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Spiff

Momentary loss of oil pressure. Z24et

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On two occasions now I have had the oil light not going off after restarting the engine while hot. No oil pressure was also verified by the pressure sensor feeding the ecu. 

I also reviewed some log files and found one occasion where oil pressure dropped momentarily and then picked up again right after starting it cold. This didn't go low enough to trigger the oem oil light switch though but still went from 500kpa to 30.

Anyone know where to start looking? 

It's a newly assembled engine with new oil pump(hv one). 

I have shut it down and after restarting it oil pressure is fine(however this morning it had to be started two times before oil pressure returned to normal. 

 

I need to change the oil and filter this weekend and I'll probably pull the oil pump too. Anything in particular I should be looking for?

 

I haven't lost pressure during driving or higher rpm I should add, only on idle right after starting it 

 

Edited by Spiff
typo

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 What is the oil pressure when driving? Normal is 345 to 450kpa.

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2 hours ago, datzenmike said:

 What is the oil pressure when driving? Normal is 345 to 450kpa.

 

I seem to have made a comma mistake in my original post. Edited that now.

When warm (oil temp around 80c) pressure is about 70kpa on idle

220-250 at 2000rpm rising to about 400-420 at 3000rpm

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10 PSI???? that's low!!!!!!!!!! I had a very worn L20B that had 17 at hot idle with the original pump and 29 with the high volume pump. Do you have the original oil pump?? If so fit it on and check again.

 

 

Low pressure...

 

Oil pick up tube loose or screen part plugged. Was gasket used between pick up and block?

 

EXTREME clearance between main and rod bearings allowing pressure to bleed away.

 

'Bad in the box' oil pump. Try another. Pressure relief valve stuck partly open?

 

Oil pressure gauge or sender bad.

 

 

If 10 PSI or 70  kpa @ idle I wouldn't be driving this till fixed.

 

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Yes, it's basically making the same pressure as the junkyard unknown mileage z20 I pulled out of the truck. So I asked about this because I've read the ka pump seems to bump up the pressure as well a little bit but several people said no you're good. Its more volume, not pressure. So I don't know anymore. What I know is a loss of oil pressure is definitely not good. 

 

Rod bearings where replaced so they should be good. 

I was asked about the oil pickup as well but I think if it was loose or anything a loss of pressure should show up during driving/higher rpm too? 

I'm gonna inspect it with a boroscope when I drain the oil. 

 

Bad pump i have considered, it really seems like the most obvious cause doesn't it?

I checked that the rotors where the bigger type but didn't dvelve deeper into it, but it seems like something regulating the pressure sticks or is open or something. So I'm thinking I'll pull it and see if I can spot anything. Unfortunately I don't have easy access to a new one. Need to order from the US or something.

 

Sender seems unlikely as its a brand new honeywell sensor and the oem pressure switch is also new and that they both fail and start working again at the exact same time on different circuits would be pretty wild.

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Don't you have the old original oil pump?? This would take 10 min to swap and try. 

 

Engines bleed oil. Through all the main and rod bearings, through oil jets at the timing gear and out of the cam bearings and the lobes. This amount of bleed is pretty much constant no matter the RPMs. The pump can only supply so much volume and much of it bleeds away so the pressure can't build. As the RPMs go up so does the volume supplied and as the amount of bleed stays the same... the pressure rises until it reaches the limit of the regulator spring and pushes it and the piston ahead of it, opening a path for the oil to be sent back to the inlet of the pump. Excess oil just goes round and round drawing just enough oil from the pan to maintain a steady 50-65 PSI. I've had a relief valve become jammed with a piece of casting flash. It couldn't open, and the pressure easily blew the oil filter at the seam. You can stack washers under the spring to increase the pressure but this does nothing for lower speeds and idle. Higher pressure will force more oil past the bearings to cool them, there is that, but only if the pump can provide enough volume to make that pressure. In racing generally 10 PSI per thousand RPMs run at. Your engine is not likely to see more than 6K so the stock pressure is more than adequate.

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Unfortunately I don't. But the thing you mention about casting flash is something I have read about while searching the net, well maybe not exactly casting flash but the regulator getting stuck on non oem pumps. 

Whatever it is, if I find something I'll be sure to update this thread. 

