Help!! 1995 306 XU7 1.8 8V running very rich
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Thread: Help!! 1995 306 XU7 1.8 8V running very rich

  1. #1
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    Default Help!! 1995 306 XU7 1.8 8V running very rich

    Hi,
    First post because I need some help with a newly acquired 306. By way of introduction, I have owned a few Renaults (R10, butchered R1135 Gordini, R12 1.4) back in the mid 70s to mid 80s plus worked on my parent's 504/505 in that era. In recent times built a kit Lotus 7 replica (clubman) and fiddled around with MegaSquirt DIY ECU. Newly acquired daughter-inlaw from the UK wanted a Pug 306 like the one she had back home.

    Found a car which was a little neglected. The ECU light was intermittent which I thought would be a simple case of a lambda sensor replacement as the car seemed to run OK. First off we replaced the cambelt, waterpump, crankshaft and camshaft oil seals and that went OK until the heater hose plastic fitting cracked up and sidelined the car. A new hose assembly was going to be ordered so I butchered the hoses and bypassed the heater with a piece 3/4 inch copper tube to make the car mobile. Then when my wife was returning home, the car failed to proceed.

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    I was able to get the car running but it was running extra rich, all 4 plugs very sooty and I thought the lambda had finally failed completely. New lambda arrives and was duly fitted. Powered off ECU for an hour or 2 and restarted (without the 10 second ignition on before cranking), I thought that the power off would reset the ECU.

    Anyway, the new lambda has made no difference, so I thought maybe another sensor failed when my wife was driving. MAP sensor seems to be OK with rest reading of 4.45Vand less then 1 volt when sucked hard. No obvious vacuum leaks, both temp sensors measure around 2k6 ohms when cold. I haven't tested the temp sensors when warm. Idle motor windings both measure 50-52 ohms. Cold cranking injector duty cycle around 12-13%. All sounds OK.

    About the only issue is that the fuel pressure regulator when tested with a tyre inflator holds pressure at an indicated 2.8 bar/40 psi. The regulator is marked at 250kpa. Is this within tolerance or should I replace? Even with the possible error of the tyre gauge, 12% high does sound a bit too much.

    Other than the marginal regulator. I am starting to run out of ideas other than replacing the Marelli 8P ECU. Opened up the ECU and it looks OK - nothing obvious such as burnt or bulging components. Has anyone sourced an ECU from the UK? They don't seem to be too expensive from there although the part numbers don't quite match... but the pinouts on my car matches the Haynes manual, so I reckon they should work OK.

    Thanks for reading so far... So... to the collective Pug wisdom, what advice can you offer??

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    1000+ Posts BIGRR's Avatar
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    You say that after your replacement of the timing belt the car went "OK" does this mean run well or run "well"?

    If running retarded (Tooth out) the engine may run hot and the ECU may enrich the motor to cool things down.

    Apparently there was problem with the harmonic balance on 306s, the outer turned on the inner boss with age and the timing pin hole does not then align correctly relative to the crank sprocket (ie TDC). Just a thought!

    Some of the experts will comment soon.

    Good Luck
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    Thank you for responding. Timing is good. Yes this car has the harmonic balancer issue where the hole does not line up but the keyyway on the cranksahft was aligned correctly before the new belt was installed. We double checked the camshaft / crankshaft timing before we removed the old belt. The camshaft and crank did not move between the old belt coming off and the new belt going on and the slack all went to the tensioner side.

    The car ran well after the timing belt was replaced and the cabin heater was bypassed. It did have the ECU light showing intermittantly which I believed was dud lambda (it turns out it had an intermittant heater connection at the sensor).

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    1000+ Posts cav91's Avatar
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    At a guess I'd go for the oxy sensor!
    My Mi16 did the same thing!
    2011 Renault Koleos manual petrol, yes it's boring, but not as boring as:
    2017 Renault Koleos auto

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    cav, fyi, the oxygen sensor is just different terminology for the lambda sensor. cheers.

