????Auxiliary Fuel Pump????

From a point at sea, to the circles of your mind, this is Artful Dodger:

It's not failure, it's a learning curve.

It acts as a primer for the main pump. As you know by now, K-Jet depends upon fairly high pressure in the fuel supply line, so the supply needs to be consistent. Without the in-tank pump the main pump can draw in air when the fuel level gets low, and this will lead to erratic engine running.

When it's hot the low pressure in the line from the tank to the main pump can cause the fuel to vapourize in the line. The pump does not pump vapour very well, so the fuel supply to the engine is compromised. If you look at the older injected Volvos, (mid 1977 and earlier) that were made in the days before auxiliary fuel pumps, you see the pump is mounted right beside the tank, and the supply line comes out the side of the tank (not out through the fuel sender like the later ones) to minimize these problems. What I don't understand, I can see adding the auxiliary fuel pump as a Band-Aid to an existing design, why didn't they just go to one pump in the tank when they designed the 700 series?

IIRC in the later 700's they did, but it wasn't until they went to the Regina fuel system.

I thought that they did for carburettor engines and only added the main pump when higher fuel injection pressures were required.

Cheers, Peter.

: > Okay guys : >

: > By now you know that I am a complete failure when it comes to the '89' Volvo : > 740GLE estate with the b230e k Jet 8v motor fuel system. So it will come to : > no surprise that I ask another dumb question... : >

: > What does the auxiliary fuel pump actually do? : >

: > Thanks! : >

: > Stewart, after hours of trawling through many car parks for an entire day. : > I was unable to find another 740 GLE owner. The closest I got was an SE. : > GL's seem popular though. I fear a 2.0 carb would be of no assistance to me : > though. : : When it's hot the low pressure in the line from the tank to the main : pump can cause the fuel to vapourize in the line. The pump does not : pump vapour very well, so the fuel supply to the engine is compromised. : If you look at the older injected Volvos, (mid 1977 and earlier) that : were made in the days before auxiliary fuel pumps, you see the pump is : mounted right beside the tank, and the supply line comes out the side of : the tank (not out through the fuel sender like the later ones) to : minimize these problems. What I don't understand, I can see adding the : auxiliary fuel pump as a Band-Aid to an existing design, why didn't they : just go to one pump in the tank when they designed the 700 series? : : -- : Mike F. : Thornhill (near Toronto), Ont. : : Change cant to ca and remove parentheses to email me directly.

Right, I was just pointing out they were several "fuel system generations" behind in making the switch to one pump only. The 850 had one pump only, and the last few years of 900 series did as well. Two pumps is a needless complication and extra expense.

No the under car (main) pump was first for fuel injected cars. Then they added the tank pump to prime the main one. I'd never heard of tank pump carb Volvos until this week, our (Canada's) last carb Volvos (1984

The 960s only had one pump as well.

However, at least with the 850s and newer (and I believe the Regina equipped cars too).. that one in-tank pump requires that the tank be dropped to access it.

With the two pump setup, you can access both pumps quite easily without dropping the fuel tank.

- alex

'85 244 Turbo

Only the 95 and newer 960 had one pump. And the tank doesn't need to be dropped on any 700/900 or 850 to remove the sender, and the pump hanging on it. I'm not sure one way or the other on the new style cars (S80 and newer), but I can't imagine why they'd be any different.