JimS did pass the time by typing:
> 1994 Jeep Grand Cherokee. 5.2 liter.
> Does not hold fuel pressure. Misfires above 2000 RPM.
>
> '94 Grand Cherokee gets fuel pressure during the first
> 2 seconds. But loses that pressure almost immediately
> afterwards. Have replaced the fuel pump and the fuel
> pressure regulator. None of the fuel injectors appear
> to be leaking.

Just to make sure you know this, the pump only runs for
a couple of seconds on startup to prime the system, then
runs all the time as the engine is running.

You need a fuel pressure gauge on the rail. Pull off the
vac line to the regulator and if the pressure jumps 4-6psi
then the regulator is fine. I suspect the pump even if it
is new.

> Where might the loss of fuel pressure occur?

That's basically it. Fuel pump check valve or
fuel rail pressure regulator. It is possible you
got a bad replacement pump. OEM or aftermarket?
The aftermarket pumps are notorious for failing out
of the box.

> The Grand Cherokee also misfires above 2000 RMP. This
> happens only with transmission in Park or Neutral, not
> in drive.

> What might cause misfires only above 2000 RMP and only
> in Park or Neutral?

crossfire, there is a TSB out there for new wire routing
on the 5.2 V8.


--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!