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    Quote Originally Posted by lmr052 View Post
    H

    Thanks for reading so far... So... to the collective Pug wisdom, what advice can you offer??
    sorry i cant offer any suggestions beyond your considerable list, but david cavanagh on AF operates a french car wreckers in melbourne. you will find his posts in the for sale sections, or just look him up to PM him. if you need an ecu to swap, then hopefully you can get a second hand one for less than the cost of a new one.

    alexander.

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    Quote Originally Posted by alexander View Post
    cav, fyi, the oxygen sensor is just different terminology for the lambda sensor. cheers.
    Yeah i realised that about an hour after posting and jumped on now to change it, but you've already replied!

    Next thought have you tried the air filter, the sensors on the thermostate housing and as you said the fuel pressure reg, then if this then fails i'd go for the ecu! Basically start with the cheap things!
    2011 Renault Koleos manual petrol, yes it's boring, but not as boring as:
    2017 Renault Koleos auto

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    Quote Originally Posted by cav91 View Post
    Next thought have you tried the air filter, the sensors on the thermostate housing and as you said the fuel pressure reg, then if this then fails i'd go for the ecu! Basically start with the cheap things!
    New air filter fitted before the cam belt. As I said earlier - the car had been somewhat neglected before us.

    Starting off cheap is good when guessing... which is where I am up to now.

    At this stage I think I will try for an ECU reset with 10 second delay at ignition on before cranking and substitute a couple of resistors or a potentiometer for the temp sensors and see what happens. This should let me know whether the temp sensors are playing up. The cold resistances don't appear to be unusual.

    Alexander, thanks for the pointer to David Cavanagh too.

    Can anyone confirm the correct pressure for the XU7 8V fuel pressure regulator? Is it 2.5 bar? I noted that ebay people are selling 3 bar units for the 16V XU7. The Haynes manual is less than helpful for the EFI stuff like this.

    Thanks to all so far

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    Quote Originally Posted by lmr052 View Post
    Hi,
    I was able to get the car running but it was running extra rich, all 4 plugs very sooty and I thought the lambda had finally failed completely. New lambda arrives and was duly fitted. Powered off ECU for an hour or 2 and restarted (without the 10 second ignition on before cranking), I thought that the power off would reset the ECU.

    Anyway, the new lambda has made no difference, so I thought maybe another sensor failed when my wife was driving. MAP sensor seems to be OK with rest reading of 4.45Vand less then 1 volt when sucked hard. No obvious vacuum leaks, both temp sensors measure around 2k6 ohms when cold. I haven't tested the temp sensors when warm. Idle motor windings both measure 50-52 ohms. Cold cranking injector duty cycle around 12-13%. All sounds OK.

    About the only issue is that the fuel pressure regulator when tested with a tyre inflator holds pressure at an indicated 2.8 bar/40 psi. The regulator is marked at 250kpa. Is this within tolerance or should I replace? Even with the possible error of the tyre gauge, 12% high does sound a bit too much.

    Other than the marginal regulator. I am starting to run out of ideas other than replacing the Marelli 8P ECU. Opened up the ECU and it looks OK - nothing obvious such as burnt or bulging components. Has anyone sourced an ECU from the UK? They don't seem to be too expensive from there although the part numbers don't quite match... but the pinouts on my car matches the Haynes manual, so I reckon they should work OK.

    Thanks for reading so far... So... to the collective Pug wisdom, what advice can you offer??
    2.5 bar is the normal pressure for the 1.8L bv engine, if it is running more than that it will use excess fuel. First I would read the codes from the ECU, this will give some insight into where the problem lies.


    Reading 306 codes

    Code Extraction WITHOUT the TAD 99 Factory Tester

    1. Connect a switched jumper* to wire 17 of connector M720 which is the green 2 pin
    connector (behind the ECU box).

    * (a wire with an in-line switch)




    Connect the other terminal of the switched jumper to a good ground source (eg. battery negative terminal) as shown below.

    sorry can't get the picture to load


    2. Turn the ignition switch to the "RUN" (ON) position.
    3. Close the switch for 3 seconds. The "CHECK ENGINE" indicator will come
    on. Open the "switched jumper" and the "CHECK ENGINE" indicator will:

    Blink once for: 1__ (tens)
    Remain off for: 1.5 seconds
    Blink twice for: __2 (units)

    Thus, a code 12 which indicates the beginning of the "TEST" sequence has been displayed.

