91 XJ 4.0 vacuum diagram

[Widnrf1j1]

Can someone please help me with a complete diagram of what plugs into what on the engine head?

Something is wrong with my set up and when I get to full operating temperature, the fuel pressure varies from 30 to 40psi. I replaced fuel pump, filter, and pressure regulator. I have also replaced the intake temp sensor and map sensor so I am very puzzled right now.

 

[ParadiseXJ]

Nothing plugs into the head, the CCV vac lines plug into the valve cover, but that's it.



The fittings are on the intake manifold, throttle body etc. but none on the head.
This diagram is for a 90 and below, but the routing is basically the same. I don't have one for a 91

 

[Transpoquick]

Unless I'm mistaken, fuel pressure is suppose to vary. How are you checking it?, w/ a gauge while it's not running or when your driving it via a fuel pressure gauge?

 

[Widnrf1j1]

I hooked up a gauge to the fuel rail and checked it. When I first started it, the pressure was 31 with the regulator hooked to the vacuum and then 40 when unplugged. After driving for about 20 minutes, it surges and will not idle smoothly. At that point, the pressure is oscillating greatly.

I did not use the correct term. I am looking for something to tell me where the vacuum lines run that connect the fuel regulator to the map sensor and any other lines that may influence the fuel delivery once the engine is warm.

 

[Transpoquick]

Sounds like the fuel pressure regulator is ok. W/ the engine running at idle the fuel pressure will increase on your jeep. Because of that when the engine is surging or loping its going to be erratic.
I think you have a vacuum leak, or a problem with the throttle body. Or both. Imo.

 

[Transpoquick]

BTW. Fuel pressure will increase w/ vac. hose disconnected, at idle.

 

[ParadiseXJ]

The Fuel Pressure Regulator does not attach to the throttle body. It is independent and attaches only to the vacuum port on the manifold. The MAP sensor attaches to the throttle body.

On the diagram, note the "color" coding. The black lines are active vacuum lines...that DO something (e.g. MOVE a diaphragm in the FPR). The MAP sensor to the throttle body, one line. The FPR to the manifold, one line. The "white lines" are passive vacuum, that move air & fumes from the fuel tank back into the intake through either the CCV or the purge canister (or both).

As far as fuel delivery goes, your coolant sensor (on the t-stat housing), O2 sensor, and Throttle Positioning Sensor (TPS) all feed the ECU for air/fuel mixture.

 

[mcnamaag]

If you search old threads of mine I had a pretty detailed layout for the earlier renix engine. It shows how to eliminate a lot of clutter and use stainless brake lines to replace the old and brittle plastic vac lines. I mapped them out covered just about any vac line in the engine compartment.

 

[mcnamaag]

I just noticed yours is a 90's era jeep. Not sure if its the same but it should be a start.