Lotus Elan

Loss Of Power At Over Half Throttle

PostPost by: rickf » Tue Jul 06, 2004 3:35 pm

I have a 1972 Elan +2 with Strombergs and Pertronix ignition. It has plenty of power till about half throttle. Over half it almost compltely loses power. Power returns when you let up. I've cleaned the carbs and put on an electric fuel pump with no improvement. Any ideas?
Cheers,<br>Rick<br>1972 Elan +2
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PostPost by: Fred Talmadge » Tue Jul 06, 2004 3:40 pm

That sounds like my S2 Elan, had a real bad miss on acceleration. Turned out to be broken & weak valve springs. Do a compression and vacuum test to be sure.
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PostPost by: steveww » Tue Jul 06, 2004 4:13 pm

Worn needles and or jets perhaps? Check that the distributor is functioning correctly - no scatter, advance through the rev range.

There is no magic fix, just work systematically through all the systems making sure thay function as they should.
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PostPost by: rickf » Tue Jul 06, 2004 4:59 pm

There's no miss. It feels almost like the throttle starts working backwards. The more throttle, the less power. It really kicks it hard when you let up. The static timing's right on, but I'll try a light on it to see if the advance is working.
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PostPost by: rickf » Tue Jul 06, 2004 5:07 pm

Speaking of ignition timing, I'd put a new Mallory distributor on a TD I had and it felt like I'd added a turbo, compared with the fifty year old Lucas unit. They're too tall with the upright cap to fit the Lotus, . Anybody make a good distributor that'll fit under the manifold with Strombergs?
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PostPost by: elansprint71 » Tue Jul 06, 2004 6:32 pm

Have you checked that the rubber diaphragm(s) in the carbs are not split?

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PostPost by: rickf » Tue Jul 06, 2004 6:49 pm

Yes, I put in new diaphragms when I cleaned the carbs. Made no difference. Didn',t mess with the needles or jets. Just cleaned everything up.
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PostPost by: simon.mitchell » Tue Jul 06, 2004 8:39 pm

Had similar symptoms on a Sunbeam Alpine once - turned out to be swarf from the tank partially blocking the fuel line and restricting flow.

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PostPost by: mickrick » Wed Jul 07, 2004 6:58 pm

Had a similar problem with my Sprint ages ago. Turned out to be dead simple. The car had just been serviced and the "mechanic" hadn't fastened the inside distributor cap clip (the difficult to reach one) properly. When accelerating the engine pulled the bodyaway from the cap - no spark, no power. When easing off the two met up again and power was restored - until the next time power was applied. Sounds so simple, but had me foxed for a while.

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PostPost by: niallf » Sun Jul 11, 2004 9:03 am

Another silly one that I have done that caused similar symptoms was to put a throttle return spring on the wrong side of a Choke cable.

When pressing the throttle, the return spring was being pulled onto the choke cable and pulling the choke on when the throttle was opened. This was on a Webered plus 2, so may not be relevant, gave me the same symptoms you're describing though.

Good luck,

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PostPost by: Rob_LaMoreaux » Mon Jul 12, 2004 1:35 am

Larry Martin on the yahoo Lotus Europa list had a similar problem last month. His twincam had nothing over 5000RPM. He put on a new cheap muffler and suddenly he had power over 5000 RPM.

Sounds to me like you are going too lean since it takes off when you back off on the throttle, so one possibility is that the piston is hitting the stop too soon and leaning out the mixture. does it have the correct spings in the pistons?
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PostPost by: rickf » Mon Jul 12, 2004 2:00 pm

The springs are natural color. Would worn needles would make it run rich? I don't know how old they are.
Cheers,<br>Rick<br>1972 Elan +2
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PostPost by: rickf » Wed Jul 28, 2004 3:40 pm

It's fixed! I was driving along yesterday and I noticed some smoke coming out from under the dash. Having owned Sunbeams, Triumphs, MGs, Jags, etc. , I wasn't alamed, but rather curious. It was coming from a black connector in the "rat's nest" of wires behind the wiper switch. The connector was really hot and a big white wire leading to it was frayed. Crimped on a new connector and the "flat spot" is gone. The bad connection must have caused a voltage loss to the ignition.

Oh, and a bonus, too! The windows go up twice as fast . No need to race the engine or push up on the glass. Just like other people! :D
Cheers,<br>Rick<br>1972 Elan +2
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