94 Ranger 3.0 Fuel Pressure Issue, any ideas? - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 05-17-2017
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94 Ranger 3.0 Fuel Pressure Issue, any ideas?

Problem: Have to cycle the key on to let the fuel pressure build up in the system for a few seconds otherwise it won't start the first try. Other than that no problems starting and seems to run ok.

Decided I'd look into it and it seems worse than I thought. Key On Engine Off I have 38psi (fuel pump stays running and will not cycle off). Engine Running is 30psi. When I shut the truck off I go from 30 psi to zero in about 10-15 seconds!

With the key cycled on but engine not running I can hear a "leak" but I can't pinpoint anything either feeling around, with soap bubbles, stethoscope trick etc. Other than it seems to be loudest at the fuel pressure regulator. I'm wondering if I'm not just hearing the fuel flowing through it though rather than a leak like maybe one of the injectors is leaking. No fuel in the vacuum line off the FPR.

Using stethoscope all injectors seem to sound normal and the same. I ohmed out the right bank which is the same side the FPR is on (left bank requires pulling the intake or is a pita at best) and they are all right at 14.8 ohms which seems in spec.

I'm not seeing a good spot to pinch off fuel lines to isolate the fuel pump, FPR, and injectors to narrow this down. Everything I see is either metal of plastic with a rubber casing (near the fuel filter). Pretty sure the plastic would crack if I tried to pinch it off.

The fact that the pump won't build even pressure to shut off and I can hear a leak or flow through the FPR makes me think injector leak or the FPR is bypassing (not sure if that's the right word) and sending fuel back to the tank?

Just hoping you guys can point me down the right path. Thanks.
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Old 05-17-2017
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When engine is cold pull off the big air intake tube from the intake manifold

Open throttle plate manually and smell for gasoline, should be no smell
Now cycle key on and off 4 or 5 times, build up some pressure, then key off
Open throttle and smell again
You will for sure smell a leaky injector

30-40psi is spec for 1997 and earlier Rangers, 1998 and up have no FPR and need 60-70psi

You can also remove Return fuel line on FPR, put a towel down and cycle key on and off 1 time, look to see if FPR is holding the fuel or leaking it out
Spring valve inside FPR should hold fuel in until pressure gets to 40-45psi
From 0psi each key on and off get about 10-15psi of added pressure

Most common 0PSI key off is the fuel pumps check valve, just a flap that closes and holds fuel pressure in the fuel line
Some one has "hot wired" the fuel pump Relay, which is why fuel pump is on full time when key is on, that is OK unless a fuel line breaks and then you can have a dangerous situation.
Look for the VIP/OBD1 connector in the engine bay
Drawing of it here: http://www.therangerstation.com/tech...ry/OBD_I.shtml

second one down
Fuel Pump slot is pointed out
Some one has Grounded that slot with a jumper wire
Probably because of the failed check valve in fuel pump

Last edited by RonD; 05-17-2017 at 08:18 PM.
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Old 05-17-2017
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Thanks for the help! From what I could find I thought I needed to be in the 60's but that must have been for the other years.

I was out doing the stuff you suggested and just now saw the edit so I've got more work to do.

Did the before/after smell test and didn't notice anything so that's good. .

I disconnected the return fuel line down by the fuel filter and I do get fuel out when I cycle the key on and seems to be well before I hit 40 psi so I'm wondering if there are multiple issues here?

Bad FPR plus someone monkeyed with the fuel pump? Because it definitely doesn't cycle off at all. When I was working on it trying to find the leak or whatever it was I was hearing it didn't shut off for probably the 30sec-1min I had the key on.

I put it back together but kinda wish I would have plugged the return to see if I could hold pressure. Oh well. Not sure I have anything laying around here to do that.
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Old 05-17-2017
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You are totally right!

I just went out and lifted up the cover and there was a wire going to the FPR relay!

I've lifted that up once before when I was working on it months ago (Taurus fan install) and completely missed that somehow.

Man, the previous owner spent NO money on the maintenance for this thing. Every "repair" i've found has been crap like this.

The FPR does look new, doesn't mean it couldn't be bad I guess.

Guess I should start with the fuel pump first and then see if I need to do the FPR?

Is there a brand I should stay away from? Or should most any pump be ok?

Not really wanting to pull the bed and do a fuel pump but at least I know. Thanks again for your help, I really appreciate it!
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Old 05-17-2017
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The liquid/fuel you hear flowing with engine off is probably over pressure from the pump being on all the time, FPR was releasing pressure over 40psi and you hear that running back to tank in the fuel Return line
Fuel pump is not suppose to be on, full time, unless engine is running


Putting in a new fuel pump is a hassle, so................I know they are expensive but Motorcraft(OEM/stock) would be the brand I would use.
You probably have the original fuel pump in there, 23 years old and still works, yes check valve failed but didn't strand you any where, lol.
Maybe you will drive it another 23 years maybe not, but nice to know fuel pump won't be an issue again.

Other than Motorcraft, I would look at reviews of the other brands, they usually have a 1 or 2 year warranty, but you still have the hassle of pulling it out and putting it back in.

Motorcraft fuel pump has 60 day warranty, lol

Hard to justify $350 vs $150 but really up to you
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Old 05-17-2017
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Makes sense. I'll look at pricing and decide what to do.

I'm more excited I've got it diagnosed than I am dreading the work.

Thank you so much!
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Old 05-18-2017
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You are very welcome

On the plus side of a cheaper fuel pump.............

Getting the bed bolts out is the hard part because they are usually rusted tight
But once they are out and then put back in, they will be easy to remove for the next few years, until they rust again, lol.
So..........if less expensive pump does fail under warranty, not as hard to swap it out

Also just a heads up, check the filler and vent tubes, they have a tendency to crack
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Old 05-18-2017
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I'm going to soak everything with kroil for a couple of days before I try and work on it.

I'm in AZ and I think the truck has been here since new so I'm hoping they come out fairly easy. Probably throw some anti-seize on them when I put it all back together.

I looked at filler tubes and they are $80! I'm not sure what I was expecting but not that, lol. I'll definitely take a look though. No reason not to do everything at once.
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