Oil Pressure

[Nitropixie 0]

Hey guys

 

Ive been looking on the forum for something like this but can't quite finding anything with similar symptoms. Wondered if any could shed some light please.

 

I have a 1.9 gti with 128000 miles on the clock.

 

Basically I have finished fitting a megasquirt. I got it running ok and took it to a rolling road today for a tune up. Got the VE table sorted then went on to the Ignition table. We had been giving it some beans upto about 6500 rpm and the oil pressure gauge started to fluctuate, so we instantly killed the power and let it idle. The oil pressure went to the minimum and oil pressure light came on with the Stop Light showing. Turned it off straight away.

 

Obviously we didn't give it anymore power runs after that. We rolled it off the rolling road and rested it for a bit. I tried starting it again and the oil pressure went up back up but was quite erratic. It built pressure as the revs increased but at idle would dip very low til eventually the light came on again. As the oil temperature warmed up it dropped down more and more til there wasn't any pressure even with a little bit of throttle.

 

Now there aren't any knocks like the big ends have gone. I'm hoping its more of an oil pump problem, or maybe the oil pressure relief valve on the oil pump itself, but have a bad feeling its going to be the big ends. Hypothesis is as the oil thins it pushes past the bearings alot easier and the erratic oil pressure is the position of the crank in relation to the bearing and the bearing just isn't knocking/worn out enough yet too knock yet. I'm pretty sure its not a wiring problem as the light comes on when the gauge is low so both sensors are operating ok.

 

Yes there was oil in the engine, dip stick oil mark looked fine. It's recently had a new oil filter.

 

My next course of action will be to take the sump off and give the oil pump a good once over off the car. If i took a bigend off for an inspection can it be put back together or is this not advisable. Plus i've just found out gsf don't sell the oil pumps, boo!!!!

[welshpug 1,657]

I would change the oil for a decent branded 10w40 and a Peugeot/Citroen original filter firstly, then see what happens.

 

Oil pumps in general do not suffer from wear badly at all, which may well explain why GSF don't do them!

 

it wouldn't be a problem to take the big end caps off to inspect the bearings and journals as long as all the nuts and bolts were torqued back up properly and all the caps+bearings went back in the same place.

Edited November 12, 2009 by welshpug

[Nitropixie 0]

I had some comma 10w40 oil and camberley autofactors oil filter, whom i have never had a problem with before. I thought about changing the oil filter first to see what that does, hmmm, good point to start i guess before i drop the oil. Will pop over to gsf and get one of theirs.

[Nitropixie 0]

plus i only got 105 hp @ flywheel, boo!!! can't remember how many torques.

 

Will have to double check timing belt isn't a tooth out (not my fault) or something more sinister. Will do a compression test on the engine.

[philfingers 5]

if you're running the std gauge for oil pressure you really need to get a mechanical one in there. I have both running, both Tee'd off at the same point. On starting the Mi pressure rockets to 90-100psi, around 30secs later the std gauge has caught up! Switch the motor off and the mechanical ones dies instantly, the std one slowly thinks about it and falls. BUT std senders do play up.

Just be certain you've got an oil pressure problem first

[Nitropixie 0]

That is probably a good idea. Where did you get your stuff from for that setup or do you know what sizes are required??

[philfingers 5]

i got it from Merlin Motorsports.

Mocal 0-100 gauge was about £30, you then need (I think!) an M10 x 1.0 T piece and pipe work etc.

Give them a call, they should be able to sort you out. I guess you'd be looking at around £50 total

[Nitropixie 0]

Right so this afternoon i took the sump off to see what damage there is to the engine. I used a sieve when draining the oil to catch any metal bits and there was none.

 

Hmmm right, maybe they are all in the sump still so took this off and still none.

 

Tried moving the oil pump chain and it moved quite freely. Now i would of thought the sprocket for the oil pump chain would of been keyed, but it seems to just use the tightening force of the crankshaft pulley bolt to keep it sandwiched and not slip. Its all my fault as i put a 36-1 triggerwheel and the pulley bolt wasn't the tightest and didn't realise it would be a problem, more fool me.

 

My question now is should i get the sprocket welded onto the sleeve (which has the crankshaft oil seal over it) as the sleeve is keyed and it just makes more sense to me. There is a few mm of space between where the sprocket and sleeve would join, and where the crankshaft oil seal is. I can always get the weld lathed down a bit if its over.

 

Or is there a better designed sprocket and sleeve all in one design off another model????

[Tom Fenton 1,542]

Just do the bolt up to the correct torque and that is your problem solved. All 1900's are like it. For some bizarre reason 1600's have a keyed arrangement. But the 1900 version works fine if you do the bolt up properly.

[philfingers 5]

have a read of this

http://www.pumaracing.co.uk/

as to what you're going to do I'm not sure without seeing it really so wouldn't like to comment

[Nitropixie 0]

Tom - thanks for that. Would you happen to know if the 1600 sprocket is the same size as the 1900 oneand would it be a direct fit?? I know where i could get one.

 

Phil - i have had a flick through this before and it's very interesting. There is quite a bit of info there though to take it all in straight away.

[Tom Fenton 1,542]

I suspect the same but don't know for for sure. But why not just do the bolt up and its sorted, "easy".