fuel pump problems

dave123449 · Post by **dave123449** » 10 Oct 2010, 22:55

I Have a 1988 760 Volvo with the pump in the tank. I do not seem to be getting any fuel. Let me begin from the beginning. My friend has a car he wants to sell and said it was running fine. Then the car would be running and just stop. They had the fuel filter replaced and it kept on doing the same thing. Then someone went to the junk yard and got a fuel pump (this is the one under the car). The car kept on giving them problems. So I checked it and found no gas going through the lines. I replaced the fuel relay switch and the in-tank pump and nothing happened. I tried testing the pump in the tank with a meter and nothing happened. I know everybody says you can hear the pump running but I hear nothing. There is a red and a black wire on top of the pump. What voltage should the pump read with the key turned on. Also do you have to prime the pump to get it started. Can you check the in-tank pump by putting it in a jug of gas and see if it pumps. Or do you have to have all the lines hooked up to keep pressure. If anyone can figure out this problem it would be appreciated.

Post by **billofdurham** » 15 Oct 2010, 11:44

Welcome to Matthew's Volvo Site.

This is possibly a little late but I have been away for a few days.

The in-tank pump should be getting 12 volts with the key turned on. Have you checked fuse #11 which covers the in-tank pump?

You can check the pump outside of the tank. It doesn't need to be in a liquid if you only run it momentarily to see if it works.

Bill.

dave123449 · Post by **dave123449** » 15 Oct 2010, 15:07

My fuses are on the left side panel on the drivers side. I have looked at the fuses and they appear to be okay. The no#11 you were talking about I did not check. On the case it says no# 30 and 31 for the fuel pump and the in tank pump. Those are the ones that appeared to be ok. Maybe they are broken but look good. Also would the radio suppression relay have anything to do with it.

Post by **billofdurham** » 16 Oct 2010, 11:34

My apologies for the wrong fuse number. I pulled up the owner's manual from Volvo Cars of America and didn't notice that they supply the 740 manual for the 760. The 760 fuses are, as you said, #30 & 31.

The radio suppression relay is actually energized by a feed from the fuel pump/system relay and only supplies power to the injectors so should have no impact on the pump.

So I can dig deeper on this is the engine the V6 or the 4T?

Bill.

dave123449 · Post by **dave123449** » 16 Oct 2010, 16:17

i have a 4T. I checked and there is no power to the main pump under the car. The relay energizes but that is as far as it goes. A pink and black wire goes from the main pump and looks like it goes under the dash with a million other wires.

Post by **billofdurham** » 17 Oct 2010, 12:15

The pink wire splits with one lead to the fuel pump relay and the other to fuse #30. The black is the earth (ground) which goes to the earth connection block at the relay board.

Have you checked the fuses for continuity with an ohm-meter? Have you checked for voltage at the main fuel pump? This came from a junk yard but is it working? You can run a jumper lead from the battery to the connector on the pump (pink lead) to see if the pump does work.

The in-tank pump stops pumping if the main pump isn't asking for more fuel. Its purpose in life is as a priming pump.

Bill.

dave123449 · Post by **dave123449** » 17 Oct 2010, 15:39

Thanks,Bill for the info. You must have understood me. The fuel filter, fuel pump, fuel pump relay and the in tank pump are new. There is no power to the main fuel pump. I put a meter on the black and pink wire but there was nothing. The wire that goes to the in tank pump showed 6.8 volts. I will try to jump the pump like you suggested.

Post by **billofdurham** » 18 Oct 2010, 12:31

I based my 'junk yard' comment on this in your first post:

Then someone went to the junk yard and got a fuel pump (this is the one under the car).

If you have replaced the fuel filter, fuel pump, fuel pump relay and the in tank pump but still have no power to the pumps then you are looking at a fuse, possible defective new relay (it does happen) or bad connections/broken wires.

There are 2 relays inside the fuel injection/pump relay. One of them should turn ON when the ignition is turned on, without turning over the engine, and the other relay, which actually turns the fuel pumps should come ON when the engine turns over/runs. You can check the 1st relay by putting your fingers on the relay module and turning the ignition on and off repeatedly. You should feel the relay click on every time. If it doesn't, that relay isn't working. Check the fuses with an ohm-meter. Also check that you have power at the fuses with a voltmeter. If the fuses are good and there is power the relay is suspect.

Bill.

waydar · Post by **waydar** » 18 Oct 2010, 21:10

Have you checked that your ignition system is working? The fuel pump relay is activated by the fuel injection computer after it reads a pulse from the ignition system. (The distributor triggers the ignition controlbox to fire the power stage, and also triggers the fuel system controlbox to ground the fuel pump relay coil.) The older cars (with LH 2.2) also have a turbo overpressure switch under the dash to shut off the fuel pump relay at pressures over the max boost pressure. And, last but not least, don't forget the timing belt drives the distributor. Always check these items before condemning fuel pumps.