Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: Bryan Boyle on Wednesday,March 20, 2024, 04:08:43 PM
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Lately I've been noticing that the TC buggy has been a bit recalcitrant to start...even with a spritz of ether...it eventually catches and then runs (ok, stromberg carbs, starting device engaged, no foot on the accelerator, dashpots topped off, etc.) and when it does warm up...after a run, seems to like to idle at 1200 or so...smooth idle, but a bit high. Dizzy is a pertronix, high-volt coil, new wires, plugs have maybe 1500 miles on them...up to now has been a couple seconds cranking but it's fired off ok. Now, not so fast.
First: is it getting gas, right? Fuel filter has fuel in it, pumping the priming lever eliminates the little bubble I saw from it sitting.
So, figured I'd investigate further...pulled the plugs (NGKs)...checked the gaps, they're where I left them (I mark the plugs with the gaps), removed the cap, some roughness on the edge of the arm contact surface cleaned up with crocus cloth, cap is clean, no carbon, all the wires are firmly seated in both the coil and the cap.
Got her started after churning a bit...stumbled to life and let it idle with carb starter mechanism engaged till it settled down and warmed up by driving around the block so I could turn the starter circuit off. Hooked up timing light (I know too much advance can make it hard to start), and (it's an adjustable timing light, so I can dial the strobe to zero her out and read the advance off the dial) find, at 1000-1200 rpm...I'm at 15 degrees advance. I'm thinking that is a bit much for idle (and may, once the engine starts, account for some of my higher idle speed.)
So, wondering (Federal engine...) what folk who have an electronic dizzy, mechanical advance, have found is a reasonable idle advance figure. I can't believe that 15 degrees is right; that never lets the compression (my 1-4 compressions are all in the 155-165 lb range) get close to TDC...and may account for a bit of hard starting.
Yes, I know carbs need a refresh (hence my questions earlier)...but they've been reasonably working until now...can't believe that they went tango uniform between an easy starting day and 2 days later...Tanks are filled with avgas/pump gas, so I don't believe there's a varnish issue or clogged jets, or I'd never get the car to smoothly settle down (as much as 1200 idle after a run is settled...lol).
Thoughts?
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The timing spec for a Stromberg TC is 5 degrees BTDC static. I think I would start there.
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The timing spec for a Stromberg TC is 5 degrees BTDC static. I think I would start there.
Should have looked that up...;) Thanks! I guess I can always loosen up the clamp and swing the dizzy a bit...and see if that makes a difference...but that's a good starting point...it only cranks over at 100 RPM to begin with...Have to look at the curves in Wilkins to see where it should be at idle, I guess #2.
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When my Stromberg TCS was hard to start, I traced it to a corroded ground strap. But I imagine you have that sorted pretty well.
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A 4-port Europa TC is set to 12° at idle and has 14° of mechanical advance which gives a total advance of 26°.
A 2-port Europa TC is set to 5° at idle but it has a vacuum retard unit so the timings are probably similar.
I always start with valve clearances. Stromberg carbs (and SUs) are very sensitive to tight valves.
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If you set a Stromberg car to 5° static, it will have a total advance of 19° and run very poorly indeed.
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Hi Bryan,
When you mention a Pertronix distributor, is it a brand new one supplied by Pertronix to their spec or the original one with Pertronix ignition replacing the points ? If the former then I guess my first thoughts would be around the advance curve they have fitted.
When Lotus had Strombergs in the UK Elans they had a 40953 distributor which came (according to Miles Wilkins) with 9deg static and 33 total advance. The Federal/European/ECE15 spec cars had a 41225A distributor with 5deg idle and 19 total advance.
If you have the Miles Wilkins book, he does a chapter on the distributor options with advance curves. There's also service bulletin issued in '73 mentioning the vac. retard unit and it looks like the static timing is 10deg dropping to 5deg at idle. If you don't have his book I can scan the relevent pages later today ?
If it all checks out then I guess the next step would be to make sure the advance/retard mech is working smoothly and returning properly. As for the carbs, I've only ever had Strombergs on one car and after a few years of hassle changed them so I'm not much help on the carbs themselves. Maybe a diapraghm split ?
Brian
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A 4-port Europa TC is set to 12° at idle and has 14° of mechanical advance which gives a total advance of 26°.
A 2-port Europa TC is set to 5° at idle but it has a vacuum retard unit so the timings are probably similar.
I always start with valve clearances. Stromberg carbs (and SUs) are very sensitive to tight valves.
Well...I'd wager it's NOT the valves, since the starting issues seem to have come on in a couple days and has been starting and running reasonably well up to now. And even if it is, I'm not going to go down the road with this particular head since I have an overhauled head with the valves shimmed properly sitting on the side (well, on its end) waiting for me to pull the lump.
