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I am a newbie to this great site and looking for some help. I have a 97' 850 t5 that I have recently had starting problems. The car when cold starts up fine and runs okay. No problem with the Turbo but have a check engine light on. It has recently lost mpg from 25.6 to 22.3. I have changed plugs, rotor cap, wires,filter and seems to run alot better but not back to the 25.6mpg it used to get. I only use 93 octane in it since new. once it is run for a 20 mile ride to work it will not start up again. It takes about 5 times before it starts. It does this only when the temp is up to normal. The fuel pump turns on and have checked the fuel pump relay, injector relay, coil, and battery with no problems. I tried to read the codes with my reader but the OBDII connection by the shifter is not working per the volvo dealership. I am currently in school with limited funds and trying to figure out what I need to check out. The dealership said it would cost around $125 to diagnose if they even can.I am mechanically inclined and have replaced the radiator and thermostat recently and should be able to some troubleshooting but am stumped at this moment.Any suggestions would be greatly appreciated.
 

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Very difficult to know where to go without a code reader.

One thing you might try is to disconnect the battery for 10-20 min to do a simple 'reset' of the computer. If it's a definite fault it will show up immediately with the check engine light but an intermittent or learned error would take a while to show up.

Are you sure your reader is not the fault?

Here's some help from the net;

Volvo 850/70 Service Light Reset

Engine 850: B5234T/2.3/20v/T5: - DIY flash code reader. - Volvo Owners Club Forum

http://volvoforums.com/forum/volvo-s70-33/obdii-scanner-usage-39916/
 

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Thanks for the info BHart, but my 850 is a 97' model and you have to reset the codes by a computer. Yes, my code reader is working. I hooked it up to my wifes car and it works fine. I believe the 97'-98' volvo 850's are the only years you can not reset codes manually.I think there is a way you can check codes under the hood but I did not see any connectors.
 

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I am a newbie to this great site and looking for some help. I have a 97' 850 t5 that I have recently had starting problems. The car when cold starts up fine and runs okay. No problem with the Turbo but have a check engine light on. It has recently lost mpg from 25.6 to 22.3. I have changed plugs, rotor cap, wires,filter and seems to run alot better but not back to the 25.6mpg it used to get. I only use 93 octane in it since new. once it is run for a 20 mile ride to work it will not start up again. It takes about 5 times before it starts. It does this only when the temp is up to normal. The fuel pump turns on and have checked the fuel pump relay, injector relay, coil, and battery with no problems. I tried to read the codes with my reader but the OBDII connection by the shifter is not working per the volvo dealership. I am currently in school with limited funds and trying to figure out what I need to check out. The dealership said it would cost around $125 to diagnose if they even can.I am mechanically inclined and have replaced the radiator and thermostat recently and should be able to some troubleshooting but am stumped at this moment.Any suggestions would be greatly appreciated.
A common failure on the 850 is the fuel pump check valve which causes delayed starting, fuel consumption, hesitation, ect... Never through parts at a car before diagnosing correctly or having the car diagnosed. The fuel pump actually operates fine but the check valve is faulty not allowing fuel pressure to build up and stay steady. Once started does your car seem fine? Try turning your key to the "ON" position without actually starting 5 or 6 times then start her the sixth time. If she starts up fairly decent then it's probably the check valve inside your fuel pump. Unfortunately the check valve can't be replaced and you'll need to replace the fuel pump itself. Best way to check this fault is with a fuel pressure gauge hooked up to your fuel rail. Run the car with FPG hooked up and see if she holds pressure after key "OFF", if the pressure drops to "0" immediately then you know that the FP check valve is faulty or you have a leak in fuel system(injectors, line, fuel rail, ect...). Good wrenching!!
 

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Did you get it fixed ?? One reason for the OBDII port not working is a blown fuse. On an 850 I think the same circuit that powers the interior courtesy lights is also the circuit that powers the connector. I'd check to make sure your interior lights work and then check the fuses under the hood just in case even if the lights do work. I have a 95 but I think the wiring was pretty much the same.
You might also be having a problem with the coolant temp sensor where the injectors are rich enough when it's cold that you get a nice smooth start but once it warms up it's either going too rich or too lean for it to start smoothly. Just a guess.
 
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