David Jenkins
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| posted on 3/5/05 at 09:31 AM |
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X-flow oil pump pressure-relief valve query
I believe that the oil pressure relief valve in my x-flow oil pump is sticking - it's been giving me 85psi on the gauge instead of the 65psi I
should have (stuck shut?) and now I can't get more than 20-ish psi (stuck a little open?).
I haven't heaved it out of the car yet (too many domestic duties this last weekend  ) but I'd like to check it, hopefully fix it, and
put it straight back on the engine in one session.
The question is, how easy is it to get the valve piston out? From what I recall, the mechanism is held in by a steel disc with a hole in the middle,
presumably crimped to the sides of the hole. If I strip it down, will I be able to fix it back in again properly, or will I need any special tools or
knowledge?
Bl**dy annoying, as the engine itself is starting to pull like a train now and I want to get out and play! 
rgds,
David
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David Jenkins
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| posted on 3/5/05 at 01:58 PM |
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What... no-one got an opinion? That's a novelty! 
DJ
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viatron
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| posted on 3/5/05 at 02:50 PM |
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Not 100 % but i am not sure that it is possible to replace just the pressure relief valve, IIRC you have to change the whole pump out.
Mac
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britishtrident
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| posted on 3/5/05 at 03:02 PM |
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From my Elan days I seem to remember it is staked in --- I think not a major problem but you might not need to strip it anyway soak it in
"Gun Wash" celulose thinners for a couple of days.
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Craig81
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| posted on 3/5/05 at 07:43 PM |
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Hi dave,
im still only getting an indicated 30 psi on mine, May be my relief vavle is sticking too!!!!!!
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clbarclay
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| posted on 3/5/05 at 07:47 PM |
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65 psi sounds way to high too me. according to haynes manual the minimum oil pressure for a 1600 @ 2000rpm is only 21 psi, so 30 would seem about
right too me.
[Edited on 3/5/05 by clbarclay]
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David Jenkins
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| posted on 3/5/05 at 08:19 PM |
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I forgot to mention - it's a high-pressure pump! Nominally 65psi - obviously varying according to revs, but 65 is the max (or should be,
anyway). Although my pressure dropped while I was out and about, I knew that 25-ish psi was just about adequate so I drove home carefully - very
annoying being overtaken by tin-tops!
Thanks for all the comments - hopefully I'll get the pump off tonorrow, and at least I'll be able to prod the piston to find out whether
it's sliding smoothly or not. If all looks OK, then it's into the engine I go...
rgds,
David
[Edited on 3/5/05 by David Jenkins]
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David Jenkins
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| posted on 4/5/05 at 07:15 AM |
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5750 - 6000 max - I haven't got any fancy rockers or anything else like that, so I'm sticking to the book max revs. I've taken up
Wallage's recommendation for an uprated pump, as I intend to work the engine quite hard...
I'm now fairly convinced it's the pump, as the relief valve is the only thing that could cause the pressure to rise so high - even if the
oilways were blocked I should still only see 65-ish psi (and I was getting oil everywhere round the engine - I looked under the rocker cover after the
dodgy run).
Tonight will tell...
cheers,
David
[Edited on 4/5/05 by David Jenkins]
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David Jenkins
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| posted on 7/5/05 at 08:49 PM |
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Update
Now I'm confused...
Took the pump off and, sure enough, the pressure relief valve was stuck. Freed it off and now I've got 75psi again (still higher than
it's supposed to be, but maybe my gauge is wrong).
What I'm confuzled about is how the relief valve actually works - when you look into the pump from where the filter sits, the valve piston is
normally fully extended into the pump cavity. Presumably this means it's in its 'no bypass' state. When the pressure comes on I
guess that the spring gets compressed, the piston moves towards the mounting face, and some oil is allowed back to the input side of the pump. Is
this right? Anyone got an exploded drawing or something? It's beginning to annoy me!
Anyway, it was stuck in the full bypass position, which explains why I had very little oil pressure.
cheers,
David
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