Is it possible to test a fuel pump relay? 9434225

[bcfischer]

I have a 1999 V70 XC in the care, custody, and control of my daughter about a 5 hour drive away. She is having some intermittent stalling issues that kind of scream fuel pump relay.

I’m ordering a new one but is there any way to test the old ones with a multimeter and/or fix one that is causing intermittent issues?

I know that the fuel pump relay is a frequent flyer topic here on the forum.

Brian

[abscate]

Someone did a dive into these internally with circuit board repair of the caps here ( Chuck?) but most diagnose by swapping a used one.

Volvo only on this part, no KAE specifically , it’s about $65

I believe Stribel is the OEM if you can source their stuff to save some bucks

[abscate]

Ozark Lee…the man , the myth. The thread kicks butt

viewtopic.php?f=1&t=9681

[Chuck W]

I recently went through a bunch of relays I had and replaced the caps in them (Mainly for spares)

Since Radio Shack is no more, I purchased my replacements from DigiKey

Part numbers for the 22uF and a 100uF capacitor that usually require replacing are Digi-Key 565-1304-ND and UVY1E101MDD-ND, respectively.

[abscate]

I recently went through a bunch of relays I had and replaced the caps in them (Mainly for spares)

Since Radio Shack is no more, I purchased my replacements from DigiKey

Part numbers for the 22uF and a 100uF capacitor that usually require replacing are Digi-Key 565-1304-ND and UVY1E101MDD-ND, respectively.

Thanks Chuck. I knew you had your fingers in these at some point.

I thought I ordered a 100 pieces of these from Mouser to mail out too, I’ll report back…..indeed, I did

by abscate » 07 Sep 2021, 03:00

Chuck W wrote: ↑06 Sep 2021, 07:08
ZionXIX wrote: ↑06 Sep 2021, 06:52

Nice work! Which capacitors do they require?
There is a 22uF and a 100uF capacitor that usually require replacing. (Digi-Key 565-1304-ND and UVY1E101MDD-ND, respectively).

Most were probably "good", but I'd actually forgotten that I had this many. I had no idea on the fitness of them all, so I figured it wouldn't hurt to just do the lot of them. Marked each with a date, so I know their status now.
I’ve ordered 100 PCs each of these, the latter are on extended back order but hopefully will arrive soon

Mvs people can pm me amd I’ll put some in us Mail.
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These users thanked the author abscate for the post (total 3):
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[jreed]

In addition to replacing the capacitors, if you pull the case off of the relay you can check to see if there are cracks in the solder joints connecting the pins to the circuit board.

viewtopic.php?f=1&t=33696

Volvo850FuelPumpRelaySolderJoint Cracks Circled 1.jpg (66.59 KiB) Viewed 1140 times

[MrAl]

I have a 1999 V70 XC in the care, custody, and control of my daughter about a 5 hour drive away. She is having some intermittent stalling issues that kind of scream fuel pump relay.

I’m ordering a new one but is there any way to test the old ones with a multimeter and/or fix one that is causing intermittent issues?

I know that the fuel pump relay is a frequent flyer topic here on the forum.

Brian

Hi,

Not sure if you found this thread yet but here:
viewtopic.php?p=612346#p612346

The post with date and time 07 Nov 2022, 14:29 has photos and layout of the board and complete schematic of the relay. However, the schematic was updated slightly in the post with date and time 11 Nov 2022, 12:04 so you can check that out. That thread also contains a couple procedures for testing the relay. I'll summarize the test procedure here for convenience.

The simpler test is to apply +12v to terminal 15 and ground (minus battery) to terminal 31. You have to get that right or you will could easily blow out the chip on the board. There's a chance that the zener will help prevent the chip from getting a reverse voltage if you reverse the connections, but i would not count on that.
With that voltage correctly applied, take a jumper and jump terminal 31 to terminal 31b. Also get those two terminals right. Right after you jumper it, remove the jumper, then jump again, then remove, then jump again, do this several times as fast as possible by tapping one end of the jumper to terminal 31b (with the other end still connected to ground terminal 31). When you do this, you should see the physical internal relay close, then open after about a half of a second. That means the relay is probably working ok.

A more comprehensive test is to connect a frequency generator that can output a TTL level square wave (voltage of the square wave is no more than +5v) to terminals 31b (positive) and 31 (negative). Set the generator to 40Hz and see that the relay closes. Then turn the generator down lower and lower to 30Hz then slowly to 20Hz then slowly down to 10Hz and see that the internal relay opens. At some lower frequency like that the relay should open. Then turn the frequency back up toward 40Hz and the relay should close again.

For mine, before i changed the two caps 100uf and 22uf the relay on mine was closed at 40Hz then when i got down to 20Hz the relay opened. After i replaced those two caps the relay was again closed at 40Hz but when i got down to 20Hz it was still closed, and did not open until i got down to about 15Hz. So the caps made it easier for the relay to stay on (and thus the pump stayed on) and that's a good sign because of course the fuel pump has to run to be able to supply gas to the engine.

If you are into electronics the schematic will show you how this works and i supplied an explanation too if you want to know more about this circuit. It's not particularly complicated but to completely understand the two monostable multivibrator sections of the chip you have to look up the data sheet on that chip and look for the waveforms given on the theory of operation. The basic operation is that if the ECU signal pulsing on terminal 31b goes away or goes to a frequency that is too low the relay opens and that's supposed to be some safety feature. With the ECU signal being normal the relay will stay closed which keeps the fuel pump running constantly.

[MrAl]

Hello again,

I just wanted to make a note that when i did the jumper on jumper off jumper on etc. test the relay was not working right so i had to connect it and disconnect it several times to get the internal coil to the relay to energize and thus close the contacts and thus turn the fuel pump on.
After i fixed the relay, all i had to do is connect the jumper from 31 to 31b ONE TIME and the relay would turn on (you can hear the click dont even have to take the cover off the relay). So i conclude that if you have to connect and disconnect that jumper several times to get the relay to turn on, or you never get the relay to turn on (no click from inside) then the relay circuit is most likely bad.

So the modified procedure is to just apply +12v and ground (+12 to terminal 15, ground to terminal 31) and then jumper terminal 31 to 31b and listen for that click, and then after maybe a half second you would hear the relay deenergize again as that is the safety feature kicking in.

You have to be very careful to get the terminals right though if you reverse the +12v and ground it will most likely blow out the chip on the board that is used to turn on the internal relay (the actual relay with the coil inside).

So to recap, as soon as you connect terminal 31 to terminal 31b you should hear the relay click, and then 1/2 second later hear the relay coil deenergize even with the jumper still connected.

I wish you good luck with it.

All the members here are very helpful so I also realized that if someone wants to mail me their relay to test i could do that for you. It's actually very simple just have to be very very very very very careful which terminals are which, and they are marked on the bottom of the relay as follows:

#15 is +12 volts (battery positive but it feeds in through another relay).
#31 is ground (minus battery which connects to the car chassis).
#31b is the ECU signal from the ECU (pulses on and off when working normally about 40Hz at idle).
#87 is the pump motor (when this terminal becomes high, which is +12 volts, the pump turns on).