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Geeman

Carbs setup (again) - '84 Turbo, US Spec

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My '84 Turbo (US spec) has the apparent usual symptoms of stumbling on light acceleration, but fine on full throttle.  I've searched and read the forum(s) etc. bought the Hammill book and the 4 tube manometer.  I've rebuilt and set up twin and triple SU carbs on other cars, no problem. 

 

This past  weekend I thought I would at least try and balance the carbs.  Not much luck, they are all over the place and I couldn't get them very close.  The car does however, seem just a bit better.

 

I want to check the floats and make sure the jets are clean/clear and I am thinking I should just reset the carbs and start from scratch, balance and mixture.

 

I bought the car from California where emissions are a pain for older cars and maybe it was set up just to pass the emissions and not optiminally.  It still has the emissions equipment like air/smog pump on it etc.  I know to the UK owners this is unknown territory :-)  Its definitely been tinkered with in the past as the tamperproof caps are gone and the tops of the brass bypass (?) screws are a bit gnarly.

 

So, armed with the tools and a modicum of mechanical intelligence, what could possibly go wrong?  How long would you estimate to get a basic set up tuned?  There is a local rolling road/dyno place that I can take it to for fine tuning later.  There are no emission requirements in my state.

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Upgrade today to remove Google ads and support TLF.

If there are no emission requirements, I would look toward scrapping all the anti-emission gear. Extra weight for little return. :)


All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

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Stumbling on acceleration can be caused by accelerator pumps not working, blocked jet or the lever seized which is on the bottom of each carb.

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Thank you for your responses.

Today I spent some time starting from scratch and retuning the carbs.  I did not check the floats yet, seems like a few bits and bobs to take off to get the covers off.

I checked the idle mixture needles and bypass screws.  All clean and in good shape.

I followed through the instructions I had and have got a marked improvement.  The biggest culpret to getting them balanced was the connector shaft and linkage between the carbs.  Front carb and rear carb were way out from each other with the manometer hooked up.  With that connector adjusted it was a simple case of adjusting the idle bypass screws a few turns to get all 4 barrels balanced.

Initially I backed the idle mixture screws out 3-1/2 turns, but I am not noticing much idle difference with a +/- 1/2 turn on each one.  So, how do you know you have the idle mixture at the best setting for each barrel?  I have a local rolling road/dyno I can take it to.  I am guessing they can only stick a gas analyser up the exhaust, that won't tell you which carb barrel maybe 1/2 a turn too lean or rich will it?

 

Thanks again

Gordon

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Hi Gordon. I have used colourtune plugs to set the idle mixture in the past. It helps if you have four - easier to compare the color between cylinders. I have also found float height to be a critical adjustment that takes some trial and error to achieve smooth running. Good luck this tuning process can take some time but you will get there in the end. John.

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Gordon, use a Colortune to set the idle mixture & you may need to re balance the air flows once their all correctly set. :thumbup:


Cheers,

John W

http://jonwatkins.co.uk

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Another update.  I will order a Colourtune.  I had another go at tuning the carbs and got it running better again.  The idle is a lot smoother and the stumbling is only slight now.  My driving style may not help as I am used to larger engines with more torque, so I pull off roundabouts and corners in third rather than maybe second gear.  When I press the gas the Esprit stumbles a bit.

I'm up to about 4-1/2 turns out with the idle mixture screws.

 

I noticed the boost gauge max's out at about 7psi but it spools up there quickly.  Is this reading OK?  The performance doesn't exactly shove you into the back of your seat, but you definitely feel the turbo cut in and I think the car is quicker than it feels.

 

Its not popping and banging and backfiring like it did when I got it, so I must be going in the right direction!

 

Thanks for the input thus far.

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7 PSI is fine and shows the wastegate is opening properly. Its when it goes over that its time to worry as it could be melted pistons time.

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I drove my Esprit to work today, its about a 10 mile drive.  Towards the end I pulled away from some lights, got into second and gave it a firm squeeze just because.  The turbo spooled up the car picked up then, suddenly it lost power and there was a huge backfire bang/pop, then it was OK again.  I am guessing this is a fuel starvation issue?  As above, I have got it running a lot better, but this caught me by surprise and it was rather embarrassing!

