After faffing about with the engine of my MX5 last week I had a petrol smell in the cockpit and it seemed the MPG had suffered.
Last night I rechecked where I had been poking and found an electrical connection adrift. It is the single spade female from the loom that connects to the spade male on the back of the plenum. The only other spade type connector in that area is at the back of the head. That one was undisturbed.
I have now re-attached it.
What is it? What does it do? Would this be responsible for the above fuel issues?
As it has been very cold/icy/snowy recently I decided not to take the MX5 out for a test after I reconnected the spade so can’t comment as to whether it has rectified my concerns.
I thought most earth grounds were bolted? This is a spade connector.
In the workshop manual - “LG/B (F)” in the wiring diagram (As can be seen from photo) goes to the “Thermo switch (Z-62)”
Now am I right in assuming the “LG/B” is light green/black? (As seen in photo)
I don’t know what the “(F)” part means
Thermo switch Z-62? I need to know what this is.
As far as I can see, electrical connectors to the cooling system on my car consist of one fan switch, on the thermostat housing (correct?)
One other water sensor (temp sensor for ECU?) on the flange at the back of the head (correct?) with another spade type sensor on the same flange just below that (dash temperature gauge?)
This might be nothing to do with the cooling system at all.
As it is attached to the plenum/fuel rail area - it’s a bit “tight” around there and I can’t reallly see what this spade female connects to - I’m of the opinion it might be something to do with the fuelling system. The car ran OK without it but, as I say, there seemed to be a fuel vapour smell in the cockpit and the MPG seemed to be down.
I wonder if it’s to do with the temp sensor, this keeps the ecu in warmup mode til the engine reaches running temp. If this is not connected you will be overfuelling when hot???
You might have something there, Jeff - this matches my symptoms of a fuel smell in the cabin - I only noticed the smell for the first time after accidentially disconnecting spade about four miles into a run. Overfuelling would also have a detrimental effect on MPG (Duh!)
Pretty sure these thermisters (2) are buried on the back of the cylinderhead on the 1.6. Certainly, when the green water temp thermister is defunct, mpg doesn’t really change. If anything, the engine will seem to run better when warm, not cold.
There is also the question if this is anything to do with the carbon canister purge valve; fumes from the petrol tank are taken up into the carbon canister sitting next to the expansion tank. Periodically, this is purged into the inlet manifold, to be burnt off. If this is faulty, the carbon saturates, and you’ll smell petrol. Change in fuel consumption might be coincidental; always gets worse at this time of year. A look at the spark plugs would indicate if you really are burning more fuel.
Yes carbon canister did suggest itself when I smelt the petrol in the cabin - first thing that came to mind, though was fuel leaking!!!
No fuel leak, though (thank goodness!)
I’ll check further tonight as it’ll still be light when I get home. I’ll try to give a better description of what the female spade connector actually connects to.
BTW, if carbon canister is saturated, would I be able to smell it around the top vents of the canister?
I’ve just looked in the daylight and it seems that the spade male is part of a small “L” shaped bracket that bolts to the plenum. No sign of any brass or insulator material there that would suggest a sensor.
I just had another look at the wiring diags, and see that the wiring to the thermo switch on the back of the head isBlue/white with Black/green. Your pic shows Black and Black /light green, it is not likely that a Black/light green wire would be earthed, all the earths that I can see on the drawings are Black single wires. There is at least one Black and Black /light green, but that’s to do with air con, wrong place in the engine bay, I would have said. I’ll have a look in my engine bay later today and let you know what I find.
whilst ya under the bonnet, get some ring connectors and some 8guage cabling, and put on a few more earths, i got about 3 off the battery going to various bolts in the boot and the battery clamp, 1 off the rocker cover to the bulkhead and inlet manifold to the inner wing (bolts already inplace) and it seems to idle and run a bit better (might jus be me tho).
(But I don’t know the 1.6)