regarding my TC. I recently installed a new stainless steel exhaust from Dave Bean. Had to remove the 2 crossover tubes and seal the 2 ports where the pipes bolted to the intake manifold. The car runs fine but it takes about 1/4 throttle to hold idle. Thinking it sounds like a vacuum leak. I sprayed around the intake with carb spray trying to detect a leak but found none. The idle screws do not even run far enough down to begin holding the carbs open to stay running. Idles at 800 RPM at 1/4 throttle opening. Any suggestions would be great.

Thanks,
Anthony Migliore

'67 Elan S3
'72 Europa TC
'05 Elise
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