Now What!? Fuel Pump?

[DNGR_RNGR]

Hope this is the right forum.

I've about had it with my '94 Ranger. Issues since day one. Imagine the following scenario:

You're driving down the highway on your way to work doing 55-60mph in 5th gear on a LEVEL section. Everything is fine. Then, all of a sudden the truck's speed starts dropping off and feels a bit rough. You give it more gas. Nothing. Truck is doing about 45mph and the RPM's are not changing. You drop to 4th gear and apply the throttle. No change. Nothing! RPMS will barely change even w/ the gear change!

At this point you have 2 options:

1. Ride out this tantrum and eventually the engine power will surge back to where it should be. Truck starts driving normal again (until it decides to have another tantrum).

2. Drop to 3rd gear and mash the gas pedal. Now the truck will start gaining power and speed, a bit rough I might add.

After choosing one of the above options, the truck will run as it ought to; like nothing was ever wrong, till it decides to do it again.

1994 Ranger S/C 4x4; 4.0L/5spd.; 3.73LS rear/31x10.5x15; 265/75/R15 Stock tire size.

What have I done (within the last 2K miles):

Cleaned MAF
Cleaned IAC, then replaced w/ new one, no change, put old one back on.
New Fuel Filter
New TPS, voltage test seemed to indicate it was faulty
New PCV valve
New air filter
New Motorcaft upper and lower intake gaskets
New Felpro Permadry Plus VC gaskets
New Thermostat, old was was stuck open
New ECT, did this for good measure while intake was off
Check resistence in coil pack; seemed fine
Ran 2 cans of seafoam thru engine
*New Motorcraft Plugs and Wires after seafoam flush
New Clutch and Slave Cylinder, Old Pressure plate had collapsed fingers
Replaced fluids in tranny and rear end

I have 2 codes:
327 EGR circuit below min voltage (is this a DPFE issue or EGR solenoid)
*172 O2 Bank 1 Lean (could code 327 possibly throw this?)

Is it possible for either of these two codes to cause the symtoms I have?

* Prior to replacing the plugs and wires, the truck had fairly new plugs and wires (cheap ones) on it. The truck was giving me fits as described and I came to find out the wires didn't seat properly in the coil pack. Replaced with Motorcraft wires and plugs. Truck ran MUCH better. Symtoms desrcibed were gone. Now they're back?

The plugs that were in the truck were Autolite copper cores. Plugs from EVERY single cylinder looked good. No signs at all of a lean condition in bank 1, which makes me wonder about the O2 code.

When the clutch was being replaced at the garage we ran into a problem. The truck refused to start. It would crank all day long, but would not fire. We had spark, fuel, and a grocery lish of codes. Came to find out there was a bad ground. Fixed that and it fired right up. All but the above codes went away. At this time we also checked the FPR (good) as well as the rail pressure. I don't remember what it exactly was, but it was with in spec (~35psi IIRC). After the truck was shut down, the fuel psi held at ~40 psi.

Also, I recently took a 200+ mile trip in the truck. 98% was all highway driving at speeds ranging from 45mph (construction zone) to 65mph. The truck only managed ~16.5mpg (usually ~15mpg Highway!). How anyone is getting 18-20+mpg is beyond me.

Could I have a fuel pump on its way out? This problem is intermitent, but happens several times on my 30 mile drive to work.

I am out of Ideas and $$$. I just want this truck to run the way it should. Sorry for the novel I just wrote. Any help or would be greatly appreciated. Thanks!

 

[MAKG]

No, a fuel pump is not going to hose the power on your EGR valve. You have an electrical problem. You need a skilled electrical diagnostician to find it. As you've discovered, you spent several times the cost of that already throwing good parts at this problem by assuming the wiring was perfect.

Your EGR is losing VREF. That may not be the only problem, but it's a place to start.

 

[DNGR_RNGR]

Thanks MAKG.

Most of what I spent so far was in replacing things that were part of maintenence, or I did it for good measure.

I didn't think that the fuel pump would hose power from the EGR. I just happen to have that EGR code. I questioned the fuel pump because it happens intermittently and because it is losing power regardless of throttle position or gear. I was just taking a guess that the fuel pump is not keeping up with demands.

Also, I am unsure about what my mechanic did to the truck. In the first post I mentioned that the truck would not fire because it had a bad ground (this seemed to come from nowhere). The bad ground came from a gray wire w/ a red stripe. This wire feeds into the TPS, ECT, ACT, DPFE, IAC and perhaps other sensors.

The way that we found out it had a bad ground was by hooking up a test light in reverse. We connected the test light to the + side of the battery and then back probed the gray/red wire in the TPS sensor. the test light would barely light. Then, my mechanic ran a wire from the neg. side of the battery and back probed it into the gray/red wire. Truck fired right up. Then he took a wire and spliced it into the gray/red wire at the test connector and ran it to the fender. Was this a no-no? Where does this wire usually get it ground signal from?

 

[MAKG]

Not the best practice, but probably not damaging. It may have only partially fixed the problem. I wouldn't use the test connector for anything but tests.

Bad grounds can cause all kinds of weird driveability problems, and the right way to fix it is to test them all and repair those that don't work well. Your diagnostician should have followed the TPS ground circuit toward the battery until the test light lit, because other stuff likely has marginal grounds as well.

When fuel pumps die, they usually have problems at high load conditions, mainly WOT at high RPM. Or else they just don't work at all. Fuel pumps are very often blamed for other problems, and I think you're doing this as well.

As a wild guess, the first thing I'd do is test that your computer is properly grounded. It has three grounds. Check them all for voltage drops to the battery with the key in "run."

 

[DNGR_RNGR]

Thanks MAKG.

I will check the computer grounds out.

The reason the wire at the test connector was used is because it was conveinent to a grounding source (the fender).

So this wire , which branches to pretty much every sensor, probably has a bad connection somewhere.