FPR Pressure Bleed Off Fix

[TommyDSM]

Well I read the Tech article on FPR Pressure Bleed Off Fix... My AFPR doesn't hold pressure and goes down to zero, and it takes my car awhile to crank over. So I want to make it so my pump gets power while car is cranking...

But in the article http://www.dsmtuners.com/forums/showthread.php?t=222511 it says
"Why two lines you ask? Because the heater relay and most other things loose power when the car is turned to "Start" meaning the fuel pump would loose power and pressure when the car was trying to start. Wiring to both the old power supply line AND the heater relay means the pump gets power as soon as the key hits the ON position and STILL gets power during the "Start" position. This now primes the fuel system prior to starting the car."

Which doesn't make sense... if the heater relay also loose power while car is cranking, how is connecting it to the relay which triggers on the relay going to make it have power? Kind of like two wrongs make a right? Maybe he means the heater relay KEEP's power while car is cranking.. Yes?

Anyone have any ideas? Also I did the rewire mod and my relay is in the back of the car... So should I just run a line from the heater relay back to the rewire relay and connect it together with the old fuel pump line that switches on the relay?

 

[larsrya8]

Does the relay turn on while the car is cranking? If the relay is on the entire time the car is cranking (and not turning on and off or something due to the "low voltage") then you shouldn't have to worry about the pump losing power while cranking. The pump doesn't need to provide that much pressure to start the car, and something like 10 volts should be more than enough.

The "fix" outlined in the article is designed to allow you to turn the key to On first, which will start the pump to bring the pressure up. Then you can turn the key to Start (when the pump would normally turn on), and the car should start immediately. With my Walbro 255HP and Aeromotive FPR, the car will start after about 1 second of cranking after sitting for 2 weeks. Basically, it starts as quickly as it did with the stock fuel setup. The fuel pressure goes down to zero after a few hours of sitting, but this doesn't stop the car from starting promptly. If I try within the first hour it'll start immediately, which is something it never did with the stock setup.

Voltage probably isn't your problem, since I'm using a Walbro 255HP with the stock wiring. I haven't even rewired yet, and you have so you should have more power at the pump than me. I would check your AFPR to make sure there isn't a piece of dirt or something preventing the regulator from closing completely. Even if you don't have pressure, there should still be fuel in the feed line (at least the part that's under the car). Not having pressure doesn't mean that there isn't any fuel there. Maybe one of the injectors is letting the fuel drain out of the rail...?

 

[eclipsh]

I just came across this thread while looking for something else. Did you get the problem resolved?

The reason for the two power lines is that each one gets power at a separate time.

So when the key is turned to the "on" position it triggers the new fuel pump relay from the heater wire but not from the old fuel pump wire.

When the key is turned to the "start" position the new relay gets power from the old fuel pump wire but not from the heater.

After starting the car the new relay gets power from both, but without fancy electronic gizmos that cannot be avoided.

I'll add these details to the tech article. Sorry for the confusion.

 

[silvercoupe97]

That link no longer works. I couldn't find it with the search option either. Where did it go? I was going to do this next weekend. Does anyone have the info saved somewhere?

 

[eclipsh]

It got taken down due to concerns about safety. There were worries that the fuel pump/engine would not shut down correctly in an accident or rollover. The last thing anyone wants is the fuel pump dumping gasoline all over the scene of an accident.

 

[silvercoupe97]

It got taken down due to concerns about safety. There were worries that the fuel pump/engine would not shut down correctly in an accident or rollover. The last thing anyone wants is the fuel pump dumping gasoline all over the scene of an accident.

I see. So there's a shut off device for the fuel pump if the car were to roll over?

 

[spinz4]

Your motor would stop and I would assume that the fuel pump would as well. Are you losing pressure buddie?

 

[silvercoupe97]

Hey Dustin, yeah, but only after shut down. I thought we talked about this before? I know I talked to someone here about it, .
I've got to check into it some more though. I don't think it has anything to do with priming the fuel line before start up because I turned the pump on before starting the car with Link and it only started a fraction of a second quicker, . I've got a bad seal and I'm guessing it's in the tank or more specifically the pump seal.
Boost leak checks don't push through the injectors, fuel filter is only ~3k old, but the AFPR gauge shows 0 from the time it takes to shut the car down and open the hood to look.

As for the emergency shut down, I'm a dork for even asking that question. My old 6g73 even had an ASD relay that took info from the crank and cam sensors and if they were off in accordance to the rest of the sensors it would shut the motor down, to include the fuel pump. It took a second for that to hit me square in the head.
Our motors most likely gets similar info before it shuts off and instead of an ASD relay it uses an MFI relay. I don't think the MAF is a part of the e-shut off since i've run the car with the MAF disconnected (ooops) and it only ran like crap until I saw the connector not connected, .
Regardless, I can see the safety issue with rewiring the fuel pump relay to energize in the "ON" position. The MFI relay or ECU wouldn't be able to shut the fuel pump relay off if it were wired up that way.

