My fuel pump adventure with my 1988 Volvo 760 Turbo Wagon

lummert · Post by **lummert** » 18 May 2012, 16:02

I have had a fun adventure with the fuel pumps on my 1988 Volvo 760 Turbo Wagon. First I had problems with no fuel pressure when the temperature has in the 90F range and the humidity was rather low. The main in-line pump quit and I installed a good used OE style main pump. The pump worked good until it got hot again with low humidity.

I tried swapping in a used in-tank pump but the 3 used pumps I tried were all bad. I even figured out how to test the pumps with fuel in a container. I tried a fairly new Bosch high pressure (49 PSI) in-tank pump meant for a early 90's Jeep Cherokee. By then the main pump was noisy. I then replaced the main pump with a fairly new aftermarket Airtex high pressure (90-100 PSI) pump from a 91 740. My MPG went to 23 MPG. Then I installed a fairly new Delphi low pressure (12 PSI) in-tank pump meant for Chevy Blazer T-10 in series with the Airtex main pump. My MPG is now 27 MPG and my fuel pressure is good and my car runs like a scalded arse ape.

Before anyone asks why I don't use new parts, I am on a low income budget and if I spend much on parts I eat less. But my friend owns a local junkyard (breaker) and I get to take any parts that I need as long as the parts are not something new that he has paid money for. The fuel tanks at this junkyard are removed and the gauge sensor removed to drain the fuel. The gauge sensor is then placed back into the tank and the tank is placed in the trunk (boot) or the interior of trucks, SUV's or wagons. So, being disabled I have more time than money which works out okay for me. My disability is not physical so I am able to work on my car, actually working on my car is similar to mental health therapy.

I did learn one thing about running 2 high pressure pumps in series. There is little or no pressure in the fuel line between the two pumps, the main pump having a higher flow rate being last in the series will out pump the in-tank pump.

angeltease · Post by **angeltease** » 26 May 2012, 03:58

How did you test the fuel pumps? I think my in tank pump has stopped working.

Post by **jimmy57** » 26 May 2012, 13:28

A properly working in tank pump will pump fuel up to engine by itself through the main pump. Pull one lead, either lead, off the main pump under car and then take fuel line off fuel rail and put it in a container to catch the fuel. Now turn ignition on, without cranking the engine over, 3 times for 4 seconds each time. Now go check to see if the container has had fuel added to it. IF not the in tank pump or its connector hose has problems.

lummert · Post by **lummert** » 26 May 2012, 23:09

I tested intank pumps off the car by placing them in a gallon container of fuel and attaching a clear PVC hose to the pump outlet running it back into the container, then connecting the pump to battery power. It is easy to see the fuel flowing through the clear hose. The inline main pump is best tested on the car because it is difficult to prime the pump without the fuel flow from the intank pump.

angeltease · Post by **angeltease** » 03 Jun 2012, 20:15

thanks for the advice turns out the wires were shot n the sock filter was ripped to shreds the pump still worked (barely) so we just replaced it anyway

angeltease · Post by **angeltease** » 04 Jun 2012, 11:30

my husband got the old fuel pump out but is having trouble getting the gas tank back on...any tips or tricks that might make it a little easier?

lummert · Post by **lummert** » 04 Jun 2012, 11:44

Number one tip: You don't need to remove the tank to replace the in-tank pump. There is a access cover that can be removed to get to the tank sending unit. Now that the tank is out it may be easier to get it back in if you remove the access cover and remove the fill tube hose before trying to install the tank. Also attach the hoses from the access hole. The access cover is found in the trunk on 7xx/9xx sedans and under a floor panel behind the rear seat on 7xx/9xx wagons.

tt460 · Post by **tt460** » 28 Jun 2012, 08:30

Is there any reason you didn't experiment with just the high pressure in-tank pump and removing the secondary high pressure in-line pump?

Seems to me this would be the best way to go since 2 pumps are consuming more electricity than 1... My thoughts are that if the in-tank pump failed, I'd find a high pressure pump to install in the tank and eliminate the in-line pump.

lummert · Post by **lummert** » 28 Jun 2012, 14:55

I have already considered the one pump system with the high pressure in-tank pump. I would have to run a new heavier gauge wire to supply needed amperage to the pump and run a new smaller diameter fuel line from the in-tank pump and sender to the fuel filter. Later in the year when the weather is cooler would be a better time for this type of experiment.

angeltease · Post by **angeltease** » 30 Oct 2012, 15:35

ok he changed out the fuel pump n got it back together the day of my last post. but when he was struggling to get the tank back on....(thanks for the tip by the way-i went in the garage to tell him about it and he had the access panel open so i figured he already knew, but apparently he didn't know you could change the pump through that panel!!) the fuel filler neck seal cracked down the side and somehow the fuel gauge doesn't work anymore...i guess thats why you're supposed to use the access panel! So it's smog year and it didn't pass the evap test, so we tracked down the seal and he replaced it, and put the car back together....it took a couple tries to get it started n it was sputtering and wanting to stall so we got it to the mobil station and put 10$ in but on the way home it cut out completely and would not start back up he tried starter fluid in the air filter. it acted like we were out of gas or something, had to have it towed home. my husband got it taken apart thinking a hose might have gotten pinched when he put the tank back on. but he says everything looks alright i was wondering if you have anymore advice for troubleshooting?
Has Spark
Fuel pumps kick on when i turn the key to on
Thanks!
Crystal