Need a consensus

[R3dfireCobra]

The fuel cleaner comment was intended for r3dfire - he's having the same problem as you and I don't think that cleaner he added will do anything. Always difficult to communicate intent on the internet...

You're definitely on the right track. I really don't think it's the filter in your case based on what you've said and what's wrong. And it's not the FRPS. And if it's the FPDM it has to be that it's having some intermittent/hard-to-diagnose problem.

I definitely think that it's not your alternator. Your voltage seems fine across the board.

If one pump was locked up, when the car commands the bump in pressure under high-temp conditions, it would make sense that the FPDC would max out and act crazy. It's hard to diagnose that without pulling the pumps though.... can you test them somehow without dropping the tank?

I never really expected fuel cleaner to resolve my issue. More of a pipedream so I didn't have to drop my tank . Im almost certain it is a failing fuel pump on my application. Car has sat for the better part of the year, I just replaced my alternator with a mechman unit as I was seeing mid to low 11's volts in my datalog. Prior was upper 12's, low 13's. Thought maybe I wasn't getting enough volts to run the pumps. I kept seeing 100% fuel duty cycle and low fuel pressure when going into boost. With the new alternator volts look good (mid 13's), but I still have the same low fuel pressure when going into boost. I need to drop the tank and look at everything: filter, lines, pumps. I doubt its a kinked line, nothings changed and the car ran flawless before. Doubt its the filter, everything is about a year old now, so that leaves me to believe its the pumps based off the data and weird noise Im hearing from my fuel tank. Ill report my findings back when I get around to dropping the tank...

 

[01yellercobra]

I haven't forgotten about this thread. Other issues have popped up and put this on the back burner.

Edit: Ordered replacement pumps from Summit. Hopefully I'll be installing them Thursday after work.

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[01yellercobra]

For those wondering, AEM 320's fit in a stock hat. I had to do some soldering and get creative with the outlet hoses. But it fired up and idled. I'll see how it acts tomorrow on the drive from work.

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[BLOWN9646]

Nice thanks slo, I'm about to pull the Stryker 340's I've had for 2+yrs back out and install the AEM 320s also. I modified the stock hat for dual fpdm setup back then, just hoping my base pressure will remain same as my tuner mentioned.

 

[BLOWN9646]

Also, what do you mean about creative and soldering with the outlet hoses??

 

[01yellercobra]

Also, what do you mean about creative and soldering with the outlet hoses??

The 320's have a different plug. So I cut off the stock ends and soldered the plugs for the pumps to the stock harness. You might not need to do that since your set up is modified.

The outlets are 5/16" and the hose they come with would get pinched if it was bent too far. On one pump I was able to reuse the hose from my old GT pumps. For the other I bent a small piece of hard line into a 180 degree bend. Then I used small pieces of rubber line to connect it to the pump and the Y fitting. I wanted to do it to both pumps, but it was 9:30 and I needed to get it back together.

FWIW I've noticed my duty cycle is about 10% less than with the GT pumps. But I haven't done a WOT hit yet.

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[BLOWN9646]

I see, thanks. Yea I'm hoping the AEM plug is identical to the Stryker's so I won't need to resolder/shrink again.

Interested to see what my duty cycle will do also (hopefully doesn't increase by much, if at all)

 

[01yellercobra]

Well, good news bad news. It did act up the same way on my drive home today. I guess it's good I know how to make it act up. But it wasn't as bad as before. This time my FPDC jumped from around 30% to 60%. The pressure was showing 55.5psi. And during this time the dashpot decay goes to hell. And I got a code from the FRPS saying it's reading high. The FRPS is about a week old. At least it seems like I'm getting somewhere.

 

[speedoflife]

Well, good news bad news. It did act up the same way on my drive home today. I guess it's good I know how to make it act up. But it wasn't as bad as before. This time my FPDC jumped from around 30% to 60%. The pressure was showing 55.5psi. And during this time the dashpot decay goes to hell. And I got a code from the FRPS saying it's reading high. The FRPS is about a week old. At least it seems like I'm getting somewhere.

Man your car just doesn't want us to figure this one out.

Is the only part you haven't swapped out the FPDM by now?

Were you still getting a CEL this time the problem showed up?

 

[bigmoose]

Unlikely but could it be a intermittent ground short on your hat or in the wiring to the FPDM? That would cause the pumps to go full tilt.

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[01yellercobra]

Man your car just doesn't want us to figure this one out.

Is the only part you haven't swapped out the FPDM by now?

Were you still getting a CEL this time the problem showed up?

