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Dry Sump F4R - No Oil Pressure



  172 Cup
Hoping there might be someone who can help out with the Formula Renault engine in my project car, which is basically an F4R but with a Renault Sport dry sump. I came to starting it up today and first cranked the engine without plugs etc to build oil pressure, but ended up spending the whole afternoon cranking and troubleshooting!

The dash read 0.2 Bar at first, but this didn't change at all whether stopped or cranking so I popped the filler cap blanking plug off and found little sign of oil around the cams. I probably cranked for 3 mins total in bursts of 10 sec but still got nothing.

Things I have checked:
Went to undo the oil filter and a fair bit of oil oozed out, so it seems to be making its way there OK.
Same story if I take the remote sender hose off the block - oil pisses out the hole.
I also took the hose off entirely and blew through it - no blockages - and oil will come out the end if I attach the hose to the block and remove the sender.
Took the return hose off the oil tank and aimed it into a pan - no oil coming through whatsoever.
Took the inlet hose off the pump to make sure I didn't do anything stupid like leave a glove in there - seems fine!

After I removed the sender it stopped saying 0.2 Bar on the dash and now just reads zero. I cranked for another 5 mins or so in 20 sec bursts and got absolutely nothing!

The sender is obviously a suspect but it definitely read 0.2-0.3 Bar the first few times I cranked, before removing it. I am suspicious that it didn't return to zero though, as the engine sat for some time without turning over while I checked things and scratched my head.

I'm out of ideas tbh, other than to keep cranking and hoping it eventually works. I've rebuilt a few engines and know sometimes it can take ages to get oil pressure, but this oil pump is gravity fed so I don't really see why it would be so difficult to prime!

Does anyone have any suggestions? Are there any things specific to the F4R that might make priming difficult, or any common things that get blocked internally? Has anyone got experience with dry sumped F4R or dry sumps in general?
 

NorthloopCup

ClioSport Moderator
If the system is/was bone dry, you'll need to prime the oil pump for definite mate. It sounds like the op relief valve could be stuck open, or its air locked and the pump isn't pumping.

Need to know if the pump is working first though. Once that has been ascertained, you can rule out if the pressure sender is faulty. Have you got a manual oil pressure gauge?
 
  172 Cup
Yeah this is where it all gets confusing, because this is a relatively simple thing.

I wet the oil filter before fitting, but didn't fill it; when I started to undo the filter, oil seeped out all the way round the seal, which to me indicates oil is reaching the filter.

I also took the pressure sender hose off and oil flowed out of there while cranking. I think the hole goes through to the main oil gallery (could be wrong though) so it seems like oil is reaching that bit OK too!

I took the pump apart when I rebuilt the engine but didn't touch the PRV as they're fixed from the factory. You can see the majority of it from inside the pump housing so I cleaned it all out.. didn't look like it was stuck open.

Seems like the pump is working to me, in light of the above.

The pressure gauge is part of the digital dash display. Not sure what the sender is from, but I assume some Renault parts bin thing!
 
  172 Cup
You can see the gauge (and the problem) in this video.

34727672362_8e8ce36742_b.jpg
 
  172 Cup
Yeah you're probably right and it makes sense to have one. Any idea who would have one in stock? Seems most places are online only for stuff like that.
 
  172 Cup
Well, a small update.. I can't get hold of a pressure tester but I'm pretty sure the sender is faulty. I span the pump with a drill until oil gurgled back into the tank through the return and got the gauge up to 0.8Bar, but then it stayed there and didn't go back down. So I disconnected and reconnected the plug on the gauge and it now reads 0.1Bar and won't budge.
 

NorthloopCup

ClioSport Moderator
Well, a small update.. I can't get hold of a pressure tester but I'm pretty sure the sender is faulty. I span the pump with a drill until oil gurgled back into the tank through the return and got the gauge up to 0.8Bar, but then it stayed there and didn't go back down. So I disconnected and reconnected the plug on the gauge and it now reads 0.1Bar and won't budge.
Senders fucked then by the sounds of that. Blast it with brake cleaner and an airline blower mate. It may have some s**t in there - ya never know. We have this happen from time to time.
 
  172 Cup
Update.. I went off and bought a mechanical dash gauge ILO buying a tester, and the short story is: zero oil pressure. It took me 3 mins of constant drilling on the pump pulley to get oil all the way up the capillary tube to remove all the air, then by the time I had screwed the gauge on the end all of the oil had drained out from the bottom up!

I also removed the oil filter to check for blockages and about a litre of oil poured out the sandwich plate while the filter was off, so I think that's just the tank draining through gravity as there can't be that much oil in the engine.

I suspect the PRV is stuck open as there's definitely a flow of oil from tank to engine, just no pressure. Annoying as it's the one thing I decided not to rebuild while the pump was apart.
 


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