Fuel Pump, or Fuel Pressure Regulator

Tiny
CRAIG JASTER
  • 1994 FORD RANGER
  • 200,000 MILES

So this is the second time I have posted on this topic. I have run through all the previously suggested tests and I'm still having the same problem. I have replaced the fuel pump, only to find that I wasted $75.00. I did come acrossed an issue that I could see would cause a fuel pressure issue. The hose that connects the pump to the sending unit was split down the side and basically shooting gasoline back down into the tank. Attached is a pic of what I removed and replaced. I'm pretty sure the pump is still good but I replaced it anyways because with the hose like that I simply dont know how long that pump has been over working itself. With the new fuel pump, I still only get 26psi running pressure, but the static pressure is holding at about 36 pis(key on engine off)
The diaphragm on the fuel pressure regulator seams to be holding a vacuum well, and isnt leaking any fuel. The injectors dont seam to be leaking off per the test I ran. I have a timing light that I'm going to hook up to it and replace the fuel filter again. Any other suggestions would be helpful.
Thanks.

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Sunday, August 26th, 2012 AT 5:24 PM

18 Replies

Tiny
ASEMASTER6371
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Pinch off the return line to the tank at the pressure regulator and see what the pressure measures.

Roy

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Sunday, August 26th, 2012 AT 5:29 PM
Tiny
KHLOW2008
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Symptoms indicates the fuel pressure regulator is faulty.

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Sunday, August 26th, 2012 AT 5:34 PM
Tiny
CRAIG JASTER
  • MEMBER

OK, the pressure went up to about 50psi. Does that explain it?

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Sunday, August 26th, 2012 AT 5:38 PM
Tiny
KHLOW2008
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Yup, that means a bad pressure regulator.

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Sunday, August 26th, 2012 AT 5:45 PM
Tiny
CRAIG JASTER
  • MEMBER

Ok, I unhooked the vacuum line off the fpr and the pressure went up to normal operating pressure 35-36 psi

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Sunday, August 26th, 2012 AT 6:11 PM
Tiny
KHLOW2008
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35-36 psi is at lower edge of specs but vacuum line should be attached.

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Sunday, August 26th, 2012 AT 6:25 PM
Tiny
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That is normal. With no vacuum, the pressure should rise.

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Sunday, August 26th, 2012 AT 7:19 PM
Tiny
CRAIG JASTER
  • MEMBER

Put a brand new regulator on it with no change in results it seams the regulator works properly without a vacuum line hooked to it?

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Sunday, August 26th, 2012 AT 7:27 PM
Tiny
ASEMASTER6371
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With vacuum, it will lower the pressure. Thats normal as I said before.

What kind of pump did you use?

Roy

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Sunday, August 26th, 2012 AT 7:33 PM
Tiny
CRAIG JASTER
  • MEMBER

The name brand on the pump is airtek.
Now the truck is getting 26psi @ idle but if I give it a little more throttle, the pressure goes up to 36psi. Naturally a higher rpm is going to require more volume @the same pressure correct? So, does that mean the regulator is operating correctly? Maybe the old regulator was bad and I just need to take it for a spin and see what happens in stead of looking at the pressure gauge.

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Sunday, August 26th, 2012 AT 7:51 PM
Tiny
ASEMASTER6371
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The regulator is fine. When you decrease manifold vacuum, the pressure increases.

The pressure is on the low side. I like to see around 35 at idle with the vacuum line on the regulator

Roy

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Sunday, August 26th, 2012 AT 8:06 PM
Tiny
CRAIG JASTER
  • MEMBER

Ok, I took it for a test drive and its still bogging down under a load, not as bad but still is. When you throttle the engine doesnt that give you more vacuum?
The pump should be more than enough to provide adequate pressure to the rail. The specs on the pump call for minimum of 80 psi and max 100 psi. Unless I got a bad pump which has happened before.

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Sunday, August 26th, 2012 AT 8:23 PM
Tiny
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No, less vacuum under load. Yes, you could have a bad new pump. Airtex is a good pump but you never know.

Roy

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Sunday, August 26th, 2012 AT 8:26 PM
Tiny
CRAIG JASTER
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Regardless of the rpms of the engine, an electronic fuel pump is going to continuously give you the same pressure, and the regulator is going to adjust the pressure into spec right?

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Sunday, August 26th, 2012 AT 8:27 PM
Tiny
CRAIG JASTER
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The only things on the fuel system that arent new as of today are injectors, fuel rail, lines and filter. The filter is the only thing left that would cause loss of fuel pressure

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Sunday, August 26th, 2012 AT 8:32 PM
Tiny
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Nope, wont do it. There is a bypass if the filter gets clogged.

Roy

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Sunday, August 26th, 2012 AT 8:35 PM
Tiny
CRAIG JASTER
  • MEMBER

Ok, so less manifold vacuum increases the fuel pressure right, so does that mean I have too much manifold vacuum at idle?
How does manifold vacuum get too high there are any vacuum regulators anywhere, I cant find any. Could that mean I have a vacuum clogged somewhere? An open vacuum line would reduce vacuum elsewhere or could my idle be set too high? Im stumped here. Could the throttle position sensor cause this?

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Sunday, August 26th, 2012 AT 8:52 PM
Tiny
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You vacuum is fine, your regulator is fine. There is no vacuum issue. It is a pressure issue possibly from a weak new pump.
Roy

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Sunday, August 26th, 2012 AT 9:11 PM

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