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Thread: 1988 RR Classic not running on petrol.

  1. #1
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    1988 RR Classic not running on petrol.

    I have recently purchased a 1988 RRC with the flapper type ECU, car has both petrol and LPG.

    On LPG the car runs very well, on petrol it doesn’t. At idle it doesn’t sound too bad on petrol although there is a lot of popping noises from the exhaust. When the throttle is pressed while parked it stutters as the revs build up. When driven on petrol it also has this misfire, has no power and doesn’t want to rev.

    While idling I went around in turn and pulled off each lead from the spark plug to see if I could hear the engine note change. When cylinder 1 or 2 were pulled there was no change to the engine note. Checked these two cylinders for spark and there was plenty. I have checked that those 2 injectors are receiving a signal from the ECU and they are.
    I also checked the fuel pressure which came to around 2.5 bar. Cleaned all the earth points and have tried the distributor from 0 degrees to 16 degrees advanced. Also tested the ECU, engine temperature sensor, throttle position sensor, vacuum advance module, air flow meter and rebuilt all the injectors with new parts and tested them for both operation and flow pattern, all these came up ok. I have measured the %CO from the exhaust and it is currently on 1.5%.

    It has spark and fuel but when I remove leads 1 or 2 it makes no difference to the running of the engine on petrol, I know I have spark and petrol getting to the cylinders. On LPG if you remove either one of these leads there is a change.

    Does the distributor in this model require mechanical advance in the distributor or does the ECU take care of the ignition timing, I have no mechanical advance in my distributor? What part of the ECU system is used when running on LPG, how do they wire up the LPG system?

    Considering how well it runs on gas is there something simple I am not doing correctly to get it to run on petrol.

  2. #2
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    To me in my experience with these damn things, it sounds like it may be over fuelling.

    How did you test the ECU? This would be the second different thing in the whole system when swapping between the two fuels. They develop dry solder joints on the injector firing circuit, causing resistance and then slowly over time it just ends up opening the injectors wider and wider to the point you don't even need a fuel pump. If you have it apart, I'd check for these, get the ECU warm and visually check as well as with a multimeter.

    Another silly culprit of issues seems to be the ECU earth point at the back of the LH head. There are two, one bunch from the ECU and another that grounds from there to the chassis.

    Have you checked timing with vac advance connected and watched the timing move as you give it a rev? This could help point in the right direction.

    For some reason I remember the CO% only supposed to be 0.5 or 1, it can be adjusted at the flapper under a red plug.

    Have you adjusted the throttle sensor to within spec? And have you watched it over the range for dead spots?

    I had an issue very similar to this over the course of 2018 with my 89, that in the end, after all the hair tearing, crying, yelling and parts cannon firing, ended up being the ECU. Two in fact! The original developed the issue over time and then the one that someone on here gave me ended up going that way while I was still testing things, but gave another set of similar problems.

    I would also not be concentrating on the mechanical side, or any system that is common to both fuels. It clearly works on gas and properly. My bet would be the electronic side for the fuel system.
    '15 Discovery 4 HSE- The family bus and the kids like it!
    '89 RRC- My favorite of the bunch!
    Ex '03 Commodore 'S' ute- 450hp of uncracked 5.7lt and 6 speed manual uteness - Still crying that its gone
    Ex '06 GLXR Triton- *Gone and forgotten*

  3. #3
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    I found a couple of websites with the ECU testing procedure, after following the steps in those the ECU checked out ok. It was mainly resistances between pins and tracking the pins on the ECU plug back to the sensors.
    The throttle position sensor was set up and works correctly across it's range.
    The timing mark moves with engine revs but as it doesn't have any mechanical advance in it I don't understand how this movement is initiated. The vacuum advance is working also.

  4. #4
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    Hi Richard.. under the files section on Aulro is the complete diagnostic testing and description for the flapper system.
    Download it...
    Re the mechanical advance.. it’s the weights in the distributor the do it, maybe yours are seized?
    If You remove the dizzy cap and grab the rotor and twist it does it move and then spring back?..it should.
    if you can see with a timing light the slot move on the harmonic balancer then the weights are moving, but by how much?.
    you could also have a leaky vac diaphragm with sits at the back of the plenum and cut off the fuel on deceleration to the injectors.
    Good luck ..keep reporting back.
    Brad
    Range Rovers Have Charactors inside them
    LROCWA Ex member 23 years
    1971 Series 2A
    2004 Discovery2a V8 Auto
    2003 Discovery2a TD5 Manual
    1982 4door man (sadly now gone)
    1989 Vogue auto
    2011 TDV8 Vogue
    What would life be without a Rangie?



  5. #5
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    It is very common with these dizzys that someone has pulled off the old rotor too hard when changing and the bob weights and springs have become dislodged.
    The best way to remove a rotor is to crush the bottom of it with a pair of channel grips.

