Need a consensus

[01yellercobra]

I'm trying to decide if I need a new alternator or new fuel pumps. I guess I could go back as far last summer. When I was stuck in traffic coming home on a cruise with the A/C on the car started acting weird on deceleration. Like as soon as I lifted my foot off the gas the A/F would go full lean like it's in coasting fuel shut off. I eventually noticed the car was hot because the cooling fan wasn't working. Swapped out the fan, everything seemed fine. Maybe a month or so later I get stuck on the side of the road because the car died. I assumed the alternator was on it's way out, got hot, and died. What made me think this was that the FPDC was 100% and the car would barely idle. The volts were in the high 12's I think. Swapped alternators, all was good until recently.

A couple weeks ago I was driving home from work. Same situation, hot weather, some traffic, A/C going. I was on the freeway and suddenly the car starts acting weird again. The FPDC is back at 100% and the car is stumbling. I turn off the A/C and eventually it runs fine and I'm able to get home. I was watching the volts on my Aeroforce and it was hitting 12.9. So I think the alternator is going again. I swapped it for a high output alternator I have, but I didn't run the high output for long because I didn't like the way it didn't charge at idle. Rather than play with pullies and belts I replaced the voltage regulator in the other alternator and swapped it back in. Drove my car to work early last week and didn't have any issues.

Yesterday I did a bit more of a drive. Ended up about 150 miles round trip. At one point I'm stuck behind traffic going up hill doing between 35 and 55. I'm watching the IAT2 and it's around 130. I'm just cruising with traffic and suddenly the car starts acting up. FPDC is back to 100% and volts is down around 13.0. But this time I get a CEL which I can't check until I get home. So I'm thinking alternator again. Oh, ambient temp is 90+ degrees. I get to my buddies and let the car sit for a few minutes. I fire it up and it's idling, but has issues when I rev. And FPDC is 100%. IAT2 is around 150 degrees from sitting, but coming down. I'm watching the FPDC and suddenly it drops to 40% and the car smooths out. I drove the car home watching FPDC and volts. I ran the A/C a couple times, but nothing happened. According to the Aeroforce my volts were anywhere between 13.0-13.8. IAT2's are in the low 120's, but I came into cooler ambient temps and the drive home from my buddies is all down hill. As soon as I get the car in the garage I turn everything on, A/C, headlights, stereo, etc and hook a meter straight up to the battery. The Aeroforce is actually dipping to 12.9 at this point, but the meter is 13.4-13.5. Which I know is borderline, but it should still be working. And the CEL was for secondary fuel circuit which is the fuel pump.

So I know I'm going to spend money. The issue I'm having is do I order new pumps, or go for a new alternator? Since the car has acted the same way on two alternators I'm leaning towards the pumps. But "low" voltage is making me think the alternator can't keep up causing electrical issues.

 

[Bdubbs]

You can data log some parameters. One I'd particularly log would be fuel pressure drop across injectors. This will help in telling if you have a weak fuel pump.

I'd assume you've kept up on fuel filter changes.

 

[01yellercobra]

The filter is good. On the way home I was wishing I had the fuel pressure drop picked in my Aeroforce. I'm taking it out of town in a couple weeks and don't want to get stuck.

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[R3dfireCobra]

Sounds like an issue I am having. Just upgraded my alternator to a mechman 170. Car has sat for the better part of a year with some start ups and short trips.

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[Roots-type]

I'm leaning towards the pumps, as well, from what you've described. My aeroforce always reads about .5v lower than what is actually being made. Something happens to that signal once it passes through the computer and the aeroforce picks it up. My head unit has a voltage readout and when I'm at full temp on a warm/hot day or night I'm usually around 13.4-13.7 at idle and cruise and the aeroforce is always reads half a volt lower than that. Voltage is always a bit higher when its cool outside.

I haven't experienced any issues like you describe so its hard to imagine the alternator is the problem since we share similar readings. Especially since you've swapped alternators and the problem persists. From reading other people's experiences, fuel pumps can be an intermittent thing until they finally just quit altogether. I wouldn't venture out on a long trip if you have another car you can take.

I bet with some more selective datalogging you'll find the issue, whatever it may be. GL

 

[bigmoose]

I had a weird issue where my car when it was returnless would once in a while start sputtering and basically be not drivable . I'd pull over and let it sit and cool. Then start it up and it would be fine. That was all just driving around part throttle.

Ended up being my FPDM. Would go bonkers when it got warm. It wasn't quite a thermal shutdown since it still slightly worked.

