Fuel Pressure parameters for Marauder

[sbutler83]

So I hooked up a fuel pressure gage to the '03 Marauder I'm working on, and it seems to be bouncing excessively compared to most vehicles I've ever looked at, however I've never tested fuel pressure on a ford with the FPDM and no return line before, either. The comparison I'm making is to a regulated return fuel system.

I am uploading a video to youtube of what I'm seeing as I speak and will link it to this page when I can, but it is bouncing by almost 5 pounds at idle and then steadily through the RPM band. This same guage if I put it on my Bronco or my diesel truck is VERY smooth.

I am troubleshooting a car with a rough idle and a Downstream driver's side oxygen sensor that is stuck rich (on the side where the fuel pressure test port is located) and I'm wondering if I have an injector issue on that side.

[BODYMAN]

So I hooked up a fuel pressure gage to the '03 Marauder I'm working on, and it seems to be bouncing excessively compared to most vehicles I've ever looked at, however I've never tested fuel pressure on a ford with the FPDM and no return line before, either. The comparison I'm making is to a regulated return fuel system.

I am uploading a video to youtube of what I'm seeing as I speak and will link it to this page when I can, but it is bouncing by almost 5 pounds at idle and then steadily through the RPM band. This same guage if I put it on my Bronco or my diesel truck is VERY smooth.

I am troubleshooting a car with a rough idle and a Downstream driver's side oxygen sensor that is stuck rich (on the side where the fuel pressure test port is located) and I'm wondering if I have an injector issue on that side.

I cannot speak for a stck MM as I never monitored FP when stock. But on mine and it is still returnless Mine does vary some on FP. Is it in the mid 40,s? or does it drop even lower? What you mentioned about return style being smoother is for sure & hence why Iam gathering parts to change to full return in the near future. 5lbs while idling seem,s excessive to me though. Personally on my MM I see 50,48 usually.

[RacerX]

Mine is within a one psi bounce at idle. Something isn't right.

[sbutler83]

Thanks, actually with a brand new fuel filter installed I'm seeing 30-35 psi throughout the RPM band.

[Odinson]

Watching fuel pressure constantly on my dashdaq 1-2 psi bounce. And that's with a broader pressure range under boost.

[sbutler83]

What values are you guys seeing for fuel pressure, Mine won't go above 32 steadily.

[RacerX]

I see 38psi to 40psi @ the rail throughout my rpms even @ WOT. NA. Boosted you'll see more. At 14psi boost, you would see about 53psi.

[sbutler83]

I am not familiar with the FPDM setup. Sounds like the fuel pump is going bad on this thing, but I was wondering if someone more familiar with this system could fill me in on wither or not there is anything else in the fuel system that could cause this with a brand new fuel filter.

Thanks.

[RacerX]

If you have any bad O2 sensors, you can chase your tail. Check those, clean MAF sensor, check FRPS (pull the vacuum line and see if you can smell fuel), unplug the IAC motor on the TB, check for vacuum leaks.

[sbutler83]

Here is the video link http://youtu.be/8JgvevAmlGY

I replaced the upstream and downstream oxygen sensors on the side that was showing issues, and the readings didn't change, so I replaced them.
The FRPS doesn't have any moisture inside where vacuum nipple. It does slightly smell of gas.

[RacerX]

I wonder if an injector is stuck open. You may be right. Hmmmmm...

[sbutler83]

It does hold pressure on the gage after the engine is turned off. How much work is it to drop the tank on one of these things?

[RacerX]

You don't have to drop the tank to get the fuel pump out if that's what you're going for. Just for the heck of it, maybe pull each injector harness one by one. Could be the FRPS. Those run about $40 though.

[BODYMAN]

I personally dont think FRPS after fighting thru 4 diff fuel problems in the past and multiple times thinking it possibly was a frps it never once was the case. This sounds like either a injector problem or the pump is getting weak and not pushing same amount of fuel at all times. I had a GT supercar pump do very similar to what youre describing. I would no doubt do like RacerX stated all easy things to do 1st. Pull the vacuum line off the FRPS and smell, If strong odor of gas it's bad. The biggest problem if it is the pump theres no way to verify it cause when U pull the pump and hit it with power it will run just not at 100%.

[sbutler83]

Well I unplugged the #6 injector while the engine is running and noticed no difference in engine operation, while the other 3 made a significant difference at idle.
I looked online at rock auto for injectors, and they all have different colors around the base. The ones on the marauder are purple, but the listed motorcraft part on rock auto appears to have a tan ring around the base in the picture. Are these different colors different injectors? Honestly I would just order the ones that had a purple base if I didn't see the motorcraft part had a different color.
I know on other ford applications the different colors on injectors were different flow rates.

[sbutler83]

With the FRPS vacuum line disconnected, the idle fuel pressure went up to 40 PSI, and revving was capable of about 50 PSI.

[RacerX]

Stock is 24#. The Motorcraft is fine. EV6, 24#. Sounds like the FRPS is bad too. Nothing worse than two probs. Check injector harness with a voltmeter to make sure it's getting voltage?

[BODYMAN]

It sure sounds like Racer is on the money. #1 tell tale sign of bad frps is exactly that .. It performs decent when unplugged.

[LANDY]

Nothing worse than two probs. Check injector harness with a voltmeter to make sure it's getting voltage? Bammmm! Also make sure you check voltage going to the pump. I wouldn't change the FRPS yet.

[BODYMAN]

Bammmm! Also make sure you check voltage going to the pump. I wouldn't change the FRPS yet.

I would agree with landy on the FRPS I would ck as much other stuff as possible before throwing a $80 FRPS in cause if it dont fix the problem You are stuck with it. Other then the Termi's with high HP I havent seen alot of them fail.

[sbutler83]

I checked 20" of vacuum in the manifold at idle, when I throw a mightyvac on the FRPS and gradually increase vacuum to 20", it gradually decreases pressure down to 30-ish.