P0191 - weird breakdown yesterday - Fuel System Issue??

[Mr.Anderson]

Just changed the fuel filter out - those "quick disconnect" fuel lines are anything but quick ... should be called "pain in the ass disconnect" fuel lines. I struggled for a good hour with two different fuel line disconnect tools (one plastic, one cast metal) neither worked, then finally went back to the auto store and bought every other disconnect tool they had on the shelf - the Leslie one is pretty good - it worked on the first try and in about 10 minutes I had a new filter on. The old filter had some pretty gross looking gas dripping out on the gas in side, so maybe that filter was the culprit.



Still thinking about just replacing the fuel pump pre-emptivley. I'm at a friends house this week but will be back on the road for the next month or more. Would rather do the job here than on the side of the road broken down somewhere. Fuel pump is 13 years old assuming it's original...



https://www.lislecorp.com/specialty-...nnect-tool-set

[86Scotty]

Spray some PB Blaster or the like in those Ford fuel line connections a couple times and a few days before you do the job. It's a pain either way but makes it easier. I agree. I think they are a lousy design.

[carpetwit]

Hi Mr. Anderson,
I got the "misfiring: code-related engine light after coming from New Mexico after about a 700 mile trip from Dallas into the Colorado High-Country: Engine performance did not slump noticeably but maybe it felt less responsive. Its a 2014 V10 with only 35K miles... nothing to it. It took several trips to an authorized Dealership until somebody recommended to add a fuel cleaner to a half tank and then repeat that process once: Engine check light disappeared after another 150 miles. It happened again recently after a longer break and having it sitting in the garage for a while. Same response but faster! Let me know if it helps...

[melk]

Try replacing the fuel pump relay, found in the fuse box underhood. Cheap and it may do it.

[Mr.Anderson]

Melk - thanks for the input. I think the fuel pump relay is OK, but I will keep that in mind if issue returns. I did see some videos on how to trouble shoot / verify the operation of the fuel pump relay.



Carpetwit - probably not a bad idea to fuel cleaner to my system. That's the same thing as fuel injector cleaner right or is it something different?



Just a quick update on this - I did replace the fuel filter when this issue cropped up and have since put down ~ 1200 miles without issue, so hopefully things continue to run smoothly. In the first 300 miles I did notice what felt like an engine misfire / intermittent loss of power on uphills while driving out but that hasn't reproduced in the last 900 miles (which had plenty of ups and downs) so not really sure what to make of it, maybe just wind gusts that happened to correlate with uphills ...

[carringb]

The driving symptoms after the filter change make sense if it was plugged. The computer has to relearn the fuel trim tables now that it’s getting more fuel Basically it now has to shorten the injector pulses to deliver the same amount of fuel, due to the higher fuel pressure.

[carpetwit]

Exactly: fuel injector cleaner, sorry, I don’t know off hand which particular one I used.

[Mr.Anderson]

Fall update here: I thought I had gotten past this issue but it reared it's ugly head again just yesterday. This was a little unexpected because I had put about 3000 miles on the van without issue since the problem happened back in August and that included driving through Rocky Mountain National park which had some seriously steep grades and elevations.

In this instance it was pretty similar: gradual loss of power, I was passing someone on fairly flat road and noticed slow response, then as I drove through a steeper mountain pass my top speed dwindled from 60 to 50 to 40 then the engine started misfiring and I got a flashing check engine light:

P0191 fuel rail pressure out of range and P0301 / 306 - misfire on cylinders 1 and 6 resp.

I stopped and restarted the engine cleared the CEC codes a couple times and was able to limp the van over the pass then when I got back on regular highway the remaining 300 miles were normal driving up to speeds of 80mph on the interstate.

somewhat of a PITA. based on this earlier thread here's what I'm thinking as possible causes:

• Low fuel in tank - no, I had more than half a tank of gas when this happened
• Fuel Filter - no this was replaced 2 months ago with a new one
• Fuel pump - I don't think so as my understanding is these just fail, they wouldn't produce intermittent problems, maybe I'm wrong here and it is going out.
• Fuel pump relay - same as fuel pump, it either works or it doesn't
• MAF sensor - maybe? Not sure it it's worth just putting in a new MAF
• Fuel injectors failing? - I think this is less likely as if the injectors were bad I'd just have misfires as opposed to the fuel line pressure issue
• something else?

Anyone have any other ideas? or could confirm my above assumptions?

[boywonder]

I'm not an expert here..but ....


...not sure how a MAF sensor issue would result in low fuel rail pressure


same for fuel injectors failing..assuming the failure mode is failed closed.....


Also the fact that you've got misfires on two cylinders would negate the fuel injector hypothesis.


The inertia switch can certainly generate low fuel rail pressure....I have a cutoff for this for security purposes and if you switch off the inertia switch it can throw a low fuel rail code if left off long enough.


My guess is fuel pump.....Perhaps contaminants in the gas tank?

[1der]

Originally Posted by boywonder

I'm not an expert here..but ....
My guess is fuel pump.....Perhaps contaminants in the gas tank?

My guess, too. Cyl 1 and 6 are the forward most cylinders on each bank.
I seem to recall there are filters on the fuel pump on the tank