Folks

It was a nice day on Saturday after getting my tires replaced on my 1990 Volvo 240 so I decided to look into testing my pre pump/intank pump. I followed the instructions on this page
In the Tank - 240 Volvo Tank Pump and Sender

on my 1990 the prepump/ in tank pump, is fuse #4 and the fuel pump relay is #6. I tried that trick of using a jumper from the right terminal of #4 to the left terminal of #6 after removing fuse #4 and I got no sound of the pump even when next to it.

I removed the bits and bobs of the cargo hold that covered the access port and tapped it while the fuse box was jumpered but no go. The condition of the top of the sending unit looked good with almost no corrosion and no rust

I get a priming/whirling sound for a second when the key is turned to ign but think it is the main pump.

Now here is the interesting part. I decided to remove the fuse for the fuel pump relay which should in theory cause the car to crank but not start since no power is going to the relay. BUT the car started and ran fine without the fuse in #4 and #6. If I unplugged the actual relay the car would only crank but not start. It seems there is a short somewhere if the car starts and runs with both the fuse for the pre pump/in tank pump AND the fuse for the fuel pump relay removed and nothing jumping it?

Any place to start looking for the issue?

 

have you checked for voltage to the intank pump?...right at the pump cover area.black connection with possibly black tar looking crap on it to hold it down to the metal..do you have the black or brown wire grounded there as well? a loner wire....

Any codes?
the main pump ground wire is under the back passenger seat left side....

 

fuse 4 is only inline with the tank pump, the main pump is not on a fuse other than the main 25A EFI fuse near the battery.. as long as you have like half a tank of gas or more, the car will usually run without the tank pump, but the main pump will be under more stress.

if hooking fuse 4 up so that the tank pump is powered causes the main pump to fail due to a short in the tank pump circuit, I would have expected that fuse to blow...

btw, the tank pump fuse on many cars also powers the O2 sensor heater... without that heater, the O2 sensor takes a lot longer to start working. and the car runs less efficiently.