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Fuel Pump Relay Issues

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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timothyj77
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Fuel Pump Relay Issues

Post by timothyj77 »

I have a 2000 V70 XC SE (128K) and I'm on my fourth fuel pump relay in the last 14 months. Is there a known issue that could be causing this? My mechanic can't figure it out. Thanks!
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erikv11
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Re: Fuel Pump Relay Issues

Post by erikv11 »

If you are buying aftermarket relays, for example made by KAE, that would definitely be a known issue. I wouldn't expect it to be as bad as three failures in 14 months but would still believe it.

If so, time to shell out for a Volvo relay. Even a junkyard relay is better than a new KAE one, in my experience. I'd probably try the latter and see if they keep dying, if not then shell out for a Volvo one.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
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timothyj77
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Re: Fuel Pump Relay Issues

Post by timothyj77 »

I agree - but the last two have been Volvo relays. I'm stumped.
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abscate
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Re: Fuel Pump Relay Issues

Post by abscate »

Test current draw on the fuel pump.

Failure mode of the relays would also indicate failure root cause
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Re: Fuel Pump Relay Issues

Post by mecheng »

How is it failing? I know the common failure point, is the solder joint.

Open one up and have a look at the coil, activate it with 12V, even a 9V batter, does the spring move. If it does test the continuity and try to see if you can peak a look at the contacts.
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ToriWhite
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Re: Fuel Pump Relay Issues

Post by ToriWhite »

I know a bad relay can cause a bad pump - so whenever your pump goes, swap the relay too to be safe.. I wonder if a bad pump can kill a relay? I wouldn't be suprised
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BEJinFbk
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Re: Fuel Pump Relay Issues

Post by BEJinFbk »

ToriWhite wrote: Mon Jan 27, 2020 3:19 pm I know a bad relay can cause a bad pump - so whenever your pump goes, swap the relay too to be safe.. I wonder if a bad pump can kill a relay? I wouldn't be suprised
I'm not sure that I understand your logic.

The relay is just a switch that turns the
pump power on and off when the ECC
tells it to. Maybe if the contacts were to
stick and the pump relay continued to
run, there might be a problem. But it
would have to run a loooong time.

Conversely, a bad pump that draws too much
current is much more likely to damage the relay.
And the main fuel system relay will cut that power
when you turn off the key anyway, so it's not going
to runaway when the car is shut off.

As far as swapping the relay just because you
dropped in a fresh pump, I'd bank that cash.
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ToriWhite
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Re: Fuel Pump Relay Issues

Post by ToriWhite »

BEJinFbk wrote: Mon Jan 27, 2020 8:01 pm
...stick and the pump relay continued to run, there might be a problem. But it would have to run a loooong time.
Don't quote me on this, but I remember reading somewhere that a frequent point of failure for pumps is a faulty relay that, for some reason, malfunctions to where it 'flickers' on and off, and that behavior hurts the pump. Of course, if you've got a multimeter and the know-how, you don't have to run off of heresay lol
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