Friend has a 1992 volvo 940 B200FT. It keeps cutting out. The OBD 1 diagnostic unit causes the lambda light to come on and reports fault codes 1-4-4 (fault in or to bosch LH2.4 ecu). He has had a mobile tuning firm out and they suggested replacing the fuel pump relay (a common fault on these cars), this had no effect. He then called the RAC who said they didn't carry the correct software, however the OBD1 system appears to have no port for connection to an external computer, the RAC guy did however suggest that the fault was not related to the ignition amplifier as the fault isn't temperature dependent. He is now toying with replacing the LH 2.4 unit or taking it to a dealers both of which are quite £££££. All wiring/connectors appear to be in good order. Any ideas?
DB
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Hi Sigma,
So many possibilites, so little space !
Seriously, this sort of problem is as much of a nightmare for the technician as it is for the owner. BUT, from personal experience, almost as common a problem as the Fuel Pump Realy is the Injector Supression Relay, usually fitted on the O/S suspension turret. Costs around £25 + VAT from Volvo, and well worth eliminating before getting into more expensive things.
DO NOT replace ECU on a whim, as it is generally the most reliable component in the system. If the above does not help try another "expert"
Regards, Adam
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Thanks for your response Adam.
He eventually went to the dealers. The dealer spent 7 hrs diagnosing the fault. Went through
Fuel relay
Radio Supression relay
Connectors to above
Earth on ecu
fuel filter
Fuel delivery-pressure and flow at rail
Turbo diaphram-was slightly split so repaired
Constant idle speed valve checked but eventually replaced with new
They reckoned that if it failed again probably ecu
Only charged for 2 hrs and spent 40mins plus showing us the work. Parts such as relays were swapped with ones from the workshop managers car to save cash. So excellent service Beckland Volvo Bham
However car failed again on friday evening so maybe ecu after all?
DB
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OK, Now when the engine cuts out does it restart If not can you quickly test for a spark, can you hear the injectors firing ( use ling screw driver ). If there a smell of unburnt feul.
If do spark no feul then I would go for the flywheel RPM TDC hall effect sensor. I have one at home I can measure but this measurement is a first level as the output voltage is the most important.
Does the car only cut out at tick over/low RPM but runs fine other wise. New sensor, and there was an revised one due to this problem. about £26. Come back Peter
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Thanks for the response Peter.
Engine cuts out but usually restarts immediately. Problem affects entire RPM range. The dealer reckoned when it cut out it still had fuel and spark, thereby pointing to the CIS allowing too much air into the charge. The car is a 1992 model and the hall effect sensor in the distributor was superceded by an RPM sensor in 1988-1989, and the RPM sensor is working fine.
Any more ideas?
Or where to get a LH 2.4 Jetronic unit cheap, but in working order?
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When the car cut out did the rev counter fall to zero and other then the ECU fault light did anything else come on/go off. Worth checking the powet to the ECI and carefully check any fuses for cracks or corrosion.
Rickies Volvo Gorebridge 01875 822677
SCB Newbridge 0131 343 1098
Good Luck.
Peter
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Peter
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