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Unstable fuel pressure

Tiny
MARIOC68
  • MEMBER
  • 1995 TOYOTA COROLLA
  • 220,000 MILES
Hi, I have problems in terms of performance, loss of power of my car, checking the fuel pressure I find unstable. The residual pressure after five minutes is approximately 17 psi.
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Thursday, April 25th, 2019 AT 10:12 AM

17 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

I attached readings for both engines.

As far as the drop in pressure that could come from an injector leaking down, pressure regulator failure or the pump itself which is what I think it is.

Roy

1.6

FUEL PRESSURE VALUES
Key ON, engine OFF, FP - B+ jumped. 265 - 304 kPa (38 - 44 psi)
At idle, vacuum hose disconnected. 265 - 304 kPa (38 - 44 psi)
At idle, vacuum hose connected. 206 - 255 kPa (31 - 37 psi)
Residual pressure after 5 minutes. 147 kPa (21 psi or more)

1.8

FUEL PRESSURE VALUES
Key ON, engine OFF, FP - B+ jumped. 265 - 304 kPa (38 - 44 psi)
At idle, vacuum hose disconnected. 265 - 304 kPa (38 - 44 psi)
At idle, vacuum hose connected. 206 - 255 kPa (31 - 37 psi)
Residual pressure after 5 minutes. 147 kPa (21 psi or more)
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Thursday, April 25th, 2019 AT 1:41 PM
Tiny
MARIOC68
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With the FP and + B jumper, it gives 44 psi. Engine started, with vacuum hose disconnected, also 44 psi (here I can notice only certain vibrations in the manometer needle).
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Thursday, April 25th, 2019 AT 2:24 PM
Tiny
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What about the pressure without the jumper?

Roy
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Thursday, April 25th, 2019 AT 2:39 PM
Tiny
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I already described it. Without the jumper, vacuum hose disconnected, 44 psi. Without the jumper, with the hose connected, erratic reading, which shows the video.
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Thursday, April 25th, 2019 AT 2:45 PM
Tiny
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Got it. I saw the video. If it does not vary with the hose off, that is good.

If it varies only with the hose connected then it looks like the regulator itself is the issue.

Roy
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Thursday, April 25th, 2019 AT 2:56 PM
Tiny
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Is there any way to verify or test the fuel pressure regulator, if this is the culprit?
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Thursday, April 25th, 2019 AT 3:18 PM
Tiny
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If you have stable pressure with it disconnected and fluctuating with it connected, then the only thing is the regulator.

Is the vacuum strong at the regulator hose?
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Thursday, April 25th, 2019 AT 3:28 PM
Tiny
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Perform a couple of vacuum tests on the intake manifold. Use two different gauges, both indicate 20 inch hg. But one with very slight fluctuation, almost imperceptible; with the other tool the fuctuacion is greater, as indicated by the fuel manometer. The two tools of different brand.
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Friday, April 26th, 2019 AT 4:39 PM
Tiny
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This tool, erratic readings with a lot of variation.
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Friday, April 26th, 2019 AT 4:41 PM
Tiny
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For that to cause it the fluctuation would have to be drastic.

You need a regulator.

Roy
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Friday, April 26th, 2019 AT 4:42 PM
Tiny
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Got it.

Does it hold vacuum when you pump it up with the engine off?

Roy
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Friday, April 26th, 2019 AT 4:43 PM
Tiny
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With this the reading is much more stable.
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Friday, April 26th, 2019 AT 4:44 PM
Tiny
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Perform a vacuum test only on the regulator (with engine off), connecting the vacuum gun to the regulator. The vacuum is maintained, reaching a maximum of 25 inch Hg.
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Friday, April 26th, 2019 AT 4:49 PM
Tiny
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Okay, then you need a regulator.

Roy
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Friday, April 26th, 2019 AT 5:02 PM
Tiny
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Ok. Tank you.
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Friday, April 26th, 2019 AT 5:54 PM
Tiny
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Excuse me, how much should the regulator admit of empty when it is in good condition?
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Friday, April 26th, 2019 AT 6:00 PM
Tiny
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It does not empty. It limits. It maintains a certain predetermined pressure.

Roy
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Friday, April 26th, 2019 AT 6:12 PM

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