Previous owner ran a BAP and GT pumps with a stock FPDM. Think this played in the death of mine. An upgraded FPDM fixed my issues. I eventually went full return.

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[01yellercobra]

Well, I drove it up to my buddies to try and get it to act up. Naturally it was fine for the trip up. I let it soak for a few minutes while I loaded something up into my trailer. Fired it back up and FPDC is now at 100% and fuel pressure isn't moving from 55.5. On the drive up it was 37-40psi. Volts are still the same.

I swapped out the FPDM with a spare I had last night. So I think when I get home I'm going to order new pumps.

And the CEL is on again. I left my X3 at home, but I'm gonna guess it's secondary fuel circuit.

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[bigmoose]

Weird. If the duty cycle is going to 100% yet the pressure really is 55psi then, and you ruled out the FPDM, I'd look at pumps next like you said. I would think if you were really at 100% duty cycle with two good pumps you'd see higher than 55psi.

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[01yellercobra]

I think the 55.5 is the max the Aeroforce shows. Naturally I'm assuming on this. I went ahead and started driving and at one point saw 6psi on the gauge. Shortly after that the engine cut out. I was able to coast a little and it came back on. The FRPS did occur to me as well.

I'm home and able to pull the codes. They're P1237 Fuel Pump Secondary Circuit (Fuel Pump Driver Module) and P0190 Fuel Rail Pressure Sensor A Circuit.

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[R3dfireCobra]

I think the 55.5 is the max the Aeroforce shows. Naturally I'm assuming on this. I went ahead and started driving and at one point saw 6psi on the gauge. Shortly after that the engine cut out. I was able to coast a little and it came back on. The FRPS did occur to me as well.

I'm home and able to pull the codes. They're P1237 Fuel Pump Secondary Circuit (Fuel Pump Driver Module) and P0190 Fuel Rail Pressure Sensor A Circuit.

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I see the exact same 6psi when I try and go WOT. If I baby it 40psi all day. If I start to get into boost it drops to the mid 20s. I'm floored because the car ran flawless at one point and had 11.7 AFR. So something has failed (ie fuel pump) or I have a blockage somewhere. But both pumps can run the car at idle at 40 psi I independently.

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[01yellercobra]

I see the exact same 6psi when I try and go WOT. If I baby it 40psi all day. If I start to get into boost it drops to the mid 20s. I'm floored because the car ran flawless at one point and had 11.7 AFR. So something has failed (ie fuel pump) or I have a blockage somewhere. But both pumps can run the car at idle at 40 psi I independently.

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Are you running a dual FPDM set up? I can't check each pump separately. After everything cooled down it ran great the rest of the way home. Even with a quick sprint up to 100mph.

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[R3dfireCobra]

Are you running a dual FPDM set up? I can't check each pump separately. After everything cooled down it ran great the rest of the way home. Even with a quick sprint up to 100mph.

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Yes, I have a return fuel setup.

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[01yellercobra]

Yes, I have a return fuel setup.

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Could it be something in the regulator is sticking or just not working correctly? Is there a way to manually override it to eliminate it as the issue?

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[c6zhombre]

There's no way a 12.9 pid voltage reading is creating the issue.....that is not an unusual reading in the middle of the summer especially on a vehicle getting daily driven and/or running around for long periods.

Its something else with the fuel related hardware, probably the pumps

 

[R3dfireCobra]

Could it be something in the regulator is sticking or just not working correctly? Is there a way to manually override it to eliminate it as the issue?

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Usually if a regulator fails the diaphragm is just wide open with no flow restriction. I'm still leaning toward a failing pump, or clog somewhere (injectors or fuel filter). Like I said in an earlier post, both pumps run and can hold 40psi at the regulator. I've checked the pumps by pulling the fuse on each and even ran the motor on one pump at idle, same 40 psi at the reg. Just weird when I get into the throttle to see the fuel pressure drop. All my vacuum lines are still attached with no sign of damage. Car ran flawlessly at one point, so something has to of failed. As of now, I put fuel system cleaner in the tank and will let that work its magic for a bit. If the same results persist Ill pull the fuel tank and look at the rest of the system.

