Oil Pump Problem?

[Snowmark]

Just sent the day refitting a DG engine so that I can rebuild my DJ (Rebuild thread coming later this week). Anyway, all went well, fired up pretty much immediately but the Low Oil Pressure Light stays on.
I had originally fitted a VDO sender so swapped back to the oil pressure switch (black one) and the light was still on. I have tested the wiring as suggested in another thread - disconnect spade, ignition on - light goes out. Earth to engine, light on etc.

Therefore I suspect that it’s an oil pump problem. I (probably stupidly) fitted an oil pump from a scrap engine I had that I don’t know the history of. It was an aftermarket one and, with hindsight, wasn’t particularly snug and could be push fitted easily.

Before I remove all the things I fitted today to get to the pump, could it be anything else?

(Didn’t run the engine for more than 5/seconds with light on so hopefully haven’t caused any lasting damage).
Thanks for any advice


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[itchyfeet]

I suspect the sensor, they are blue now but 30 year old ones are black, it should be open circuit for the light to be out so if it's permanently closed circuit you will get this.

For the pump to be giving a genuine low oil pressure light it would be done below 0.25 bar which is unlikely even with a worn pump when cold.

Cold pressure even with a rubbish pump is likely to be 3-4 bar.

If you are working on it tomorrow you could swing by and borrow the gauge and a new blue switch if you like?

[Ciaraneng]

Are you talking about the pressure switch between the push rod tubes or the DOP one near the pump? If so, I believe it should be a blue (0.25Bar switching pressure) switch rather than a black (1.4 Bar switching pressure) one.

Also, if you have (or can borrow) an oil pressure test kit you could test if you really have low pressure by cranking it with the coil disconnected. I had a faulty pressure switch that gave me similar worries after a rebuild. I would rule out the pressure switch before going at the pump.

Finally, if you have low pressure at the switch between the tubes, did you fill the oil filter with oil before fitting? It might be an air lock between the oil pump and the oil pressure switch.

I'm a newbie myself so it would be good if a more experienced DG owner could confirm the above before any more cranking/starting/pump work.

[Ciaraneng]

I suspect the sensor, they are blue now but 30 year old ones are black, it should be open circuit for the light to be out so if it's permanently closed circuit you will get this.

For the pump to be giving a genuine low oil pressure light it would be done below 0.25 bar which is unlikely even with a worn pump when cold.

Cold pressure even with a rubbish pump is likely to be 3-4 bar.

If you are working on it tomorrow you could swing by and borrow the gauge and a new blue switch if you like?

Good stuff Paul. You got in ahead of me.

I didn't realise the 0.25Bar switches were once black.

[itchyfeet]

mmm having reread the post you has a VDO sender connected so essentially you have tried two sensors.

So as it ran for only 5 seconds you may not have pressure with a completely drained down pump and gallery, did you fill the oil filter with oil?

[Snowmark]

It is the low pressure one between the push rod tubes. I don’t think it’s a faulty switch as the light remained on when I originally had the fly lead and VDO sender unit in place.

I filled the oil filter before fitting and there doesn’t appear to be any leaks at this time.
I ran this engine all last year and have never even had so much of a flicker out of the light - I realise things can change once an engine is sat around, I just concluded it would be the oil pump.

I probably have a blue switch somewhere so I can check with a different switch once I get back to it - although so expect the same result as the VDO sender also showed a problem.

Possibly a basic question but, when I unscrewed the banjo bolt for the extension, should there have been any oil leakage? Because there wasn’t - does the switch sit higher than the oil level?




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[Snowmark]

Thanks for the offer, Paul - not planning on doing anymore on it until after I’ve been to yours on Friday......wouldn’t want this to distract from the task in hand!


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[itchyfeet]

Possibly a basic question but, when I unscrewed the banjo bolt for the extension, should there have been any oil leakage? Because there wasn’t - does the switch sit higher than the oil level?

about he same as oil level but not really relevant as this is in the high pressure gallery after the pump and filter, some oil will come out hot not much will come out cold as it's drained down.

Borrow the gauge Friday then.

Also can crank the engine with ignition disconnected to try and get oil pressure up first but often it won't with an empty system.

[itchyfeet]

Thanks for the offer, Paul - not planning on doing anymore on it until after I’ve been to yours on Friday......wouldn’t want this to distract from the task in hand!


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really?

get the 1.9 going first surely?

[colinthefox]

Which oil pump cover gasket is fitted? If it's a thick one the pump will never self prime due to excessive end clearance. The cover gasket should be 4thou IIRC, and the gasket kits I've seen have only thick ones.

[Snowmark]

Hmm, not sure - I guess the outcome is the same, still need to get to the oil pump.

Could well have been the ‘aftermarket’ thicker gasket I used....


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[itchyfeet]

Hmm, not sure - I guess the outcome is the same, still need to get to the oil pump.

I would try pumping some oil into the pump to prime it by removing the oil filter and squirting some in, worth a try and then fit a guage and crank with ignition off to see if some pressure comes up.

yes a thick gasket is not great for oil pressure but it may be OK and no point wasting too much time on this if you can get it primed and check pressure you may be able to live with it for the time it's in use.

I'd have to have a look to remember if it's the centre threaded spigot or off set hole but if you were to squirt oil in both it would help more because the other is the gallery.

you definitely didn't touch the oil pressure relief valve did you?

[Snowmark]

Pretty sure I didn’t .......because I don’t know where it is!
I assume it would just get disturbed by cleaning up the case etc?


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[ajsimmo]

I'd slacken off the oil filter, crank engine until oil leaks from filter, retighten then start up.

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[Snowmark]

[quote="ajsimmo"]I'd slacken off the oil filter, crank engine until oil leaks from filter, retighten then start up.

Thanks for the advice - fingers crossed it’s something as easy as this.




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