Technical No Oil Pressure & Won't Start

[tinyfiat]

Car drove home fine after a 30min drive. Shortly later it refused to start. Battery is good and starter rotates but engine won't fire.
One sparkplug is good, other is not great but still sparks.

When I turn on the ignition, the oil pressure light DOES NOT light up.

Ordered new spark plugs and an oil pressure switch hoping it's just a simple fix.

Any ideas on how to further diagnose or possible causes?

Thanks in advance.

 

[Toshi 975]

The time to worry is when the oil light stays on when you Rev the engine so that could be switch , bulb or wiring. If the engine was running ok then I would start by checking the points gap, valve clearance , fuel pump etc

 

[tinyfiat]

Forgot to mention I have an electronic ignition.

 

[AndrewHarvey]

Pull fuel line to carb off.
Turn over with an assistant viewing that a healthy "spurt" is coming out
These cars seem to have an inherent restart when hot problem - that cars with electric fuel pumps seem to not suffer from....

 

[timgarman]

I had very low oil pressure recently.

Timing chain had already been replaced so we checked the gauge was working properly, tested with a mechanical gauge, no blockages anywhere. Then pulled the oil pump out. Found bigger gaps between the gears than the accepted tolerance suggested, so replaced the gears and primed them well with grease. Pulled the sump off and checked the crankshaft plugs which were ok. (Also made sure the new camshaft fitted the oil pump shaft – that's another story, see my thread "Oil Pump Gears.")

Removed the foreign body from the head :bang: and now have 3 bars :slayer:

 

[tinyfiat]

Already checked fuel line to carb and that was fine.

Hoping it's not the oil pump as that will mean a trip to the garage

 

[tinyfiat]

I have a Lumenition ignition kit, Optronic I think as there are some optical sensors in the distributor.

Is there a way to check if this is working correctly?

 

[AndrewHarvey]

Simply put a spark plug tester in before the lead connection to the spark plug
It will show whether you've got a spark or not
Available in halfords or on line

 

[Toshi 975]

If all of the components and wiring are correct on the oil light circuit the sudden loss of oil pressure could be due to one of the two core plugs blowing out from the side of the crankshaft. This immediatly looses all oil pressure. If you remove the sump after draining the oil you can inspect the crankshaft and when this happens you will find the core plug in the bottom of the sump. I have repaired one of these with the engine in situ with a new core plug.

 

[AndrewHarvey]

Or the switch is furbarred....

 

[tinyfiat]

The title for my thread might be misleading. The red oil pressure light on the dash does not illuminate when I turn on the ignition. It used to light up before now. So if the sensor is fine, I have adequate pressure before I've cranked the engine, which shouldn't be the case.

The oil pressure sensor is in the post so hopefully that will fix it.

Does the oil sensor merely indicate oil pressure on the dash, or does it play a role in controlling the engine too?

Haven't tested the electronic ignition as suggested earlier but from what I've read these things should be maintenance free. Does that go for the matching coil too?

 

[fiat500]

The oil pressure sensor does nothing except for complete a circuit from the oil-light to earth via its casing and the engine block. It does this when there is low or no oil-pressure, ie, when engine is stopped, idling when very hot or idling too slowly or with wrong grade of oil or no oil or very, very low oil.

From the point of view of this possibly being an electrical problem, assuming that there is a current to the oil light and the bulb is working, the fact that it does not illuminate means either the cable from it to the oil-pressure sender is broken or not attached to a terminal at one or both ends, or the sender is faulty, or the casing of the sender is not earthing. If the low petrol light is working and the ignition light is on when the key is turned, this confirms that there is a current at the bulb that indicates low pressure. It is possible that the earth-strap to the engine, which should attach to the securing-strap bolt of the dynamo and one of the nuts securing the rear panel, is loose or faulty. This might also cause non-starting.

 

[AndrewHarvey]

Try a jump lead between engine and a bare metal part of the car ,- bumper will do
Try it then
Also then pull off oil pressure connector and with help viewing lamp - touch it to the main engine or bodywork

 

[tinyfiat]

I'll have to wait a few days before any further attempts.

The starter turns fine so wouldn't that eliminate a bad earth?

 

[looigi]

Haha, you would think so, but no.

I once had a situation with a customers truck years ago. The engine started and ran fine, but the speedo started to wobble about madly while driving.

