electrical or gas. problem

Hello all,
I am looking for a little help. I have practically worn out the threads on every forum to get a solid answer to my prob.
To begin, my rig is a 34' 1993 Fleetwood Bounder, 8 cyl ford 460, EFI with 39,000 miles and 320 hrs on Gen,. Purchased Oct 2010 with 32,000 miles, towing a 97 Jeep Wrangler.
The timeline and issue is as follows:

Ran like a top for over a yr. Then we noticed that when we came off the freeway, at the end of the ramp, on take off, it would stutter a bit then smooth out, sometimes quite severe. If you eased into the throttle it would get through. Then the problem would dissappear. This has only happened a couple times.

Next, and I am not sure why we looked into it, but the driverside exhaust maniflod was cracked by #1 cyl...had it replaced.

When we had it smogged after the first 2 yrs, the cap failed the pressure test, installed new one. We don't remember having any issues after that.

Now for the latest, We went on a trip last Thanksgiving with big hills and approx 800 miles not taking the Jeep this time. It ran like top the whole trip.  Parked it and  last weekend went to take a small trip with the jeep, it acted similar to when it would stutter off the freeway ramp except much worse. This time every excelleration brought sputtering and loud pops from dead start or whenever accelerating below 1500 rpm. Above 1500 rpm it runs like a top. It idles very well. Towed the Jeep the 150 miles each way having to manually shift to keep the rpms up.

OK, now for what we were told and what we have done:

Our vehicle mechanic said it sounded like its in the ignition system. Now fyi about half the threads I have followed say the same thing.
The other half say its a clogged sock on the fuel pump or a clogged filter.

Put a gas pressure tester on the right fuel rail, and pressure was 29-30 psi, but on hard acceleration drops to about 23-25 psi.
Replaced... Fuel filter...Distributor cap...rotor...coil...no change in performance.

Now before I drop the gas tank and start replacing hoses and socks can anyone offer some solid advice.

Is it fuel issue, eletrical issue, maniflod issue?????

Please let me know if you have experienced this type of problem.

Thank you in advance for your help.

The first thing I would want to know is has the fuel pump been replaced in that chassis.  If it is the original, change it as the original had problems similar to what you are describing.

I had a SeaBreeze on a '94 Ford with the same engine.  I seem to recall I had similar problems in about late 96 or early 97 and it was the fuel pump.

Good Luck,

Sure sounds like the problem we had with a 1993 Itasca Suncruiser with the Ford 460. We had the fuel pump replaced and the problem was cured.

BTW, if I remember correctly, its been many years ago, the fuel pressure should be 40 psi. Perhaps, you should check with a Ford dealer so you know what the pressure should be. If it should be 40 psi and you are dropping to 23-25 psi, your fuel pump is likely to be the problem. Our problem was more troublesome when the fuel level was low--on a full tank the problem didn't seem to exist. Hot days also caused more problems than cool days.  You might keep that in mind when testing your fuel pressure.

Let us know what you figure out.

R

Third on the fuel pump.  29 lbs static pressure is too low, the shop I took my 1994 Ford F53 to with similar problems took one look at the pressure and correctly diagnosed the fuel pump as the problem.

The fuel pump is located inside the fuel tank and requires dropping the tank to get at it, so the less gas you have in the tank, the easier it is for the crew to do the work.  The shop that did mine jacked up the rear of the motorhome, then used a roll-around transmission jack with a flat platform head to support and lower the tank.

The original pump design used sliding seals on the impeller that eventually wore down and leaked pressure.  When the pump problems started showing up in the late 90s, Ford changed the design to use roller seals.    Any replacement pump you get will have the newer design.

The freeway offramp ramp stuttering is because the EFI changes the air to fuel ratio depending on the reading it gets from the oxygen sensor in the exhaust.  When you're running on the freeway with low fuel pressure, the EFI commands the injectors to draw more fuel to keep the mixture correct.  Coasting down the offramp, the fuel delivery is shut down, allowing the fuel pressure to increase.  When the engine drops to idle at the end of the ramp, the injectors are set much too rich from the freeway travel and it takes several seconds for the EFI to read the oxygen sensor and reset them.