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Testing/Experimenting with Fuel Pump Relays

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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Testing/Experimenting with Fuel Pump Relays

Post by SonicAdventure » Tue Dec 31, 2019 8:53 am

I have several fuel pump relays for 850/x70 vehicles and I'd like to know how I can bench test them.

I have two red OEM 9434225 models, one is made in Germany, one is made in Hungary. The Hungary-made one came out of a '99 non-turbo V70. I believe the German-made one came out of my old '98 non-turbo V70 but I'm not 100% sure.

The yellow relay, part number 9434013, made in Germany, appears to be OEM, and came out of a '95 non-turbo 850 sedan.

I believe my cold weather 850 non-start fails are due to the fuel pump relay. When the ambient temp raises into the mid 30's, the car will finally start and stay running, usually after a semi-loud whirring or clicking sound from the area of the relay. The sound lasts about 5-8 seconds and does not reoccur until after it fails to start again another time. Then, reliably, the buzzing will happen again when it finally stays running.

I know the preferred method is to just plug in a new relay and if it runs it works, but I'd like to know how to bench test these outside of the car. As the P80 chassis is starting to dry up at the junkyards around here, I am usually now collecting these working or not whenever I come across them.

All this aside, what is the optimal relay to use in a '96 non-turbo 850?

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Re: Testing/Experimenting with Fuel Pump Relays

Post by SonicAdventure » Tue Dec 31, 2019 8:55 am

Here are the relays I have:
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5E4BA4B8-89ED-4E0E-AE09-74603D86F7A8.jpeg
5E4BA4B8-89ED-4E0E-AE09-74603D86F7A8.jpeg (111.18 KiB) Viewed 67 times

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Re: Testing/Experimenting with Fuel Pump Relays

Post by misha » Tue Dec 31, 2019 9:49 am

Yellow one is used in '95 & some '96 850 with Jetronic and M4.3 managements.

Red ones are used in some '96 and ALL '97 850 with M4.4....should also be used in '97 & '98 s,v,c,xc70 .
I don't know if yellow and red ones are interchangeable.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
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Re: Testing/Experimenting with Fuel Pump Relays

Post by SonicAdventure » Tue Dec 31, 2019 11:26 am

What about the '99 and '00 models? Are they their own thing too because of the ignition differences?

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Re: Testing/Experimenting with Fuel Pump Relays

Post by abscate » Tue Dec 31, 2019 12:44 pm

SonicAdventure wrote:
Tue Dec 31, 2019 11:26 am
What about the '99 and '00 models? Are they their own thing too because of the ignition differences?

The 9434225 relay will fit the “ bastard “1999 and 2000 models, too.
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Re: Testing/Experimenting with Fuel Pump Relays

Post by abscate » Tue Dec 31, 2019 2:58 pm

On the bench testing, have you tried cold soaking it in the freezer for an hour?

By saying” cold soaking it on the electrical bench” you can charge $200/ hour for using engineer-speak

“ put i n freezer” is a mere $15/hour phrase
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Re: Testing/Experimenting with Fuel Pump Relays

Post by erikv11 » Tue Dec 31, 2019 6:32 pm

Definitely OK to swap the relays around from newer to older P80 cars. There is nothing special about the ones in 99 and 00 cars.
'95 854 T5-R, Motronic 4.4, 185k
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Re: Testing/Experimenting with Fuel Pump Relays

Post by SonicAdventure » Wed Jan 01, 2020 6:34 pm

Setting the multimeter to 2k ohms, red to terminal 15 and black to terminal 31, both of these red relays read ~1.75 at ambient room temp.

Removing the red covers, on the same multimeter setting, the silver caps in each relay are reading ~.44 and the brown caps in each relay are reading ~.55.

Do these sound like “in-spec” readings? I admit to being pretty new at using multimeters. I’m trying to use these as a control against what I think is a failing relay in my car, which I am about to pull and do similar tests with...

I’m also including photos of the yellow and red relays without their caps for those who might like to see what they look like on the inside.
Attachments
811A4DFD-0956-4DC2-B68A-AB62D722B6F3.jpeg
Red and yellow relays, “back”?
811A4DFD-0956-4DC2-B68A-AB62D722B6F3.jpeg (92.71 KiB) Viewed 25 times
C4A6AA12-2D0E-43AE-B11F-1A606D4FA0F1.jpeg
Red and yellow relays, “front”?
C4A6AA12-2D0E-43AE-B11F-1A606D4FA0F1.jpeg (99.17 KiB) Viewed 25 times
25FFBC9B-87B1-4B27-8224-496AFE7D656B.jpeg
testing red relays
25FFBC9B-87B1-4B27-8224-496AFE7D656B.jpeg (131.82 KiB) Viewed 25 times
Last edited by SonicAdventure on Wed Jan 01, 2020 8:01 pm, edited 3 times in total.

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Re: Testing/Experimenting with Fuel Pump Relays

Post by abscate » Wed Jan 01, 2020 6:39 pm

You can test for an open relay, but evaluation the coil and pull in isn’t really possible with a VOM

You can find a really dead one, but not one that is failing on hot/ cold
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Re: Testing/Experimenting with Fuel Pump Relays

Post by SonicAdventure » Wed Jan 01, 2020 8:05 pm

abscate wrote:
Wed Jan 01, 2020 6:39 pm
You can test for an open relay, but evaluation the coil and pull in isn’t really possible with a VOM

You can find a really dead one, but not one that is failing on hot/ cold
Ok. Assuming my fail to start issues are caused by freezing temps affecting an iffy relay, if I removed the suspect relay and kept it cold, what would be the tell-tale sign, a certain meter reading in one of the caps?

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