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Old 11-25-2020, 10:43 PM   #1
mschultz373
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Join Date: Mar 2020
Location: dirty coast
Default fuel pressure spec

what's the spec for a 94 940 Turbo? running LH2.4. I hooked my gauge up at the rail and it read ~45psi. seemed to hold for a few minutes after turning off, too. It was a quick read before leaving the shop for the night.

I read on some 'volvo answers' site that that's high, but I figured I'd come to the experts and ask.

I have yet to test pressure at the fuel supply line to the main pump. should that spec be the same?

what does it mean if my PSI is above/below the spec? I've been getting terrible gas mileage (14-16mpg) so I wonder if she's running rich, but I don't know for sure if that'd be verified with a pressure reading or not.

thanks as always yall
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Old 11-25-2020, 10:52 PM   #2
90volvo
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I believe thats right on? But Im sure some experts will tune in .
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90 Volvo 240-my current setup.
B230ft rebuilt -8.8 comp. -Stage 3 rsi cam
3 inch ex.-GTX3076r turbo ballbearing.
ebay intercooler-3 inch IC piping- Oil cooler with 10an hose.
port stock intake (weak, having a custom intake by viking fab.)
Megasquirt 2-1300cc injectors (running E85)
530 head with big valves ported and assemble by culberro

sons car- 93 240-15g turbo-chipped-95,000 miles. Slick car

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Old 11-26-2020, 01:11 AM   #3
2manyturbos
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It should read 45 PSI with the vacuum line disconnected. With the vacuum line connected at idle the gage should read ~ 39 PSI.
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Old 11-26-2020, 02:53 AM   #4
mschultz373
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vac line at the FPR? I had that connected. so... does that mean my FPR is broken?
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Old 11-26-2020, 03:12 AM   #5
2manyturbos
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Was the engine running when you took the reading?
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Old 11-26-2020, 03:52 AM   #6
mschultz373
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Yea, engine @ idle in P.

I'll take more thorough, careful readings at both the rail and supply line in the morning to confirm this finding.
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Old 11-26-2020, 04:48 AM   #7
2manyturbos
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That isn’t that far off. I’ve seen that much variation before without problems. Measure the pressure again with the engine idling and the vacuum line off and plugged.
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Old 11-26-2020, 10:12 AM   #8
OttoB
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My engine was running quite normal with 70 psi fuel pressure. Idle was too fat but surprisingly lambda correct the afr quite well.
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Old 11-26-2020, 02:36 PM   #9
mschultz373
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i think everythings fine. reading this morning was ~41psi @ idle in P with vac line attached, went up to ~50psi without vacuum. held the 41psi for 20+min after turning car off. I couldn't get a read at the valve before the main fuel pump - connected the gauge but it read 0 - but I suspect that valve may be clogged or something. the car has been running mostly fine, in D at idle it can feel rough and vibrate a lot but i think my motor mounts are completely toast.
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Old 11-26-2020, 03:22 PM   #10
2manyturbos
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It's fine. I usually see 41-42 PSI at idle with the vacuum line connected. 45 with it disconnected.
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