Oil Pressure Oddness

[eeyoreish 892]

Normally my Esprit takes a few seconds (maybe 5-10 max)  to register oil pressure on the gauge at startup after a few days. From what I've read that's normal so I just let it idle until the gauge registers then everything's fine. 

On Thursday I noticed that (a) the gauge took probably twice as long to register pressure and then (b) when it did the gauge is reading higher than normal. Not right up to 7 bar but around 6. Still varying with engine speed a little as usual but generally much higher than I'm used to.

I read a few posts here about loose sender wires so I've checked and cleaned both connections even though nothing was loose. No change. Oil is up to level and has been throughout.

Any ideas? Duff pressure sender seems the next logical move unless anyone has any other suggestions?

[CarBuff 200]

First, try correcting the ground path to the sender by loosening/tightening one of the bolts holding it to the engine block.

[eeyoreish 892]

Thanks, I’ll give that a go. So far I only checked the 2 spade connectors on top.

Can the sender be removed completely without losing any oil? Engine off obviously...

[CarBuff 200]

No, don't remove anything.

 

Just restore a good earth connection by backing off ONE bolt (reached from underneath) a flat or two. Repeat a couple times. Wiggle & jiggle! 😊

 

(It's the dissimilar metals thing.)

 

 

++++++++++

 

There are parts substitutions for the 7 Bar sensor (at least here in the USA).  If needed I could dig them out of my pile of Esprit trivia.  💪

[eeyoreish 892]

5 hours ago, CarBuff said:

There are parts substitutions for the 7 Bar sensor (at least here in the USA).  If needed I could dig them out of my pile of Esprit trivia.  💪

That would be great if you could please. Just in case... SJ want about £70 for one!

In the meantime I'll try loosening and jiggling the bolt ☺️

[CarBuff 200]

OK, here's the info I saved. It was posted in 2012

<<<This was a sender for a Carebont gauge from an S4s ...still 7 bar.  (yours would be VDO)>>>

 

Quote

 The gauge is a 0-7 bar gauge.  7 bar = 101.526 psi, so I reasoned that I'm unlikely to find a 0-7 bar sender, but I could find a 0-100 psi sender, which is close enough.

 

What I found was this:

Oil Pressure sender

From Syracuse Diesel

Datcon 107833 ( made by Stewart-Warner)

price in 2012, incl. freight, was 82.50 and it's worked perfectly ever since.  Price from US Lotus sources was $120.

 

Syracuse Diesel: 315-463-8573

EMAIL:

syrdiesel @ yahoo.com 

Address:

5975 Court Street Road

Syracuse, NY 13206

here's their web site:

http://www.syracusedieselandelectric.com/syracuse-diesel-products/

 

 

 

[eeyoreish 892]

On 17/09/2018 at 12:29, CarBuff said:

No, don't remove anything.

Just restore a good earth connection by backing off ONE bolt (reached from underneath) a flat or two. Repeat a couple times. Wiggle & jiggle!

 

Had another look at this today. I don't seem to have any fixing bolts as such, the sensor itself has a hex on its stem suggesting it is screwed into the block?

What I did find is a plastic ring hanging round the base of the sensor. You can just see it in the left of the first pic. The second pic is after I removed it. Seems to be some kind of brittle plastic or resin. Logically it must have dropped off the underside of the sensor even though the underside looks ok with a mirror. Does this still mean the sensor is naffed?

The same symptoms persist. Yesterday I let the car idle for over a minute before the gauge came up but once the gauge is registering up I'm getting good pressure even when idling hot. After a short park up the pressure registered much quicker, probably 10 secs.

Does anyone know if the pressure light is wired through the gauge or sperately from the sensor? I'm asking because my usual 'what did i do just before it started to go wrong' question reminds me that I onbolted the binnacle during fitting of the new coolant pipes. Maybe it's a gauge connection issue?

[CarBuff 200]

The sender is screwed into a mounting 'base' which is then screwed into the block.

The attached picture has the number 3 on the sender. Those bottom bolts directly under the sender are the ones I suggested to fuss with. You can even reach them from the underside without removing the engine...

[eeyoreish 892]

Because it looks like proper access to the sender is impossible without removing the starter or oil filter I'm favouring getting a new sender unit before I dive in, then at least I can replace it and eliminate it as a cause of the problem. The broken sealing ring also makes me think the sender is probably past its best...

