Hello all, I've had a 96 f250 7.5l for about 2 years now, love the truck but I got a few codes id like to resolve and I'm hunting consensus amongst people more versed in these platform than myself. Note the symptoms I'm experiencing 1. Generally low performance, lack of power under load. 2. Hard/no start after truck is warmed up.

Here are my codes and plan of attack
P1443, possibly plan on replacing the evaporator purge valve
P0401, possibly plan on replacing the egr valve
P0171, fuel pressure is 40 psi at idle, since both banks are lean i think air is getting in somewhere upstream of the lower intake manifold.
P0174, same as above

Also I live in the country, while it wouldn't be my first choice I'd be willing to bypass the whole EGR system if itll make things alot easier. Could I just unplug the vac line from the egr valve to eliminate any leak thats happening? Thanks for your time.

 

shameless bump

 

Is this a California spec truck?
What that fuel pressure measurement done with vacuum attached to the regulator or removed? That is an OK number for no vacuum but is high for vacuum attached.
You need to inspect all parts of the EVAP and EGR systems as the problem could be just be a broken vacuum line. If this is an OBD2 truck the EGR system cannot be eliminated.

 

I do not believe it is a California spec truck. That fuel pressure was with everything hooked up, ive yet to unplug anything. But seems OK enough that it shouldn't be causing a lean condition. Must be a leak somewhere I suppose.

It is OBD2, ill go back and douse everything in starting fluid, maybe ill find the leak. I don't mind having a engine light on, but you're saying just removing vac from the egr valve (to keep it closed) is probably not a good idea?

 

That fuel pressure is high then it should be 32-35psi at idle. Check that there is vacuum on the line at the regulator, if there isn't install a new vacuum line from the vacuum tree to the regulator.

The type of EGR system on this truck cannot be deleted or disabled without setting a bunch of codes and a check engine light, so don't start unplugging things it will just make things worse.

The lean codes could be caused by a problem with the EGR, there should not be any vacuum on the line at the valve at idle, if there is then the control solenoid is malfunctioning. Here is a diagram of how that system works, the PCM regulates the exhaust gas flow into the motor via the EVR based on operating conditions and feedback from the DPFE sensor, and when working properly the systems operation should be transparent.. meaning it should not have any negative effects on engine operation.

 

Thank you for your time and explanation. This is great.

 

Okay, so no vac at the egr at idle, thats good and I also can't find any leaks. However I did find out some one capped off the FPR, when I take the cap off (and put the vac line on like it should be) I'm now getting weak fuel pressure like 20 psi. So is this a bad FPR or bad fuel pumps/clogged filter. Both pumps are showing the same fuel pressure. Obviously when I cap off the regulator fuel pressure rises. Whatchu think?

 

If the fuel filter hasn't been changed recently definitely do that first. Given the truck generally runs lean this evidence points at weak fuel pumps or a really dirty filter, I bet if you left the FPR unplugged and could setup the pressure gauge to view it while driving you would also see that pressure drops under load.. which should not happen. If everything was working correctly and vacuum was attached to the regulator you would see pressure rise from 32psi towards 40psi whenever the engine is loaded(and vacuum drops).

 

Ill replace the fuel filter (hopefully tomorrow) and report back.

 

Ok, so replaced the fuel filter (quick disconnect lines were super fun). Its noteworthy that the tank side of the old filter was extremely dirty (looked like charcoal water) and had alot of sediment.

After replacing the filter, fuel pressure at the rails now is 30-31psi at idle, when I remove the the vac to the FPR it climbs to 40 or so. Let the truck idle for a long time, then took it to the neighborhood hill and didn't note any surging or hesitation. I've yet to get another code. But I'm expecting at one (egr related hopefully not lean) ill keep an eye on it.

Thanks for the help!

 

That is what the fuel pressure should be so sounds like the filter was way overdue for a change, engine performance and overall operation should improve noticably over the next few drive cycles.

 

I have a California spec Mass air OBD2 7.5 F350, and I have had some lean code problems as well! When I first got this truck it had 140,000 miles on it but seemed to run fairly well, but I felt it was down on power.. Since it had high mileage I bought a set of supposedly new injectors and replaced them. No change in performance whatsoever! I then started getting codes showing lean conditions! I had to finally take truck to Ford dealer to repair truck so it would pass California emissions, and long story short, I ended up getting a new Ford recon long block installed. At that time I requested that Ford dealer install 2 new exhaust manifolds and all fasteners and they did. Now 2 years later, I find check engine light on again and have to have Cat replaced to pass emissions! The day after Cat replaced the drivers side exhaust manifold develops a crack on #5 cylinder! I check temps on each exhaust port with a digital temp gun and find #5 is running way hotter than most of others. My conclusion is that the injectors were probably not new and the lean condition of fuel system contributed to early demise of Cat and the crack of a new exhaust manifold! My plan now is to replace the injectors with the originals, which I had checked and cleaned and flowed by a pro. and also replace exhaust manifold and then recheck exhaust temps and pray I am right !!! My feeling is these 7.5 California engines are running so lean from the factory, that if anything in fuel delivery system becomes out of spec, bad things happen fast!!! Good luck with yours !!! .