NB8A OIL PRESSURE GAUGE OPERATES IN REVERSE ORDER?

mx51982 · Postby **mx51982** » Tue Jul 20, 2010 11:40 pm

Hi guys, as some of you may have read in a previous post to a closely linked but different issue, i am having trouble with my oil pressure gauge operating when the ignition is switched on (all electrics activated), however it switches off completely once the car has been started..? Has something been put in the wrong way? Im not going to go into details as I have done so already, but just for those who don't know, I had the head reco'ed as a precautionary measure, and i don't think everything was put back properly. I have sought a mechanics advice, but i thought it was worth a try asking the many knowledgeable people on this forum.

Car is, MX5 NB8A MK1.

Thank you
mx51982

93_Clubman · Postby **93_Clubman** » Sat Jul 24, 2010 1:32 pm

On the early NA8 at least, there's only 1 wire that connects to the oil pressure gauge sensor, so it's not like it can be reversed - it's either connected to the sensor or not. The sensor itself is fitted to the block below the intake manifold toward the rear of the block. So check there's a wire attached to it, as the assumption might be because pointer activates, everything's connected, whereas pointer activation may simply be due to ignition on.

mx51982 · Postby **mx51982** » Sat Jul 24, 2010 7:22 pm

It's connected i know that much, could it be caused by the plug itself? Maybe changing would help..

Juffa · Postby **Juffa** » Sat Jul 24, 2010 9:28 pm

I'm puzzled (not hard). How do you mean the gauge is actived when the ignition is on? On my '92 the gauge didn't move until the engine was started and there was oil pressure. Then again, the later models are know to have a 'on/off' gauge that does not move with oil pressure. Make sure you have good contact between the pressure sensor on the engine block and wire to the gauge, this has been known to be a cause of bad readings on earlier models.

J.

mx51982 · Postby **mx51982** » Mon Jul 26, 2010 8:10 pm

[quote="Juffa"]I'm puzzled (not hard). How do you mean the gauge is actived when the ignition is on? On my '92 the gauge didn't move until the engine was started and there was oil pressure. Then again, the later models are know to have a 'on/off' gauge that does not move with oil pressure. Make sure you have good contact between the pressure sensor on the engine block and wire to the gauge, this has been known to be a cause of bad readings on earlier models.

J.[/quote
Ok maybe i can rephrase. The gauge activates when the ignition is switched to the auxiliary/on position, but not start. I may be using the wrong words as i cant remember the last time i looked at the markings on my ignition barrel. Basically when you turn the key to the point where all the electrics are switched on (before the motor has cranked over), the gauge comes on. However after the ignition is switched all the way until the car starts, the gauge immediately drops and seems to not be working.

Juffa · Postby **Juffa** » Tue Jul 27, 2010 11:14 am

Ok. Back to your original post. You mentioned the head being reconditioned and you alluded to other things happening/being done. I'd suggest checking that all electrical connections are good, i.e. make sure all plugs connections are good and tight, all earth connections have good contact with the engine head and body and the same for the battery connections.

If there is another thread where the alluded to items are mentioned then please link that here so we can get the bigger picture.

J.