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New fuel pump and relay but still no fuel pressure!

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

nikolajs
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nikolajs

Re: New fuel pump and relay but still no fuel pressure!

Post by nikolajs » Tue May 16, 2017 8:44 pm

Ok - so I was never able to start the car with the MAF plugged in. It did however start and run OK (driveable) with the MAF unplugged, but was then obviously throwing a MAF code. I ended up getting a new MAF and as soon as i plugged it in, the car started right up and so far runs and drives like it should. I've driven about 50 miles, no check engine light so far.

The only weird thing is that I don't think I ever had a MAF code before the sensor stopped working. After it stopped working, it was too late to diagnose with the code scanner/computer as the code was being thrown because I had to have the MAF unplugged for the engine to run (which I found out more or less by trial and error...). I have a feeling it was the MAF all along, and the $ spent on the fuel system parts may have just been "collateral damage".

Anyway, Misha- thanks for your help.

nikolajs
Posts: 22
Joined: Fri Jul 17, 2015 7:31 pm
Year and Model: 98 V70 T5, 97 850 NA
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nikolajs

Re: New fuel pump and relay but still no fuel pressure!

Post by nikolajs » Tue May 16, 2017 9:20 pm

Ok - so I was never able to start the car with the MAF plugged in. It did however start and run OK (driveable) with the MAF unplugged, but was then obviously throwing a MAF code. I ended up getting a new MAF and as soon as i plugged it in, the car started right up and so far runs and drives like it should. I've driven about 50 miles, no check engine light so far.

The only weird thing is that I don't think I ever had a MAF code before the sensor stopped working. After it stopped working, it was too late to diagnose with the code scanner/computer as the code was being thrown because I had to have the MAF unplugged for the engine to run (which I found out more or less by trial and error...). I have a feeling it was the MAF all along, and the $ spent on the fuel system parts may have just been "collateral damage".

Anyway, Misha- thanks for your help.

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rspi
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rspi

Re: New fuel pump and relay but still no fuel pressure!

Post by rspi » Wed May 17, 2017 4:00 am

I'm still stuck on the car starting with no fuel pump relay???
'95 855 T-5R M, Panther - 22/28 mpg
'98 S70 GLT, Lil' Red 25/32 mpg
--------------------
Volvo's of past: '87 740 GLE, '79 262C Bertone, '78 264, 960's, '98 S70 GLT, '95 850 T-5R YellowVolvo Repair Videos

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misha
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misha

Re: New fuel pump and relay but still no fuel pressure!

Post by misha » Wed May 17, 2017 5:10 am

Me too,but it seems that it was overfueling and flooding the engine because of maf.
Fuel pump relay does not control just the pump...it controls a few sensors,which should be Maf and o2.
When he removed the relay...system had pressure in fuel rail enough to start and run engine for a few seconds...and removing relay acted just like he disconnected the maf.Main fuel injection relay controls injectors,coil.....so the car started and run with that relay disconnected untill there was fuel in fuel rail.

I hope that replacement Maf is oem Bosch 0 280 217 107.If not,you will have the same Maf problems pretty soon.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

precopster
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precopster

Re: New fuel pump and relay but still no fuel pressure!

Post by precopster » Wed May 17, 2017 7:22 am

That doesn't explain how some folk can place a jumper in the fuel relay position and have a perfect running car for weeks. This post has just done my head in.
Current cars:2002 XC70, 2006 Ssangyong Rodius (Stavic), 2006 XC90 2.5T, VW Transporter 2.5TDI

www.precisioncarmodules.com.

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misha
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Re: New fuel pump and relay but still no fuel pressure!

Post by misha » Wed May 17, 2017 8:52 am

It explains everything IF relay itself is bad...and the thicker jumper wire is-it is better....for testing purpose,of course.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS

scot850
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scot850

Re: New fuel pump and relay but still no fuel pressure!

Post by scot850 » Wed May 17, 2017 11:52 am

There is another possibility worth checking on. I have seen a couple of times where there has been shorts happening under the fuse box where the fuel pump relay is fitted in front of the drivers side windshield wiper (not the kidney shaped main fuse box in the engine bay). The wires in those cases had crumbled and the insulation had fallen off and caused various shorts to occur. It may explain how the car ran without the fuel pump relay in place. Also, a less likely issue is to check there is no issue with the B+ cable in the main fuse box. Check the nut and the cable end are nice and shiny, but also look carefully under where the cable bolts down as mine had melted all the insulation in there!
Volvo V70R engine B+ cable fuse box end (3).JPG
Neil.
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2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - New project and test bed - Sold

cn90
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cn90

Re: New fuel pump and relay but still no fuel pressure!

Post by cn90 » Wed May 17, 2017 5:20 pm

The original post gave a lot of hint: "Unplug the MAF and the car ran better". Even without codes, that is a "give away".
Stick to Bosch MAF and you will be fine.

The fuel relay is a bit more tricky to diagnose: but a jumper wire (info in forum) is definitive diagnosis.
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

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