98 3.0 fuel pressure questions


ks8780

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I have a '98 3.0 Ranger with perhaps 300,000 miles on it. Not sure as odometer motor is bad and is stuck at 199,000 and hasn't worked since I bought it. I am wondering what fuel pressure should be ? I have found 30-40 psi and others say the 98's should have 55 psi. Mine is suffering from low power and poor starting. Sometimes starts about like a flooded carb engine or starving for fuel perhaps. With the high miles I suspected injectors so I put them in tonight and I THINK it may have more power I'm not for sure. Seemed to start fine but will see in the morning for sure.

I am chasing the left and right bank lean codes. My fuel pressure is 39 psi at 2500 rpm. drops pretty quick when you shut off engine. Wondering if this is in spec or low. Replaced fuel filter a while back and it only has 1 inlet and 1 outlet IIRC.

I was going to put on a new FPR when I did injectors and ordered this one

https://www.rockauto.com/en/moreinfo.php?pk=1113221&cc=1304514&jsn=1012

Looks different from the one on this truck. Mine is at the front of right fuel rail and is much smaller with a vacuum line attached to it if I am looking at the right thing. I did not take it off to see if the new one would mount up anyway.

I have no idea how old the fuel pump is or if it is the original but if I am supposed to have 55psi I am leaning toward a weak pump.

Any help appreciated.
 


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Dirtman

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If there is only ONE fuel line going to the engine you have a returnless system and NO fuel pressure regulator (it's part of the pump) you have a fuel pressure damper. If you have TWO fuel lines to the engine you have a return system that has a regulator not a damper.

They changed the system in 98 to a returnless system (only one line to the fuel rail) so if you have an early 98 you may have the older return style system. If you have a returnless system your fuel pressure is very low. If not it's fine.

With the return system and a regulator 35-40psi is good. With a returnless system and a damper it should be 60-65psi.

With either system the pressure should hold with the engine off. For weeks... if not you have a leak in the system. (Usually it's at the injectors, or regulator/pump). Either will cause hard starting and stumbling until pressure builds back up.

What exactly are the codes you are getting?



*edited to make more sense of my incoherent rambling*
 
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ks8780

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They are PO171 and PO174. Engine Vacuum seems good and I cannot find any vacuum leaks. I am 99% sure my filter has 1 inlet and 1 outlet but will look tommorow for sure.
 

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1998 and up Ranger use a Returnless Fuel system that should run 55psi pressure engine running, and drop no lower than 25psi engine/key off

You will only see 1 fuel line in the engine bay, comes up from the frame on drivers side


As Dirtman said you do not have an FPR on the engine, what you have is a pulse damper, vacuum line is there in case it should leak.

1997 and older Rangers used a Return fuel system and did have an FPR on the engine, they ran 30-35psi engine running, 40 if you disconnected FPR vacuum hose
The part you ordered is for 1997 or older

Your pressure is too high for 1997 and too low for 1998, so its a returnless system with low pressure

You do have an FPR but its in the gas tank, part of the fuel pump assembly

Yes, 1998 and up Rangers have fuel filter with 3 hoses attached, 2 go to the gas tank, but it CAN just have just 2 fittings there were both types used, 1998/1999

Its possible you just need to replace the filter, $15 so I would do that next


There is a test you can do after engine is warmed up
Turn on the key
Press gas pedal down to the floor and hold it down all the way
Try to start the engine, leave pedal down all the way
Engine should NOT start, it should NOT fire at all, fuel injectors are shut off

Now let off gas pedal and it should start, if so then no leaking injectors

Lean codes are from the low fuel pressure

Probably need to change fuel pump assembly

For now try cycling the key on and off 3 times before starting, that will build fuel pressure back up if its dropping to 0psi when it sits
 
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Dirtman

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Double check the lines, if there's one your pressure is way too low and could definitely be a weak pump.

I edited my first post because after reading it I couldn't even understand what the hell I was trying to say lol. Figure out which system you have. Should be returnless BUT I've seen goofy crap with "transition years".
 
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ks8780

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While putting in the injectors I could only find 1 line going to fuel rail, steel braided line coming up from left frame rail to the tiny fpr or damper. It has the spring type fitting on the top or there abouts. The regulator or damper is about the diameter of a bottle cap and around 1.5" high vacuum line attached to bottom. I will check more tommorow and report back. Thanks
 

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For sure Returnless, should have 55psi

Could be broke/cracked lift hose in the gas tank, but long shot and you still have to pull or lift the bed to check in any case
 

Dirtman

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My only concern is that it seems odd that a returnless system would fail and have the PERFECT pressure of a return style system...
 

ks8780

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Will check more in the morning. If I do need a pump my local Napa has 3 in stock. Delphi, Bosch and there Napa brand. Any preferences ? These are all just the pump kit not the complete hanger assembly. I assume the regulator is built into the pump itself?
 

Dirtman

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I HIGHLY recommend trying to find a motorcraft pump if that ends up being the problem. Aftermarket fuel pumps are notorious for being garbage. Motorcraft is what's in the tank now and it's lasted 21 years... your lucky to get a year out of other brands. Not that bosch or Delphi are known to be crappy brands, the main thing to avoid is no name brands, store brands, or anything off ebay/amazon. But motorcraft is the best option by a wide margin.
 

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Make sure your ranger is indeed a 98 and not built for 99. The reason why is in case it is flex fuel.
 

ks8780

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Ok checked things out some more. Fuel filter has 1 in and 1 out. Appears I have a damper instead of FPR. Fixed a small leak on my fuel pressure tester and have 41 psi at 3000 rpm and has been holding 41 for 5 minutes so far after shutdown. I have a fresh filter to put on as old one is a couple years old. Truck build date 10/97. I will try to attach some pics. Pics to big try again later
 

Dirtman

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41 is still low for a returnless system. If you've done the filter I'd definitely be considering the pump.
 

Craig0320

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41 is still low for a returnless system. If you've done the filter I'd definitely be considering the pump.
Yup. 55-58 minimum.
 


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