I have a 2002 f-550 w/7.3. The engine is running rough and hard to start. When it does start there is no throttle response until it warms up. I was told that maybe there is too much blowby. how do I go about checking the crankcase pressures and what would I need to do that? Is it possible that the hpop is not putting out enough? And What should the pressure be of the crankcase & hpop? There are on codes and never was any. HELP

 

I haven't heard of blow-by causing this kind of trouble. Does the engine ever smooth out? What grade of oil are you running? anything higher than 10w/40 could cause problems. Could be GP harness... tough to tell. but odds are if the hpop fires ONE it'll fire em all.
The lack of response is possibly the throttle assembly... maybe someone who knows more will chime in.

 

Pop off the oil cap while the engine is running, you should have a steady mist coming out meaning it's normal. If it's chugging, then you have excessive blow by.

As far as the hard start and rough running issues, is this only on cold starts? Or do you have the same issues after the engine has completely warmed up? Makes a big difference on when exactly you are having issues. Right now without knowing more, it could be anything from the glow plug system, to oil problems, fuel issues, wiring, exhaust backpressure valve, etc.

Let us know what exactly you are experiencing and when, try to be detailed and we can help you out more. Without trouble codes, it's harder to diagnose something over the internet.

 

It only happens when the engine is cold. Everything works fine after it is warmed up. But if you let it sit for about 5 or 6 hrs. then it's the same thing. I checked for codes. None. I also checked the glow plugs and all wiring. Fine. what I don't understand is Why would there be no throttle response? Then as it starts to warm up the throttle is starting to respond gradually? Then after full warm up I get full throttle response. I also checked fuel pressures and they are all in limits. The exhaust butterfly is functioning. I can see it working when you start it up. The oil is changed & I'm using 10w40.

 

This is more than likely the cause. The exhaust backpressure valve functions are controlled by the PCM. Not only does the PCM determine the valve position by oil and air temperature, but also by the actual exhaust backpressure readings. There is a sensor that mounts in the front of the engine next to the idler pully that is the exhaust backpressure sensor. It connect to a metal tube that runs to the passenger's side exhaust manifold. This tube eventually gets clogged with soot, and the exhaust backpressure sensor can no longer get an accurate reading. So when you put your foot on the pedal, the butterfly valve stays closed longer because the sensor cannot "see" the correct amount of backpressure.

Remove the sensor from the tube, and take a long thing wire brush to the tube to scrape it all out. Also gently clean off the sensor and put everything back together. That should give you a little more throttle response when the engine is cold.

 

Thx pocket. I'll try that and let you know if it works.