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Car cranks but won't run. No response on diagnostic ports A2 and A6 850 1994

posted by  benglar on  Sat Oct 3 18:36 CST 2009
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last visit: Mon Jul 5 09:23 CST 2010
[RELATED]

'94 Volvo 850 sedan, automatic transmission, not a turbo

The car cranks properly but the engine will not start. Dashboard lights appear normal while the starter motor turns.

While troubleshooting I discovered the engine coolant temperature sensor had failed and replaced it.

Here's the current problem: when using the diagnostic port, there is no LED response from A2 (MFI) and A6 (fuel) when I push the button for a second. Also no response when I hold the button for 6 seconds, the start of the process to clear the codes. The LED lights whenever the button is pressed but there is no answering LED activity from A2 and A6. The LED acts normally for other ports, including the transmission.

I have verified electrical continuity between A2/A6 and the B5 pin on the MFI and fuel computer boxes. I have verified that the main engine relay works.

Can someone please tell me which are the power pins on the fuel & engine computers so I can verify that they are getting power?

Any other troubleshooting ideas? At this point the Volvo diagnostic manual says I should try swapping in new engine and fuel computers. But gosh, I just don't have spares.

Thanks for the help.






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