I have tried to avoid removing and rebuilding the carbs, but I think I will have to soon.

Is this sort of backfire/pop/bang not uncommon?  Anything to look for to remedy it?

Thanks again

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Could one of the jets been partially blocked and then cleared itself.

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Could be the fuel pressure regulator is not working properly or fuel pump, so insufficient fuel pressure when the carbs were pressured by the turbo.

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Backfiring is caused by unburnt fuel in the exhaust which is often due to ignition problems.  Might be worth checking that you have a strong and reliable spark. I had a backfiring issue caused by the wiring in the distributor having an intermittent connection.

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On north american models there is a valve just above the rubber pipe connecting the turbo to the manifold. Mine is an 83 so it is probably the same. This valve has been giving me trouble and has caused my car to loose power at just over 4000 rpm when at full throttle. This valve is not in European cars and I was told to remove it on this forum. Yesterday I adjusted it to be open all the time and now the car has full power and will pull 6500 easily; however, I now have the same problem as you with the inability to pull away from lights without revving high and slipping the clutch. This was not an issue before. I believe that fully opening this valve has entered a much leaner low RPM state. I had the valve explained to me yesterday at a car show as required to lower the rpm quickly when letting off the throttle. I noticed that this is the case. If I rev it up it settles down to an idle very slowly. You may want to check this valve and see if it is sticky.I have attached a picture for your reference.

 

Hope this helps.

post-19151-0-49501700-1435514380.jpg

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Thanks again for the feedback.  Paul, my car appears to be the same setup as yours.  I haven't had time to go in and check things again yet, but sometimes when I switch the engine off, there is a delay of maybe a couple of seconds then a loud bang.  As Brian pointed out this is probably unburnt fuel igniting in the exhaust.

I let the car idle for a minute or two before switching off too.  On one hand its embarrassing, but seeing as I'm in gun totting America, I don't want it to happen around a police officer!

I am still getting familiar with the car and need to give it a thorough service and check over re ignition, timing, and carbs.

 

So little time these days!

 

And oh the joys of US emissions equipped British cars!  They are like chalk and cheese compared to the home market cars sometimes.

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I have a little update on my situation as it seems to be very much like yours. Right after I replied to your post I decided to try and adjust this valve as the car was not running well with it held open. I took the following steps:

1. watched to ensure the vacuum actuator operated when the car was started. It did

2. with the car shut off I loosened the adjustment screw and manually closed the valve and at the same time fully retracted the vacuum actuator. Note: I tried this because I could not find any documentation in my service manual on how to adjust this valve. There is no reference to this valve at all.

3. Went for a test drive.

 

Results:

Car has proper acceleration when applying slight throttle application.

Car will take off from a stand still with very little rpm applied

Car will respond to full throttle quickly and pull 6500rpm plus with no issue at running temperatures over 90C as our temperature was 33C(90F) on Sunday and the car was running a little hot after many red light stops.

 

The world is back to normal which includes the bang of the un-burned gasses in the exhaust a couple seconds after shut off. This has been a characteristic of the car since I have owned it. 

 

My experiences with this issue started when I notice a deformation in the cam on this valve actuator. This deformation was causing the valve to stick partially closed. This caused a lack of power over 4000 rpm when the car was at running temperature, over 90C.

 

You may want to refer to my post (in this section) called "1983 Turbo diffuser Assembly shut off Valve issue". In that post you will see illustrations of the valve and the breakdown of the parts and the close up picture of the worn cam on mine. 

 

Let me know if you need any more info on this and I am interested to know if your issues turn out to be the same.

 

Paul

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Paul, thank you for this information.  My car has no problem revving when hot as yours has.  Did you have someone start the car so you could watch the actuator or can you do this by yourself?  I have read your other post too.

 

When I start my car from cold (not using the choke) it will idle at about 1100-1200 rpm then once its gets warm the idle will suddenly drop to about 950rpm.  I am not sure its supposed to do that seeing as the choke is manual.  When I pull the choke, it does work, but when push the choke knob in the cable flexes and the linkage won't close.  You have to push the choke lever at the carbs back manually.  I checked the mechanism for stiffness and seems OK.  Maybe it need a new choke cable due to age.

