Crazy high fuel pressure (50-60lb) on '02 3L

[Rustydawg]

Guys

I was working on my buddy's 2002 3.0L Ranger today, we changed the fuel filter on spec then took it for a ride to see if a hesitation was cured.

I think the problem is worse now. I put a gauge on the fuel rail and we're seeing between 50 - 60 psi, and pulling / applying manifold vacuum at the pressure regulator doesn't move the pressure at all. It bumps it around a bit, but no real change.

Manifold vacuum is pretty solid at about 17".

Sounds like a shot fuel pressure regulator to me, but I haven't worked on this newer stuff. With my '92 I would expect around 45 psi and it should drop a bunch with manifold vacuum applied.

To make matters worse, it looks like the regulator is part of the fuel rail?? What were they thinking?

I think the regulator is shagged - is this a common problem? Anyone seen anything similar on a similar vintage 3.0?

Thanks
Russ.

 

[dbp]

You should be at 30-40 psi...sounds like the regulator to me.

Your injectors still are using the same open/close time so the engine is getting too much fuel---hence the running like poo problem.

 

[Sasquatch_Ryda]

Completely normal.

Fuel Pressure for a 2002

Key on, engine off 414-448 kPa (60-65 psi)
Engine running 414-448 kPa (60-65 psi)

Fuel pressure is controlled by the fuel pressure regulator which is mounted to the fuel pump bracket within the fuel tank.

 

[masterbrenden]

50-60 is about right for the ranger 3.0
my 98 run great at 72psi
and my co- workers and i have checked a dozen+ times and it is in spec

i just checked mitchell1 maluals and they say 56-72(gas) 47-63(flex fuel)
hope this helps

 

[Sasquatch_Ryda]

The specs I posted are out of the Ford shop manual.

 

[masterbrenden]

i will listen to a ford manual before mitchell

 

[Rustydawg]

Hmmm.... OK.

So the fuel pressure we're seeing is within spec.

What's the point of what appears to be a bypass regulator on the fuel rail? It is connected to what I assume is manifold vacuum.

I notice that the fuel filter has three fittings on it, so I can buy that the pressure regulator is in the tank and the rail is maintained at 65 lbs or so. But what is this device with the vacuum line then?

Can I assume that fuel rail pressure is supposed to remain constant under all conditions - so long as the engine is running?

Thanks for the feedback - I'm learning something here...

EDIT - Woah, I'm getting ahead of myself. My gauge reads 60 lbs full scale and we never saw it touch 60.

 

[dbp]

hrmm...I apologize if that spec I gave was wrong, I just grabbed the info from:

http://www.therangerstation.com/tech_library/3_0performance.html

I'd have to check at work tomorrow, but I mean enough people say that's in normal range that I'd tend to believe that link above is wrong.

 

[Rustydawg]

I think I have some of the fuel system figured out. The problem is I'm used to an old-school return system with the bypass regulator on the fuel rail.

This newer stuff has a regulator at the pump to deadhead about 60 lbs delivered to the fuel rails, and they are further regulated at the rails relative to intake pressure.

I don't think we're looking at a fuel delivery problem. The hiccup is right around the time the auto trans kicks down a gear, or shortly after. Then it will rev right up to the shift point and carry on.

 

[lorenambrose]

Hmmm.... OK.

So the fuel pressure we're seeing is within spec.

What's the point of what appears to be a bypass regulator on the fuel rail? It is connected to what I assume is manifold vacuum.

I notice that the fuel filter has three fittings on it, so I can buy that the pressure regulator is in the tank and the rail is maintained at 65 lbs or so. But what is this device with the vacuum line then?

Can I assume that fuel rail pressure is supposed to remain constant under all conditions - so long as the engine is running?

Thanks for the feedback - I'm learning something here...

EDIT - Woah, I'm getting ahead of myself. My gauge reads 60 lbs full scale and we never saw it touch 60.

On the fuel rail is a fuel pressure damper. It reduced occillations in the pressure which are common when the regulator is in the tank. It does not "regulate" anything.

 

[Rustydawg]

On the fuel rail is a fuel pressure damper. It reduced occillations in the pressure which are common when the regulator is in the tank. It does not "regulate" anything.

I'm not convinced that it doesn't regulate anything.

If it is merely a damper, why is it connected to manifold vacuum?

I see a blip in fuel pressure at the test point when I apply or remove manifold vacuum from said damper - I can assume that it affects pressure within the rail.

 

[TomB1269]

What is the mileage (60k to 75k), just a slight almost misfire like fell also most like it was going to misfire and then changed its mind? These are symptoms of syncro shaft failure. Push it hard and you may find a high end misfire (5000-5500 rpm) and that mis will start to workllower down in the RPMs. The misfire symptom is what I felt after having just done a set of plugs and wires. 3 weeks of work, asking mechanics, checking the web, I fianlly had an anylizer put on and still nothing could find why the misfire which had dropped down to 3100 rpm warm. Ford found the sncro shaft, there is a TSB about monitoring EGR pulses for counts over 150 or something. Have not had an issue since, (38k miles since)

 

[Rustydawg]

Never heard of a 'syncro shaft' TomB, whassit do?

Mileage is about 65 000 or so. When it misses it falls on it's face HARD, bucks a few times (like someone is turning the key on/off) but this is only usually at WOT. Then it will carry on OK.

It could still be a fuel issue, I've only had the pressure gauge on it at idle. Best to take it for a drive while watching the pressure under full load.

Haven't seen any check engine light yet. This truck lives with the fuel gauge at 1/4 tank max so I wouldn't be shocked if the fuel pump is shagged.

 

[lorenambrose]

I'm not convinced that it doesn't regulate anything.

If it is merely a damper, why is it connected to manifold vacuum?

I see a blip in fuel pressure at the test point when I apply or remove manifold vacuum from said damper - I can assume that it affects pressure within the rail.

It is vacuum referenced. The fuel injectors set up pulsations in the fuel rail that at certain frequencies can cause an imbalance in the fuel delivery to the injectors. The vacuum line is there to assist the spring at a predetermined engine load. It is not very sensitive.

Bottom line is the damper smooths fuel pressure oscillations in the rail and has no affect on the regulated pressure.

 

[Rustydawg]

It is vacuum referenced. Bottom line is the damper smooths fuel pressure oscillations in the rail and has no affect on the regulated pressure.

OK, thanks for expanding on that. So pressure at the test point should be steady ~60 psi regardless of vacuum or engine load - I'll try rigging up my pressure gauge and take it for a drive.

Does the ECM see manifold vacuum on these returnless systems via a MAP sensor or similar?