Anyone here had experience with old fuel/fuel varnish? This volvo 960 I picked up had sat for God knows how long. The fuel gauge didn't work, so I pulled the sender and it was completely gummed up, the pump also didn't work. The tank is actually full of fuel, and I'm not sure if it's old or not as the car actually starts/runs (the in tank pump is only a lift pump). Should I drain the tank, or just add heaps of additive? Would you do anything else?

Marvel Mystery Oil and add it to tank.

I'd drain that old crap out. Also change the filter.

>>28496507 (OP)
That's not normal looking to me. I've never had this problem even on old cars where the gas was known to have evaporated but if I did I would drain the tank and flush it with starter fluid or some other solvent. For that sending unit I'd just hose it down with brake cleaner until it was moving good and you can get all the gunk out.

>>28496538
Filter will be changed.

>>28496582
I spent ages today fixing the sender, I had to physically scrape a layer of varnish off these contact points. I tried just spraying it with solvent, but it wasn't enough

>>28496507 (OP)
there's a bunch of chemicals you can try, the dangerous ones work well.
imo, if at all possible, just sidestep all of this
get a new tank, pump, filter, fuel hoses.
and blow a bunch of brake clean through the hardlines
and after you install everything, put a gallon of fuel in and hotwire the pump , with the engine end hosed to another container, just for the extra flush.
also clean your injectors and injector rails.

In my limited experience, lacquer thinner seems to cut through gasoline varnish the best, just make sure it's dried out before you seal it and put gas in it.

>>28496507 (OP)
Do this: >>28496622
>get a new tank, pump, filter, fuel hoses.
Its not worth the time and effort to fix all of that. The old gas tank is likely rusting too.
It reminds me of these videos I watched of a guy fixing an old truck that had old fuel that turned into varnish and he tried replacing the fuel pump and it didn't work out in the end:
https://youtu.be/fvhbZzISaGI?t=760

https://youtu.be/7_rJrORU36A?t=3460

>>28496773
It's a plastic tank. If it was rusty I would consider replacing it, but even removing it is a real mission because of the IRS. I'll buy a bottle of injector cleaner today, and try running it undiluted on this to see if it actually works.

>put fresh fuel in
>rev the fuck out of it

>>28497426
That's all I've been doing to it anyway lmao, probably get some extra power if it's running fuel from this decade.

>>28497420
anon, i promise you, swapping out a tank is a lot cheaper and a lot easier than getting a new engine.
don't be a retard, take the L, swap the tank/pump/filter/hoses.

>>28496507 (OP)
B12 chemtool will work. You need anything with pea.

Update:
I broke the sender while reinstalling, added 4x the amount of petrol additive, I took the car out for a good thrashing on some gravel roads, now I have a transmission code. Hell yeah.

>>28498329
You're supposed to ease a car back onto the road, retard, hammering down right after making it run just breaks shit that would have come back with a normal drive.

>>28498329
Appreciate the update. Good luck /o/non