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What's the fuel pressure supposed to be at the schrader valve on the fuel rail?

Tiny
SANDSTORM58
  • MEMBER
  • 1998 DODGE GRAND CARAVAN
  • 3.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 361,000 MILES
Brand new fuel pump (bosch) because old fuel pump showed signs of a problem but not getting but 12-14 psi at the rail (schrader valve) with the key in on position. I had to replace the outbound fuel line from pump to filter after finding a leak, replaced with rubber fuel injection hose instead of nylon tubing.

what's the fuel pressure suppose to be at the schrader valve on the fuel rail. I thought it was to be at 49 psi which is what my book calls for.

the reason why I ask is because prior to changing the fuel pump the pressure was dropping below 42 psi and gradually but immediately at that then I found the fuel leak.

what could be causing such low fuel pressure after a new fuel pump w/new was installed fuel filter is less than a year old, new injectors, new spark plugs, new o2 sensor upstream (this is when everything began coding when changing the sensor), and a few other fuel related items. I need help on this one‼
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Monday, August 29th, 2022 AT 1:14 PM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Here are the fuel pressure specs as you requested.

Fuel Pressure

Key On, Engine Off. (Approx.) 338 kPa (49 psi)

Note: Using the DRB Scan Tool, access ASD Fuel System Test. The ASD Fuel System Test will activate the fuel pump and pressurize the system.

CAUTION: When using the ASD Fuel System Test, the ASD relay and fuel pump relay remain energized for 7 minutes or until the test is stopped, or until the ignition switch is turned to the Off position.

You must have a bad fuel pump because even the fuel pressure regulator is inside the fuel pump module, check out the diagrams below. I would get an AC Delco unit for it from Rockauto. Com.
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Tuesday, August 30th, 2022 AT 9:43 AM
Tiny
SANDSTORM58
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I actually have fuel pressure at the pump and higher than 50 PSI. I tested it to see if the fuel filter might be defective or semi-clogged and that seems to be the case here. I'm changing the fuel filter then will retest the system once I have it all back together. Suspect someone dumped crap into my tank so when I had it down last week, I emptied it and cleaned the tank out.
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Tuesday, August 30th, 2022 AT 10:12 AM
Tiny
KEN L
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Yep, it happens, let me know when you have it back together. Good job checking the fuel filter.
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Wednesday, August 31st, 2022 AT 11:12 AM
Tiny
SANDSTORM58
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  • 16 POSTS
Installed a new fuel filter unit and put it all back together. Not getting full pressure at the rail so had a helper turn the key to "on" while I was under the car. Every fuel pump I've ever had that's in-tank hums at that position, but this brand-new pump stops after a couple of seconds very abruptly like a thud. I put my hand on the top ring and felt it abruptly stop after keying "on". Am I right by saying I have a defective pump? Pressure only went to about 14 PSI and stopped within a couple seconds. I checked the Fuel Pump Relay and it's running fine.
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Wednesday, August 31st, 2022 AT 11:45 AM
Tiny
KEN L
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Yep, good call, I would get a Motorcraft pump for it, it costs more but you won't be doing the job again.
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Friday, September 2nd, 2022 AT 8:45 AM

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