Confusion on 5.0OSi-E motor

[lonewolf41]

I have a 5.0OSi-E motor in my Regal. My understanding is that this motor is identical to the 5.0GXi-E with the only difference being that the OSi uses the XDP outdrive while the GXi uses the SX outdrive. Therefore, everything should be the same for mine as a 5.0GXi. Although a google search says that the OSi uses TBI while the GXi uses PFI, I can find no data to back that up. I think they both used TBI in the first (A) version of the motor(s), but after that, they both use PFI. Can anyone confirm or refute that conclusion?

Now for the "fun" part. I have been fighting low power issues for a while. Last year, it developed a knock. Hard to tell if pre-ignition or something in the bottom end. The knock sensor (that I knew about...more on that later) tested bad, so I replaced it but it did not change. I finally concluded bottom end and a second opinion from a local marine mechanic also thought the same based on the sound. Finally getting around to rebuilding the motor. Here's where it gets strange. According to the Seloc manual I have (diagram posted below that is supposed to cover C, D, & E versions), there is only one knock sensor. Per Volvo's website, I have the correct EFI manual for this motor...even though it only covers 5.0OSi-A through D, and the wiring diagram also includes only one knock sensor (color diagram posted below too). When I got the motor out a few days ago, I noticed that there was another knock sensor on the starboard side of the motor. I had seen the port knock sensor and knew it was there and when the manual said there was only one, I assumed there was just the one I knew about, but that is apparently not the case.

Does anyone have a wiring diagram for this motor? The ones I have seem to be wrong. All the colors and every other sensor seem to match what the diagrams have, but now I am questioning the accuracy of the diagram. It looked like the wires going to both of the sensors were the same color (black and green) which seems a little odd itself. Now I am wondering if it may have actually been a faulty knock sensor and I just replaced one and not both. I am not sure how they are wired...I assume not in series...but hard to know without a valid wiring diagram. Did I wind up with some unicorn engine or is there really supposed to be 2 knock sensors and Volvo just didn't bother to update the wiring diagram?

TIA

 

[ejnichol]

Go to this website and look and around. It shows the 5.0 OSI-E-J, and a ...-JF.

Do not see one that stops at dash '-E'

Under Engine Controls, Ignition. It list 2 knock sensors. No drawing or wiring diagram. I think they could be located under intake manifold in the engine v valley.

Drill down to your engine sub series and and review.

 

[alldodge]

A knock sensor detects pre-ignition, it doesn't detect a rod knocking. It doesn't really matter if the motor has one or two knock sensors. If motor has two sensors they are daisy chained together

 

[ESGWheel]

I have a 5.0 GXi-E and there is not a wiring diagram for this MPI (PFI) engine. However, based on a lot of hunting around on this forum, I have come to understand that the schematic for the GXi-C is the same, attached. While I have not tested this wire for wire, I have found it to be correct. I put a note at the top of the diagram fm the person who said it was the same but forgot to record the ‘who’. It shows only one knock sensor.

 

[lonewolf41]

I have a 5.0 GXi-E and there is not a wiring diagram for this MPI (PFI) engine. However, based on a lot of hunting around on this forum, I have come to understand that the schematic for the GXi-C is the same, attached. While I have not tested this wire for wire, I have found it to be correct. I put a note at the top of the diagram fm the person who said it was the same but forgot to record the ‘who’. It shows only one knock sensor.

Thanks. That is identical to the one in my manual. Does your engine have 2 sensors?

 

[lonewolf41]

Go to this website and look and around. It shows the 5.0 OSI-E-J, and a ...-JF.

Do not see one that stops at dash '-E'

Under Engine Controls, Ignition. It list 2 knock sensors. No drawing or wiring diagram. I think they could be located under intake manifold in the engine v valley.

Drill down to your engine sub series and and review.

When you say "this website", are you referring to iboats.com?

 

[lonewolf41]

A knock sensor detects pre-ignition, it doesn't detect a rod knocking. It doesn't really matter if the motor has one or two knock sensors. If motor has two sensors they are daisy chained together

My theory was if the knock sensor was faulty, it would not detect the pre-ignition eventually leading to the engine chewing itself up. Not sure how 2 work. Is it a backup system or does one detect one side and one detects the other? I'm not sure what else would lead to the noise.
The other thing that would happen is when the knock would start up at around 3000-3500 rpm, the engine would begin loosing power and I would be lucky to keep it above 2500 rpm. I guess I'll find out in a few days once I get the engine torn down. Thanks.

 

[ESGWheel]

Does your engine have 2 sensors?

Diagram shows only one and i have never questioned it. I'll take a look next time i'm in there. As for 2 sensors: a lot of V8s in cars have 2 sensors, one for each bank, not a back up.

 

[alldodge]

My theory was if the knock sensor was faulty, it would not detect the pre-ignition eventually leading to the engine chewing itself up. Not sure how 2 work. Is it a backup system or does one detect one side and one detects the other? I'm not sure what else would lead to the noise.
The other thing that would happen is when the knock would start up at around 3000-3500 rpm, the engine would begin loosing power and I would be lucky to keep it above 2500 rpm. I guess I'll find out in a few days once I get the engine torn down. Thanks.

It would be vary hard to hear Pre-ignition in a boat. If it was heard it would more of a ping. If your hearing something like a hammer hitting the side of the block, then that's a knock and it comes from a rod

 

[ESGWheel]

Your original post highlights you were experiencing loss of power “for a while” prior to the knocking developing. One possibility is due to unnoticed low oil pressure the bearings were heating up excessively and thus binding causing the loss of power. Continued low oil pressure finally resulted in at least one rod bearing letting go, hence the knock.

Assuming your engine is still able to be run suggest two things: (1) using a mechanical oil pressure gauge check the pressure under a wide range of RPMs. Ensure the engine is warmed up for this check. (2) Then post that, with still a warm motor, do a compression test. Loss of compression is another reason for loss of power and would be nice to know what that is to help prepare for the rebuild > example if around 80 PSI in multiple cylinders may be looking at an overbore with new pistons.

Here is the point: a rebuild with a focus on only rod bearings may overlook other issues and once back together you are looking at repeating history.

 

[alldodge]

My theory was if the knock sensor was faulty, it would not detect the pre-ignition eventually leading to the engine chewing itself up. Not sure how 2 work. Is it a backup system or does one detect one side and one detects the other? I'm not sure what else would lead to the noise.
The other thing that would happen is when the knock would start up at around 3000-3500 rpm, the engine would begin loosing power and I would be lucky to keep it above 2500 rpm. I guess I'll find out in a few days once I get the engine torn down. Thanks.

It would be vary hard to hear Pre-ignition in a boat. If it was heard it would more of a ping. If your hearing something like a hammer hitting the side of the block

 

[ejnichol]

When you say "this website", are you referring to iboats.com?

The link didn't paste up. Here it is. Click on gas and scroll down ..

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