Going to fiddle with the timing (least cost option right now); Brian: it's the pertronix replacement (the original lucas was hacked apart to take the retard capsule off and the bushings are shot). The diaphragms are new (well, 2 years old) and were installed last time I pulled them apart. Like I said, it's been starting and running fine up until now...only the last couple times did it give me fits. I'll check the timing first next time I get her started; like I said, at 1000-1200 rpm, she's showing 15 degrees advance. I'll try dialing the dizzy back a bit and see. Easy things first before getting into a massive tear down.
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I bought 4 syringes from the chemist (honest I am not an addict) and use them to squirt petrol directly into the inlet trumpets of the 40DCOEs.
If that does not get at least some firing, I know the problem is on the ignition side.
Squirting ether sprays into the trumpets was getting costly, so I thought why not use petrol.
With engine timing, I use a strobe to get about 35 BTDC on about 3500 RPM and that seems to work. Anything less and I get misfires and bangs when I switch off.
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Brian:
it's the pertronix replacement (the original lucas was hacked apart to take the retard capsule off and the bushings are shot). The diaphragms are new (well, 2 years old) and were installed last time I pulled them apart. Like I said, it's been starting and running fine up until now...only the last couple times did it give me fits. I'll check the timing first next time I get her started; like I said, at 1000-1200 rpm, she's showing 15 degrees advance. I'll try dialing the dizzy back a bit and see. Easy things first before getting into a massive tear down.
Ok, the diaphragms should be ok although we do seem to have issues with the quality of some rubber components and modern fuels over here and a split could give the "it was fine yesterday but today it's a dog" symptom.
Even so I think you're right to re-set the timing and see if that sorts it out. I have the older Pertronix which means I can set it static with a bulb, I'm guessing that option isn't so easy with your set up but you can always guesstimate a few degrees and see if it's easier to start. And once it's running you can get an accurate setting and see if it advances/returns from blipping the throttle.
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I hate to disagree with BDA, but if I set my tc engine at 5 deg btdc, it would run terribly. I currently have my 1000 rpm timing at 14 deg btdc
Lotus retarded timing to achieve emissions.
I don't know is retarded timing affects starting.
Anyway, I would set timing at 10deg btdc and see how she starts.
If you want some info on where to set it for optimum performance, then let me know. I have some spreadsheets which show everyones opinion on tc timing, including my own.
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The timing setting for the Strombergs is dynamic. So it is 5°BTDC WITH THE VACUUM RETARD HOOKED UP. This means the mechanical setting is the same, just the vacuum retard pulls it back. If you set it up at 5° using a test light and turning the engine over by hand, it will be massively retarded and run like crap.
If you have disconnected the vacuum retard, a very good idea, then set the timing to the recommended 12° setting for the Dell equipped Europas.
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The timing setting for the Strombergs is dynamic. So it is 5°BTDC WITH THE VACUUM RETARD HOOKED UP. This means the mechanical setting is the same, just the vacuum retard pulls it back. If you set it up at 5° using a test light and turning the engine over by hand, it will be massively retarded and run like crap.
If you have disconnected the vacuum retard, a very good idea, then set the timing to the recommended 12° setting for the Dell equipped Europas.
Interesting. I'll try cranking it back a few degrees (there is some minor adjustment range in the hold-down clamp without releasing it from the dizzy) to see if that changes the dynamics from where it is now (15-16 degrees at idle). The dizzy on the lump right now is only 2 years old; the original was hacked apart to remove the retard long before I acquired the car (in fact, wasn't even clamped down but was stuck in its place in the engine) and pretty much worn out...new one has no vacuum capsules.
Thanks for the suggestion.
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Given you have an aftermarket distributor, I think I'd give Pertronix a call to see what advance curves they've put in it.
Why ? well I've enclosed a couple of page scans from Miles Wilkin's book as pictures will explain it far better than my words. It looks to me like Lotus used 2 distributors with Strombergs and they had different advance curves and initial static timings but at 15deg. you're way ahead of every curve so something has gone wrong and getting some basic data would help figure out where you should be.
Personally I think I'd try the 40953 settings first because if Pertonix have one distributor for the TC engine it might be the one with the higher advance curves. My reasoning is that I had a quick scan at the Pertonix website to look up the options and basically you can pick any Elan or Europa and "it fits" so maybe they just have a generic advance ?
Anyway, I'm following now so let's hear how you get on twiddling that distributor !
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A 4-port Europa TC is set to 12° at idle and has 14° of mechanical advance which gives a total advance of 26°.
A 2-port Europa TC is set to 5° at idle but it has a vacuum retard unit so the timings are probably similar.
I always start with valve clearances. Stromberg carbs (and SUs) are very sensitive to tight valves.
To what are you referring, with "2-port" vs. "4-port" TC, JB? I honestly don't know what you mean!
-Vince
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My guess 2 port = Zenith Stromberg head, 4 port = Weber/Dellorto head.
