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06 Oct 2013
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TOPIC: Question low voltage to in tank fuel pump

low voltage to in tank fuel pump 3 years 9 months ago #1126

  • rick1
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i only get about 8 volts going to in tank fuel pump when key is turned on. I jumped the relay pins 87'2 and 30 and i get 12volts, i changed the relay, same thing. i hear the main in line pump run when i jump the relay, but still the in tank doesn't run ??? Where can i go next??? Its an 85 740, 4 cylinder

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Last Edit: by rick1. Reason: vehicle descrition

low voltage to in tank fuel pump 3 years 9 months ago #1127

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rick1 wrote: i only get about 8 volts going to in tank fuel pump when key is turned on. I jumped the relay pins 87'2 and 30 and i get 12volts, i changed the relay, same thing. i hear the main in line pump run when i jump the relay, but still the in tank doesn't run ??? Where can i go next??? Its an 85 740, 4 cylinder


Welcome to the Forum.

Below are links with possible solutions to your in-tank problem(s).

As you read along keep in mind that fuse numbers, relay locations, etc. changed from year-to-year for the 740 model but the troubleshooting procedure is the same.

Sometimes a fuse with poor conductivity and/or a bad ground can cause electrical problems.

How many miles/years on the in-tank pump?

George Dill

tinyurl.com/qzzp65a

www.brickboard.com/RWD/index.htm?id=1401597&show_all=1

tinyurl.com/mojw9v3

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low voltage to in tank fuel pump 3 years 8 months ago #1145

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Thank you for responding George, the in tank pump was supposedly replaced a few months a go. Again, when key is on, I only get about 8 volts to it.I metered the connector feeding it in the trunk. However, when it tried trouble shooting the fuel pump relay by jumping terminals 30 and 87/2, i get 12+ volts to it. i clearly hear pump run. Replaced relay, but same thing. Tried a different used EMU, but same thing. Car will start with starting fluid spray, but then cuts right off. Its not getting fuel. It's an 85 740, 4cyl., and I can not find a radio suppression relay anywhere. I replaced both pump fuses although they looked fine,Does anyone know Where i should look next?? I don't think my main in line pump is running. Does this car have a fuel pump cutoff switch anywhere?? On line parts stores show pictures of a "fuel pump cutoff switch" for a 1985 volvo 740, and sell them for about $70.00, but I can not find one on this car.

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Last Edit: by rick1. Reason: did more testing

low voltage to in tank fuel pump 3 years 8 months ago #1146

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rick1 wrote: Thank you for responding George, the in tank pump was supposedly replaced a few months a go. Again, when key is on, I only get about 8 volts to it.I metered the connector feeding it in the trunk. However, when it tried trouble shooting the fuel pump relay by jumping terminals 30 and 87/2, i get 12+ volts to it. i clearly hear pump run. Replaced relay, but same thing. Tried a different used EMU, but same thing. Car will start with starting fluid spray, but then cuts right off. Its not getting fuel. It's an 85 740, 4cyl., and I can not find a radio suppression relay anywhere. I replaced both pump fuses although they looked fine,Does anyone know Where i should look next?? I don't think my main in line pump is running. Does this car have a fuel pump cutoff switch anywhere?? On line parts stores show pictures of a "fuel pump cutoff switch" for a 1985 volvo 740, and sell them for about $70.00, but I can not find one on this car.


Could be a failing ignition switch and/or faulty fuel pressure regulator and/or a faulty fuel injection relay Volvo Part Number 3523608.

Your car has a fuel pump check valve mounted on/near the external fuel pump Volvo Part Number 1326899.

If the radio is OE the suppressor should be built in to the system.

Which relay did you replace and where did you source it?

George Dill

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low voltage to in tank fuel pump 3 years 8 months ago #1147

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Again, thanks for responding. The relay i replaced was the fuel pump relay, which looked good to me, I opened the old one up, actually it has two relays in it. I can feel it click with my finger on it when i turn the key to the on position, can i rule out the ignition switch? It was replaced in the car about a year ago(someone tried to steal the car). Can I also rule out the in tank pump which runs when i jump the fuel pump relay pins 30 and 87/2, also runs if i apply voltage to fuse #11 as per the volvo forum discussion you sent the first time. As soon as the new or old fuel pump relay is back in place, as well as the fuses, the key's on position makes the relay click, but won't make that in tank pump go, and i test its connection,still with the key on, its only getting about 7.5 volts. When i try to test the in line pump according to that same forum instruction, #1 fuse voltage to #11 fuse terminal closest, nothing. ?? Not really sure how that test could work anyway, #1 main tank fuse is still out?? Jumping the fuel pump relay pins 30 and 87/2 only make the in tank pump work. Can I jump any pins to make the in line pump run?? Or how do I test that in line pump without removing it?? Any help will be greatly appreciated!!

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low voltage to in tank fuel pump 3 years 8 months ago #1148

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Can I by pass the signal from the fuel pressure regulator long enough to here these pumps run?? Or can I test the pressure regulator without a gauge?

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