Fast Idle problem with DS 21 ie and modern ECU replacement
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Thread: Fast Idle problem with DS 21 ie and modern ECU replacement

  1. #1
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    Default Fast Idle problem with DS 21 ie and modern ECU replacement

    Hello,
    This is my first post/message so forgive me if I get things wrong.
    I own a D Special which had an a DS21 i.e. engine and 5 speed gearbox upgrade (?) some 20 years ago. I have owned car 2 years
    I recently changed a fuel injector (it was leaking) to a slightly experimental type.
    When I restarted car, the idle speed was a rather furious 3000 rpm.
    I have checked the obvious things like

    • disconnect throttle cable
    • disconnected new injector (and all the others also)
    • disconnect cold start system
    • checked for air leaks
    • checked sensors etc but to no avail


    Any one got any thoughts on what might be the problem

    I was also thinking of upgrading system to a Microsquirt ECU etc.
    Anyone hear if this has been done?


    Regards
    Blueduck

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  2. #2
    Tadpole
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    Hi Blueduck,

    Have a close look at the Auxiliary Air Valve and the hoses around it. This device operates outside of the rest of the system and when not working properly it is very difficult to get the D-jet system to work. You'll find it on the side of the engine under the injectors and inlet manifold. It's job is to increase the idle speed when the engine is cold by allowing more air into the system.

    On the inlet manifold there are two rubber hoses for the crankcase breather system that connect to a plastic 3way junction near the bulkhead, its also worth checking these for cracks.

    There have been a few VW and volvo guys who have made the conversion, see the link below for one of them.
    TheSamba.com :: Type 3 - View topic - BOSCH D-Jetronic Megasquirt Adapter

    Beware that the injectors on the early D-jet systems are low impedance and run off 3V not 12V
    Michael

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    Michael,
    Thank you for that information.
    The Air Control Valve (now a Nissan item and located on top of the valve cover) and the cold start system all were working as they should before I changed the injector. Its a bit hard to check now because the air tempertaure is high and thus the system does not come into play
    However, I have, as part of the checking, disconnected the Auxiliary Air Control Valve hose at the said Valve and blocked it off. And if I the open the hose, letting air into the manifold, the engine runs even faster .... suggesting too much fuel (rich).
    I have also vacuum checked the 2 (new) hoses going to the Vacuum Switch and the Vacuum Sensor and there are no leaks there
    In my own mind I have eliminated everything except the ECU but I nervous even disconnecting that item to check further.

    I looked at the VW site and the Megasquirt does seem to do the job. Its a fair amount of work but you end up with a system which enables you, if you want, to use modern ... and much cheaper components (to reiair the Vacuum sensor is about A$600 and an ECU might cost $800 if you can find one which I cannot.
    You can also use an O2 sensor to operate the injectors and if you really keen, delete the distributor and the trigger points etc and have individual coils for each spark plug
    Regards
    Ian Downie

  4. #4
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    The hardest part about disconnecting the ECU is undoing the screw on the cable clamp, its very difficult to damage the unit itself. That said, removing it won't necessarily tell you anything. They were never designed to be repaired and bosch never published any data about the internals.

    What you can do with the unit out is use a multimeter and check the various sensors and all the wiring in the loom. I'll try and hunt up a link to the citroen manual specifically for this engine. There's also a VW troubleshooting manual for the d-jet system

    As it happens, my ds21 is in pieces and the ECU is sitting on a shelf. You are welcome to try swapping it in to see if it makes a difference.

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    ian. Are you sure the 12v vs 3v injector is not your issue?

  6. #6
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    I would have thought running an injector designed for 12v on 3v would just cause a misfire and rough running. The injectors in the ds are non polarised, being grounded by the ecu as opposed to I think k-jet where they are permanently grounded to the engine block.

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    It could be one or more of the injectors but I have disconnected the 2 pole plug from each of them in turn and the engine revs drop in each case (from around 3000 to 2400 rpm),
    But I think that all the injectors are over feeding fuel and that's why I am looking at the ECU now
    By the way, why am I a "tadpole"
    And, Faulsky, I will take up your offer of a swap if I can get the ECU disconnected tomorrow
    Please let me thank you for all you suggestions
    Ian Downie (blueduck)

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    Hi Bluey.If your engine is running too fast its getting excess air in somewhere.No amountof excess fuel will make it race without the air to go with it.BTW I have a facility for testing EFI computers.
    Woody

