Fuel System O ring question

[Bercilac]

I've been trying to track down a poor hot and cold start problem on my 280s and found a crumbling pressure regulator O ring in the metering head (Kjet).

The only O rings I have in stock are Nitrile aircon items (green, same colour as the original one that was mashed up), one of which was the perfect size and has got me going again.

Trouble is I don't now if these are really petrol resistant and have not managed to find any info on the Web. I'm leaving one in a jam jar soaking in fuel to see if it dissolves or starts to break up but I though I would ask here if anyone knows.

I have found this: "Nitrile (also known as NBR rubber and Buna-N) is the seal industry’s most widely used and economical elastomer. This is partly because it displays excellent resistance to petroleum-based oils, fuels, water, alcohols, silicone greases, hydraulic fluids." but does that apply to modern fuels that contain 5% ethanol?

[phillpot]

Looks like 5% shouldn't be too much of an issue?



Useful Website ...... Polymax

[Olas]

This compatability chart shows that Viton is compatible with 100% ethanol, so the 5% present in our current fuel is not an issue or reason for concern.

https://www.calpaclab.com/viton-chemical-compatibi...

[Bercilac]

That's brilliant info, thank you.

[v8s4me]

Leave the O-ring in a jar a petrol for a few days. If it comes out in one piece it will be fine.
Simples

[Bercilac]

Four days in a jam jar of Esso's finest and there is no sign of melting O ring :-)

[v8s4me]

No Ethanol in Esso stuff.

Why not try a jar of supermarket pee and see if there's any difference? And when you've finished you can use it as hand wash. Covid-19 vs petrol? There can be only one winner

[chrisch77]

Olas said:

This compatability chart shows that Viton is compatible with 100% ethanol, so the 5% present in our current fuel is not an issue or reason for concern.

https://www.calpaclab.com/viton-chemical-compatibi...

But OP doesn’t have a Viton O ring, he has Nitrile....

[Bercilac]

7 days into operation soak yer ring and the Nitrile is winning. I went for a jar of Tesco's finest, fortunately people can't stockpile petrol as easily as bog roll :-)

[v8s4me]

Bercilac said:

7 days into operation soak yer ring and the Nitrile is winning. .......

Bercilac said:

....... fortunately people can't stockpile petrol as easily as bog roll :-)

You can bet some idiot somewhere is!

[KelvinatorNZ]

If you wanted a proper replacement, These are a direct fit, https://www.deloreango.com/nz/hot-start-o-ring-kit... (PN 102807A if the link doesnt work)

[Bercilac]

Thanks KelninatorNZm great tip. Looks like the Renault engine in the DeLorean has plenty in common when it comes to fuelling. I always fancied an electric DMC.