Hello all,
I have a 98 Discovery LE 4.0.180k miles. Runs rich with black smoke,soot fouled plugs, lacks power, won't run above 3k rpm. High fuel pressure 50 psi. Replaced pressure regulator...no change. Checked engine vacuum, 10". Can fast idle and close the throttle and blip vacuum up and fuel rail pressure jumps down to 35. Unable to locate any vacuum leaks by spraying ether around intake area. Removed and plugged brake and other vacuum line with no change.
I suspect late ignition timing. Could this be Crank position sensor? ECM?
Compression is good overall one low cylinder but not enough to kill the vacuum.

 

Don't guess, if you think you have low vacuum, test it with a gauge. What about fault codes, do you have any? No, it is not the ECM or your crank sensor.
What are your 8 compression numbers?

 

What is normal vac at our altitude Mike?

 

Aside from traditional physical engine issues, the O2 sensors could also be out of range (codes?) and making things ultra rich. And as we have seen from other owners, sometimes the previous owner disconnects or paints over the engine light - always a good idea to scan for codes with your own scanner or at a parts store for free.

 

I am blanking on that, sorry.
Might run by an auto parts store, I believe they rent the gauge.

 

Measured vacuum at 10" with a new guage. Codes were converter. Replaced Thermistor, and thermostat, thought it might be cold and never warmed to operating temp. I have confirmed low vacuum to be the cause of the high fuel pressure by the fuel pressure dropping to 32psi when the throttle is closed quickly from around 2k rpm. !0 inches of vacuum at idle, rises to 15 at around 2000rpm then engine misses and sputters while blowing soot at the exhaust. Compression test is all cylinders 160 to 170 with number 4 cylindor 135.

 

I don't believ O2 sensors. While trying to diagnose found crankcase about 2 to 3 quarts high. When I pulled the drain plug there was a strong smell of gasoline. Fuel rail pressure was 50psi. High fuel pressure overloads the injectors and excess fuel runs down cylinder walls to contaminate crankcase. After replacing fuel pressure regulator with no change checked vacuum. I've thought about running a vacuum line from another vehicle to the fuel pressure regulator to see if that cures the rich problem. Haven't tried that yet but the engine cannot function properly with 10" vacuum measured where the brake line attaches to the manifold/top cover.

 

Reading codes P1313 and PO125

 

That says Cat and temp...not my problems with over pressure in fuel symptom.

 

Also vacuum guage is dead on steady indicating no burnt or sticking valves.