Well it is actually, with no load on the motor vacuum goes back up close to the idle value after a split second as rpms increase, the only way to get a valid measurement of fuel pressure at rpm is with the vehicle in motion and the engine under load... ie: hammer down in 4th from a slower speed where the engine struggles hardest to accelerate the vehicle

 

During the test you do not let the RPMs go up, you are just snapping the throttle.
The vacuum will drop and the fuel pressure goes up. But this may not tell the whole story as the one in the video above passed the pin #6 grounded with the engine not running, the engine running snapping test in the shop but failed out on the road under WOT.
It had a new fuel pump, fuel filter and FPR put on by another shop before it came in.
The problem was that junk in the tank would plug the sock when the 460 was on the road and using a high amount of fuel.
It was a 1997 460 E4OD with OBD-I EEC-IV.

 

Yes exactly.. I suspect the OP just held the throttle open and that is why the test is invalid.

 

I think you''re within tolerances on fuel pressure, but I'm still wondering about fuel flow given your comments about the filler tube (we chatted about this debris possibility at the pump before)..........here's my latest take aways:

- Fuel Delivery ---not completely sure, pressure seems "ok", but that doesn't mean fuel flow is adequate given that "debris" possibility at the pump, elsewhere. High probability

- Burnt exhaust valves /warped head-- possible with the long term leak, and the otherwise noticeable effects would end up being "gradual", not all that noticeable over time. Higher burnt valve likelihood if carb'd, but less likely on EFI . Low probability on the valve. Medium probability on the warped head.

- Compression - power problems started around 80K, you've meticulously maintained the truck and this doesn't seem possible as the IR check confirmed (temp) functioning of cylinders, but in the absence of a test we can't say good or bad. Low probability.

- Computer - age--misbehaving/playing with fuel mix (e.g. excessive soot at exhaust, no codes, but still checking out via self diagnostics (111)). Medium probability

- O2 Sensor -- new, but they fail quicker than most believe and certainly a player in the mix as it may misbehave and not throw a code (sometimes headers and distance from head affect its normal sensitivity/functioning). Medium probabiliy

 

Those are the readings. Each reading I listed was checked threee different times and that's what I got.

That's just about what I got except for mine was 29psi at idle with vacuum connected instead of 30-32psi. Revving the engine barely made the needle move whether I had vacuum connected or not. The needle only slightly fluctuated; I'm talking about a 1 or 2psi movement.

 

I tried every which way to get the needle to jump more than a degree or two: Snapping the throttle from idle, steadily revving it from idle, bringing it up to about half throttle then snapping it a few times from there; still no difference.
The test was valid. I am very meticulous by nature. Being thorough was key in my line of work for many years but that's enough about that.

 

I do believe I have debris but you have to remember, when it first started to loose power I replaced everything but the fuel lines which are not kinked nor are they rusted out. It could be that my fuel pump got weak and I replaced it with a new unit that wasn't much better. Remember, they are almost all made in China or Mexico these days!

Very high probability. Since no exhaust manifold on the market could fix the exhaust tick with manifolds or headers then I'm positive the head is warped at the exhaust port. Still, I doubt this would effect power so significantly.

Agreed.

With everything else checking out fine I'm starting to think the computer could be giving up the ghost at an early age. The truck ran like a champ until it sat for about 8 months(I had to let it sit). Once I started driving it again the rear brakes were dragging. If felt severly down on power as it does now so I replaced the drums and pads. Brakes were no longer dragging but it still felt low on power. There could have been corrosion in the computer. It sat in very damp portion of my barn.

Same scenario as fuel pump. It could have been faulty after sitting and the new one I replaced it with could have been a defect as well. It didn't throw codes so I ruled it out.

I could throw a whole bunch of money at it like another new fuel pump, filter, O2 sensor, etc. but I really hate to spend so much money on a truck I don't wish to keep driving. It's a regular cab and I need an interior with more room and I want to go back to the good ole days of carburetion. I have a '78 F250 Supercab that I want to fix up and when I do, my "easier to maintain" fuel injected truck is history.
I've worked on many fuel injected vehicles and my wife and I own EFI vehicles for their modern conveniences since we have kids so I'm no stranger to them. However, this is the first EFI truck that I've owned; I've always been someone who prefers the time-tested classics. I've had this F350 for 15 years and it has been pretty reliable up until the last 5 years due to mostly electrical component failures. The previous six 73-79 F-series and Broncos that I had in the 40 years before that gave me less issues combined than this one truck ALONE.
I know fuel injection and computers have their merits but I'll take a good ole carbureted 70's Ford over any newer EFI truck even if the newer truck starts quicker in the winter, has more "claimed" power, and is better on fuel.
I have engines from all the way back to the 40's that still run like a champ and have almost nothing electrical on them other than the spark plug that fires them. Let's see how good all the electrical components on computer-controlled engines will be holding up in 75 years!
So back to the probability of the issue being the O2 sensor or the computer; yes, the chances are pretty good they could be the culprit with the unreliable nature of a vehicles electrical components.

