57 replies to this topic

[661]

Help please, again!

Reconditioned engine in my rebuild. Full of oil, filter primed, all connected up and ready to fire. Plugs out and turned many times ( to adjust the timing) but no oil pressure on the auxiliary gauge. The gauge works as grounding the wire to the sender raises the needle. Could be the sender I suppose but it's brand new and  additionally, when you take the oil filler cap off and turn it over I'd expect to see oil gushing around, all looks pretty dry up there.

Only other change in the build is that I replaced the oil feeder pipe from the filter housing for a flexible stainless jobbie but I can't see that that would stop the pump priming. Any thoughts. I really don't wont to start a dry engine!

[Guess-Works.com]

You need to prime the pump manually if it was not done by the builder...

Remove the oil feed pipe from the block put the car in 4th gear and push backwards while pumping oil down the hole with an oil can... The pump will then fill up with oil and create the necessary suction to bring the oil up from the sump...
 

[661]

Thanks, I pushed it back perhaps 3 car lengths, tried again and still no pressure. It took perhaps a kitchen funnels worth of oil. How far back and how much oil seems reasonable? Now I've turned it over, does the oil I put in no longer count and I'm starting from afresh?

[nicklouse]

sounds like you have primed the pump.

 

so other options. stuck pressure relief valve.  missing O ring between block and gear casing.

[nicklouse]

oh I also like to have a mechanical oil pressure I fit to the oil pressure take off for use when starting a fresh build as I know it works and get a "real" reading.

[661]

OK, after 40secs or so of gritting my teeth, we have pressure. Only 20 psi at turn over.

Engine was then started (small triumph in the build!) and again, 20 psi at idle and 40 with some revs. Is this enough?

[mk3 Cooper S]

.  missing O ring between block and gear casing.

+1

[Guess-Works.com]

OK, after 40secs or so of gritting my teeth, we have pressure. Only 20 psi at turn over.

Engine was then started (small triumph in the build!) and again, 20 psi at idle and 40 with some revs. Is this enough?

 

No.

[661]

•  

   

  OK, after 40secs or so of gritting my teeth, we have pressure. Only 20 psi at turn over.

  Engine was then started (small triumph in the build!) and again, 20 psi at idle and 40 with some revs. Is this enough?

   

  No.

   

   

  OK. Well that's that sorted then
• Correct grade oil, reasonably warm garage. Could I have an air block somewhere? I don't want to run the engine for too long other than to show off that it fires. Where best to start?

[nicklouse]

 

•  

   

  OK, after 40secs or so of gritting my teeth, we have pressure. Only 20 psi at turn over.

  Engine was then started (small triumph in the build!) and again, 20 psi at idle and 40 with some revs. Is this enough?

   

  No.

   

   

  OK. Well that's that sorted then
• Correct grade oil, reasonably warm garage. Could I have an air block somewhere? I don't want to run the engine for too long other than to show off that it fires. Where best to start?

 

air block no not possible. air leak very possible. the O ring I mentioned earlier. possibly a stuck oil pressure relief valve.

 

check the valve first.

[Guess-Works.com]

Honestly, I'd be pulling the motor out and giving back to who ever built it...

 

on a fresh build at room temperature you should be seeing 30-40 psi @ idle and somewhere up to 80 psi at speed...

 

You could check the oil pressure relief valve but IMO there's something wrong with the engine build.

 

or...

 

Put a mechanical oil pressure gauge on it, as the gauge may be lying

Edited by Guess-Works.com, 16 January 2015 - 04:00 PM.

[661]

Honestly, I'd be pulling the motor out and giving back to who ever built it...

 

on a fresh build at room temperature you should be seeing 30-40 psi @ idle and somewhere up to 80 psi at speed...

 

You could check the oil pressure relief valve but IMO there's something wrong with the engine build.

 

or...

 

Put a mechanical oil pressure gauge on it, as the gauge may be lying

Thanks Guys,

If the following assumptions are correct:

- missing that 'o' ring would create such a loss in seal that I'd get no pressure at all

- the pressure relief valve spring was dry so it would suggest no bypassing of the well seated, non scored cup (and I've just swapped it

  for the one off the old engine)

- if I can get hold of a mechanical gauge and the pressures are still poor

 

 

then.......the engine build is sh1te

??

Edited by 661, 16 January 2015 - 04:19 PM.

[Cooperman]

As above, check with a mechanical gauge.

Also check that the pressure relief valve plunger is not stuck slightly open. This can happen after a new build if a tiny piece of swarf gets stuck in or under the plunger. Make absolutely sure it slides freely with the spring removed and fully closes.

[661]

As above, check with a mechanical gauge.

Also check that the pressure relief valve plunger is not stuck slightly open. This can happen after a new build if a tiny piece of swarf gets stuck in or under the plunger. Make absolutely sure it slides freely with the spring removed and fully closes.

I'll try and tap my friends for a mechanical gauge on a 1/8th NPT thread.

 

How do I check the valve fully closes? It goes in fine, slides around, but I would of thought if it were slightly open oil would be on the spring when you dismantle it? I suppose I could squirt the cavity with some oil with the spring cup removed.

 

I have an awful feeling I'm delaying the inevitable realisation I've been sold a dud.

[Guess-Works.com]

The oil pressure relief valve works like putting your thumb over the end of a hose, not like a bleed nipple, so oil does not go past the thimble... If something stop the thimble moving from close, you end up with excessive oil pressure ( this usually blows the seal on the oil filter ), if the valve is stuck open then you end up with no oil pressure...