Long post so sorry…
One thing that will kill the fuel pump is loss of flow due to debris within the tank blocking the in tank fuel filter while the pump is being commanded to pump fuel… Such causes the pump to overheat because of lack of fuel flow. The pump dies but there should be evidence of such crud within the tank and crud within the sock filter as well as evidence of pump overheating if the pump is dismantled.
Fuel pump voltage issues may also have similar overheating evidence to that of fuel starvation when a pump is dismantles. Such can occur when the fuel pump connector pin is dodgy as in the photo I posted. The only difference is that tne fuel in the tank won’t have crud within causing a blocked fuel filter.
Chemical (liquid) contamination, like paint stripper (yes it occurred), water, or too much alcohol won’t really kill the pump as it will still flow through the fluid which will cool the pump (unless the contamination turns the fuel to jelly but that’s easily seen). Such contamination would cause issues for the smooth running of your engine but the fuel condition is easily determined with a dealer fuel test kit (which can cost for $100 to $300 odd and almost all dealers would have in-house). One can even use a clean 2ltr bottle of coke which you fill up from the tank and then let sit for a while to see what condition it’s in, look for stratification or rubbish floating within. Bad fuel is generally easily determined in-house and uses little if any shop disposables.
Picking up a bad batch of fuel isn’t uncommon. So the question you should ask yourself is when did you last fill up before dropping the car off at the dealer. If it was some 200 or 300 kms before you dropped the car at the dealer, it’s not likely it’s a fuel issue
If you filled up the day before and have only done 20km, you may not yet know of the bad batch of fuel you bought
I really doubt that the dealer dropped the tank and crud fell into it during removal (unless your car is covered in mud and they were basically stupid careless). But even if stupid careless, i’d think they’d do something to fix their pooch screw as it’s easy to do when the tank is on the ground.
Can a dealer drop a full tank of fuel. Well with a car on a hoist you can unbolt an engine which is resting on a cart and then lift the car further up and roll the cart and the engine now sitting on it free and clear away, so yes a dealer with a hoist can do lots of stuff DIYers at home can’t Including dropping a tank full of fuel. But more than likely they’d just pump the fuel into other containers and make the job easier… if they do such, the question would be were the containers clean or was that where the contamination came from
Being that the tank was removed to fix the fuel sender, and it cost $1k? just for the removal and reinstallation, I’d have asked them to check the tank intervals and the fuel sock for debris and taken appropriate action to clean/replace stuff depending on what they found. In fact the a good dealer should have suggested such. And given that the connector pin is a known defect, you’d expect that the dealer would carefully inspect the connector whenever the ability to do so arrises.
Loosing trust with a dealer makes life hard but I’d hope going forward they’d fix the exhaust, diffuser and the other underlying issues they should have spotted (and you could have checked if they just discussed it with you at the time the tank was dropped). But who knows what happens when and if they get their back up… many businesses don’t like to own up to pooch screws.
Whatever the case, I doubt getting an off site fuel analysis would be helpful (since the dealer kit is generally enough for most fuel contamination issues and when listed on a dealer service invoice is enough for insurance companies to accept a claim). A full on fuel test requires a 5 litre sample and can cost around $1000 and can be useful in small claims court. So I wonder what type of fuel test they are doing an who’s going to pay for the test
Going forward I’d be playing my cards close to my chest and getting them to offer info on what they’ve been doing… Often they forget what they've said and walk themselves into an admission at which point you’ll have the, by the short and curlies.
But keep cool and realise it may have been bad fuel all along, if not the connector issue.
It’s sad hearing about your problems but it’s why I’ve started to service my car again after one dealer had the front tire at 10pm i after ticking ”checked tires and tire pressure” on the invoice and another dealer finished their work without tightening the brake lines on ten abs unit (leaving me with no brakes at the first traffic lights)…
Hope you get a good outcome and all issues are resolved without cost to you.