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Oil Pressure Sender

5753 Views 25 Replies 9 Participants Last post by  Beerman
At key on, engine off, the oil pressure gauge pegs on my '88 (VDO gauges). -eek-

Should read zero.

Even when the Oil Pressure sender is disconnected, it pegs.:confused:


Does the gauge read higher with MORE resistance, or LOWER with more resistance?

If the first scenario (meaning I have a duff sender or open wire), can I connect the sender wire to ground without blowing anything out? :facepalm


Will be checking continuity tonight or tomorrow...
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· Glutton For Punishment
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The connectors on the engine for the no pressure light, and for the pressure sender, are right next to each other. Perhaps you got them backwards? Pretty sure it reads no pressure if the wire is disconnected / open connection.
 

· Wingless Wonder
1988 Esprit Turbo, 2005 Elise BOE Supercharged
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7,033 Posts
Discussion Starter · #4 ·
The connectors on the engine for the no pressure light, and for the pressure sender, are right next to each other. Perhaps you got them backwards? Pretty sure it reads no pressure if the wire is disconnected / open connection.
Then I have a short. :mad: Getting 12 ohms on the white/brown wire when disconnected at the EHC (Engine Harness Connector, under the header tank).

At least I managed to take pics of the wire positions for these components. They MIGHT be backwards (I'm quite capable of that type of goof)...but if I should read zero at the gauge with the harness disconnected, I'm shorted. <sigh>
 

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By all means, you need to fix the gauge problem but on an initial start I like using a good, old fashioned, mechanical pressure gauge. That way I KNOW what is going on. Most electric oil pressure gauges will peg on low resistance to ground. Pull the sender wire at the gauge in the binnacle and see what happens. Chances are you got the other end by the motor either on the wrong spot or maybe the wire got pinched somewhere.
David Teitelbaum
 

· Wingless Wonder
1988 Esprit Turbo, 2005 Elise BOE Supercharged
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Discussion Starter · #6 ·
Update: Problem solved.


I found the pictures I took before disassembly of the engine. Hooked up the wires as pictured, verified that the EHC was fully together, and VIOLA! At key-on, the oil pressure needle just moves off it's resting place, and indicates zero. Just like it oughta.


I attached the pictures below in case anyone needs a reference in the future.


Pic are: sender and oil temp switch disconnected. Hookups of oil temp switch and sender. Views are from over the transmission, facing forward.
 

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· Wingless Wonder
1988 Esprit Turbo, 2005 Elise BOE Supercharged
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Discussion Starter · #8 ·
Hi Jim,

Might have been an improperly positioned wire (wrong terminal) or loose EHC.

Once the problem was observed, my helper ripped all the wires off the sender and oil temp switch. Arrgh. :facepalm So, it was unclear where they belonged.

My original tags had been removed by that time and we tried to look at the electrical schematics to hook up the wires but we were unable to find a way to I.D. which terminal was which, especially on the sender.

Only took about 20 minutes to search through all the pictures I had taken and find the original configuration... :mad:

That's why I posted the pics...might help someone in the future. :up:


(OR...I could blame everything on that leaf in the pictures, I dunno.) rotfl
 

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Old thread, new question here I'm hoping someone can help me with.

I'm making some changes to my Frankenlotus - '88 Esprit with 347 SBF stroker. Adding some gauges/information for monitoring the engine.

1. Regarding the oil status, the stock '88 Esprit has?
A. Oil pressure sender for gauge?
B. Low oil pressure sender for dummy light?
C. Oil temperature sender for gauge?

A, B, C....or some combination?

In Carbuff's pictures above, it appears there's an oil pressure sender for the gauge (the larger sensor) and also an oil temperature sender (the smaller sensor), is that correct? My '88 gauge cluster does not have an oil temp gauge.

Thanks in advance.
 

· Registered
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Some older pics here. Have about 1,000 miles on the car now. Engine has all the go fast bits. Did some dyno tuning over the winter. At the wheels: 406hp at 5,800 rpm/411tq at 4,250. The dyno video seems to be too large of a file size to load here - will try to put it up on YouTube and post a link.
 

