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Crazy spiking 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

S60UT
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Joined: Wed Jun 14, 2017 2:31 pm
Year and Model: 200 S70 T5 swap
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S60UT

Crazy spiking fuel pressure

Post by S60UT » Mon Sep 23, 2019 2:32 pm

So StevO has been outstanding trying to get my car (S70 T5 swap) to boost up to 15psi. He did all he could do tuning/toubleshooting and my max boost is anywhere from 6-9 psi. Im still getting CEL for turbo flow problems, one time it was flow to high and then it was flow to low. One thing we noticed was the fuel pressure was spiking from 45 to 80 and it repeats this spike every 5 seconds. I told him i had recently installed a Walbro 255 pump. He thought i may have bought a counterfit from these guys
https://walbrofuelpumps.com/partfind...yl.+2.3l-30812
So i installed a fairly new after market pump laying around and the pressure held to 45 psi. 3 weeks later and this aftermarket pump is spiking the same way the Walbro did therfore i dont think i purchased a fake Walbro. I have swapped out 3 Fuel Pump relays with no difference. What prompted me to test the pressure again was surging and bucking driving up to Park City yesterday its about a 2K ft ascend. Any ideas of what could be causing this spike ? I really doubt its the pumps. And i will back off from the low boost issue, but this fuel thing has become a safety issue now.


01 S60 T5 Manual
00 S70 GLT
00 S70 GLT SE T5 Swap

jimmy57
Posts: 6390
Joined: Fri Nov 12, 2010 9:25 am
Year and Model: 2004 V70R GT, et al
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jimmy57

Re: Crazy spiking fuel pressure

Post by jimmy57 » Mon Sep 23, 2019 8:41 pm

Check for obstructions in the return line from the fitting the FPR is set into under the passenger firewall/footwell area. The FPR is held in by a V band clamp. If the fuel can't get back to tank then the pressure spikes to the relief valve pressure. That releif valve is built into pump and can't shed that much fuel so the max pressure in that case may vary.



S60UT
Posts: 24
Joined: Wed Jun 14, 2017 2:31 pm
Year and Model: 200 S70 T5 swap
Location: Utah
Has thanked: 0
Been thanked: 0
United States of America
S60UT

Re: Crazy spiking fuel pressure

Post by S60UT » Wed Sep 25, 2019 7:43 am

Jimmy57, thanks for the suggestion, I have a MY 2000 w/out the return system. Any other ideas would be greatly appreciated.


01 S60 T5 Manual
00 S70 GLT
00 S70 GLT SE T5 Swap

jimmy57
Posts: 6390
Joined: Fri Nov 12, 2010 9:25 am
Year and Model: 2004 V70R GT, et al
Location: Ponder Texas
Has thanked: 2 times
Been thanked: 179 times
jimmy57

Re: Crazy spiking fuel pressure

Post by jimmy57 » Wed Sep 25, 2019 7:59 am

You still have the FPR, it is back in line near fuel filter and tank.
I found a pic online that is from this site. I didn't find it searching this site, thank to whoever posted it.
You do not have the required permissions to view the files attached to this post.



S60UT
Posts: 24
Joined: Wed Jun 14, 2017 2:31 pm
Year and Model: 200 S70 T5 swap
Location: Utah
Has thanked: 0
Been thanked: 0
United States of America
S60UT

Re: Crazy spiking fuel pressure

Post by S60UT » Wed Sep 25, 2019 2:41 pm

Jimmy you are the best !! My FPR was fine, but your suggestion led me to the solution. When i swapped in the T5 engine from a 01 S60 the fuel line connectors were different. I ran a new fuel line from the filter to the engine. I didnt realize when i cut the old line out, I was supposed to run the new line into and out of the plastic housing that the FPR bolts into. Not until i removed my FPR today did i realize it was an integral part of the fuel system. Its holding steady at 57 PSI and the fuel pump stopped squealing. Now on to my low boost issue. Thanks Again !!


01 S60 T5 Manual
00 S70 GLT
00 S70 GLT SE T5 Swap

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