 

[steve]

The ECU watches the CAS or the crank/cam angle sensors to see if the engine is running.
If it sees pulses if turns the fuel pump on. There is a timer included in the code in case it misses a pulse. So three seconds after the pulses stop the ECU turns the fuel pump off.
If you get into an accident where the engine doesn't stop then it doesn't turn off the fuel pump.

A good working fuel pump and regulator should reach and hold the correct fuel pressure in less than a second. If yours doesn't then it's leaking more than normal somewhere. Hotwiring the pump isn't the solution.

If your fuel pressure drops so fast that it reads 0 by the time you get to the hood to read it you have a huge leak. The two most common places are the pump to hardpipe o-ring and the return port in the FPR.

All Walbro installs are suspect due to the poor fit of the Denso check valve on the Walbro stem.

It's surprising how many "high quality" AFPR's seem to have problems sealing the return port. Don't expect then to hold pressure like the stock FPR but they should hold pressure for a couple mins.

Steve

 

[eclipsh]

Thanks for that info Steve

 

[tqmx1]

Talking about fuel pumps not shutting off in case of a roll over, most if not all FI motorcycles have a Bank Angle Sensor installed in them any angle over 60degrees it shuts off the fuel or what ever else is tied to it. Also Fords have a Gswitch in the trunk for the same reason.

 

[taylorspl]

I had a Ford Ranger for my old work truck. I jumped it offroading and it stopped running. Mechanic said there's an inertia switch that kills the power to the pump in case of a bad accident. Not all cars have these, I know the 2g doesn't, not sure about the 1g.

 

[steve]

I know the 2g doesn't, not sure about the 1g.

Not in the 1G either. We have plenty of other parts to stop them from running.

Steve

 

[eclipsh]

You mean all the parts stamped with three diamonds?

 

[spinz4]

Hey Dustin, yeah, but only after shut down. I thought we talked about this before? I know I talked to someone here about it, .
I've got to check into it some more though. I don't think it has anything to do with priming the fuel line before start up because I turned the pump on before starting the car with Link and it only started a fraction of a second quicker, . I've got a bad seal and I'm guessing it's in the tank or more specifically the pump seal.
Boost leak checks don't push through the injectors, fuel filter is only ~3k old, but the AFPR gauge shows 0 from the time it takes to shut the car down and open the hood to look.

As for the emergency shut down, I'm a dork for even asking that question. My old 6g73 even had an ASD relay that took info from the crank and cam sensors and if they were off in accordance to the rest of the sensors it would shut the motor down, to include the fuel pump. It took a second for that to hit me square in the head.
Our motors most likely gets similar info before it shuts off and instead of an ASD relay it uses an MFI relay. I don't think the MAF is a part of the e-shut off since i've run the car with the MAF disconnected (ooops) and it only ran like crap until I saw the connector not connected, .
Regardless, I can see the safety issue with rewiring the fuel pump relay to energize in the "ON" position. The MFI relay or ECU wouldn't be able to shut the fuel pump relay off if it were wired up that way.

Im having the same issue after putting my fpr in. No leaks or anything pretty ###.

 

[silvercoupe97]

The ECU watches the CAS or the crank/cam angle sensors to see if the engine is running.
If it sees pulses if turns the fuel pump on. There is a timer included in the code in case it misses a pulse. So three seconds after the pulses stop the ECU turns the fuel pump off.
If you get into an accident where the engine doesn't stop then it doesn't turn off the fuel pump.

A good working fuel pump and regulator should reach and hold the correct fuel pressure in less than a second. If yours doesn't then it's leaking more than normal somewhere. Hotwiring the pump isn't the solution.

If your fuel pressure drops so fast that it reads 0 by the time you get to the hood to read it you have a huge leak. The two most common places are the pump to hardpipe o-ring and the return port in the FPR.

All Walbro installs are suspect due to the poor fit of the Denso check valve on the Walbro stem.

It's surprising how many "high quality" AFPR's seem to have problems sealing the return port. Don't expect then to hold pressure like the stock FPR but they should hold pressure for a couple mins.

Steve

Thanks for that bit of info Steve. Come to think of it. I didn't start having the start up issue until after installing my FPR. The start up isn't the issue, it's the fact that it takes that much more time and cranking to start up. That leads to a leak in pressure, in my instance. I'll check my AFPR for this reason. I know that Aeromotive has had it's fair share of leaky AFPRs.


Dustin, we'll have to get together and do a fuel leak work day. I'm coming over next Wednesday, .

 

[spinz4]

Cool not a problem man! You will have to check out the new 2g!