The FPDM was the first thing I swapped. I got P0193 code for high rail pressure. Which would make sense since I was seeing 55psi on the gauge. But since it's the drop across the injectors I would think it's commanding the pressure. I half tempted to throw a different tune to see if I messed something up in my current tune.

Unlikely but could it be a intermittent ground short on your hat or in the wiring to the FPDM? That would cause the pumps to go full tilt.

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I looked over the hat wiring when I did the pumps. Everything looked ok. I have a wire upgrade going to the FPDM. I haven't run the extra wire down to the tank yet. I'd have to check the body side of the harness.

On the bright side I'm one step closer to running E85.

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[01yellercobra]

I think I'm going to say it's something with the charging system. I put about 300 miles on it today. No codes and acted up once. But just barely. I was in traffic in LA on the 101. For those that know, the 101 sucks. Anyway, crawling along with the A/C on and stereo going eventually it goes a little wonky. I think the A/C, plus the fan, plus the stereo, plus slow speeds is causing the alternator to get hot and it can't keep up. On the drive home I didn't have the A/C on, but the stereo was cranked because the windows were down. I could see my dash lights dimming. I had my son double check and as soon as I paused the music it stopped. I have a 500 watt amp hooked up to a 10" sub in the trunk. So I don't think my charging system is necessarily failing. I just think it can't keep up when everything is going.

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[Bdubbs]

I think I'm going to say it's something with the charging system. I put about 300 miles on it today. No codes and acted up once. But just barely. I was in traffic in LA on the 101. For those that know, the 101 sucks. Anyway, crawling along with the A/C on and stereo going eventually it goes a little wonky. I think the A/C, plus the fan, plus the stereo, plus slow speeds is causing the alternator to get hot and it can't keep up. On the drive home I didn't have the A/C on, but the stereo was cranked because the windows were down. I could see my dash lights dimming. I had my son double check and as soon as I paused the music it stopped. I have a 500 watt amp hooked up to a 10" sub in the trunk. So I don't think my charging system is necessarily failing. I just think it can't keep up when everything is going.

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What are you running for a alternator? Didn't you just buy an upgrade?

 

[01yellercobra]

What are you running for a alternator? Didn't you just buy an upgrade?

I'm currently running a stock alternator. Or what's supposed to be stock. I have a 200amp alternator on the bench, but I need to get a smaller pulley for it. With the stock pulley it doesn't charge at idle. Rev the engine up to 1000rpm and it charges just fine. But you know how it goes with changing pullies. Once you do that you have to measure for the correct belt length.

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[Bdubbs]

I'm currently running a stock alternator. Or what's supposed to be stock. I have a 200amp alternator on the bench, but I need to get a smaller pulley for it. With the stock pulley it doesn't charge at idle. Rev the engine up to 1000rpm and it charges just fine. But you know how it goes with changing pullies. Once you do that you have to measure for the correct belt length.

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Gotcha. I think you really need to get that 200 amp on. My nation's is still staying 14.3-14.7 at warm idle. Only thing that bugs me is the flickering battery light at high rpms.

 

[01yellercobra]

Gotcha. I think you really need to get that 200 amp on. My nation's is still staying 14.3-14.7 at warm idle. Only thing that bugs me is the flickering battery light at high rpms.

I do too. I was doing some looking and measuring this morning. I think if I replace one of my 90mm idlers with a 100mm I can keep my current belt with the smaller alternator pulley.

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[01yellercobra]

Went ahead and ordered a 2.25" alternator pulley. It's the smallest I could find. I also ordered a Metco 100mm idler to replace one of my 90mm pullies. Hopefully I'll be able to install everything next weekend.

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[c6zhombre]

Those stock hats really look like junk.....I'd toss that sucker as far out into the Pacific Ocean as you can and order a fore hat with new wiring

 

[01yellercobra]

Those stock hats really look like junk.....I'd toss that sucker as far out into the Pacific Ocean as you can and order a fore hat with new wiring

Lol. That is on the to do list. But not any time soon. My son just got his license in June. We're looking at remodeling our kitchen. And then we'll be saving for our vacation next year. Big mods for the Cobra are way down on the list unfortunately.

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[WheelStander]

Fwiw...
I had the exact same symptoms for a few months, ended up checking everything like you did, going through a couple of different alternators and a couple different batteries before the issue was resolved. It wasn't until I replaced both at the same time that symptoms abated. Ended up with a PA and Motorcraft Battery. 5K miles in NC heat with AC on, no issues. Also 12.9 volts from the pid is what I'll usually see, I double check.