Oil Light NOT flashing at start-up

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Oil Light NOT flashing at start-up

Postby chris7ian » 26 Jun 2017, 12:32

The 'test' oil light flash before start-up ,with the key in the first position, doesn't always flash.

Sometimes it operates as expected, other times nothing. In those instances I either wait or turn the key off and try again until it eventually flashes it's test sequence.
Obvioulsy this is far from ideal as I'd never want to risk driving the bus if the light fails to perform... Any advice what to check - loose connection somewhere? BUt where?! :shock:

thanks
1989 2.1 MV auto
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Re: Oil Light NOT flashing at start-up

Postby bigbadbob76 » 26 Jun 2017, 14:25

First place I'd look is the connection to the pressure switch between the cylinders on the left side of the engine,
you may need to remove the tin plate that protects the pushrod tubes before you can get at it.
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Re: Oil Light NOT flashing at start-up

Postby chris7ian » 26 Jun 2017, 14:25

Thanks, will do
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Re: Oil Light NOT flashing at start-up

Postby itchyfeet » 26 Jun 2017, 16:32

bigbadbob76 wrote:First place I'd look is the connection to the pressure switch between the cylinders on the left side of the engine,
you may need to remove the tin plate that protects the pushrod tubes before you can get at it.


exactly, second place to look is where this short brown wire joins the loom ( 2 pin connector by black box) I had a break in the brown wire once had to replace it.
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Re: Oil Light NOT flashing at start-up

Postby AngeloEvs » 27 Jun 2017, 21:46

Worth pointing out that the OIl LED is driven off the DOPS circuit (Dynamic Oil Pressure System or better known as BOD- Buzzer of Doom) which supplies the pulses to cause the LED to flash. (DOPS introduced on post 86 models). It may be a connection issue between the BOD PCB and the ribbon cable connector to it (located in the instrument cluster) or the LED making poor contact in the socket. On pre 86 models the LED was directly connected to the oil pressure switch.
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Re: Oil Light NOT flashing at start-up

Postby chris7ian » 18 Jul 2017, 09:12

Thanks all, I've been on holiday since posting so I've only just around to taking a look. I've had a quick wiggle of the wires at the Oil Pressure Switch which seemed to fix the issue... until the next time it was started up. It could've also been a coincidence since leaving the key in position one for a bit has sometimes had the same result! :D I've yet to look at the ribbon connector in the dash pod

Anyway, whilst I'm down there I figured I might as well renew the switch itself but I don't know which of the four colours sold by Brickwerks is the one I need as I've not removed the old one yet, so my question is: Does anyone know the correct switch for a 1989 2.1 MV engine?

Blue 0.25 bar [3.68 psi]
Grey 0.9 bar [13.23 psi]
Black 1.4 bar [20.58 psi]
White 1.8 bar [26.46 psi]

Thanks
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Re: Oil Light NOT flashing at start-up

Postby kevtherev » 21 Jul 2017, 06:13

chris7ian wrote:Thanks all, I've been on holiday since posting so I've only just around to taking a look. I've had a quick wiggle of the wires at the Oil Pressure Switch which seemed to fix the issue... until the next time it was started up. It could've also been a coincidence since leaving the key in position one for a bit has sometimes had the same result! :D I've yet to look at the ribbon connector in the dash pod

Anyway, whilst I'm down there I figured I might as well renew the switch itself but I don't know which of the four colours sold by Brickwerks is the one I need as I've not removed the old one yet, so my question is: Does anyone know the correct switch for a 1989 2.1 MV engine?

Blue 0.25 bar [3.68 psi]
Grey 0.9 bar [13.23 psi]
Black 1.4 bar [20.58 psi]
White 1.8 bar [26.46 psi]

Thanks
c7
Isn't there an information piece on brickwerks switches?
Its blue for petrol.


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Re: Oil Light NOT flashing at start-up

Postby ajsimmo » 21 Jul 2017, 07:09

It's the blue switch (low pressure, normally closed) between the pushrod tubes that makes the oil light flash when you turn on the ignition. I'd recommend changing that one 1st, then look at the wiring to it.

The other switches you list are the different options for the normally open high pressure switch (for the DOP circuit (BOD)), which is located in the front of the engine under the water pump pulley.

If your engine is in tiptop condition (ie it maintains 2bar oil pressure at 2000rpm, even when well above the 80°C test temperature) then it's the white one. But many engines struggle to achieve such high pressure at high temperatures when middle aged, so the black switch is then the one - high enough switching threshold to give a meaningful warning if pressure suddenly drops, but not so low that it's too late! The grey one is half the recommended pressure, so is only useful for an engine on its last knockings. If you need that one to stop your BOD, it's really new engine time.

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Re: Oil Light NOT flashing at start-up

Postby chris7ian » 25 Jul 2017, 13:20

Thanks guys - I found the article on Brickwerks after posting (I should've updated the thread) https://www.brickwerks.co.uk/brickwerks ... -switches/
ajsimmo, very useful info thanks :ok Thankfully no buzzer yet, just the intermittent test flash issue
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Re: Oil Light NOT flashing at start-up

Postby chris7ian » 06 Feb 2018, 10:46

OK, Update: So I've had the oil pressure switch replaced but I still have the intermittent oil light test on the dash on start-up... It seems to work when the weather is damp which leads me to believe there is a loose connection in the wiring
Someone suggested the flexible PCB is to blame, but as other than this the electrics work perfectly well I'm not so sure...
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Re: Oil Light NOT flashing at start-up

Postby itchyfeet » 06 Feb 2018, 13:03

more likely the wire at the switch end as it's not usually damp under your dash! Replacing the switch is worth doing to rule it out but the wire is just as old, if it does not connect you don't get the light.
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Re: Oil Light NOT flashing at start-up

Postby ajsimmo » 07 Feb 2018, 07:20

The flashing oil light isn't part of a test sequence, it is just showing low oil pressure because there isn't any until the engine turns. Turning the ignition on and off until you get a light isn't fixing anything, it just means you have an intermittent fault which is most likely a bad connection (it could also be a faulty DOP circuit board, but I've never seen that happen). The blue ribbon printed circuit on the back of the dash is fragile and prone to damage if it's been fiddled with, so that's a possibility. Particularly check the point where the black DOP connector is attached, back top of speedo side. I've had to hard-wire that bit before to get a working oil light. Or it's on the engine wiring. Thorough methodical testing is what's needed here.

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Re: Oil Light NOT flashing at start-up

Postby itchyfeet » 07 Feb 2018, 07:32

The flashing light is a test of the low pressure switch circuit because it's normally open with engine running so if the wire falls off you would not know without looking for the light before starting.
More important with early engines and only one switch.
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Re: Oil Light NOT flashing at start-up

Postby hightop ratty » 07 Feb 2018, 10:14

My old engine red light used to flash continuously (my 2.1 petrol on carb) - but the temp guage worked fine.

I changed the spade thingy behind the dash (otherwise the temp guage didn't work).

Picking my van back up on Friday - with the shiny new rebuilt 1.9 petrol engine - can't wait is understatement :-)
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Re: Oil Light NOT flashing at start-up

Postby ajsimmo » 07 Feb 2018, 21:46

hightop ratty wrote:My old engine red light used to flash continuously (my 2.1 petrol on carb) - but the temp guage worked fine.

I changed the spade thingy behind the dash (otherwise the temp guage didn't work).

Picking my van back up on Friday - with the shiny new rebuilt 1.9 petrol engine - can't wait is understatement :-)
That's a different flashing red light on the temp gauge. We're talking about the oil light, which flashes on a late, and steady on an early (and it's not a test).

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