Auto Choke Stalls Car when it Auto Returns

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tomsmy
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Auto Choke Stalls Car when it Auto Returns

Post by tomsmy » Wed Jun 08, 2016 6:35 pm

Hello All,

So I just bought my first FB RX7 (1983 GS). I am a very proud owner as she is in excellent condition after being lovingly cared for by one older owner for the past 33 years!

So my car runs great (has a brand new Mazda 12A crate engine that as <1000kms on it!). The issue I am having is during a cold start. I have searched extensively but have not been able to find an answer to my problem. If I have overlooked a thread please accept my apologies.

So what happens is as follows:

I pull out the choke and she turns over and idles no problem. I adjust the choke to about 2000rpm and let the car warm up. The problem is that when the car reaches a certain temperature the electro magnet turns off and the choke returns – stalling the car. So I have been using a peg to hold the choke out for another few minutes to get the engine a little warmer and then I manually feather the choke back in and it holds idle at 750 rpm.

So my question is – can I adjust the temp at which the choke auto retracts? Or is this a sign of a deeper issue?

Not sure if this is related but I have noticed that at an intersection sometimes I have to blip the throttle prior to pulling away as the power seems to go a little dead (more than you would expect from normal clutch/throttle balancing).

On another note – how easy is it to reach redline in these cars? The reason I ask is because she reaches 5500 -6000rpm just fine but then feels sluggish to reach 7000. Is this normal? The only car I have to compare to was my old 450 bhp turbo FD…..but most things feel slow compared to that!

Thanks in advance for your help.

Tom

codge
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Re: Auto Choke Stalls Car when it Auto Returns

Post by codge » Wed Jun 08, 2016 6:54 pm

Hi Tom. Sounds very much like a carburettor setting or a clogged fuel filter issue to me.

For example, I never use the choke magnet to time out the choke.....I bang the choke in as soon as I've reached the main road from my street. 'Gus' will then pull happily without choke but of course I have to catch him again on the choke knob at the next few road junctions or he will stall.
Yours seems to be still stalling even after a bit of running.
So if my car will do it (at sort of 10C to 20C ambient temps) then yours should?

Fuel filter clogging will show up under heavy load conditions.....ie difficulty getting up to high speed in 5th gear on a motorway / clearway. The car will just start to slow up as the fuel supply gets strangled.
Filter is an easy routine job.....you just get an armful of petrol doing it!

tomsmy
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Re: Auto Choke Stalls Car when it Auto Returns

Post by tomsmy » Wed Jun 08, 2016 7:07 pm

Thanks for such a fast reply!

So i did do a load of routine maintenance (oil, oil filter, fuel filter, gearbox oil, rear diff oil, seafoam in tank to clean).

At the same time i also upgraded the exhaust to the full Racing Beat street system. I have noticed more power & quicker acceleration from 5000 to 7000 rpm. it just feels a little slow (but then i'm used to the turbo kicking in)

i still need to do the spark plugs and leads (this weekends job) so that may help?

Thanks again, Tom

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ian65
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Re: Auto Choke Stalls Car when it Auto Returns

Post by ian65 » Wed Jun 08, 2016 7:20 pm

sounds like fuel mixture to me and it's running lean. If it was a clogged filter it would struggle for fuel when running on choke but you say it seems to run ok on choke..... once the choke goes in, the engine leans out and cuts out.... by putting a peg on the choke to hold it on you're just making the mixture more rich.
Adjust the mixture screw on your carb.
You should be able to rev it through the red line no problem..... in fact, you should be able to rev it until the rev warning buzzer goes off.
1986 Series 3 13B Turbo II
http://rx7fb.com/viewtopic.php?f=2&t=2400
1992 Peugeot 205 1.9 GTI
1975 Honda SL125 Street Scrambler

tomsmy
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Re: Auto Choke Stalls Car when it Auto Returns

Post by tomsmy » Wed Jun 08, 2016 7:28 pm

Hello!

So just to clarify myself - before driving away, i do feather the choke all the way in and remove the peg, she then runs and idles without stalling.

Does the fuel mixture change when the engine temp gets hotter? I just find it confusing that doesn't stall if i let it run a few minutes longer than the auto choke normally would let it....

I'll have a play with the idle mixture tonight and see what happens!

Thanks

DB RX63
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Re: Auto Choke Stalls Car when it Auto Returns

Post by DB RX63 » Wed Jun 08, 2016 7:35 pm

Don't ignore electrics, I had a similar problem and new plugs, leads and distributor cap cured the problem completely. Prior to that I did all the obvious fuel system things including carb rebuild to no avail. Sometimes what seems like fuel issues isn't always the case.
Met Blue Series 2 Elford Turbo
S3 Rally Car (under Construction - Nearly Finished !)

tomsmy
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Re: Auto Choke Stalls Car when it Auto Returns

Post by tomsmy » Wed Jun 08, 2016 7:44 pm

Thanks for your input!

I have new spark plugs and leads at home yet to be installed. So i will get those in ASAP.

Are the distributor caps something to be replaced on a semi regular basis? I can get new ones here fairly easily.

Urgh, so much to learn! I guess that's what happens when your car is older than you are!

codge
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Re: Auto Choke Stalls Car when it Auto Returns

Post by codge » Wed Jun 08, 2016 9:18 pm

Only if the Distributor Cap has eroded interior 'contacts' or there's an obvious fault like a crack.

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DKWW2000
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Re: Auto Choke Stalls Car when it Auto Returns

Post by DKWW2000 » Wed Jun 08, 2016 9:37 pm

Hi Tom,
I found a old post from CODGE (Dave) on how to set Mixture/Idle, I had similar problem but making a very small adjustment as per following resolved all the issues :D

"Carb setting......all from memory. Need to recheck in Haynes manual.
Get it Running and engine hot.
Set speed around 1000 with idle speed screw.
Screw in mixture screw gradually until it just starts hunting (speeds up /then down /then up /then down......bit like a slow horse canter).
Back off mixture screw very gently until running is as smooth as you can get.
Reset idle speed screw to a nice tick over...900 rpm or thereabouts"
RX7 FB S3 - RX7 FC TII Vert
Rotaries Previously Owned:-
2 x NSU Ro 80s - 2 x S2 RX7s - Suzuki RE 5 - DKW(Hercules) W2000 - Norton (Krauser) Commander

codge
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Re: Auto Choke Stalls Car when it Auto Returns

Post by codge » Wed Jun 08, 2016 11:17 pm

Yes, agreed, that's the routine for carb setting.

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