 

I will try and find time to look into this over the up coming long weekend here in the US.  We are 'enjoying' 30+ deg C heat with high humidity at this time of year.  It makes the simplest of tasks on a car very hot and sweaty.

 

Once again, thanks all for your input.

 

I will report back.......

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No one was here so I moved the actuator freely when engine shut off. Had only the resistance of the diaphragm. When I started the engine it fully retracted which closed the valve. This is why I believe removing this valve from the system as recommended by others, would affect the air fuel mixture when throttle is either closed or minimally open. The air fuel mixture will be calibrated to this valve being closed. Putting the valve back in to the system fixed all my issues. Maybe I just lucked out with the adjustment but I like to think I thought it out enough to get the adjustment correct.

As for the choke, yours may be slightly different to mine. I have not had to close the choke fully. I give a couple of pumps to the throttle and I pull the chock very slightly so that it initiates a high idle and turns on the choke/low fuel light on the dash. After a couple of minutes I push in the choke, the light goes off and the idle lowers to approx 950. The idle is not very consistent. It will sometimes drop if I am sitting at a light for a long time. If I rev it up a bit it cleans up and idles smooth again. May need some small balancing adjustment. 

The backfire after shutting off the car can be a little embarrassing at times depending where I am. Sometimes it doesn't happen but I have not really figured out a pattern as to when it does or does not happen.

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I have an 83 and can tell you from experience is to install a AFR gauge. Innovate is the one I use and its invaluable in seeing what exactly is going on while driving.

The backfire when you shut the car off is either; 1. leak at the exhaust manifold at the cylinder head. 2. To lean on idle mixture.  The number 4 exhaust nuts will loosen up so check them . I have ARP stainless studs/nuts installed and I have to check them periodically. The light throttle (off idle) stumble I found to be the accel pump jets dumping too much fuel. I eventually went to the smallest which I think are a 33. 

On warmup (when using the choke) the ignition advance will go to full advance to help idle. Once the car reaches operating temperature it shuts off the advance (even if you don't move the choke pull). 

Try setting your initial ignition timing to 12 degree BTDC and turn the idle screws out to the highest steady throttle (its about 4-5 turns off bottom) . Adjust the idle sped to about 950RPM. 

Another thing to try is If your car still has the 52 idle jets try bumping up to the 56. Leave the rest of the jets alone.

If you get super adventurous…….  Install new floats, float needles and set the fuel level to 27mm.  (google it) 

 

Best,

Jeff

 

 


www.espritturbo.com

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Jeff thanks for this.  I looked at the Innovate website.  Do you need to fit an O2 sensor to the car, or do the carb Turbos already have one of this vintage?

I'm still getting the bang after shut off, but only if I have been driving the car a bit harder before hand.  If I leave it to idle a bit before shutting down, its usually OK.

I just haven't had the time to go through it again.

Is it easy to access the idle jets without dismantling the carbs? 

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I have an 83 and can tell you from experience is to install a AFR gauge. Innovate is the one I use and its invaluable in seeing what exactly is going on while driving.

The backfire when you shut the car off is either; 1. leak at the exhaust manifold at the cylinder head. 2. To lean on idle mixture.  The number 4 exhaust nuts will loosen up so check them . I have ARP stainless studs/nuts installed and I have to check them periodically. The light throttle (off idle) stumble I found to be the accel pump jets dumping too much fuel. I eventually went to the smallest which I think are a 33. 

On warmup (when using the choke) the ignition advance will go to full advance to help idle. Once the car reaches operating temperature it shuts off the advance (even if you don't move the choke pull). 

Try setting your initial ignition timing to 12 degree BTDC and turn the idle screws out to the highest steady throttle (its about 4-5 turns off bottom) . Adjust the idle sped to about 950RPM. 

Another thing to try is If your car still has the 52 idle jets try bumping up to the 56. Leave the rest of the jets alone.

If you get super adventurous…….  Install new floats, float needles and set the fuel level to 27mm.  (google it) 

 

Best,

Jeff

 

 

An AFR gauge is really only useful for setting up running jetting. Its no use at all for idle or acceleration as it simply reads off the scale at these times. O2 sensors have a very narrow band over which they give a meaningful reading.

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