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This was the mid '80s. I did an oil and filter change on my 521 on the weekend. Monday I drove to work, mostly in town with about 4 miles of highway and then back to in town driving. When I got to work oil light came on and oil everywhere and filter split open. Went to the local chain store and told them what happened and no questions asked they gave me oil and new filter and I drove home. Same thing filter exploded. Now I know it's no freak accident. I sat and thought about it and took the oil pump off and disassembled it. When I removed the relief spring the piston was stuck with a small chunk of casting flash jammed in it. I scraped it off with a butter knife, put together and all was fine.

 

In town the pressure was lower than when revved up on the highway. Either way very lucky it didn't seem to harm the engine.

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i use the melling pumps but i do take them apart and deburr them as you can break chunks off with a pick if you try hard. might not come off from oil flow but better be safe.

id pull the relief valve out and make sure it moves ok. if it doesnt bind up great and throw a couple little washers behind the spring while your at it for a little more pressure.

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I use used KA pumps that I know were off working engines.

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Yeah we didn't really get any ka's over here. Nearly all the trucks where diesels, s13 and 14 had the ca or Sr. So rockauto is the place for me. I see they have hitachi, Melling and a couple of others. The hitachi is marked as "actual oem part", is that right? 

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All the ones I've seen have the Hitachi symbol on them.

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the melling ones are their own casting, and have either m90 or m111 on the side of them. they are cast iron and not aluminum like the hitachi/oem ones.

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1 hour ago, scooter said:

the melling ones are their own casting, and have either m90 or m111 on the side of them. they are cast iron and not aluminum like the hitachi/oem ones.

Is this a bad thing or a good thing? 

 

Back to my engine; I drained the oil today, could not see anything blocking the pickup. The pump however.... 

Follow this link for pictures of the rotors and regulator piston https://photos.app.goo.gl/cXwkDL6Wxw3zH1HB7

Looks like someone has tried to run gravel through it. I also see signs of rust so it's clearly been stored dry for a long time. 

The regulator piston was hard to remove, like it was catching or sticking. 

Also turning the pump over by hand you feel it catching on a couple of places as you turn it. 

 

The oil was also shimmering, sadly all that glitters is not gold but I guess that is to be expected with carnage like this. 

Cut up the oil filter too and found some small metallic pieces in it. Also found tiny pieces of rtv and generally a lot of crap in the filter, I guess that doesn't help with pressure either... 

 

 

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Here is a log from today as i started it. you can see the oil pressure fluctuating very much. Perhaps because the oil is cold the pressure gets so high the regulator piston gets pushed back and sticks before it works loose again and the cycle repeats untill the oil/engine gets warmer??

Or something is blocking the inlet or something. I don't know...

oljetrykk.png

 

 

I'm thinking I'm gonna replace the oilpump, new oil and filter and cross my fingers and say a little prayer.... There might be damaged bearings, there might not be, It's not making any abnormal sounds (yet). So we'll see how that goes..

Edited by Spiff

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Looks like high volume pump. I see some scratches.

 

Regulator should be free to move but have a spring. Find out why stiff to move  because this is likely the random low pressures.

 

Scratches could be from engine blowing up in the past and the pump ingesting chunks. Then rebuilt with old pump. Wouldn't be a big stretch of the imagination to assume a chunk is stuck in the regulator.

 

I never use RTV in any amount that it would squeeze out inside the engine and end up in the pan. Probably over use on valve or oil pan surfaces.

 

 

Inspect the bore of the relief valve see why sticking and fix.... better yet replace. Even if just a regular pump. It will be safer than total loss of the engine due to oil starvation.  

 

 

Scratches???

2kZws9l.jpg

 

I pulled this pump from a KA powered S13 engine and took it home only to find this when I took it apart. The pump would barely turn by hand. I went back and rolled the engine over and there was a rod through the side of the block.

 

Why use an aluminum casting? Well it's very unlikely the rotors will jam and snap in a soft metal and in addition hard particles can embed in it also just like a soft rod or main bearing.. 

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29 minutes ago, Spiff said:

Here is a log from today as i started it. you can see the oil pressure fluctuating very much. Perhaps because the oil is cold the pressure gets so high the regulator piston gets pushed back and sticks before it works loose again and the cycle repeats untill the oil/engine gets warmer??

Or something is blocking the inlet or something. I don't know...

oljetrykk.png

 

 

I'm thinking I'm gonna replace the oilpump, new oil and filter and cross my fingers and say a little prayer.... There might be damaged bearings, there might not be, It's not making any abnormal sounds (yet). So we'll see how that goes..

this the pump thats in question on church of L series right now on facebook and ive allready replied my thoughts on there... NFG.

