Author Topic: Merc 135 v6 1986 Oil sensor  (Read 3496 times)

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Offline UKMike

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Merc 135 v6 1986 Oil sensor
« on: August 04, 2018, 01:59:03 PM »
Hi one and all,

Can someone tell me exactly what the "Oil sensor" that's mounted on top of the oil mixture pump on my 1986 merc 135 v6 does? The part numbers is 12430A4. It is a sensor and it links in with the Oil warning module but I can't seem to find out on exactly what it reports on or how it works, I assume it runs off the rotation of the oil pump spindle. Does it judge how much oil is mixed? I thought the marks on the pump set that mixture.

Thanks again in advance for sharing your knowledge :)

Best
UKMike
« Last Edit: August 04, 2018, 02:12:15 PM by UKMike »

Offline UKMike

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Re: Merc 135 v6 1986 Oil sensor
« Reply #1 on: August 04, 2018, 02:21:20 PM »
Please see attached sensor:

Online Hyperacme

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Re: Merc 135 v6 1986 Oil sensor
« Reply #2 on: August 04, 2018, 03:21:57 PM »

Offline Plugcheck

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Re: Merc 135 v6 1986 Oil sensor
« Reply #3 on: August 04, 2018, 03:38:00 PM »
Just some digging from the internet, it appears to be what you thought it was, a sensor to monitor the oil pump turning.  Used in conjunction with other sensors to insure engine is receiving lubrication.  Can't  find any info if the sensor reports amount/pump speed versus RPM.  Are you having issues?    I'd bet Rich knows more about the system, maybe he will comment.
Michael
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Online Hyperacme

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Re: Merc 135 v6 1986 Oil sensor
« Reply #4 on: August 04, 2018, 05:03:34 PM »
I know the V6's have/had a plastic gear that drive's the oil pump.
Was / is a problem spot.

Offline UKMike

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Re: Merc 135 v6 1986 Oil sensor
« Reply #5 on: August 05, 2018, 02:28:18 AM »
Thanks guys,

That's totally answered my question. It appears that the electrical plug item I was asking about monitors the rotation of the pump somehow and is there to sound the alarm should the pump stop working, it's nothing to do with the amount of oil mixed with gas, that's set by the throttle linkage. So when my alarm went off the other day a couple of times it would suggest I need to replace the spindle and plastic cap end that is used for the connection to the spindle, it must be wearing out.

Thanks again all, you've saved my skin, I would have kept running it and could have blown my pistons and alike.

Thanks again  8)

Offline Retro Performance

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Re: Merc 135 v6 1986 Oil sensor
« Reply #6 on: August 06, 2018, 07:23:21 PM »
I think the sensor monitors rotation only....in a failure the system produces a rapid beep...in a low oil condition (engine mounted tank) the system sounds a slow beeping and in an overheat the system sounds a constant tone.....I think thats right but my memory is as old as me.
« Last Edit: August 07, 2018, 06:03:11 AM by Retro Performance »

Offline Rich_V174SS

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Re: Merc 135 v6 1986 Oil sensor
« Reply #7 on: August 10, 2018, 09:40:35 PM »
Sorry I'm late to the game. The sensor does monitor rotation of the oil pump spindle. These engines had a plastic worm gear on the crank shaft that would often break causing the oil drive shaft to stop rotating. Replacement of the worm gear would mean having to tear the engine apart to get to it. If I remember right I think the warning system compares pulses from the sensor in relation to pulses from the ignition switch box to determine it's rotational speed in respect to engine rpm.
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Re: Merc 135 v6 1986 Oil sensor
« Reply #8 on: August 10, 2018, 10:11:17 PM »
Think it would have been cheaper to replace plastic gear with a metal one then to add a sensor ..
Guess not ?

Offline UKMike

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Re: Merc 135 v6 1986 Oil sensor
« Reply #9 on: August 11, 2018, 03:41:00 AM »
Thanks all,

I have bought the metal gear but hadn't realised it would mean stripping the engine down to replace it, need to find out how to do that as otherwise I have no option but to premix :( I've also purchased a new sensor and new oil warning module and can try with those new things, guess only time will tell.

Thanks again for all the input :)

Best
Mike

Offline aquamaniac

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Re: Merc 135 v6 1986 Oil sensor
« Reply #10 on: August 13, 2018, 06:13:14 PM »
Mike,

If the plastic gear on the crankshaft is damaged, those broken plastic pieces are inside the engine. Even if you decide to remove the oil injection you should tear into the powerhead to clean out the debris.

Weren't you going to "rebuild" this engine?

I believe that if you remove the oil pump drive shaft you can inspect the worm gear on the crankshaft for damage.

Offline UKMike

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Re: Merc 135 v6 1986 Oil sensor
« Reply #11 on: August 14, 2018, 12:27:37 PM »
Thanks and yes ill take a look first, I am rebuilding her to part but am really worried about trying to break the the seal between the cylinder head and the block, this is because I'm worried that it's been together from new and I have no doubt that the main studs will be solid, so if they get sheared off in the block when trying to break the unit in half I have real big issues which could leave me in a position where I need to buy a new motor, we just can't get these motors here in the UK, even the parts need to be sourced form the states so something as simple as a nut and bolt can take weeks to arrive or may well not even be available any more. I found that out when I split the lower unit to put in more mounts...

Thanks for the advice though and I will check underneath the oil mixer to see what the status is before I do anything else. :)