Faulty Fuel Pressure Sensor

Enki said:
What's it peg at?
Click to expand...

As far as desired vs actual pressure, it seems to match up exactly to what my ECU sets as the desired pressure, all the way up to just barely under 1900 (at which point the PRV has already cracked open anyways and is actively bleeding pressure). I couldn't find any hard numbers for rating like I could when I contacted Bosch about their sensors, but I figured since modern i4 EcoBoosts are based on MZR L3-VDTs it might've worked (plus ST users report similar HPFP throughput as speeds), and as far as my testing goes, it seems to do just fine as a replacement for a Bosch sensor.

I honestly don't feel like pulling my intake manifold off again just to swap back to my Bosch sensor (at this point I've got a collection of 4 fuel pressure sensors lol, my bad original, *38, *53, and the Ford sensor), so I'm just going to leave to Ford one on and I'll report back if I notice any issues or premature failure.

Also important to mention: the sensor in question has to be from a 2015+ ST specifically. RS's use a different connector housing, even though the pinout is the same, and 2013-2014 STs used a different sensor.
 
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Update on the FoST high pressure fuel sensor experiment:

After a having the Ford sensor on for a bit, I started to notice a very loud screeching on cold starts. After some troubleshooting and testing, here's the conclusion: the Ford sensor will see slightly less than actual fuel pressure (I would typically see ~1600 when ordinarily I would expect ~1800). It seems to be there is a small resistance difference between the two sensors. Occasionally I would see the Ford sensor hit 1800-1900. I'm not entirely sure why this is, to be honest, given that that would mean that the actual pressure would be around ~2.0-2.1k, but I'm on an 1850 valve, not a 2150.

Neither here nor there. In my daily driving with it, I noticed nothing out of the ordinary. No knocking of any kind, no lagging, otherwise no performance issues at all. So for my car it was fine. What I'll say, with everything in mind: I would not advise using the Ford sensor. However, if you don't do anything harsh on your car and just drive it like a princess, it may be a viable replacement for the OEM Bosch. Make your best judgement here. Just because I never saw any problems (outside of the cold start screeching and the slightly lower fuel pressure readings) does not mean you will have the same (as a side note, the screeching would subside completely whenever the engine was at operating temperature).

That concludes this experiment.
 
dinnerplate said:
Occasionally I would see the Ford sensor hit 1800-1900. I'm not entirely sure why this is, to be honest, given that that would mean that the actual pressure would be around ~2.0-2.1k, but I'm on an 1850 valve, not a 2150.
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The PRV flow rate is sized to the stock internals; upgraded internals easily overrun this flow rate, causing pressure to be higher than normal.

Edit:
For others wanting to run this sensor but want to avoid the screeching, you can likely adjust (lower) this section of your HPFP pressure tables in the tune by about 10-25%:

HPFPEdit.png
 
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I sadly have a failed fuel rail sensor as well. I actually just found a sensor that was on ebay saying it is a replacement of my actual oem part number. I'm very skeptical so we will see. I am assuming the fuel safe permatex is a viable sealant to use?
 
I found a sensor after hours and hours of searching and calling places over several days. It was on ebay and hopefully it fixes my issue as it gives the oem number for the sensor reference. Time will tell but here is the link!

https://www.ebay.com/itm/303471762991

I'll keep you guys updated on whether it works completely or not. I sure hope it does!
 
StreetSpeed6 said:
I found a sensor after hours and hours of searching and calling places over several days. It was on ebay and hopefully it fixes my issue as it gives the oem number for the sensor reference. Time will tell but here is the link!

https://www.ebay.com/itm/303471762991

I'll keep you guys updated on whether it works completely or not. I sure hope it does!
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So reviving this thread as it is an issue again I believe. The sensor listed was short and didn't seat enough to seal so it leaked. @JohnnyTightlips sent me a replacement that was used but factory at least. I have since had no issues until recently.

Now once my car has warmed up it starts to kick and buck and I see my hpfp readings go from 1600 or whatever to zero and immediately back to normal. I think the sensor is failing causing a hiccup when this occurs. Only other thought is if the wiring is somehow shorting out somewhere. Super frustrating. I wish I could run an adapter that allows for a generic sensor lol
 
Enki said:
Could be your ITFP as well. Done the KOEO test? Let it sit overnight then key on and check rail pressure, should be 40-60.
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No I haven't done that. I have an AEM 340 I think that is only a year or two old. So to do the test I just koeo and then check it the next morning when I turn the key on?
 

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Enki said:
Yeah you could also log just the fuel rail pressure (only that) during a cold start and see what it does.
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Ok I'll do that in the morning. It has been sitting about 5-6 hours at least since I started it earlier and that pic is what it was. I have a log of driving when it happened I think. Would you wanna check it out?
 
You could do that log test right now if you wanted, it's sat long enough to cool down. Only log fuel rail pressure though, nothing else. This will give the best resolution.
 
AFR doesn't look to really change that much, which suggests to me that it's the sensor fucking up (or some other electrical gremlin).
 
Agree, is possible that the sensor is bad. I wouldn't run the car like that. Look at that graph... But before you put a new one, I'll strongly suggest to check the harness and grounds. A quick test with the key on engine off, wiggle the harness and see if the fuel pressure voltage change erratically.

1767396927202.png
 
OMISPEED3 said:
Agree, is possible that the sensor is bad. I wouldn't run the car like that. Look at that graph... But before you put a new one, I'll strongly suggest to check the harness and grounds. A quick test with the key on engine off, wiggle the harness and see if the fuel pressure voltage change erratically.

View attachment 33884
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I'm going to go ahead and do that test tonight and see what we get. I'll post the results here after a while :)
 
OMISPEED3 said:
Well, then you need a new sensor. It reads 0 volts @ ~58 psi. I believe it should read a little bit over 0.5 volts. I might be wrong.
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Yeah I have no clue but I ordered a replacement that is supposed to work. It is the part number for a cx-7 but supposedly is interchangeable. We will see come Tuesday when I get it. If that doesn't work I'll be buying one from Summit Racing that is twice as much but also says it is a replacement.
 
StreetSpeed6 said:
Yeah I have no clue but I ordered a replacement that is supposed to work. It is the part number for a cx-7 but supposedly is interchangeable. We will see come Tuesday when I get it. If that doesn't work I'll be buying one from Summit Racing that is twice as much but also says it is a replacement.
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What part number did you get?
 
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