Ok, the fuel pump / hard starting issues on the 1990 240 DL my grandson and I are fixing up for him has taken an interesting turn. Long story short I found out that the in-tank pump and fuel sender were not getting 12V with the key on. Troubleshooting revealed that every fuse in the fuse box was getting 12V with the key on EXCEPT fuse number 4 (primary fuel pump/ Lambda sond, and heating element fuse). The fuse box and contacts themselves are in pretty good condition, and I really do not relish messing with all the wires (plus the cost) of putting in a new fuse panel if I could even find one. Plus, we have about 50 spare fuses laying around waiting to be used.

That said, two questions come to mind to fix it. First, I am assuming that 12V comes into each fuse on the box from the LEFT side fuse contact. Am I correct? Second, could I solder a jumper wire from another fuse's left side contact to the left side contact of fuse number 4 so that it now gets 12V. or is 12V power to fuse #4 come from the switching of the fuel pump relay?
Please let me know what you think. Many thanks

 

The fuel pumps only get power when there is spark (or the engine is spinning depending on the ign system) - so that if the car is in an accident and the engine stops running- there is no power to the fuel pumps to prevent fuel leakage (accident = damaged fuel lines, etc.)

 

Ok, so you are saying there will not be power to the in tank pump unless the engine is cranking or running?

The issue I am having is that when the key is in position 2 (on, not start/crank) all the idiot lights come on and such, but there is no power at the yellow and red power wire at the connector in the trunk for the in tank pump. I can not hear the tank pump running either, but the main pump works ok. I metered out ALL the wires from the fuse panel to the tank pump connector, from the fuse panel to the fuel pump relay connector, to the main pump, etc......All wires check out just fine including battery power to the fuel pump relay connector..

Also, I recently drained the fuel tank and put 5 gallons of fuel in it and the fuel gauge does not register at all.

I thought the in tank pump would run with the key in Pos 2.

 

The pump will not run unless the ECU detects pulses from the crank position sensor. Therefore you will not hear the pumps run except for a second or so when the key is first turned to the II position. This site explains very nicely how to diagnose fuel pump problems:

In the Tank - 240 Volvo Tank Pump and Sender

 

Ok, that explains the readings I am seeing with my meter. The system works a bit different than what I am used to but easily understandable. Thanks for the good links. Is there a good way to check the operation of the gauge without removing it from the dash (i.e applying ground or power to one side)

Thanks

 

The gas and fuel gauges (on a 240) are fed a regulated voltage to hopefully keep them accurate. (because the voltage in a car varies from 11-14.5 volts.)

The fuel sender and temp sender are variable resisters. Fuel sender is wire wound, temp sender is a thermister.
Those gauges are bolted to the circuit board - sometimes those nuts come loose and prevent the gauges from working.

Yes, you can ground the wire to the fuel sensor to test the gauge - but just momentarily - you WILL MELT the gauge if you do that too long. So for just a second to see if the gauge moves. Unplug it in the trunk and ground it for a second there.

 

Thanks for the tip. Tested the gauge and it worked fine.

 

If you are having trouble getting the in-tank pump to run and the fuel gauge is not working, more than likely the problem is the seal where the wires pass into the tank. The top of the sending unit tends to rust out ruining the seal and breaking the connections. This should be covered in the link I posted earlier. If this is the problem, the only solution is to replace the sending unit. When using the aftermarket sending units (only ones available), pay attention to the wiring as the have known to been improperly wired. Before installation, compare your old wiring with the new to ensure proper operation of the pump/sender.

Also, keep your float ball from the old sending unit if it is a factory original unit. I have had problems with the aftermarket float having leaks - eventually filling up with gas. If this happens you can use the factory original float which was of better quality.

 

Question......is there supposed to be a rubber seal between the top of the tank and the bottom of the sending unit? There was no seal present when I took the old sending unit out.

 

Yes - a 949276

 

First clean all your ground wires use small wire brush or fine sand paper and put dielectric grease on them go down to the kick panel in the passenger and check the connections on the ECU and the few relays down there. Get a new fuel filter also. These older volvos suffer from a poor fuse box design and they have an issue with the ground wires getting corroded