The car has WAY over 200k miles on it but like many of the old 240's, the odometer quit working long ago. I figure it has closer to 400k. The fuel pump has no undercoat on it. This was a california car, and then spent 8 years in Columbus, Ohio where the salt rusted the heck out of it. It is the rustiest 240 that I have seen (underbody is soo rusty) and the fuel pump/filter are of course super rusted looking (I know that the pump is aluminum).

It started and I drove it home with no issues. I will try the jumper trick at the fuses to see if it does it again. I have driven 240's for 40 years, and have never had to replace a fuel pump. I had some kroil at work and got up under it and sprayed the bolts down so when I do pull it, it may be easier to get the rusty bolts to break. Yes, I always carry a fuel pump relay, an AMM, and the ignition module that bolts to the drivers inner fender. Thanks guys!

"MMO wouldn't touch that part of the pump anyway, right?"

It would, but I agree with Phil, it couldn't harm it. If the maker suggests adding it to fuel, he knows it will surround the brushes and commutator of all fuel pumps.

Also with Phil on checking the wiring terminals before suspecting the pump. If they look good, you could "test" for a bad spot on the commutator by using a jumper wire, with fuse 4 removed, from B+ at fuse 6 to the left side of fuse 4 socket. Repeatedly make the connection listening to be sure the pump motor starts every time. Assuming it is the original Bosch pump, I would think it could last a whole lot more than 200K miles, but then again, it can be abused by fueling habits and long time without a lift pump.
--
Art Benstein near Baltimore

"Technically, Windows is an 'operating system,' which means that it supplies your computer with the basic commands that it needs to suddenly, with no warning whatsoever, stop operating." -Dave Barry

Hi,

It would help if we knew about how many miles are on that pump or on the car itself.

Checking the fuses and having that good relay was very smart of you!
Owning these Volvo’s will always be a good practice to have that kit!
Be glad you don’t have the newest cars as all the pumping stuff is inside the fuel tank and the parts are as high or higher than the labor!
They will want as much money to fix the newer cars, as they will be worth, at half the ages of ours!

The original Bosh pumps that come on these cars or you buy later, can easily go 200,000 miles.
Past that, you can be on borrowed time with the longevity of brush wear inside the pump.

The best thing is to insure that the wire connections on the pump are tight and clean.
The females part of the connectors clip can get weak and not fit as tight as it use too.
If the pump has been replaced by an off brand pump the connectors may have been spliced or other wise jury rigged to work on it.

You will need to crawl under there to inspect the pump housing anyway.
You will want to be aware of noticing to see it still has sprayed body coating on the outside of it. If it does, it’s probably the Bosch original pump and it’s time to replace it.
If the rear end of the pump it looks shiny and new, then the pump has been change at least once and maybe only once, depending on the overall mileage of the car! The coating “helps confirm” it’s a low mileage car! Do not always take that to the bank though, it’s just something to consider when buying used!

Marvel Mystery Oil shouldn’t do any harm to the pump at any time. I’m skeptical that it does anything, when mixed in several gallons of gasoline, as it’s too thin already.
It might do more of “something,” if you put in your ears to remove ear wax!
I might give it some merit if used in the engine oil and that is questionable!
I use a few drops their air tool oil in my equipment and have experimented with MMO on other things of that nature.
I compare, MMO to Rislone, both an oil additive, to be more of a detergent cleaner for piston rings and valve stem guides. Both remove varnish resin from hydraulic lifters, but these engines don’t use them.

As far as hearing a noise out of that pump upon shut down, is very unlikely, as it is only a roller pump. Hearing it sounding off louder later, I can believe that.
Smacking it and it started working again is a normal scenario!

If it’s excessively worn or the connections down there are going bad, then, it should be treated as a good heads up warning to jump on it!

Phil