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Bringing a 740 back to life

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Old Mar 20th, 2021, 22:32   #21
bob12
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Just a newbie here .... to this thread and confess haven't read thoroughly so may have missed something that's been said along the way.

Smell petrol on removing a plug? Tacho flicking on cranking?
Have you tried immediately putting your foot to the floor on the accelerator pedal as soon as it doesn't start, i.e. after 2/3 seconds? If not do so and, hold accelerator to the floor while continue cranking without stopping until hopefully it fires up! You might flatten the battery if it's not up to the mark!! Assuming it's LH2.4 the first xxx 590 ecu's had a problem.

Bob
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Old Mar 20th, 2021, 22:39   #22
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Just a newbie here .... to this thread and confess haven't read thoroughly so may have missed something that's been said along the way.

Smell petrol on removing a plug? Tacho flicking on cranking?
Have you tried immediately putting your foot to the floor on the accelerator pedal as soon as it doesn't start, i.e. after 2/3 seconds? If not do so and, hold accelerator to the floor while continue cranking without stopping until hopefully it fires up! You might flatten the battery if it's not up to the mark!! Assuming it's LH2.4 the first xxx 590 ecu's had a problem.

Bob
Just to bring you up to date Bob, as far as i've understood things anyway, the OP has a spark and the CPS is pulsing the ECU so the fuel pump relay is operating, new main fuel pump but the in-tank one is currently suspect - either stuck/siezed or maybe not getting power.
No fuel reaching the fuel rail apparently but i had wondered about the ECU seeing as it's an early LH2.4 - anything else that comes to mind on that?
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Old Mar 20th, 2021, 22:52   #23
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Quote:
Originally Posted by bob12 View Post
Just a newbie here .... to this thread and confess haven't read thoroughly so may have missed something that's been said along the way.

Smell petrol on removing a plug? Tacho flicking on cranking?
Have you tried immediately putting your foot to the floor on the accelerator pedal as soon as it doesn't start, i.e. after 2/3 seconds? If not do so and, hold accelerator to the floor while continue cranking without stopping until hopefully it fires up! You might flatten the battery if it's not up to the mark!! Assuming it's LH2.4 the first xxx 590 ecu's had a problem.

Bob
Thanks for the comment. I did try the flat to the floor, but there is no fuel at the fuel rail. Going to try and get the pumps on the tank moving in the morning and see if this gets fuel moving to the rail.
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Old Mar 20th, 2021, 22:59   #24
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Just to bring you up to date Bob, as far as i've understood things anyway, the OP has a spark and the CPS is pulsing the ECU so the fuel pump relay is operating, new main fuel pump but the in-tank one is currently suspect - either stuck/siezed or maybe not getting power.
No fuel reaching the fuel rail apparently but i had wondered about the ECU seeing as it's an early LH2.4 - anything else that comes to mind on that?
Thanks Dave Of the top of my head other than what's being followed through on fuel delivery is the Fuel Pressure Regulator on the end of the rail and, the 'radio suppressor' but if all the tests have been done they shouldn't really affect the lack of juice!!

Bob
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Old Mar 20th, 2021, 23:20   #25
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Thanks Dave Of the top of my head other than what's being followed through on fuel delivery is the Fuel Pressure Regulator on the end of the rail and, the 'radio suppressor' but if all the tests have been done they shouldn't really affect the lack of juice!!

Bob
One of the tests i advised further up Bob (checking voltage on the green wires to the injectors) should have proved the RSR is working, from what i understand there's no fuel, pressurised or otherwise reaching the fuel rail so it's looking very like the in-tank pump at the moment.

Hoping my suggestion of percussive maintenance to the back end of the tank shifts it and the ATF helps lube things back to a running standard again.
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Old Mar 21st, 2021, 00:46   #26
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Final comment - I wonder what flash code numbers the in-built OBD 1 reader is throwing up on both settings .... not that it's an accurate diagnostic tool being in its infancy stage.

Bob
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Old Mar 21st, 2021, 01:00   #27
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Final comment - I wonder what flash code numbers the in-built OBD 1 reader is throwing up on both settings .... not that it's an accurate diagnostic tool being in its infancy stage.

Bob
I reckon one of the following :

1. MAF
2. AICV
3. Both 1 and 2
4. None.

If the in-tank pump isn't pumping and therefore the main pump is only pumping air, the MAF won't see increased airflow when the engine should be running and isn't and the ECU won't see increased engine rpm from the AICV being opened more so the ECU decides they must be faulty while completely overlooking the lack of fuel because it's Bosch and nobody could believe you wouldn't have petrol coming from the fuel pumps!
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Old Mar 21st, 2021, 01:27   #28
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Like your thinking man .... pump up the volume. Thank goodness I don't have these little niggles .... currently 745 battery on Spring charge and, the V70 is a just a dreamboat until it goes pear shaped! Bob.
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Old Mar 21st, 2021, 01:38   #29
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Like your thinking man .... pump up the volume. Thank goodness I don't have these little niggles .... currently 745 battery on Spring charge and, the V70 is a just a dreamboat until it goes pear shaped! Bob.
Likewise - i've discovered i should have a "Diagnostic Connector" under the bonnet of my 760 (LH2.2) that only reads "live" faults as in no memory. Apparently it can be accessed with an LED (with series resistor) fed from the +ve terminal of the battery while the ignition is on and/or engine is running. Allegedly in one mode at idle, it can be used to set the fuel mixture by getting the LED to flash on/off for equal lengths of time (50% duty cycle) by adjusting the mixture screw in the MAF.

I've yet to confirm the location and operation of it but might prove useful one day if i can't get any sense out of the usual checks if something goes belly-up!

I suppose a hand-held oscilloscope could be used instead of the LED to actually measure the duty cycle but i wonder how accurately it would set the mixture.

When i'm bored one sunny day i'll investigate this feature to firstly confirm its existence, secondly the operation of fault code reading and lastly while hooked up to the Gastester, to see if the mixture can be set accurately.
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Old Mar 21st, 2021, 11:27   #30
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Tried the tap and slap a few times this morning but no luck on getting her started. I’ll order the ATF and give that a go and see if we have any luck.

Just a thought, but as I changed the pump and filter under the car, could I have done anything wrong here? You can hear the pump now, and all the pipes and screws put back together properly with no leaks.
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