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2002 V6 3.8L & 2003 Mach 1
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Discussion Starter · #1 ·
For the past 8 months or so I've been battling with a high fuel pressure issue. Initially I thought fuel pump had gone bad. Replaced pump and maybe a month later pump died again. When I pulled pump second time it had a hole blown out side of hose on fuel pump assembly. I can't remember if original pump had this issue or not. I didn't have the time to work on it more at the time so I took car to a shop. The shop then proceeded to replace pump at least 4 or 5 times of the course of 4 months or so. The majority of time I know it was the same hose on the fuel pump assembly that would end up blowing out. We probably went through 3 different brands of fuel pumps. Eventually I lost confidence in the shop's ability to resolve the issue so I brought the car back to my place and am attempting to resolve the issue on my own. Any help would be greatly appreciated.

I couple of weeks ago I put a new pump in, but this time around I removed the stock hose on fuel pump assembly and upgraded with this before I installed the new pump:

Other than hoses on fuel pump blowing, car seems to run fine.

I have replaced Fuel Rail Pressure Sensor (FRPS) and Fuel Pump Driver Module (FPDM) without any noticeable differences.

I've been using the ODBII port with bluetooth adapter to capture diagnostic data to an Android phone using Torque app.

With car starting up cold and left idling until it reaches idling temp (aprox. 10 minutes) you can see what car, and especially fuel pressure is doing in graphs below.
Rectangle Slope Line Plot Font

For a closer look at fuel pressure look at this graph...
Rectangle Line Font Slope Parallel

You can see spikes going from 40 PSI to 65 PSI and then to around 85 PSI. My understanding is that 40 PSI is standard, but a range is allowed by Ford up to 50 PSI or so. I assume these pressures are coming from FRPS given that I am getting them through ODBII port.

I have a lot more data that I can provide, raw or in graphs, if needed.

I drove the car on the freeway (i.e. 70 MPH) for over an hour a few days ago and what I noticed was that the car ran pretty much the entire time at 40 PSI while on the freeway and air intake temp was low, but as soon as I got off freeway car would quickly go up to 65 PSI and stay there for the most part. Likewise air intake temp would also go up during this time. I then parked car and left it for approx. 2 hours. Then came back and started car and it went quickly to 65 PSI as I drove around town with various stop and go traffic for lights, etc. I only drove for around 5-10 minutes and was seeing fuel pressure spikes up to 85 PSI, but otherwise car was staying at around 65 PSI. Again, parked car, left it for an hour or so. Came back, started it back up, and car quickly went back to 65 PSI where it stayed for about 5-10 minutes until I got on freeway. I then drove on freeway and fuel PSI quickly went down to 40 PSI as did air intake temp. Car then stayed at 40 PSI for the next hour while on freeway, but soon after I got off freeway and intake temp went up, fuel pressure also went up.

It seems like their may be some relationship between air intake temp and fuel pressure?

Just a few other observations/thoughts that may or may not be relevant...

One time after testing car and having it idle while I captured data, car reached 65 PSI and then I shut car off. I then turned key to "on" position on ignition, but did not start car. I assumed this would run fuel pump to prime fuel system as it normally would and I saw fuel pressure push all they way to 95 PSI. Apparently car electronics are not smart enough to detect that fuel pressure is already high and therefore not run pump? I was concerned about leaving fuel pressure high and so I used shrader valve/port on fuel rail to relieve pressure. I took appropriate safety precautions to capture fuel spray and not let it get on engine and start a fire. Fuel that came out was noticeably hot. Not scolding, but definitely very hot. Not sure if that is a concern or expected.

I have a K&N red reusable filter that I am sure is long overdue for a cleaning. I have not gotten around to doing this yet, but perhaps this is also related?

Fuel filter has also been replaced.

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