Club 80-90 Forums

Hi forum
1988 T25
Dg1.9 petrol
20-50 mineral oil


Did have a look over the forum but couldn’t find an exact match to my issue
Of an intermittent oil pressure warning that goes off once engine warm

Lasts for a few seconds and goes off and returns a few mins later then goes off again.

Engine sounds fine and no smoke, temp seems fine and doesn’t rise, oil looks good, no contamination

Will book it for a pressure test as a priority.
It hasn’t had an oil or filter change for a while so will have that done too

Will it be ok to get it the 5 miles to the garage?

In meantime will check wiring to sensors inc wiring blocks, earth and behind inst cluster
Thanks
D

Hi
welcome to the forum
looks to me like you already know the answers 

Visually check the wiring in the engine bay , pay particular attention to the twin white plug and socket With the two brown wires from the two oil pressure switches , near the thermostat housing just above the LH Head, they are known to go a nasty corroded green colour on the contacts 
also check the insulation on this wiring has not been damaged by either heat or chaffing 

replace the oil pressure switches 

change the oil ( 15w40 mineral ) and filter ( Mann W719/12) and if non of that solves your issue , a pressure test . 

 

Thanks for picking up on this

In peoples experience is the nature of the fault being intermittent an indication of a faulty sensor, wiring issue or even oil degradation I wonder?

Logic would suggest if the fault were mechanical it might be a continuous and regular alarm sounding.
Rather than Occasional sounding?
I will start with suggested actions and go from there, updating the thread in turn
Many thanks
D

Following this thread with interest! I had a new exhaust and oil pressure switch fitted yesterday - now I’m parked up on the Peak District trying to find an answer to the very same problem

KeithB wrote: ↑19 Sep 2020, 12:21 Following this thread with interest! I had a new exhaust and oil pressure switch fitted yesterday - now I’m parked up on the Peak District trying to find an answer to the very same problem

The oil pressure switch you need to locate is in the region of the water pump and Pulley.    This is the switch that will activate the Buzzer,   it should connect to chassis with the engine running.   If the wire to this switch has become disconnected then the buzzer will sound.    The spade terminal needs to be checked where the wire is crimped as the wire can break at this point. If this is the switch that was replaced it needs to be checked to make sure it is the correct type and normally open circuit, once the engine is started ith should connect to chassis.

The other oil pressure switch close to the pushrod tubes is for the oil Pessure LED.

 

When you say the warning goes off, does that mean the light and the buzzer ?

The "high" pressure switch is only functional when the revs are over 2000 rpm, oil pressure is lower when the engine is hot, and will rise when revs are higher, so maybe it is only going off in the 2000-2200 rpm range for example.

Couple of simple things you can so as part of the diagnostic

Firstly locate the "high" oil pressure switch, what colour is it. This "should" tell us what rating is currently fitted.
Secondly, remove the electrical connection and put it to earth - there is probably a spade on the dizzy. If the warning no longer goes off, then it's either the switch or actual low oil pressure.

Moving to a 15W40 oil will likely reduce oil pressure a little from what you have today, everything else being equal. Many people use / recommend that. Personally I use 20W50 and have also seen a 15W60 being recommended by ajsimmo

It's also possible that it is nothing more than a poor connection onto the spade on the switch (as Angeloevs suggested), so clean the connectors and give the connector a little nip before you replace it.

Ok will get the old switch out and figure out which one I need to get for a 88 bus seems like there are a few options: update just ordered the grey and white one as pretty cheap and just want to get going on it

I spliced a new wire and spade feeding it and still buzzer and light happening
Also cleaned up spade connectors as best I could
The alarm is now coming on pretty much instantly and not waiting to be warmed up so perhaps that is indicative of something?

J

Did you earth the cable as suggested ?

What happened ?

What colour switch is fitted at the moment ?

No haven’t had a chance to earth it yet
Haven’t got the switch out yet either so just ordered both so as to be able to get on with the work
Will update when I can get some time and part arrives
J

Ok earthed the switch off dizzy and warning light and buzzer still coming straight on...
Indicate possible bad connection behind inst panel or even faulty pcb?
Thanks again

Right, that's the important bit. Shows no problem with the switch or the actual oil pressure



I think you need to do a trace on that wire back to the dash, as a starter, possibly take a look at "relay" 42/43 - that's the DOPS logic / buzzer and associated wiring.

There are potential problems with the PCB and voltage regulator, but do the simple stuff first

Modules 42/43 are for the low coolant warning system.

There is relatively simple modification that reverts back to the earlier oil pressure warning fitted to pre 1987 vans.  This mod will have the warning led directly controlled by the oil pressure switch and dispenses/disables the buzzer circuit.

They are, brain fade, thanks for pointing that out, helping somebody else with that at the moment.

Best explain the mod you are thinking about..... snipping the green RPM signal wire, or something else ?

Thanks chaps
So currently looking at tracing yellow wire back?
I would say it does feel on the brittle side
Cleaned the spade connectors on the white connection block
It returns to a plastic box with cylindrical connectors, I guess I need to continuity check at each junction
Then

Check L shaped pcb?

Checked behind inst panel, no obvious Corroded connections there

No relays worth looking at here?
J

Where you have traced back to is known as the "junction box", and in there there are a couple of 7 pin round connectors.

Grab your wiring diagram from here http://syncrosport.com/info/wiring/

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