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    Quote Originally Posted by blueduck View Post
    Michael,
    Thank you for that information.
    I looked at the VW site and the Megasquirt does seem to do the job. Its a fair amount of work but you end up with a system which enables you, if you want, to use modern ... and much cheaper components (to reiair the Vacuum sensor is about A$600 and an ECU might cost $800 if you can find one which I cannot.
    You can also use an O2 sensor to operate the injectors and if you really keen, delete the distributor and the trigger points etc and have individual coils for each spark plug
    Regards
    Ian Downie
    I haven't done it on a DS, but I did megasquirt an SM IE. I used a BMW TPS, a Mercedes ATS (turns out to be the same as the original SM sensor), a BMW CTS; wide band O2 sensors and a Volvo IAC. I use the MS for fuel only triggered from the low side of the ignition coil (with Pertronix). Works like a champ except for a slight hunting at idle since I used the closed loop idle option. Would do it again in a New York minute since the reliability is so much improved with modern, over the counter sensors.

    http://tinyurl.com/hd233kd
    Cheers,
    John T.

    61DS19 LHM BVH; 71DS21 BVH; 73SM 3.0; 73SM EFI; 73SM 3.0 (son's)

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    Hello citreonenthusiast,
    Your understanding is in front of mine by some way.
    But harking back to original problem, I had a partial breakthru today. A fuel injection specialist tested leaks in system and says I have a bad leak from one of the inlet manifolds.
    I will try and fix tomorrow. And will let you all know what happened.
    He also suggested that I do not replace my current system with anything Why? Because everything on the d tronic ... including ECU can be fixed in Melbourne.
    But I still am interested in upgrading
    Regards
    ian
    Iann

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    Hello all,
    Things have moved on, An efi specialist, Jeremy, took one look at the car running and said "you have an air leak". He traced it down quickly by spraying carb cleaner near the inlet manifold ... you could here the engine start to die immediately. And he said that it is the number 3 inlet at least.
    So I took that inlet manifold off and, yep, the gasket was broken. I replaced these gaskets (they are composite gaskets that came with head gasket kit) about 3 months ago when I changed the head gasket. But I was never happy with them as they were obviously meant for a carburettor car and they were not a good fit. I will now replace them all .. anyone know a ready source of gaskets. Any one have any experience with "card board" inlet gaskets
    Regards
    Ian
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun

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    Brian,
    Thanks for that. If I get stuck I will know where to go
    Regards
    Ian Downie
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun

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    There is one gasket under each tube. You could try gasket paper and cut them to suit the inlet tubes. I have some spare loose gaskets that are probably the correct items as they line up to a spare tube I have. About 70mm between bolt holes with one end elongated and ID is 46mm. Possibly DS or maybe CX leftovers, but they are a composite sandwich, not paper. If you think they will do the job for you, send me a pm and I'll post them to you.

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    Hello all,
    Well I have replaced the inlet gasket that was disturbed when I replaced the leaking injector on cylinder number 3 (with a Standard FJ 118 injector ... US$50 and brand new ... which is supposed to be a replacement for the Bosch 280 150 036 injector).
    Now the engine starts properly and idles (just) when cold. When hot it will not idle unless I prop open the throttle valve by 3 mm or so at which point it runs very roughly. It does not much like revving either. There is plenty of "suck" on the throttle body inlet.
    Finally it also runs very tappety ... on one as yet unknown cylinder especially so
    If I remove spark plugs leads one at a time, the engine dies most on cylinder 3 suggesting the Standard injector is working well. I have had trouble with all the old Bosch injectors so I am tempted to replace all these Bosch injectors with the new Standard injector
    Does any one have any pearls of wisdom here?
    Should I do the tappets again?
    Should I replace the injectors?
    Regards
    Ian
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun

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    Standard FJ118 is correct, I verified with the factory that it is specified as having a 36.15 lb/hr flow rate. It sounds as if your auxiliary air valve is working. Did you try fiddling with the air bypass screw? Maybe if you open it a bit it will idle better after the aux air valve closes.

    You might also try adjusting the valve lash. That would make the tappety sound and also could affect the idle
    Cheers,
    John T.

    61DS19 LHM BVH; 71DS21 BVH; 73SM 3.0; 73SM EFI; 73SM 3.0 (son's)

  16. #16
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    The 036 injector is an ideal replacement for the original injectors and works perfectly on a DS without any other changes to the EFI. However, it is designed for a push fit hose with a ferule and not a hose clamp and the diameters of the fuel rail and 036 injector barb are a bit of a mismatch. Think carefully about your choice of hose and how you will fit it so it will not leak down the track. The Standard injector is supposedly a direct replacement, so should in theory do the same job, but you have no idea whether the actual flow rate matches the others injectors. I should be close enough to get the car to run OK, but ultimately, you want a set of flow-matched injectors of the same type.

    Is the AAV working or stuck?

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    To David and John,
    Thanks for quick reply.
    Yes, I will do the tappets again.

