850 GLT Cranks But Doesnt Fire

roostermod · Mar 25th, 2009, 16:19

Hello Members,

I have a 97 850 glt that suddenly died on the hwy going about 70 mph. The engine cranks over but does not fire. checked fuel rail and it is getting fuel, checked coil and is getting faint spark only when i ground the coil wire but wont arc, also the spark plug when removed and grounded also will not spark, changed plugs, cap and rotor, with no success. Before buying coil or any other sensor, i ran diagnostics and came up with two codes: a P0115 Eng. Coolant Temp cicuit & a P0722 Output Speed Sensor circuit no signal. Some techs have told me that the Output speed sensor is the fault and by replacing it it should fire right up, but they dont seem as if there that sure on it, before i go buying parts that may not be the problem like a coil or something, does anybody know what might be the problem?, is this is a common problem?

Any help would be greatly appreciated...

Thanks!

liuleichan · Mar 25th, 2009, 20:53

I suspect you wouldn't get spark with a faulty cam position sensor?

Can you be sure that the leads and coil lead are OK? Coils don't tend to go for that much on ebay, might be worth trying a cheap 2nd hand one.

Also, the reference to coolant temp sensor may be worth checking out, but I doubt you'd experience the no-spark thing with it, though.

Wooffy · Mar 25th, 2009, 21:14

Unlike most other cars the 5 cylinder volvo engine uses the Camshaft sensor to create the signal for the coil to be triggered via the ecu. Also the injection and ignition are seperately switched where as most other cars rely on just the Crank sensor with the cam sensor being used only to adjust the injection timing fractionally.
They can be tested without the need for any diagnostic kit apart from a multimeter. I can't remember of the top of my head if they are hall effect or inductive loop as there is a different way to test either of these. If it an inductive loop one just unplug it and set your multimeter to volts ac, attatch to the sensor and get someone to crank the engine. You should get a reading of around 0.5volts ac. If not it's knackered.

Volgrrr · Mar 26th, 2009, 05:59

Quote:

Originally Posted by Wooffy

I can't remember of the top of my head if they are hall effect or inductive loop

Hall effect.

roostermod · Mar 28th, 2009, 23:46

so if its giving me that output speed sensor code, that would be the cam sensor?

Chris_Rogers · Mar 29th, 2009, 11:00

No, the road speed sensor is part of the gearbox and not the engine.

Try connecting an LED (check polarity and voltage) across the input to the coil amp, it should flash as each spark is commanded by the ECU.

If there is a flash then the problem is with the coil, amp or it's earthing, if not then I would suspect the camshaft postion sensor.

roostermod · Mar 30th, 2009, 18:06

Coil it is!, replaced it and its running better than before. Thanks to all for the help.

Mar 25th, 2009, 16:19	#1
roostermod New Member Last Online: Mar 30th, 2009 18:06 Join Date: Mar 2009 Location: Los Angeles	850 GLT Cranks But Doesnt Fire Hello Members, I have a 97 850 glt that suddenly died on the hwy going about 70 mph. The engine cranks over but does not fire. checked fuel rail and it is getting fuel, checked coil and is getting faint spark only when i ground the coil wire but wont arc, also the spark plug when removed and grounded also will not spark, changed plugs, cap and rotor, with no success. Before buying coil or any other sensor, i ran diagnostics and came up with two codes: a P0115 Eng. Coolant Temp cicuit & a P0722 Output Speed Sensor circuit no signal. Some techs have told me that the Output speed sensor is the fault and by replacing it it should fire right up, but they dont seem as if there that sure on it, before i go buying parts that may not be the problem like a coil or something, does anybody know what might be the problem?, is this is a common problem? Any help would be greatly appreciated... Thanks! Last edited by roostermod; Mar 25th, 2009 at 16:24.

Mar 25th, 2009, 20:53	#2
liuleichan Premier Member Last Online: Apr 17th, 2019 22:01 Join Date: Dec 2001 Location: .	I suspect you wouldn't get spark with a faulty cam position sensor? Can you be sure that the leads and coil lead are OK? Coils don't tend to go for that much on ebay, might be worth trying a cheap 2nd hand one. Also, the reference to coolant temp sensor may be worth checking out, but I doubt you'd experience the no-spark thing with it, though.

Mar 25th, 2009, 21:14	#3
Wooffy Growing old disgracefully Last Online: Aug 29th, 2013 15:40 Join Date: Mar 2009 Location: wirral	Unlike most other cars the 5 cylinder volvo engine uses the Camshaft sensor to create the signal for the coil to be triggered via the ecu. Also the injection and ignition are seperately switched where as most other cars rely on just the Crank sensor with the cam sensor being used only to adjust the injection timing fractionally. They can be tested without the need for any diagnostic kit apart from a multimeter. I can't remember of the top of my head if they are hall effect or inductive loop as there is a different way to test either of these. If it an inductive loop one just unplug it and set your multimeter to volts ac, attatch to the sensor and get someone to crank the engine. You should get a reading of around 0.5volts ac. If not it's knackered.

Mar 28th, 2009, 23:46	#5
roostermod New Member Last Online: Mar 30th, 2009 18:06 Join Date: Mar 2009 Location: Los Angeles	so if its giving me that output speed sensor code, that would be the cam sensor?

Mar 29th, 2009, 11:00	#6
Chris_Rogers VOC Member Last Online: Apr 10th, 2017 16:55 Join Date: Jan 1970 Location: South Kent Coast	No, the road speed sensor is part of the gearbox and not the engine. Try connecting an LED (check polarity and voltage) across the input to the coil amp, it should flash as each spark is commanded by the ECU. If there is a flash then the problem is with the coil, amp or it's earthing, if not then I would suspect the camshaft postion sensor.

Mar 30th, 2009, 18:06	#7
roostermod New Member Last Online: Mar 30th, 2009 18:06 Join Date: Mar 2009 Location: Los Angeles	Coil it is!, replaced it and its running better than before. Thanks to all for the help.

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