Let's talk about fuel issues -- Fuel Pressure Drop under Acceleration

[Paps]

Good catch! But i didn't understand what you explained about that T valve thing...lol
Do you mean that white plastic union that holds passenger line? Any pics?
If you removed that part, you'll only able to use half a tank, right?

 

[petersonb]

Good catch! But i didn't understand what you explained about that T valve thing...lol
Do you mean that white plastic union that holds passenger line? Any pics?
If you removed that part, you'll only able to use half a tank, right?

Yeah that's the part. I know it's more than a T, but that was the easiest way to describe it. I know I'll only be able to use half the tank, but that will get me by until I can replace this part.

I'll just cut it hard to the right every once in a while! Throw some gas over into the driver side of the tank LOL

 

[petersonb]

Any pics?

Bad photo, but you can see the part behind/through the hoses.

 

[Paps]

Thanks for sharing, i may take a look there too.

 

[petersonb]

I feel like an ass, but the problem is STILL there. It must be heat that's making everything worse. It usually sits for a while, while I make whatever change I'm making. During that time, I'm guessing it cools down enough, then the problem doesn't show, and I think its fixed.

It didn't pass the 115mi test, but there's another thing I can check off the list. I'll replace the fuel filter tonight, then there's only the FPDM, Fuel lines, and injectors.

Anything I'm missing?

 

[Makdaddy]

Maybe silly but did you look at the vac line feeding the fuel regulator?

Can you read vacuum on a gauge? if so is it good when the fuel pressure drops?

 

[petersonb]

Maybe silly but did you look at the vac line feeding the fuel regulator?

Can you read vacuum on a gauge? if so is it good when the fuel pressure drops?

I will look at that line as well. Maybe a small crack that isn't bad when its cold. But opens up when the rubber is softer and warmer...?

I have a boost/vac gauge. 11-12psi boost at WOT, as expected. Doesn't mean the line going to the FPRS isn't bad though!

 

[muztangman93]

Sounds like something electrical to me. Once it gets heated up it doesn't function correctly.

 

[petersonb]

Sounds like something electrical to me. Once it gets heated up it doesn't function correctly.

I've replaced the fuel pump, pressure sensor, I've disconnected the boost a pump.... Am I correct thinking that the fpdm is the last remaining electrical thing? Couldn't be the PCM, could it?

 

[Paps]

Bad relay? Got that problem before

 

[muztangman93]

Relay possible. Also do you have the upgraded wiring kit. If not Id do that for sure

 

[petersonb]

Bad relay? Got that problem before

Relay possible. Also do you have the upgraded wiring kit. If not Id do that for sure

I will check relays too; forgot about those!

I have the wiring upgrade with relay next to the FPDM. I'll check that as well.

 

[petersonb]

I'm back to thinking it's the pump.

Today I went on a 300mi trip. 200mi into it (after 3hr of highway driving in 90*F), I went to pass someone, lost all power, coasted to a stop, had about 20psi rail pressure, car was still idling but very rough. I shut it off and couldn't start it again.

Pulled the sensor off the rail, no fuel in it at all. Put it back but car wouldn't start.

Disconnected the battery for 60 sec. Still didn't start.

At the fuel hat, I disconnected the line and there was no fuel in the line. Popped the ring off the hat, turned the key on and off while watching the pump in the tank. It was definitely running, but wasn't moving any fuel. Disconnected the line from the hat, turned on the key, it ran for a bit, then a little bit of fuel shot out, but not much.

I switched out the pump with the old Aeromotive Stealth 340Lph, turned the key on while watching it in the tank, and it immediately picked up fuel and I saw a rise in pressure on the rail.

So that would mean I got a bad fuel pump from americanmuscle.com, and its fine when cold, but after running for a long period of time, I start to see problems.

Is that likely? Heat causing problems with the pump?

 

[muztangman93]

Now it kind of sounds like your bap might be overheating. When it happens again bypass it and see if its okay after that.

 

[petersonb]

Now it kind of sounds like your bap might be overheating. When it happens again bypass it and see if its okay after that.

I tried that on the second 1200mi trip a few weeks ago. The difference was that I was only cruising, not accelerating, and pressure *slowly* dropped until the motor stalled.

The first (and only thing) I did at that point was take the BAP out of the circuit. A few hundred miles later, same problem.

I thought the same thing as you at first, but there must be something else.

I've been reading a lot about the Aero Stealth 340s failing.... So many that S&H no longer sells them. Bobby mentioned to me on the phone the other day that they'd had quite a few failures, then moved to the Walbro 405 and hasn't had any problems.

That helps me believe that I received a bad one.

 

[Paps]

Swap relay next time it happens.

 

[petersonb]

Swap relay next time it happens.

I'll get an extra before I go back.

The guys at S&H Performance (Bobby and Greg) have been a HUGE help the last few days.

Bobby sent me his stock FPDM so I could rule that off the list...

Gregg is overnighting me a new Walbro 465 (450Lph) pump today....

I'm going to rule out the pump next. If all of this was because I got ANOTHER bad pump from Aeromotive, that'll be some shit.

 

[petersonb]

Got my pump today (HUGE thanks to Greg at S&H Performance.... bought my pump and $60 overnight shipping on his credit card to save time, and let me pay him back once it was all ordered... we were on a real tight schedule! But I don't know many other people who would buy something for a complete stranger on their credit card, then have it shipped to that person?!? I digress....)

Installed the pump today, did some WOT pulls. Still runs lean, but it's been that way since I bought the car, so I assume it's the tune anyways (gonna fix that with Lito in the next couple of weeks).

The highest FPDC I saw on the data log was 32 (or 64%) in 3rd gear, WOT, 5700rpm.

...I can live with that!

I'm driving 1.5hr to a lake tomorrow, then 1.5hr back, so that will be the test!

I've done this a couple times, so I'm still kind of hesitant to say "it's fixed" ....

I'll update this tomorrow after my trip.

Bottom Line: I think it was the fuel pump originally, then the Aeromotive pump replacement was ALSO bad.

Time will tell.

-Brad

 

[petersonb]

I dare say the problem is actually fixed this time!

After driving 1.5hr there, I stomped on the gas in 2nd, held it to red line, and no drop in pressure.

After the drive back home, I tried it again with no issues. I tried several times along the way, and never had any issues with fuel pressure.

Tomorrow is a 2hr drive, there and back, 4hr total. I hope to not have any problems then either!

Thanks everyone for the help! Never recommend Aeromotive pumps to anyone though!

 

[Makdaddy]

Hope that got it

Good Luck and what a bitch of a problem