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8.1GXi-D loss of power

Old 06-30-2020, 11:17 AM
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Default 8.1GXi-D loss of power

I have a loss of power on my VP 8.1 again. Last season it popped up and I did a 100% overhaul of the fuel system, nothing fixed it. I replaced the plugs and it came back to life.

This season it's been getting worse every outing. The engine sounds like it's either missing or has very retarded timing. I replaced the plugs and it seemed to sound really healthy the first idle when I started it after, but immediately went back to the same old under power and subsequent idle.

I have spark on all cylinders, and just for good measure I replaced the fuel filter and ran it on a 5 gallon jug. No change. Im leaning towards it's being a coil. Would be cheap enough to replace them all if the OEM Automotive ones work, not so practical if you have to buy Sierra or VP. Are there really differences between the automotive and marine ones?

Also, when I was doing to plugs I found this sending unit had completely rusted out and broken connection. Port side by the furthest back spark plug. From exploded views it's either coolant or oil pressure. I figure if this was critical, it would be in limp mode, but all my gauges work, so it has to be a computer input.

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Old 06-30-2020, 04:53 PM
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Need a serial number
Need to scan the motor for codes, I would bet you have one from the busted sensor

Also need to do some corrosion prevention
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Old 06-30-2020, 07:23 PM
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Since the plugs were out, good time for compression check too
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Old 06-30-2020, 09:41 PM
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Originally Posted by AllDodge View Post
Need a serial number
Need to scan the motor for codes, I would bet you have one from the busted sensor

Also need to do some corrosion prevention
​S/N 3869264

​​​Any suggestions on a preventative coating? Its looked like this since I got it, but always down to do better.

Scanners at my dad's place and I'm seeing him saturday.
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Old 06-30-2020, 09:42 PM
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Originally Posted by PA.WOODCHUCK View Post
Since the plugs were out, good time for compression check too
Was on the lake on vacation and only had my carry on tools I keep on the boat. Sucks too because the two port side middles are a real *****
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Old 07-01-2020, 07:02 AM
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Unable to find the S/N

https://www.volvopentashop.com/epc/en-US
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Old 07-01-2020, 07:22 AM
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Originally Posted by AllDodge View Post
S/N is illegible, that's the part number I think for the motor? The plate is destroyed. Does the S/N matter if it's narrowed down to the exact model (i.e. 8.1GXi-D)? Would seem like poor configuration management if parts varied within models.
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Old 07-01-2020, 04:35 PM
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Think its part 4 or 5

https://www.volvopentashop.com/epc/e...%2F7744390_063
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Old 07-01-2020, 04:57 PM
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Originally Posted by AllDodge View Post
​​​​​​
of those two, it would be 4 because the hanging wire is a spade connector. Thanks.
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Old 07-01-2020, 05:37 PM
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Originally Posted by tgell001 View Post
​​​​​​
of those two, it would be 4 because the hanging wire is a spade connector. Thanks.
What effect does the oil pressure sensor play in the spark advance table? Or I guess more broadly, what effect does it have on performance. I would think it would go into limp mode not just lose power.

There are also two sensors for oil, I'm assuming this one is for the gauge and the one with a lug is for the computer? Even though my gauge still works.

Last edited by tgell001; 07-01-2020 at 05:52 PM.
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