 

as for iron vs aluminum.. its arguable. I say the iron is better because the tolerances stay tighter cause iron doesnt grow like aluminum. one could argue aluminum is better as there could be less chance of galling or siezing because the aluminum acts like a "bearing". The aluminum pump is also lighter than the iron one if your trying to shed as much weight as possible.

 

 

Edited by scooter

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13 minutes ago, datzenmike said:

Looks like high volume pump. I see some scratches.

Regulator should be free to move but have a spring. Find out why stiff to move  because this is likely the random low pressures.

Scratches could be from engine blowing up in the past and the pump ingesting chunks. Then rebuilt with old pump. Wouldn't be a big stretch of the imagination to assume a chunk is stuck in the regulator.

I never use RTV in any amount that it would squeeze out inside the engine and end up in the pan. Probably over use on valve or oil pan surfaces.

Inspect the bore of the relief valve see why sticking and fix.... better yet replace. Even if just a regular pump. It will be safer than total loss of the engine due to oil starvation.  

Scratches???

I pulled this pump from a KA powered S13 engine and took it home only to find this when I took it apart. The pump would barely turn by hand. I went back and rolled the engine over and there was a rod through the side of the block.

Why use an aluminum casting? Well it's very unlikely the rotors will jam and snap in a soft metal and in addition hard particles can embed in it also just like a soft rod or main bearing.. 

 

I'm carefull with rtv myself as I have experienced it almost blocking the oil screen of my old motorcycle, some of the pieces where red rtv but I haven't used any red rtv so It must be something that has been somewhere in the engine from before.

I tried to rub the bores and rotors with a fine wet sanding paper but it didn't help, the pump is still really hard to turn by hand.

I wonder; if it's hard to turn by hand, surely it's gonna put an extra load on the engine? could it affect idling if it's sticking enough? I have had a hard time dialing in the idle on this, I'll put it at 800rpm and it'll run fine there and then some other time it's barely staying alive... 😕

 

I've ordered a new one now, fedex usually take a week or so from the US.

 

11 minutes ago, scooter said:

is this the pump thats in question on church of L series right now on facebook?

 

as for iron vs aluminum.. its arguable. I say the iron is better because the tolerances stay tighter cause iron doesnt grow like aluminum. one could argue aluminum is better as there could be less chance of galling or siezing because the aluminum acts like a "bearing". The aluminum pump is also lighter than the iron one if your trying to shed as much weight as possible.

 

Yes I've posted about this on that group too

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the Melling is made in USA . They seem ok as I ran one also but cant find where I put it but its a HEAVY.!!!

I say get Hitachi if possible..My 1st L motor I have done I used a USED oil pump and its still good.

 

My 521 I have 195K miles on this one

Edited by banzai510(hainz)

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 Should spin easily by hand empty.  I've used an electric drill to spin them up to pre lube an engine before starting. The little amount of effort to pump oil at idle is almost nothing.

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1 hour ago, datzenmike said:

 Should spin easily by hand empty.  I've used an electric drill to spin them up to pre lube an engine before starting. The little amount of effort to pump oil at idle is almost nothing.

 

Yeah nah this is not by any means easy to spin by hand. Damn I regret tossing the z20 pump now 😛

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Never throw away 'stuff'. Dump it somewhere under cover where you can find it if you really look for it.

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UPDATE:

Been a while but after i got the new oil pump I also decided to check the big end bearings and also the timing chain tensioner looked weird from underneath so I poked it and it fell out, this prompted the timing cover to be removed and basically the tensioner was so far out I decided to order a  new timing set, along with rod bearings. Waiting for parts from the US took a couple of weeks.

I got it all together today and everything seems to be in order, so far so good. Oil pressure is constant and about 1 bar higher than it used to be with the old pump. Timing is also tighter and doesn't drift when I lock the timing like it used to. Also seems to be less noisy. Will be going for a test drive tomorrow, fingers crossed!

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On 11/15/2019 at 3:19 PM, Spiff said:

UPDATE:

Been a while but after i got the new oil pump I also decided to check the big end bearings and also the timing chain tensioner looked weird from underneath so I poked it and it fell out, this prompted the timing cover to be removed and basically the tensioner was so far out I decided to order a  new timing set, along with rod bearings. Waiting for parts from the US took a couple of weeks.

I got it all together today and everything seems to be in order, so far so good. Oil pressure is constant and about 1 bar higher than it used to be with the old pump. Timing is also tighter and doesn't drift when I lock the timing like it used to. Also seems to be less noisy. Will be going for a test drive tomorrow, fingers crossed!

any update on what the bearings looked like?

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