As I'm not happy paying £80 for a sender from SJ I had a look round and turned up this VDO 0-7 bar sender on eBay for £22.50. Does anyone see any reason why this won't do the job? I assume (maybe wrongly) that thread size and pitch is common?

https://www.ebay.co.uk/itm/VDO-TYPE-10-1-teeth-7-Bar-OE-VDO115607-Ford-Bmc-Oil-Pressure-Light-Switch/182861125447

The SJ one seems to be weirdly marked '1.2 +/- 0.15 bar'. Not sure why??

[fjmuurling 66]

The 1.2 +/- 0.15 bar marking is the switchpoint value of the pressure switch.

[sailorbob 266]

This thread suggests the OE sensors are either 0-5 bar or 0-10 bar and the parts manual range of 0-7 bar is incorrect.

Also, that eBay sensor doesn't appear to be VDO as the vendor states 'VDO type'.

[eeyoreish 892]

Thanks Derek. Hmm.. tricky.

My car is a '90 with a 7 bar VDO gauge so perhaps different to the later cars? The Deroure parts list does indeed list the sender as 0-7 bar. Looks like the eBay one at least has the right thread size.

Not sure why Lotus would use a 10 bar sender with a 7 bar gauge?

[eeyoreish 892]

So today I removed the oil pressure sender to see what reference numbers are on it in the hope of finding a new one that isn't nearly £100... It is marked on 5 of the 6 hex nut faces with:

30/127

0-10 bar

1.2 +/- 0.5 bar

B082N6062F (matching the parts list for a 0-10 bar sender)

12.89 (I assume the manufacturing date since my car is a 1990)

Theres no reference to VDO on it, and I wonder if the presence of the Lotus part number stamped on such a small and apparently generic component could mean that it's a Lotus specific part??

I'm not even sure this is my problem but it seems the logical place to start. I'll do some Googling but any help identifying a cross reference would be appreciated! @swindon_alan This is your kind of challenge!?

 

[swindon_alan 1,693]

Hello @eeyoreish Neil. Ummm, this is a tricky one! I've had a trawl and a look around and I think the part number for the sender is probably VDO 360-081-030-127C, going by the VDO catalogue numbering system. That's taking the reference from your description. However, that doesn't exist anywhere on the Internet which makes me think that it probably was a special for Lotus from VDO, particularly as it has the Lotus part number on it. I would think it is to do with the specific warning light switching value. So the spec we are looking for is:

Pressure range: 0-10 bar
Warning contact: 1.2 +/- 0.5 bar
Thread: M10 x 1 conical short (I'm guessing at this from the above - that's 11mm length on the spec which does sound VERY short!)

The closest in the catalogue are the -039C which is a bit low on the oil pressure warning light and the -041C which is high (probably not a bad thing!) but has knurled contacts:

 

Either way, you're probably up in SJ dosh territory if you want genuine VDO. You can probably find lookalikes of the two above on eBay like you did for the 7 bar one which would do to test if it is the sender causing the oddness (ignoring the warning light mismatch for now). They all look as though they have the same sender resistance range.

Lotus parts manual info for reference:

[eeyoreish 892]

Thanks @swindon_alan, brilliant as ever and very helpful info. I had a blunder about on the internet yesterday for the Lotus part but no luck apart from SJ. Looks like it might still be available from Lotus too if I want to spend £191! I'll have another trawl round using your info but like you say I might well end up at SJ anyway...

Having read plenty on TLF and the Excel forums yesterday about slow pressure build on the gauge it seems the possible culprits are:

• Faulty sender - easiest and first thing to try
• Worn distributor O ring - allows air to be sucked in, reducing pressure. I'll order one from Lotus and swap it out
• Oil pick up strainer blocking up - would be a more gradual problem I think?
• Olive on the Oil Pick up pipe worn/broken - allows the pump to suck air as well as oil, slowing down the build up of pressure
• PRV in the oil pump is sticking - preventing pressure building properly. 

The last 2 are the most likely I think given my reasonably sudden symptoms, although pressure has always taken a few seconds to rise at tickover so there could be some other contributing parts like the dizzy O ring. 