    The dizzy should be oiled under the rotor, or the outer part of the shaft will not move with advance.
    As Bradtot said the centrifugal advance should be able to be moved relatively easily about 20degrees and then spring back.
    It's a dizzy off job if the bob weights have fallen off.
    Regards PhilipA
    These engines are known for sticking exhaust valves if run on short trips on petrol, and this could explain the popping you hear. The test is to remove a tappet cover and hit the inlet and exhaust valves sharply with a hammer . If OK the hammer will bounce and the valve move.
    Another thought. Have you had a look at the camshaft. Lobes can get completely or partially worn down over time.

    Another another thought. I cannot help but remember when a poster here many years ago posted a picture of his injectors on a 14CUX, and they were all seized from lack of use. I sold him a good set of Lucas injectors that I had and it fixed the problem. I know you tested and rebuilt them, but I have seen rebuilds fail .Have you pulled the injectors in question and seen whether they spray into a glass?

  6. #6
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    I have put on another distributor I had with mechanical advance, this is working correctly when checking the harmonic balancer with a timing light.

    After rebuilding the injectors I tested their spray pattern but have not pulled them from the motor and rechecked them.

    I took the ECU out of its case today and plugged it in. When flexing one of the boards the idle and sound of the motor was changing, at one stage it actually ran quite well.

    Konradical, how did you ultimately fix your ECU. Now mine is out I hope I can repair it.

  7. #7
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    Quote Originally Posted by Richard Kaye View Post
    I have put on another distributor I had with mechanical advance, this is working correctly when checking the harmonic balancer with a timing light.

    After rebuilding the injectors I tested their spray pattern but have not pulled them from the motor and rechecked them.

    I took the ECU out of its case today and plugged it in. When flexing one of the boards the idle and sound of the motor was changing, at one stage it actually ran quite well.

    Konradical, how did you ultimately fix your ECU. Now mine is out I hope I can repair it.

    Hi again the EcU drive transistors go dry solder jointed, basically resoldering any sus joints with a hot soldering iron. I have in the past done around 5 with the dry solder problem and all worked after, there were many symptoms of faulty engine management nothing specific...go and find a good electronic tech that has a magnifer and a good soldering iron and they should be able to fix...If your in Perth I can have a look otherwise find someone close to where you are...I am or was an electronics tech...LOL😎😎
    Brad
    Range Rovers Have Charactors inside them
    LROCWA Ex member 23 years
    1971 Series 2A
    2004 Discovery2a V8 Auto
    2003 Discovery2a TD5 Manual
    1982 4door man (sadly now gone)
    1989 Vogue auto
    2011 TDV8 Vogue
    What would life be without a Rangie?



  8. #8
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    Quote Originally Posted by Richard Kaye View Post
    I have put on another distributor I had with mechanical advance, this is working correctly when checking the harmonic balancer with a timing light.

    After rebuilding the injectors I tested their spray pattern but have not pulled them from the motor and rechecked them.

    I took the ECU out of its case today and plugged it in. When flexing one of the boards the idle and sound of the motor was changing, at one stage it actually ran quite well.

    Konradical, how did you ultimately fix your ECU. Now mine is out I hope I can repair it.
    Richard, ultimately I was able to source another ECU and get myself going. I am a little suspect on this one though.

    Both of my ECU's tested good as well, this if you read my posts at the time, I was tearing what little I have of hair out!

    Initially to test the theory I ran a soldering iron over the injector sections of the board, adding a bit of solder as I went. It wasn't neat, but, it did run 100% better. The only issue was I could only drive at night (Was living in the NT's Top End at the time) as it would struggle with driving at speeds over 80km/h.

    A mate of mine has told me of a technique of heating the whole board up to a set temp quickly then cooling. Was not keen to try this.

    I believe any company that can repair circuit boards would be able to carry out the repairs. Recently I discovered that CoolDrive Distribution offer a service for ECU repairs. I believe they charge about $180 initially and then depends on the repair the extra cost. I will be going down this path so I can have a spare or better yet, a decent one powering me along.

    Also, while I remember, where the transistors mount to the frame of the housing, there is supposed to be heat paste there. All of mine were dry or non-existent.

    Hope you can get her up and running sweet!
    '15 Discovery 4 HSE- The family bus and the kids like it!
    '89 RRC- My favorite of the bunch!
    Ex '03 Commodore 'S' ute- 450hp of uncracked 5.7lt and 6 speed manual uteness - Still crying that its gone
    Ex '06 GLXR Triton- *Gone and forgotten*

  9. #9
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    It's a dodgy photo copy, but this is the CoolDrive repair centre I was talking about earlier.
    '15 Discovery 4 HSE- The family bus and the kids like it!
    '89 RRC- My favorite of the bunch!
    Ex '03 Commodore 'S' ute- 450hp of uncracked 5.7lt and 6 speed manual uteness - Still crying that its gone
    Ex '06 GLXR Triton- *Gone and forgotten*

  10. #10
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    I think over the weekend I will have a go at resoldering the injector circuit of the board, cant make it worse than it is. I am also looking around for a replacement ECU with the part number PRC7440 if anyone has a working one they want to sell.

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