    1. Wait for the "CHECK ENGINE" light to come on continuously.
    2. Close the switched jumper for 3 seconds. The "CHECK ENGINE" indicator will come
    on.
    Open the "switched jumper" and the "CHECK ENGINE" indicator will:
    Blink (tens)
    Remain off for: 1.5 seconds
    Blink (units)

    Remember the first set of flash codes is the (tens) and the second set of flash codes is the (units). The combination of the (tens)+(units) is the displayed fault code. Take note of all the stored codes.
    Repeat steps 4 and 5 until a code 11 is displayed. Up to 5 codes may be stored in the fault memory. Code 11 signals the end of the test sequence and there are no other codes stored. Refer to the fault code chart.
    Repair the indicated faults or repeat the test. Be sure to disconnect the "switched jumper" and turn the ignition switch to the "OFF" position before attempting repairs. Disconnecting components and wiring harness connectors with the ignition switch in the "RUN" (ON) position may set additional codes and cause permanent damage to the Motronic system.

    To erase the fault code memory turn the ignition switch to the "RUN" (ON) position.
    Perform a test sequence up to a code 11
    Depress the switched jumper for more than 10 seconds
    The "CHECK ENGINE" indicator should be "ON" and all fault codes should have been cleared.



    11 End of Test Sequence.
    12 Beginning of Test Sequence.
    13 Air Temperature Sensor.
    14 Injection NTC Sensor.
    15 Fuel Pump(s) Relay.
    21 Throttle Switch (Idle Position).
    22 Idle Regulation Electro-valve.
    31 Self-Correction Richness Regulation.
    32 Self-Correction Richness Regulation.
    33 Air Flow Sensor.
    34 Canister Purge Electro-valve.
    35 Throttle Switch Unit (Full Load Position).
    41 Engine RPM Sensor.
    42 Injectors.
    43 Detonation Sensor Regulation.
    44 Detonation Sensor.
    51 Self-Correction Richness Regulation.
    52 Self-Correction Richness Regulation.
    53 Battery Voltage.
    54 Electronic Control Unit.

    cheers Pete

    I am gunna get another 403 on the road........one day

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    Pete,
    Thank you very much - your post is gold.

    The post makes a reference to the "Motronic system". Is this applicable to Marelli as well? The description sounds like it.

    I will investigate and let you know how I get on. I have been researching the resistance characteristics of the ntc temp sensors and it seems like my readings may be a little on the high side.

    Anyway, I will see what the ECU tells me.
    Regards, Richard

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    I'd also check up to see whether disconnecting the battery does reset the fault codes. It's not the case on all cars.

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    Quote Originally Posted by lmr052 View Post
    Pete,
    Thank you very much - your post is gold.

    The post makes a reference to the "Motronic system". Is this applicable to Marelli as well? The description sounds like it.

    I will investigate and let you know how I get on. I have been researching the resistance characteristics of the ntc temp sensors and it seems like my readings may be a little on the high side.

    Anyway, I will see what the ECU tells me.
    Regards, Richard
    Motronic is Bosch.
    I'd replace the timing pully if it has slipped, if they fail they can cause the cam belt to break (auxilary belt flies about) with expensive results.
    Graham

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    Quote Originally Posted by GRAHAM WALLIS View Post
    Motronic is Bosch.
    That is what I thought too.

    I found the instructions for the TAD4-99 at http://www.peugeotlogic.com/workshop...e/testcone.htm

    It covers both the Marelli and the Bosch systems without different instructions so the same procedure should work for Marelli.

    Thanks for the advice on the crank pully too Graham.

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    Quote Originally Posted by PCOATES505 View Post
    1. Connect a switched jumper* to wire 17 of connector M720 which is the green 2 pin
    connector (behind the ECU box).
    I realise this applies to a Bosch Mototronic but does anyone know which connection for the Marelli 8P?

