96 ranger 3.0L V6 fuel pressure

[98v70dad]

What is the fuel pressure at the rail supposed to be?

I just measured mine and I get 38 psi pretty consistently after pressuring it up by turning the key to allow fuel pump to spin up 3 times and then looking at the gauge.

I get about 32 - 34 psi with the engine running. Higher psi at idle and lower as rpm's go up.

I'm getting really poor acceleration performance and I'm working on figuring out the cause. It hasn't always been as bad as it currently is. I think the fuel pressures I've measured are well below spec but I don't have the spec figures to compare against.

Things I've done, in order: (I have no codes and truck has 72,000 miles on it +/-)

1) new coil pack - minor improvement
2) intake manifold sea foam treatment - who knows - maybe a little improvement - the smoke is fun
3) exhaust inspection with hammer and flashlight - no holes noted - nothing rattling - exhausts last a long time in the south.
4) fuel pressure measurements (results above) - filter was replaced about 30,000 miles ago (2 years)
5) MAF cleaning with MAF cleaner
6) new air filter - old one was 2 years old - a little dirty but not horrible.

 

[RonD]

Yes, that fuel pressure is correct for 1986 to 1997 Rangers, in 1998, and up, it was increased to 55psi with a Returnless fuel system

Static pressure doesn't tell you load pressure, try raising RPMs to 2,500(approx.), and hold it high, see if pressure is slowly dropping, it shouldn't, if it gets below 25psi then change fuel filter and see if that helps
If not then may have to change the pump
BUT....................you should get LEAN codes when fuel pressure drops below 20psi, so I doubt its fuel related

Another power robber is partially blocked exhaust, you can test for that with a Vacuum gauge

Failing EGR system can steal some power, but I would expect Codes

CAM sensor will certainly effect performance on the 3.0ls

 

[98v70dad]

Yes, that fuel pressure is correct for 1986 to 1997 Rangers, in 1998, and up, it was increased to 55psi with a Returnless fuel system

Static pressure doesn't tell you load pressure, try raising RPMs to 2,500(approx.), and hold it high, see if pressure is slowly dropping, it shouldn't, if it gets below 25psi then change fuel filter and see if that helps
If not then may have to change the pump
BUT....................you should get LEAN codes when fuel pressure drops below 20psi, so I doubt its fuel related

Another power robber is partially blocked exhaust, you can test for that with a Vacuum gauge

Failing EGR system can steal some power, but I would expect Codes

CAM sensor will certainly effect performance on the 3.0ls

Thanks. Buried in the info I posted is the pressure under load - around 32 psi was the lowest I read at a pretty high engine rev (I'd guess about 3000 rpm). It would initially drop to around 32 under load and then maybe rebound to 33 psi and hold steady. At idle it was around 34 psi and steady.

A guy at another website posted the specs for static fuel pressure for a 96 3.0L and stated that it was 45 psi. There is a lot a garbage info out there - even in the Ford shop manuals. I've bought them before and found them to be so full of errors they were useless to me. Anyhow, that's why I started this thread hoping someone could give me the right answer. I've got a Haynes manual for the ranger somewhere but those aren't always right either.

Cam sensor was replaced about 2 years ago (30,000 miles). Can't remember if I bought motorcraft or junk. Sometimes with a time deadline junk is all I can source on a weekend. As you know, that thing is buried in the back and difficult to get to. I'm planning to pull it this weekend and see what I put on. I replaced a lot of stuff like that 2 years ago and I couldn't get motorcraft for 2 of the parts and I can't remember which ones they were.

 

[98v70dad]

Yes, that fuel pressure is correct for 1986 to 1997 Rangers, in 1998, and up, it was increased to 55psi with a Returnless fuel system

Static pressure doesn't tell you load pressure, try raising RPMs to 2,500(approx.), and hold it high, see if pressure is slowly dropping, it shouldn't, if it gets below 25psi then change fuel filter and see if that helps
If not then may have to change the pump
BUT....................you should get LEAN codes when fuel pressure drops below 20psi, so I doubt its fuel related

Another power robber is partially blocked exhaust, you can test for that with a Vacuum gauge

Failing EGR system can steal some power, but I would expect Codes

CAM sensor will certainly effect performance on the 3.0ls

RonD, I got a vacuum gauge and measured my vacuum. Engine running at idle its about 16 or 17 in and steady. With the AC on it drops an inch or so and remains steady (fluctuates a little up and down as the ac clutch goes on and off). At 2000 or so rpm's it goes up to around 20 in and remains steady. Does this rule out an exhaust obstruction?

I expected the idle vacuum to be a little higher but I don't really know what its supposed to be. Is there a spec number for that?

 

[RonD]

Yes the steady vacuum at around 2,000rpm would mean exhaust is most likely not the issue, if it was partially blocked then vacuum would slowly drop as "back pressure" in the exhaust builds up

Vacuum depends on your elevation above sea level, 0-2,000ft should be 18-21", engine size doesn't matter for vacuum

To test for exhaust blockage open throttle all the way and vacuum should drop to under 2" then let throttle snap closed and vacuum should instantly go up above idle vacuum then drop down to idle vacuum
If exhaust is blocked then it will react slowly, slow drop to 2" then slow to increase back to idle vacuum

 

[98v70dad]

Yes the steady vacuum at around 2,000rpm would mean exhaust is most likely not the issue, if it was partially blocked then vacuum would slowly drop as "back pressure" in the exhaust builds up

Vacuum depends on your elevation above sea level, 0-2,000ft should be 18-21", engine size doesn't matter for vacuum

To test for exhaust blockage open throttle all the way and vacuum should drop to under 2" then let throttle snap closed and vacuum should instantly go up above idle vacuum then drop down to idle vacuum
If exhaust is blocked then it will react slowly, slow drop to 2" then slow to increase back to idle vacuum

Thanks. I'll try it again later when the rain stops.

When I changed the air filter the other day I found the filter box loaded with pine nuts (lots of pine trees here). There was probably two or three tablespoons of them which is pretty odd. The nuts don't just easily fall out of the cones - they have to be removed by squirrels or chipmunks. While I was doing the vacuum test this morning it occurred to me that something may have built a nest in the intake air tube. I can't get my hand in there (I tried) but I'm going to try to see if that is obstructed - not sure how to do it. Pine nuts don't just jump off the ground and get stuck in the air filter.

 

[98v70dad]

So today I checked my throttle cable and found that I had almost 3/4" of slack in the cable. I put on three large zip ties and my performance has been completely restored. Amazing really.

Amazing that Ford would design something so marginal. Seriously. I'm a design engineer and have designed stuff for rockets - a rocket scientist and an amateur mechanic. Steel doesn't stretch 3/4" inch unless it has a couple hundred thousand pounds on it. Its the connections and other stuff in the system that cause the slop, probably a bunch of cheap crap and lots of plastic between the gas pedal and the throttle.

Also amazing that such a simple thing that cost about 5 cents and took 10 minutes fixed it.