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· Wingless Wonder
1988 Esprit Turbo, 2005 Elise BOE Supercharged
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7,033 Posts
Discussion Starter · #11 ·
The gauge sender provides readings for the dash. I suspect they are different among years, as the makers of the gauges and the values (5 BAR vs 7 BAR) were different. The original sender told the BOSCH ECU when the temp was more than 70 - 75C., in order to reduce cold idle.

Later 4 cyl cars DID have an oil temp gauge. Those parts may be a path to monitor the values that you want.
 

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Thanks carbuff, appreciate your response.

Still wondering the original question however. What are the two oil sensors in your pictures? Specifically:

1. Oil pressure sensor?
2. Low oil pressure warning sensor?
3. Oil temperature sensor?

Be great if you could shed some light specifically on that if you know.

Thanks
 

· Wingless Wonder
1988 Esprit Turbo, 2005 Elise BOE Supercharged
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7,033 Posts
Discussion Starter · #13 ·
Automotive tire Motor vehicle Electrical wiring Synthetic rubber Gas


The silver 'can' (red arrow) is the pressure sender for the dash gauge. This also is supposed to illuminate the OIL pressure warning light, but ours has never worked. (The tell-tale oil works at key on, engine off)

The lower piece (yellow arrow) is the oil temp switch.
 

· Wingless Wonder
1988 Esprit Turbo, 2005 Elise BOE Supercharged
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Discussion Starter · #15 ·
Also important to note is that they are not all the same, there are two different types depending on the year and on the gauge.
Yep, I mentioned that....

Does anyone have specs or pictures on newer cars that would help @Beerman ?

I remember seeing pics of a couple of newer cars from @Sanj a few years ago, on his now-missing 'Turbo SE' pages... might have been on a discussion of starters or something.



A local S4s owner replaced his failed pressure sender with this one:

Oil Pressure sender​
From Syracuse Diesel​
Datcon 107833 ( made by Stewart-Warner)​
price in 2012, incl. freight, was $82.50​

But I'm very sure that sender is for a 7 BAR VDO gauge, not the 5 BAR fitted in an '88 dash.
 

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Thank you gents, that's very helpful information.

One follow up if you know: is the "oil temp switch" a sensor for an oil temperature gauge? Or just a dummy light?

I know my particular '88 doesn't have an oil temp gauge, and I'm not aware of a dummy light. I'm installing a 2" VDO oil temp gauge in place of the turbo boost gauge (don't need that with my 347 Ford...), hence, the curiosity regarding the "oil temp switch."

Thanks!
 

· Wingless Wonder
1988 Esprit Turbo, 2005 Elise BOE Supercharged
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Discussion Starter · #17 ·
is the "oil temp switch" a sensor for an oil temperature gauge?
It is only a SWITCH, on-off. Actuates when oil temperature reaches 25C.

Look at the Service Notes section LF (for '88), Page 57 and 58. (Might be different pages on Section LD for you '86 - '87 HCi owners). The Low Temp Switch is shown near the lower - left corner of the sheet.



The low oil pressure idiot light (oil can with a drip :giggle: ) is directly below the speedometer, next to the yellow square, which became the Check Engine Light when GM MPFI was implemented. (Aren't you glad we don't have one o' THOSE?).
 

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Thank you Carbuff, that's super helpful. Much appreciated.

I'll take a look in the service manual - have that in the garage with a lot of greasy fingerprints on it.

I love my '88...the only thing that was kind of a drag in this engine conversion was the relocation of the rear brakes to outboard from inboard. That took a fair bit of engineering and thought and work. But otherwise, it's all been pretty manageable with time and patience and a bit of skill.

Thanks again.
 

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Later cars had an oil temperature sender located where the yellow arrow points in Carbuff's photo above, it's a fair bit smaller than the switch in his photo. You could repurpose the wire that goes from it to the dash to drive your oil temp gauge. I assume you'll be installing new senders on the V8 anyway? Are you keeping the factory oil pressure gauge, or???
 

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The silver 'can' (red arrow) is the pressure sender for the dash gauge. This also is supposed to illuminate the OIL pressure warning light, but ours has never worked.
The reason your light has never worked is because that Lotus saw fit to disconnect the light below 1600 RPM via the RPM relay to avoid scaring customers on hot days when the oil light started to flicker at idle. The light works, you've just never experienced low oil pressure above 1600 RPM!
 
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