    According to the relevant 306 Haynes circuit diagram (Diagram 13), the diagnostic connector has 2 wires and connects to pins 10 and 15 on the Marelli 8P. Wire numbers are 1337 and 1338 respectively. Which should I choose to connect to earth for the diagnostic codes? Alternatively, looking at the car's diagnostic connector with the loop of the metal clip on the top, is the connection of the switched jumper to the left or right pin connector?

    What if I connect the switched jumper to the wrong wire? Does anyone know what damage this may do to the ECU? What is the second wire for? RS232 or TTL data signals?

    Any other tips?

    Thank you all, Richard

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    Quote Originally Posted by lmr052 View Post
    I realise this applies to a Bosch Mototronic but does anyone know which connection for the Marelli 8P?

    According to the relevant 306 Haynes circuit diagram (Diagram 13), the diagnostic connector has 2 wires and connects to pins 10 and 15 on the Marelli 8P. Wire numbers are 1337 and 1338 respectively. Which should I choose to connect to earth for the diagnostic codes? Alternatively, looking at the car's diagnostic connector with the loop of the metal clip on the top, is the connection of the switched jumper to the left or right pin connector?

    What if I connect the switched jumper to the wrong wire? Does anyone know what damage this may do to the ECU? What is the second wire for? RS232 or TTL data signals?

    Any other tips?

    Thank you all, Richard
    Looking into the connector, with the loop on top, RHS terminal, connecting to the wrong one does nothing, in my experience

    cheers Pete

    I am gunna get another 403 on the road........one day

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    My '89 Mi16 had been running similar to yours for years, throwing up an occasional CHECK ENGINE light, which was 51 or 52, something to do with self-enrichment. I started checking: the NTC sensor was OK, the wiring seemed to be OK, but it was only because I jammed the probes into the connector at the sensor. The connector for the NTC sensor was not sending any value to the ECU. Making that connection good solved my problem.

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    Update. Pete's advice on accessing the ECU diagnostics was spot on. I seem to have cleared or reset the codes so there was no info there.

    Whatever the issue is, it is deteriorating to the point the car will rarely start. I have been able to confirm:
    - The ECU will detect codes (e.g. detects TPS disconnected)
    - The engine will sometimes start and run very feebly (1000 rpm or so full throttle when I use a 120 ohm resistor instead of the coolant temp sensor). Engine has no power.
    - There is power to the fuel pump and the ignition coils (twin relay working).
    The engine when it sort of runs sounds like the ignition is severely retarded. Even when I coaxed into semi life, the ECU detected no errors. The fact it can semi run tells me spark and fuel power are OK. All this points to timing of spark relative valves and crank, caused mechanically or electronically. Mechanical is my current hunch.

    I am planning to double check the cam timing (as suggested by BIGRR) - I am wondering if a key or something didn't go back together correctly and the timing is progressively getting worse. I will investigate and report back.

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    Update.

    Sheared key on Camshaft sprocket, possibly due to overtightened cam belt. Drilled and filed thesprocket to suit a 4mm shortened woodruff key. After the repair, engine started and ran perfectly.

    Thank you all for you interest and help - apologies for the bum earlier steer. At least I now know how to diagnose the ECU. Looks like the lambda replacement fixed the intermittent ECU light too.

    Now... time to overhaul the brakes. Looks like the rears are Girling, not sure about the fronts. Time to go surfing aussiefrogs to learn some more!!
    Last edited by lmr052; 3rd April 2011 at 07:25 PM.
    PaulRoper likes this.

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    This is an old post..
    But... I hope my problem is the same. Started out as an 'ok' running 8v , but headgasket sucking in water..
    Head Off.. there wasnt much left of the old gasket.. Cleaned it up, replaced the HG. Belts were done 12 months ago..
    it just hasnt run right since rebuild.. asthmatic performance. - Lean, now rich and rough..
    Wiring and sensors Ok, but did find a porous MAP air line.. Next week.. pull all that apart (again) ..double/triple check timing from basics

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    Replaced the Crankshaft pulley tonight. There was about 10mm difference in the location of the 'locking/alignment' hole.
    Tomorrow will tell, when I get it back together.

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