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I believe he probably means 2 port Federal Stromberg head had two carbs so shared a "throat" between the carb and the head.
Rest Of World Dellorto heads had two twin choke carburetters and a throat between each carb and just one cylinder - no sharing.
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Heads that take Webers or Dellortos have four intake ports. Heads that take Strombergs have two intake ports.
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Thanks, gentlemen!
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Going to reclock (and move the wires one pip to the right) the dizzy to give me more adjustment range; right now, the wire pips on the cap are up against the bottom of the inlet. At idle I'm seeing 16-17 degrees advance...can't move anti-clockwise any further. Both mentioned that would possibly account for the hard starting I've been witnessing lately. Also going to throw in a fresh set of sparkers. Can't hurt.
Talked to a couple wrenches I have been dealing with since the 80s and work exclusively on Lotus...with the pertronix, they usually set for 12 degrees at idle. Wish me luck...will report back...;)
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Well...reclocked the dizzy (and moved all the wires by one place anti-clockwise...but...discovered the below inside the cap.)
Darn.
Reason for reclocking is to move the spring cap snaps away from the bottom of the intake. This is the second time that the cap has been machined by the rotor...my fault in installation, I'm thinking. Mea culpa.
New cap and rotor on its way. But still going to keep it reclocked: took all plugs out. Screwed in compression gauge in #1, tranny in 4th...moved car manually till gauge registered compression on 1. Moved till read 10 degrees on flywheel. Chocked, checked where rotor was. Paint mark on dizzy body. Close to where I moved the #1 wire. lightly clamped. Will install new cap when it comes in.
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Bummer! That's not close to the dumbest mistake I've made!
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Bummer! That's not close to the dumbest mistake I've made!
I could write a book detailing all of the bonehead mistakes and it wouldn't be finished yet. New cap and rotor on its way. Old one looks ok.
I'm not entirely happy with the 'sturdiness' of the clips holding the cap on. Thinking if I get it to a point where the cap clips are in the 'clear', there won't be any reason for vibration or such to dislodge them and offset the cap on the dizzy body. Of course, I could always throw a long ty-wrap around the body to hold the clips in place. I think some mfrs had the right idea of using screws to keep the cap solidly on the body. But, we have to work with what we have available, right?
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When the rotor arm rotates, does it describe a true circle, or an oval?
Is the distributor itself rotating properly, or is the cam that triggers the spark eccentric?
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I'm pretty confident my bonehead book would be thicker but let's not make this into a competition! :D
Is the Pertronix dizzy taller or fatter than the Lucas one? I know it's tight under the carbs but I'm surprised it's that tight!
Be thankful you don't have a screw down dizzy cap or you'd have to take the dizzy out to take the cap off!! If you do use a ty wrap to hold the clips in place, I might wrap the ty wrap around the tabs of the clips rather the center since squeezing the clips would tend to loosen the tension holding the cap.
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When the rotor arm rotates, does it describe a true circle, or an oval?
The spring clips that hold the cap down are not the most robust (as compared to the original 25D dizzy clips and Lucas cap) and the cap can be easily displaced which means when it is, the cap itself is off-centered just a bit and the rotor carves the contacts (proof is the 2 that are machined by the rotor; the opposite ones show signs of arcing from the increased clearance between the rotor and the cap.)
Is the distributor itself rotating properly, or is the cam that triggers the spark eccentric?
The issue lies within the design/material used for the spring clamps. It's an electronic dizzy, so there is no cam, only moving part is the rotor (and advance weights). This is the second time this has happened, so...thinking of ways of modifying/adjusting the clips to make them hold the cap on more securely.
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I'm pretty confident my bonehead book would be thicker but let's not make this into a competition! :D
Is the Pertronix dizzy taller or fatter than the Lucas one? I know it's tight under the carbs but I'm surprised it's that tight!
Be thankful you don't have a screw down dizzy cap or you'd have to take the dizzy out to take the cap off!! If you do use a ty wrap to hold the clips in place, I might wrap the ty wrap around the tabs of the clips rather the center since squeezing the clips would tend to loosen the tension holding the cap.
Pretty much same measurements, not too worried about that. It is a bit tight in there...I pulled my old dizzy (the original Lucas one) out and stripped it down last night...to clean it up maybe? They do make a P-tronix kit for it...nah...Not going to let this defeat me...I've come up against some of the best bodges Lotus designed into the Europa...not going down in flames over a distributor...lol
As for the ty-wrap...exactly where I thought it should go. I'm going to try slightly increasing the arc of the clips and the amount of "bite" on the end where it holds down the cap to see if I can get some added 'clamping' pressure before resorting to a (d)po fix of a ty-wrap...;)
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I'm pretty confident my bonehead book would be thicker but let's not make this into a competition! :D
Agreed, no competitions.
A new thread then? ;D