By now if someone were to have printed all my posts about finding an elusive O2 problem (very sluggish sometimes non responsive on Bank 2), you would have a novel.

Got some feedback on fuel trim on the Tuning forum, but have a question related to the engine itself. I alluded to this on an earlier post and someone mentioned to replace the regulator. I have some more precise data and thought I would get a solid yeah or nea on replacement.

This am I disconnected both O2's (one at a time) and metered voltage coming in, and voltage on the heater circuit. On both sides, voltage in was 12v but occilates wildly. Voltage on the heater circuits was 7 or 8 v, and occilated too. I take that to be good. Both sides the same, and I know that Bank 1 gives a good response ala my XcalII datalog. This tells me to look elsewhere besides and electical harness/pcm problem.

I have previously checked for intake leaks with propane, and backpressure on manifold. neither showed any signs of leakage.

Rechecked this am the fuel pressure and various vacuum lines. All vac lines showed 22in Hg of vac. no leaks from what I can see. I monitored the fuel pressure regulator/dampner, found on the fuel rail, psgr side. Fuel pressure was a steady 52psi. Ford dvd manual says it should be 50. Turn engine off, pressure drops to 48 and holds. Manual says it should be within 5 psi of max. That looks ok.

Last test - disconnect vac line from regulator and plug. Attach vac hand pump to regulator and apply vacuum. Increased the vac to 25, 30 in Hg. No change in fuel pressure. Released vac, no change. Reconnect manifold vac line to regulator and rev engine. No change in fuel pressure.

The dvd manual says if there is no change in pressure, replace the regulator. My question is simply, what kind of change should I have seen, and does the diagnosis seem correct to replace the regulator.

I hate not having enough knowledge to do this correctly, but I sure an thankful this board is here.

"Failure is the best teacher. I try to make at least one mistake every day".

 

On another forum whilest researching the fuel pressue regulator, I found a discussion about a returnless fuel system (ford Ranger actually), where they were discussing fuel pressure regulation. What caught my eye is the mention of the fuel pulse damper - on the fuel rail. My dvd manual mentions that too, and I've seen the thing on the rail refered to as a regulator and damper. A question was asked as to why the DAMPER has a vac line attached to it, if it does not regulate pressure.

The answer was, the vac line catches fuel (a safety overflow) in the event that the damper diaphragm ruptures. So in essence, it would not respond to my fiddling with the vac line. I would have to fiddle with the vac line at the REAL regulator which is on/in the fuel tank.

Oh man, am I getting confused. Even the Ford dvd manual isn't clear.

So, this thing on the fuel rail is a damper, and the vac line does not control it. Is that correct?

 

IF..you have a 2 pipe system there is no damper involved.
The vacuum to the regulator is there to allow a small downward pressure shift at high/normal intake manifold vacuum levels.
The shift is usually not more than 10 psi and lowers the pressure at idle when the injection does not need so much fuel..
At starting, the intake vacuum is low so the regulator does not do much aside from it's basic builtin regulation design.
At starting and cold start, the pressure is up by intent for richer injection.
At WOT and lower intake vacuum the pressure is up to feed injection by intent for power.
Even if you took the vacuum off and plugged it, the motor won't run much different by observation and feel.
You applied 30 inches of vacuum to the regulator! Don't do thoses things. They can be damaged because they are not designed for that much.
With the motor running and all normal hose connected, read the pressure, then remove the hose and observe the change. That is the normal operating range.
Another thing that can happen is with a rolling idle over a wide rpm range, will also change fuel pressure thru the regulator control and tend to 'add' to the roll by fuel changes in addition to the primary fault causing the roll, as a secondary result.

 

Hmm. Not sure what you mean by two pipe system. Can you please clarify?

Couple of things.... i think I have a returnless system. The pressure on the vac line was around 22in hg (-70 kpasc). But I hear ya about the high vac. I did it in increments to observe change in fuel pressure. None.

Nothing I did changed the pressure. Not even a smidge. That's why I'm thinking it is a damper. The parts guy at Ford printed me a page from his computer. I asked about the regulator. he said, yeah, the thing on the fuel rail. I said I thought that was a damper. "Oh yea, damper" he says. Oye.

Reving the engine also produced no change in fuel pressure when the vac line was off or on. I'm thinking that is becuase this thing really doesn't use the vac line for operation; just an overflow for gas in case of a rupture.

Nobody seems to know for sure what this thing is or how it is supposed to work.

Thank you for your help though, Bluegrass. I read your posts all the time and always learn something new. Is there any way to really find out what this thing is on the rail?

 

Two pipe is a feed/return system that circulates the fuel.
Pump pressure is dropped to the required injection manifold pressure by the regulator, with the remaining going back to the tank.
The single pipe system was the change, to reduce the fuel agitation in the tank, reducing the more evaporitive fuel element suspended above the liquid fuel level.

A single pipe system has a pressure sensor that controls the voltage to the pump as a means of adjusting volume feed rate and help regulate pressure.

Look under the truck at the feed line and see if there is a second line that would be a return.