Replacing the pick up pipe olive requires removal of the sump and auxiliary housing (therefore cambelt too) so that's a much bigger undertaking. It also means I should address the valve clearances and cam tower oil leaks at the same time leading to a much longer off the road period. Can the sump be removed with the engine in place??

For now I'll swap the sensor and dizzy O ring and see where that gets me...

[mdw 283]

Yes the sump can come off with the engine in place.  I had a £5k lotusbits rebuilt engine and from first start up  that also was slow to build pressure so I guess they all do it. Its a bit worrying  but in the end I just used to keep an eye on the pressure when hot at idle and 3.5k rpm and forget the rest otherwise I would have never started it.   I also found it odd just how long it took for the oil to warm up   ( from  the cooler hose at the front).   But without a thermostat it was running through the coolers from start up so cooling from the moment it started. 

 

[eeyoreish 892]

Yes, mine's always been a bit slow (a few long seconds) which I read was kind of normal so I've lived with it until now. But on the last few drives it's taken over a minute of idling before the gauge has registered anything. Hence I suspect something 'new' has happened.

It's the slightly higher running pressure that's got me foxed, hence I'm considering the sender as at least part of the problem. New dizzy O ring on order and trying to track down a reasonably priced new sender of the right spec.

For the moment I'm reluctant to drive it until I've at least got it back to where it was.

[CarBuff 200]

When I start my engine, there is an subtle change in engine sound when the oil pressure starts to build. (slightly quieter)

 

If you can hear this difference, and the gauge is reading zero, then I would suspect that you are right about it being a gauge or sender issue.

 

Of course, the proper way to verify is to connect a mechanical oil pressure gauge and see what THAT reads.  When I was questioning my gauge's reading, I hooked the mechanical gauge in at the oil feed braided line, right at the turbo. (The braided line is to the LEFT of the #3 on my picture of Sept 29)

[eeyoreish 892]

So last night I ventured an email to the VDO technical helpline and today I (surprisingly) received a reply from them. They can't identify the original 30/127 part number but they offered up this as the closest replacement. 

At 1.35 +/- 0.15 bar it looks pretty close to the original 1.2 +/- 0.5.

@swindon_alan what do you think? Could be a goer?

Is it definitely M10*1 thready that I need??

Still looks like £70 from VDO though unless I can find one elsewhere 😩

[swindon_alan 1,693]

I saw that one Neil, but it is a parallel M10 thread and not tapered? It looks tapered in the S&J pic but that might just be my eyes. If there''s no washer or gasket then it will be tapered I think. That one is the same price as the other two above, even from the one Latvian supplier on eBay.

[swindon_alan 1,693]

PS I really would go with Atwell's suggestion @eeyoreish Neil, this universal jobbie is under £20 and you can screw it into the oil pressure switch/transducer thread and watch the gauge while someone starts the engine for you. You can reuse it in the future/lend it to me and then it is money not wasted.

[eeyoreish 892]

Thanks Alan, good spot on the thread, mine is  indeed tapered!

That pressure gauge looks handy so I think I'll probably invest in one of those before I spend £80 on a new sensor I might not need.

[eeyoreish 892]

Test gauge bought. Hopefully at the weekend I'll be able to find out if my gauge is lying to me. If it isn't, I'll have saved £60 but will have a bigger problem to solve...🤔

Thanks for all the advice so far. I'll post an update after I've run the test.

[eeyoreish 892]

Today I replaced the distributor O ring. The old one was flat and brittle and there was a weep of oil by the dizzy so it needed changing for sure.

Connected up the manual gauge and started her up. First start after a couple of weeks and the gauge rose to about 4 bar after 10-15 seconds. Not bad. Turned off and restarted  straight away, again pressure in just a few seconds. Left it for an hour and went back to start it again, this time idled for a minute and still no pressure showing on the manual gauge 😡

Conclusion is then that it's not the sender but something else. I don't understand why it built pressure the first time unless it's a sticky PRV..?

Anyway, I've now started to strip it down to remove the auxiliary housing and inspect the oil pump, PRV and pick up pipe/olive. It's cambelt off time so a PITA of a job, drop oil, drop water, remove carbs etc etc...

Recent house sale falling through means I'm not in the mood but it ain't going to fix itself.

 

[CarBuff 200]

Could you sense a difference in engine SOUND that would indicate if the oil pressure actually was building?