 

"-Key on, Engine off, regulator vacuum connected/disconnected--38 PSI

-Engine idle, regulator vacuum connected--29 PSI
-Engine idle, regulator vacuum disconnected--38 PSI

-Engine on, wide open throttle, regulator vacuum connected--32 PSI
-Engine on, wide open throttle, regulator vacuum disconnected--38 PSI"

Something is preventing the pressure from increasing at WOT. The OP stated earlier that the pickup ran like this before he did the fuel pump replacement, which would seemingly rule out debris clogging the pickup sock.

Is there anything between the regulator and the vacuum signal that would keep the vacuum high? If the vacuum line is clear and goes directly to manifold vacuum, then there is a restriction in the supply side of the fuel system.

You may have to do your work over, along with disconnecting the fuel lines everywhere and blowing compressed air through opposite of fuel flow. Maybe the fuel varnished in the lines and is now breaking up and creating a restriction.

 

After thinking this over again it sounds like the FPR vacuum line is hooked to the vent system after the vent check valve.
The FPR vacuum line should go right to the intake and no place else.
"-Engine on, wide open throttle, regulator vacuum connected--32 PSI"
I see no other way the vacuum would remain high during the one test above.
You need to put a "T" in the vacuum line to the FPR while the fuel gauge is connected and check your vacuum as you check your fuel pressure.

Did you replace vacuum lines?



/

 

I think you may be confused? The 32PSI I wrote down was not a reading of vacuum pressure, it is fuel pressure. As for where the vacuum hose on the fuel pressure regulator goes, it goes straight to this item I circled. It goes to the backside of it but it's hard to get a picture from that angle so this is the best I could show. The item pictured has a total of 6 hoses coming from it:

Top--There is one large rubber vertically mounted hose that provides vacuum to the brake booster
Driver side--There is the port which the fuel pressure regulator gets it's vacuum from and beneath it is a capped off port.
Passenger side--There are two ports, one of which I know provides vacuum for the interior heat system, the other I'm not so sure about.
Facing 10 O'clock postition--The final port which has a short vacuum hose attached to it which is then capped with a bolt. Obviously someone has tampered with it at some point but that was before I purchased the truck and it was running fine when I bought it, just not so much anymore. I don't know if this is suppose to actually go to anything but no codes are thrown in it's current state and I know removing it will only affect the vacuum for other systems. Anyone know what it's for?

 

No I was not confused.
Any time your have "-Engine on, wide open throttle, regulator vacuum connected--32 PSI" the fuel pressure should be around 40 psi. If not you are going to have almost no power at all.

 

While I have nothing to add to this post OP, I will say that looking from the beginning of this post to the end, you have been rude to a lot of people trying to help you. I understand getting frustrated when people aren't picking up what you're putting down but being a smart *** isn't conducive to what people are trying to do here, which is help.

 

OK then this is not good you should see fuel pressure jump when the throttle is snapped open so you either have a problem with the vacuum signal to the regulator, a bad fuel pressure regulator, a clogged fuel filter, or a weak fuel pump.

 

Just because that is what you have interpreted does not mean it is so. I may be direct, to the point, and try to keep others on track, but in no way, shape, or form have I given any smart *** remarks. I challenge anyone to not be a little short with someone when a guy keeps asking you if you're sure you don't have an MAF sensor on a vehicle you've been working on and maintaining for almost 15 years and another one wants to wax semantics regarding the date of manufacture of YOUR vehicle when you know when it was made better than they do since it's YOUR vehicle. These guys were just getting off topic and I don't see how trying to get them back on track is being rude?
I can't help it that one person out of the many might take offense to me just because I don't dance around an issue.
Calling someone a "Smart ***" because that is what YOU think they are being is not "Conducive" to helping me figure out my problem so if that's all you have to add then you can just go read some other posts from beginning to end. Yes, that was me being a smart ***. See the difference?

 

This might be irrelevant, but if the engine is running and the vacuum line to the FPR is removed, shouldn't the fuel pressure go to 40 PSI?

I re-read all the posts and it seems to me that the FPR may not have been replaced. If so, I call bad FPR. Easily tested: attach fuel pressure gauge, start engine, disconnect vacuum line. Pressure better go up or it's a bad FPR.

Just sayin', ya know.

Ray