FPBV or Backpressure sensor - Diesel Forum

br8643 · 09-02-2008, 10:36 PM

I have a 2000 ford powerstroke that i ruined most of the injectors in by running motor oil. I also had the glow plugs replaced and the wiring harnesses replaced.

In the morning when i first start it or after it has set for an extended period of time it has a slightly rough idle and seems to be constipated. If you really put your foot in it, lt will go.

The backpressure sensor code was in it but the mechanic said that was because of the excess fuel that was being dumped due to the injectors failing.

Does anyone have any ideas on what it could be or if the FPBV or backpressure sensor could be causing any of these things. It runs fine when warm and the fuel mileage is good and there is no smoke.

klhansen · 09-03-2008, 05:10 PM

The EBP valve should only operate at low ambient temps (I think it's 40F or below) and cold oil temps (below about 140F). If the EBP sensor is out of range either high or low, the PCM is supposed to disable the EBP valve.

Since you have a code for the EBP you should check that out, although I've never experienced the EBP valve closing when it shouldn't. What you're describing sounds like a normally operating EBP system.

If the nozzles on your injectors are severly worn, the spray pattern will not be as fine as it should be and the fuel will be harder to ignite. Hitting the go pedal bumps up the injection pressure and compensates for a bad spray pattern somewhat. So if you still have the bad injectors, I'd be looking at them.

BTW, you might want to find a mechanic that really knows PSD's. Excess fuel wouldn't cause an EBP code.

br8643 · 09-04-2008, 10:51 AM

All the injectors are new. Could it be a faulty injector or bad nozzle possibly? I wonder about some type of sensor since it quits when it reaches operating temp?

klhansen · 09-04-2008, 05:42 PM

Quote:

Originally Posted by br8643

All the injectors are new. Could it be a faulty injector or bad nozzle possibly?

Yes, you could have gotten a bad injector. Are they NEW or rebulilt? Have your mechanic run a cylinder contribution test and see if one throws a code.

Quote:

Originally Posted by br8643

I wonder about some type of sensor since it quits when it reaches operating temp?

Could be an issue with cold HP oil versus hotter oil. The injectors are driven by oil pressure and the thicker (colder) oil doesn't flow as well as hotter oil. There isn't really a sensor that I can think of that would "flip a switch" like that, although the Engine Oil Temp sensor is used to control injector timing.

Just speculating, but testing will tell the tale.