To cut a long story short, the engine was earthing through the speedo cable because the engine earth strap had busted. We found it quite quickly once I saw the red hot cable when we started it to go for a test drive!

Chris

 

[tinyfiat]

Here's an update as I tried a few things today.

Installed two new spark plugs with default gaps of 0.65mm - No joy

No jump leads so wired a cable between engine and body for earthing - No joy

Replaced the oil pressure sensor - Now the dash light comes on but still won't start

Battery voltage is 12.09v but also used a jump pack - No Joy

Checked fuses, one of the spade connectors was cracked so replaced it - No joy

After trying to start it all day I examined the NEW sparkplugs and 1st was clean but 2nd was sooty. This probably means something to somebody

:bang:

 

[fiat500]

Not hard to sense your frustration. I felt like that when accidentally, but unknown to me, got water in the carburettor and engine and took a day and a half to work it out.
The trouble is that even if your engine is now good to start it may be so cold and damp with unburned fuel that it's touch and go, even with a good, charged battery and clean electrics etc.
I think you have two options.
1. Follow through the logical starting procedure available in most Haynes manuals and eliminate everything as you go.
2.If you are confident of yours and the ability of a person towing you. try a tow start.
In the past, with other old vehicles, option 2 has always worked in these circumstances.

PS. A long shot but has worked for me. Take out the plugs and blowtorch the endsuntil they are unbearably hot, then somehow manouvre them back in without burning yourself or losing them down the cowling.

 

[Vitesse]

Does it fire at all when you attempt to start it?

Try taking one of your spare spark plugs connect it to the HT lead and rest it on the block so that the thread of the plug is earthing, then switch the ignition on and turn the engine over manually using a spanner on the nut on the end of the Dynamo shaft, see if you can get the plug to spark. You may have to rotate the engine through a full cycle just to be sure. Or you can do the same thing and just spin the starter via the lever and see if you get a spark on the plug. Make sure you switch the ignition off after you have done the testing or you could burn the coil out.

Tony

 

[AndrewHarvey]

Be absolutely sure you have a spark. The
Be sure there is fresh fuel spurting out of the pump every turn of the starter .
If above is good - think carb or tappets
If it "chunters" (obviously firing but erratically) but does not "catch" think timing

 

[Vitesse]

Just found this on another forum regarding timing maybe worth giving this a go. Obviously ignoring the bit about the points, as you don't have them.

Bryan Rylance was a bit of a guru in the classic 500 world.

"No matter what the issue is, having the timing incorrect is not going to help at all and will make it difficult to diagnose any other issues. Here's how to set the timing using a small bulb as a static timing light. This was shown to me by the late Brian Rylance and has made static timing a breeze, especially on a dark roadside!

Make up a test light as shown in the picture (apologies, I'm no artist!). Use a bulb carrier or just solder some wires onto a 20 watt car bulb (Brian reckoned 20W worked better than a smaller bulb as at 12V it cuts out without a fading glow so it is easier to get an accurate on/off position). Fit crocodile clips to the ends of the wires or if your coil uses spade connectors you can fit a male spade connector to one wire and female to the other.

1. if possible, remove spark plugs (this makes turning the engine both easier and more precise)
2. remove the the distributor cap and set the points. This may take a few attempts (if they look at all pitted then either remove and replace or repair as per Haynes).
3. turn the engine using the pulley until the timing marks are at 10 degrees BTDC and the rotor in the distributor is pointing roughly at the thin wire going to the coil and condenser. The number one cylinder should now be at 10 degrees BTDC.
4. the thin wire that runs from the coil to the distributor is the low tension wire. Disconnect it from the coil end and fit the test bulb into the circuit, as per the picture. Be careful not to short out the circuit - keep the bulb and connectors clear of the car and engine.
5. switch on the ignition (DON'T try and start the engine!)
6. loosen the nut that clamps the distributor slightly so that the distributor can be turned by hand but is still slightly stiff.
7. if the bulb isn't already lit, turn the distributor slowly clockwise until it lights up.
8. now turn the distributor very slowly anti-clockwise until the bulb goes out.

The timing is now set at 10 degrees BDTC on number one cylinder. Tighten up the distributor, turn off the ignition, remove the test light and reconnect the coil. Refit spark plugs, cap etc."