 

[speedoflife]

I don't think any fuel cleaner is gonna help you at this point. You're going to have to stop hoping this problem will just go away. There is a problem somewhere that will only go away by being fixed.
- Check your FRPS.
- Check fuel filter (probably not it)
- Drop the tank and check that the pumps are not seized/failing
- It could be also be something strange like a pinched hose (homemade PPRV delete maybe?) or a clogged PPRV (like this guy https://www.svtperformance.com/foru...ap-terminator-pumps-and-2-3l-whipple.1133135/ )
- Make sure your FPDM is not overheating

 

[SecondhandSnake]

Just throwing this out there-
I think the 55psi may be an intentional and desired output. If I'm not mistaken, when the ECU sees high IATs it bumps up the fuel pressure to prevent vapor lock. I saw it a few times on some of my datalogs when it was hot out and I was at low load. Then as soon as IAT dropped back down it went back to the normal 39psi base pressure.

Now that could be part of the equation. High ambient temperature leads to high IATs leads to increased base pressure, and between that and the heat you're overheating the FPDM. Is it still the stock one and pumps? I've got duals and the wiring upgrade and even with that happening I don't see an issue.

 

[01yellercobra]

I don't think any fuel cleaner is gonna help you at this point. You're going to have to stop hoping this problem will just go away. There is a problem somewhere that will only go away by being fixed.
- Check your FRPS.
- Check fuel filter (probably not it)
- Drop the tank and check that the pumps are not seized/failing
- It could be also be something strange like a pinched hose (homemade PPRV delete maybe?) or a clogged PPRV (like this guy https://www.svtperformance.com/foru...ap-terminator-pumps-and-2-3l-whipple.1133135/ )
- Make sure your FPDM is not overheating

I don't know where you got that I'm trying to fix it with fuel cleaner. I haven't run any kind of cleaner through it. Nor am I hoping it just goes away. I have been trying to troubleshoot the issue so I'm not just throwing money at parts. I prefer not to do that.

FRPS isn't blown. In my experience when they blow the car runs like crap all the time. That being said I did change mine since it threw a code.

Fuel filter might have 10k on it. I need to check my records.

If I get to the point of dropping the tank then I would be assuming the pumps are bad and would be swapping them out. I'm trying to make sure they could be the problem before getting there.

The PPRV in this tank was deleted about 11 years ago. Used a mix of submersible lines and the stock hoses that come with the GT pumps.

Swapped out the FPDM with a spare as I mentioned and it acted up again the next day.

Just throwing this out there-
I think the 55psi may be an intentional and desired output. If I'm not mistaken, when the ECU sees high IATs it bumps up the fuel pressure to prevent vapor lock. I saw it a few times on some of my datalogs when it was hot out and I was at low load. Then as soon as IAT dropped back down it went back to the normal 39psi base pressure.

Now that could be part of the equation. High ambient temperature leads to high IATs leads to increased base pressure, and between that and the heat you're overheating the FPDM. Is it still the stock one and pumps? I've got duals and the wiring upgrade and even with that happening I don't see an issue.

I had the same issue last summer when stuck in traffic. It's so rare that my IAT gets that high that it's hard to trouble shoot. But it does seem to be happening with the high IAT. Once it comes down everything goes back to normal. I tried to get it to freak out yesterday, but traffic was moving too much to get the IAT above 122. Engine temp doesn't seem to affect it.

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[speedoflife]

I don't know where you got that I'm trying to fix it with fuel cleaner. I haven't run any kind of cleaner through it. Nor am I hoping it just goes away. I have been trying to troubleshoot the issue so I'm not just throwing money at parts. I prefer not to do that.

FRPS isn't blown. In my experience when they blow the car runs like crap all the time. That being said I did change mine since it threw a code.

Fuel filter might have 10k on it. I need to check my records.

If I get to the point of dropping the tank then I would be assuming the pumps are bad and would be swapping them out. I'm trying to make sure they could be the problem before getting there.

The PPRV in this tank was deleted about 11 years ago. Used a mix of submersible lines and the stock hoses that come with the GT pumps.

Swapped out the FPDM with a spare as I mentioned and it acted up again the next day.

I had the same issue last summer when stuck in traffic. It's so rare that my IAT gets that high that it's hard to trouble shoot. But it does seem to be happening with the high IAT. Once it comes down everything goes back to normal. I tried to get it to freak out yesterday, but traffic was moving too much to get the IAT above 122. Engine temp doesn't seem to affect it.

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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?

 

[speedoflife]

After some google research on the secondary fuel circuit CEL, I would put money on it being a dead fuel pump or a bad connection between the FPDM and the pumps.

Luckily that's a small area to have to dig through. Though dropping the tank sucks.