    The Auxiliary air valve was working a week ago. I will check again

    Now you both have confirmed that the Standard Injector is a direct swap, I will buy 3 more. John, you live in the states. I bought the first Standard Fuel Injector from Rock Auto at US$40 each. Now they are up to US$60 plus each. The best I can do elsewhere is about US$55. Do you know a good place stateside for buying injectors?

    Regards
    and thanks Ian
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun

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    Try eBay www.ebay.com.au/161830780249
    or Amazon https://www.amazon.com/Standard-Moto...Standard+FJ118

    Obviously add freight. The eBay listing wants about US$30 to post 3 of them to Australia.

  19. #19
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    What condition is the ignition circuit in? it is pointless trying to diagnose problems with the EFI if it isn't 100%, you end up chaising your tail through the wiring looms. Rough running and hesitating can be caused by a failed or failing condenser, they area inexpensive so worth replacing anyway. if the car was idling and running alright before changing the injector I would be having a look at and cleaning all the connectors in the EFI loom. Things like the idle mixture screw don't suddenly go out of adjustment. Its worth checking the temperature sensors against manual 586/5 DS21 Technical data handbook.

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    Michael,
    Of course you are correct.

    I had done most of what you are suggesting except the coolant temperature sensor and more thoroughly checking the various looms

    I will also change points and condenser

    But I am keen to get/install 3 new injectors so that I have a complete "set"

    Regards

    ian
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun

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    Hello all,
    Since last post I have
    1. Installed new points
    2. Installed new condenser
    3. Installed new spark plug cables (except the high tension cable to coil)
    4. Replaced trigger points (that's fiddly) with some almost-new, second-hand ones that I had
    5. Re-adjusted tappets and checked 3 times using the method in manual

    Now the engine starts easily and idles as it should except!!! ....
    1. One tappet is very noisy ...should I use the method of "9"?
    2. I am sure that it is only idling on 3 cylinders (removing spark lead on cylinder 4 seems to make no difference to idle speed. Removing each of the others produces a varying fall in idle speed
    3. Car idles for many minutes but then black smoke and petrol smell from exhaust and engine dies. There is also a dribble of petrol exiting the the throttle body ... I thought perhaps the cold-start injector had started to leak so I removed it. Problem seems to have gone away but I have yet to check cold start injector
    4. Car will not rev properly and sounds like only 3 cylinders operating
    5. And just to add to my frustration the throttle cable has jumped off the idler wheel. Access to this area of car makes it difficult to refit

    Any thoughts on what to do next?

    Regards
    Ian Downie
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun

  22. #22
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    Check that idler wheel carefully,they,re plastic and tend to disintegrate,I made a brass one for mine!
    Woody

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    Compression test. Tapping sound may be a seized valve in #4
    Cheers,
    John T.

    61DS19 LHM BVH; 71DS21 BVH; 73SM 3.0; 73SM EFI; 73SM 3.0 (son's)

  24. #24
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    Sounds like the cold start has started leaking or one of the components that control it have gone. It is controlled by the thermotime switch, which is screwed into the side of the block under the inlet manifold and the third relay on the battery cage depending upon which revision of the system you have. The injector should operate when the starter is engaged and IIRC should only ever operate for 8 seconds once the engine is running.

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    Hello,
    Thank you for your feedback.
    In the last week I have
    1. Re-fitted throttle cable. My car has a brass idler wheel which spins freely. All the components looked in perfect condition except ccable itself. . I think the cable fell out of its correct path because the adjustment under the plenum chamber was loose (now corrected) and the throttle body was not returning to its rest position reliably. I will need a new throttle cable at some time. I have also added an extra spring (soft) to the throttle body to make sure that the butterfly returns properly.
    2. Sorted out the rest position on the throttle body and the idle adjuster. It seems that they operate like the same components on a carburettor

    Done nothing else with noisy tappet. Hope it is not a sticky valve as the head was reconditioned last year. Could it be a bent pushrod?
    Am waiting for offset feeler gauges to arrive ... also putting off finding out whether I have a serious problem or not. Will do compression test at the time ... thanks for the idea

    Have not finished with Auxiliary air valve/Cold start injector. Some one replaced the original Citroen AAV with a Nissan item which operates on an electric current and bi-metallic valve. It works and is simple and is located on top of plenum chamber. It leaks a tiny amount of air fully closed (which takes about 5 minutes). In principle the Citroen system is better, I know but....
    I need to run the car with the cold start disconnected from plenum chamber but still connected to fuel pipe to see if it does indeed leak
    Thank you all again
    Ian
    Blueduck (aka Ian Downie)
    1974 Citroen D Special with DS21i.e. engine and 5 speed gearbox
    MGB GT V8 B.... bullet--proof and great fun

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