No John its because the designers actually for once thought about acess for servicve of the pump...Ever heard of rust? If main pump fails, car stops.. Lay on back, swap pump...Car goes..
Main pump intank, pump fails...40-70 times the pain in butt getting maybe whole tank out, getting sender/pump cover off, blah blah...
But in this situation, you have two pumps that could fail, not one. Just as a thought experiment: would adding a
third pump that also has to work to make the car run properly make the car more reliable, or less reliable?
To voluntarily make critical component access more annoy when there is no compelling reason to is nothing short of madness. (I like driving cars down roads where there is occasionally a lotta egg to tennis ball sized rock ricocheting all over the place...in such case any pump---or anything---under the car critical to getting home is nuts...so it gets moved to a safe EXTERNAL location..
The compelling reason is because there needs to be a pump in the tank for optimal effectiveness. Otherwise they'd have just not bothered with the intank pump. Well, that's how all those D-Jet cars worked, perhaps the K-Jets too??? How'd that happen? Anyhoo...
Assuming there needs to be a pump in the tank to work best, and also assuming that the fewer gizmos that need to all be working at the same time to make the car go is better, then having one pump in the tank would be better than having one pump in the tank and one pump under the car. Also, the pump in the tank is protected from tennis ball sized rocks. Well, as well as all the gas is I guess.
And the bigger volume pumps equivalent to the Bosch 044 are just a bit fatter in diameter than the normal 8v Volvo pump I think 60mm dia vs 52mm, 196mm LOA vs 180 something..The big deal was BIG 14mm ID inlet...that's what got me excited...Oh baby oh baby...
They big volume pumps, were there, just back then those poor dumb engineers didn't have aces to the millions of pages of Forum wisdom, so they didn't know that little 100-150 hp cars needed 225l/hr pumps for daily driving like is now a well establish FACT...
I wasn't referring to 800GPH spare Atlas rocket parts, just a pump of the size needed to (in an OEM engineer's mind) adequately supply the car with an appropriate amount of fuel when it was half worn out 20 years later. I was supposing that the physical size of a smallish OEM volume pump back then was just a bit bulky for them to contemplate fitting through a small gas tank bung, so they just left it outside, and put a cute little low pressure high volume lift pump in the tank because it was so much smaller. These days, both the bungs (on newer cars) have gotten bigger (why not), and the physical size of a pump that can deliver all the fuel the engine needs has gotten smaller, so thy're really no larger than those old lift pumps were.
I can post official drawings of 400bhp turbo Ford rally cars showing right there scrawny little 150 l/hr pumps....Oh the huge manatee!..
I like cool drawings. Do eeeeet!
Thank god we have the collective wisdom of the world's forumz.
Hear! Hear!