Fuel pressure sensor help.

[Silver 03 Cobra]

Pumped03 has been having problems blowing the FPS's for a few months. The car is not a daily driver and has blown 5-6 sensors over 1000 miles. I've been trying to figure it out. He has a 2.80 upper and six pound lower and a chip for his mods. Here's a chronological list of events.

1. Car developed a knocking sound a few months ago. I couldn't figure it out. I thought it might be the alternator or an idler. I was driving it home to swap out my idler pulleys when the car lost boost. When I opened the hood it looked liked the belt was broke. I grabbed the belt and it wouldn't come out. I looked down and his alternator pulley had fallen off. I guess the nut got loose somehow and the loose pulley was causing the knocking sound until it fell off. Mark ordered a Metco under drive pulley and I installed it.

2. I installed an Autometer Tach Adapter and window switch and did the boost by-pass mod the same weekend.

3. A shop in Charlotte installed a solid axle and a Plasma Booster a few days later.

4. Car starts to blow FPS's blowing the diaphragm everytime. Since the car is not daily driven and winter arrival, Mark let the car sit for several weeks.

5. Mark gets his 03 out and is getting it ready to drag but is concerned about the bursting FPS's. Mark has two 03's so I had him swap the fuel pump driver modules a few days ago hoping this may be his problem.

6. I did a brake job on it and installed a LFP HE on it a few days later. The battery went dead with just the radio playing after six hours. Mark took it to Autozone and they said the alternator was bad.

7. Mark calls a Ford dealer and orders another alternator. He asks the parts guy about the FPS's. The parts guy said he had heard that a bad alternator could cause FPS's to fail.

8. I swap the Metco pulley onto the new alternator and installed the new alternator on his 03. Mark has his chip out to be reprogrammed so we decided to put the chip from my 03 on his since they both have the same computer code.

9. Mark removed the boost by-pass mod.

10. The car actually ran better with my chip and we thought we had it solved but tonight the car went whack again. Mark called me on his cell.

When I got there he said he didn't think it was the FPS because the vacuum lines didn't have any fuel in them. The car has a fuel pressure gauge and the car showed fuel pressure in the "On" key position. Mark carries an extra FPS so we decided to swap it out and the car fired right up. Apparently the electrical sensor went bad without the diaphragm bursting. All the other times the FPS went bad the diaphragm bursted.

We have eliminated a few possibilities. Mark said he's sure he is not hitting the rev limiter. The car has a different fuel pump driver, different chip, new alternator and the boost by-pass mod removed. The only thing left is the computer or the fuel pumps.

Is it possible for the computer to go bad? If it were bad, would the car still run great but could cause a FPS to fail? Mark said he thought he may have hit the dump valve tonight. There is something different this time since the diaphragm didn't burst. Anybody got any ideas? Any help is greatly appreciated.

 

[Silver 03 Cobra]

TTT

 

[stangin]

What is the fuel pressure? I would monitor the fuel pressure and see if it does not have radical changes causing the sensor to break. Someone correct me if I am wrong, but isnt the pressure controlled by the chip? Could the tune/tunes be causing the pressure to fluctuate radically? Maybe you can de-tune it for a while and see if the sensor fails again and try to rule that out.

 

[Silver 03 Cobra]

With his original chip, it would pull 40 psi at idle and run over 60 psi at WOT. With my chip it idles at 30 psi, about the same mine does with the same chip. It goes to around 60 psi at WOT. It has an Autometer electronic fuel pressure guage on it. I think that if it got a pressure spike it may be so quick the gauge would not even register it.

The thing that bugs me this time is that with my chip, the FPS failed but it didn't burst the diaphragm. With Mark's chip, it bursted the diaphragm on 4-5 sensors. That's why I think it may be the computer or the fuel pumps. We've replaced everything else unless there is something else that controls fuel pressure other than the FPDM (fuel pump driver module).

 

[2K3BRA]

Is the 60 PSI putting alot of undesigned stress on the FPS? Alot of the tunes I see usually keep fuel pressure around 40, 60 seems really over necessary.......I agree de tune it and see if it still happens. I think its the crazy high fuel pressure. But thats just my .02

 

[Silver 03 Cobra]

TTT

 

[Silver 03 Cobra]

TTT

 

[ToxicByte]

Hey Larry,

What size injectors? That much fuel pressure with stock '03 injectors could be the problem... I would probably remove the the Plasma Booster for a while also. Seems like it started when you installed that.

Later
Richard

 

[Silver 03 Cobra]

Hey Richard,

The injectors are stock. The Plasma Booster was installed by a shop in Charlotte. I didn't know anything about a PB. I looked it up on their website and they had an article on 5.0 Must and MM&FF magazines. The PB has eight wires where each wire goes to an individual coil pack. In the one article I read they connected each wire from the PB right at the coil. The shop that installed the PB chose to install it at the terminal connector next to the firewall on the passenger fender. Somehow they knew what wire to connect to since there is a lot of wires in the bundle. It looks like it could be easy to make a mistake. I know sometimes there can be wires of the same color in a bundle. I guess you can pull the coil cover and look at what color wire is on the coil and then look for it at the terminal. The safest way would then be to probe it with a meter to make sure it is the correct wire. If one of these wires from the PB were connected to the FPS, it makes me wonder why it wouldn't cause a MIL and the engine to not run properly. Secondly, I wonder how it could cause the diaphragm to burst unless the diaphragm is actually the sensor itself and over loading it with current could break it down. We are checking it out right now.

Are you hooking up with us to go down to MW in Myrtle? I guess it'll just be me, Mark and his brother and I think we are heading out Thursday morning heading to Darlington first.

 

[WS6JJP]

subscribing...since i went through 2 of them myself.....mine went both times because of hitting the rev limiter

 

[beabout]

Just a question to add to the discussion.

Does Ford or any aftermarket folks make a stronger or heavy duty Fuel Pressure Sensor?

 

[Swervedriver]

Originally posted by 2K3BRA
Is the 60 PSI putting alot of undesigned stress on the FPS? Alot of the tunes I see usually keep fuel pressure around 40, 60 seems really over necessary.......I agree de tune it and see if it still happens. I think its the crazy high fuel pressure. But thats just my .02

I'm pretty sure SilverSnake is talking about total fuel pressure where you are talking & thinking about fuel pressure differential.

Any chipped Terminator with a 6LBS pulley will have a total fuel pressure of 54-55PSI since the PCM adjusts the pumps to keep ~a 40PSI differential above manifold pressure. This car in question should be boosting to 20PSI (40+20=60...).

 

[Silver 03 Cobra]

It is total fuel pressure on the fuel rail.

Ford has a revised FPS. I'm not sure if they are installed on later models. Mark's 03 was a first run and he picked it up on 7/02 and it had the old part. I'm not sure about the first couple he blew but I know he made an effort to get the revised FPS and I think at least a couple of them were blown also. He ran the same pulley combos, engine mods and chip from 2/03 till 10/03 with no problems and I know he hasn't changed his driving style and he pulls boost 90 percent of the time . I haven't talked to him today. He was going to check the wires late last night. If we find anything we'll post back.

 

[pumped 03]

TTT

 

[maoun]

they were right above...too high a pressure causing it to blow...lower the pressure