I've been trying to resolve a hard-starting/rough idle/stalling issue on my 91 econoline with a 4.9L I6.

Vacuum seems to be good - holds steady around 25in. I think the vacuum reservoir (coffee can) is bad since the vacuum out is only 10in or so and the vacuum in is around 25in...or is this by design? I took the coffee can out altogether while testing other things to remove it from the equation.

In the last few months I've replaced:
- few vacuum lines that were in bad shape.
- EGR valve and position sensor - old units were definitely bad - old EGR valve was completely blocked and corroded shut
- Throttle position sensor - resistance jumped all over the place while testing it
- Idle air bypass valve
- MAP sensor - seemed to run better without the vacuum line attached to it, but the new unit doesn't seem to work much, if any, better than the old unit. so maybe the old unit is good after all?
- iginition coil - the post on the old unit was badly pitted

Also cleaned the distributor cap and rotor contacts. Ran the engine in the dark and didn't see any arcing.

Within the last 5k miles I replaced the dist, wires, and plugs.

Fuel pressure check:
Last night the pressure didn't seem to build with the key on, engine off, although I did hear the pump running. Cranking the engine several times finally got it running, fuel pressure was around 45-50 PSI. Once the engine finally starts it will not keep running unless I pump the gas. It will run for 20-30 seconds, then sputter out. It's better when it warms up and will sometimes run for a minute or two before shutting off.

After warming up the engine I unhooked the vacuum supply to the fuel pressure regulator from the vacuum tree. The idle increased but smoothed out, fuel pressure rose to about 60PSI. If I plugged the now-open vacuum port, idle settles back down but the engine runs rough, but the engine does not stall. Just keeps on running. Plugging the vacuum supply to the pressure regulator drops the fuel pressure back down to 45PSI and the engine will eventually stall again. Makes me think it's the regulator? Or is the fuel pump not supplying enough volume?

I left the fuel pressure gauge on over night (was 50PSI at 9:00PM) and this morning at 9:00Am it was zero. Seems to stay pressurized for at least 15-20min though. How long should it stay pressurized? This morning though the pressure built to 40 PSI with KOEO. Turned ignition off then back on (but didn't crank the engine), pressure built to 50PSI.


KOER codes yield (looks like a few more things to address...):
126 - Manifold Absolute Pressure (MAP) or Barometric Pressure (BP) – signal values higher or lower than expected (with NEW MAP sensor)
172 - HEGO indicates lean
225 - Knock Sensor (KS) signal not detected during Dynamic Response Test (Engine Run Self-Test).
332 - Insufficient EGR flow detected. (I'm pretty sure the EGR solenoid is shot - I never get a vacuum coming out of the regulator but there is definitely vacuum going in)
412 - Cannot control RPM during Engine Run Self-Test – high RPM check.
556 - Fuel Pump (FP) relay – primary circuit failure.
632 - Overdrive Cancel Switch (OCS) – no switch action detected during Engine Run Self-Test

Not sure how I can get a 556 if the engine is running?

Sorry to be so long-winded... thanks for any info! I've learned a lot from this forum by reading old threads.

Eric