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1994 850 no start: fuel, spark, but no injector pulse

Volvo 850 Made from 1993 to 1997, this Volvo line was available in both a wagon and a sedan, both with were graced with several trim levels.

1994 850 no start: fuel, spark, but no injector pulse

  #1  
Old 03-26-2014, 09:49 AM
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Default 1994 850 no start: fuel, spark, but no injector pulse

My 850 (non-turbo) won't start. It was an intermittent problem for a short time and now is consistent, has not started for months.

Fuel pressure to the rail is good. Spark plugs are firing. Compression is good.

No injector pulse!

OBD Port A2 shows a dim light, but won't show any codes. What does this mean? I suspected ECU failure, but replacing ECUs did not help (see below)

I replaced:
* Fuel injector relay
* Fuel pump relay
* cam position sensor
* crank sensor
* two ECUs (cp02 6.2) and (cp01 5.1 - ignition)

Still no start. Checked lots of wires, found no problems. Battery voltage looks good. Any suggestions?

When this problem first appeared, the engine fan would run when the engine was cold - perhaps a temp sensor problem? But could this be related to a no-start? I suspect it was an unrelated problem.

What other component could prevent injector pulse but still give me spark?

Thank you for your advice!
 
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Old 03-26-2014, 11:09 AM
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So, you are saying that you are NOT getting fuel into the cylinders? Tried to start the car a few times, pulled the plugs and they are dry? Have you tried starter fluid?

A bad temp sensor can cause hard starts (and maybe no start). A car needs: 1. Fuel; 2. Spark; 3. Air; 4. Timing; 5. Compression.

 
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Old 03-26-2014, 03:54 PM
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Is the relay that is closest to the battery under the cover on the top of the radiator buzzing?
 
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Old 03-26-2014, 07:14 PM
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You say you have no injector pulse; i.e. you have 12v on both sides of the injector connector while cranking?


Or do you have 0v on both sides of the injector?
 
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Old 03-27-2014, 12:08 AM
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Originally Posted by boxpin View Post
Is the relay that is closest to the battery under the cover on the top of the radiator buzzing?
mine does this what does that mean?
 
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Old 03-27-2014, 03:13 PM
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Originally Posted by boxpin View Post
Is the relay that is closest to the battery under the cover on the top of the radiator buzzing?
yes, that relay (fuel injection) was buzzing, so I replaced it with a new one. no more buzzing relay, but still no start. does this tell us anything?
 
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Old 03-27-2014, 03:21 PM
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Originally Posted by gdog View Post
You say you have no injector pulse; i.e. you have 12v on both sides of the injector connector while cranking?


Or do you have 0v on both sides of the injector?
12V on both sides.
 
  #8  
Old 03-27-2014, 07:45 PM
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Originally Posted by mtps View Post
12V on both sides.


Did you ck continuity between grey pin side of injectors to pin A9 on ECM?


If that's good I would start cking input signals into the ECM. Generally if ECM sees correct spark signal, then it will close the fuel pump relay and start firing the injectors. Maybe ck your throttle position sensor (TPS) signal?


I am assuming you have schematic?
 
  #9  
Old 05-30-2014, 10:30 PM
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Hi folks, I finally got the car to start again so I thought I'd follow up for others who may have a similar problem.

After exhausting everything I could check myself I took the car to a good mechanic. He eventually found bad grounds to the ECU, located in hard to reach places like behind the starter. Rather than re-run wires to those places, which would require taking apart the intake manifold and other things to reach it, he ran a new ground to the frame right in front of the battery. Now the car starts/runs fine.

A lot of trouble caused by some bad wires!
 
  #10  
Old 05-31-2014, 01:14 AM
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Originally Posted by mtps View Post
A lot of trouble caused by some bad wires!
Yeah, they're kind of important..

Thanks for reporting what you found.
 
  #11  
Old 06-08-2014, 10:31 PM
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Ditto, thanks for the follow up.
 
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