I HAVE LOST ALL VACUUM FROM THE ENGINE TO THE VACUUM MANIFOLD ON MY 1997 7.3 TURBO-DIESEL F250 4WD. WHERE CAN I FIND VACUUN SYSTEM DIAGRAM SO THAT I CAN TROUBLESHOOT IT?

You don't say whether it is petrol or diesel and whether it is a turbo model and what sort of age it is.
The diesel versions are apt to become clogged throughout the egr valve and ports and the intake becomes very oily but a clean should only be needed about every year. This is not typical of the petrol engines.

The oil must be coming from somewhere and there must be quite a lot of it being turned into carbon/sludge in order to be blocking the egr valve so often and that might be at least part of the trouble. There is probably just as much oily carbon going down the exhaust so eventually the CAT will become so blocked it will increasingly rob the engine of power.

The butterfly valves in the intake manifold are part of a design that varies the length of the intake tract in order to increase volumetric efficiency over a wider engine speed range. The engine management decides when to switch the vacuum supply on. Fault diagnosis can be a rather involved and protracted procedure depending which engine is fitted.

I suggest the source of the oil should be investigated and recified if possible before you change the manifold, though removing the manifold could be part of the process of diagnosis. It could be leaking valve stem oil seals or a leaky turbo if fitted, or something more serious. The manifold probably doesn't need replacing and I think it producing more power after you fiddled with it is coincidence...

First put right what you see and what you know and then worry about the other stuff.

1. Without vacuum applied to the regulator, the 3.3L engine fuel system operates at 55 psi (379 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 46 psi (317 kPa).
   
2. Without vacuum applied to the regulator, the 3.5L engine fuel system operates at 48 psi (331 kPa). With the engine idling and the manifold vacuum applied to the regulator, the system operates at approximately 39 psi (269 kPa).
   
3. The fuel system pressure varies with the different amounts of manifold vacuum applied to the regulator. If the pressure is NOT correct, record the pressure and remove the gauge.
   

Hello redeemer524,

Below is the diagram. I hope this helps.



Regards,
netvan

Ford Focus engine diagram Ford Focus engine diagram - Ford Focus engine Zetec-E 1,8-2,0 l 16V Ford Focus engine diagram - Ford Focus engine Zetec-E 1,8-2,0 l 16V

1 - a tank of the hydraulic booster of a steering; 2 - a plug mouth oil-jellied; 3 - a tank of a working liquid of a braking system and clutch; 4 - the assembly block of safety locks and the relay; 5 - an air filter; 6 - a windshield washer reservoir; 7 - the accumulator battery; 8 - the identification tablet; 9 - a measuring instrument of level of oil; 10 - an expansion chamber of system of cooling.

Ford Focus engine diagram Ford Focus engine diagram - turbo-diesel of 1,8 l Endura-DI Ford Focus engine diagram - turbo-diesel of 1,8 l Endura-DI

1 - a tank of the hydraulic booster of a steering; 2 - a plug mouth oil-jellied; 3 - a tank of a working liquid of a braking system and clutch; 4 - the assembly block of safety locks and the relay; 5 - an air filter; 6 - a windshield washer reservoir; 7 - the accumulator battery; 8 - the identification tablet; 9 - a measuring instrument of level of oil; 10 - an expansion chamber of system of cooling.

Suspect a problem with a check valve in the vacuum lines somewhere. When you ask for "power", the manifold vacuum dives. This is affecting your ventilation. It is not supposed to happen as you know.

Many ventilation controls use engine intake manifold vacuum as power to move miniature air valve actualtors. Actuators may be balanced by springs. Springs pull one way, vacuum (controlled by the dash knobs) pulls against springs. When the throttle is opened (accelerator pushed hard) the manifold vacuum drops.

When the vacuum drops, then the spring would be strongest and pull the control valve over. When the throttle goes back to normal--- vacuum is back up, and air flow changes again.

There should be a check valve in (one-way valve) in the system so that the vacuum is held during periods of acceleration. If this valve is stuck open by wear or contamination, everytime you ask for power you would lose the vacuum in the controls.

A full diagram of the system is needed to trace this which I do not have.

This should give you a place to start or at least know what you are hearing if you have someone troubleshoot this.

jp

Try this site from Diesel Giant. Good pics and layout. They also have a schematic in pdf. http://www.dieselgiant.com/mercedesvacuumtroubleshooting.htm

"Have you replaced your air filter lately?" think about the ford commercial tune on that one lol!

Exhaust Gas Recirculation (EGR) System The exhaust gas recirculation (EGR) system recirculates exhaust gas into the intake manifold (9424). This lowers combustion temperatures and reduces the formation of oxides of nitrogen (NOX). The amount of exhaust gas reintroduced and the timing of the cycle varies by calibration. Timing and volume are controlled by the powertrain control module (PCM) (12A650). The EGR valve (EGR valve) (9D475) is vacuum actuated. The vacuum hose routing diagram is shown on the Vehicle Emission Control Information (VECI) decal. EGR operation stops when the engine temperature is cold, to improve driveability. The PCM controls the EGR solenoid vacuum valve (9D474). When energized the intake manifold vacuum outlet fitting and cap (9A474) allows exhaust gas to be circulated in the engine to be burned.

I think you can get this diagram on All data, about 12 bucks or so a year

http://www.alldata.com/products/index.jsp
Good Luck

Well, the 'T' in your model number is the answer; Turbo.

Non-turbo engines produce vacuum nearly all the way through their operating range since the engine functions as an air pump on the intake cycle to obtain the oxygen required for combustion.

The turbo, which is probably kicking in at around that 1800 revs, produces an overpressure so the engine can accommodate more fuel, be it diesel or gasoline.

Your engine and the turbocompressor, are doing exactly what they were designed for and your system (which I have personally used) not only doesn't do anything useful, is also causing a loss of your overpressure.

Take it off-