Cool, I am not losing it. Project34 knew that there are two relays to control the fuel pump speed on the 2000 GTP. One uses a resistor, which is for the low speed. My wiring CD says that the resistor is mounted somewhere on the frame?? So now, if I have got this correct, the output from C2, pin 3 turns the fuel pump on, and it will be on high speed. Output from C2, pin 39 pulls the relay to the low speed position. So, it sounds like most everybody is using the output from C2, pin 3 only. Which was my original question; does the fuel pump care if it is running at high speed all the time? I guess not, huh?
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11:03 PM
PFF
System Bot
darkhorizon Member
Posts: 12279 From: Flint Michigan Registered: Jan 2006
dont worry about running the 2speed deal, just wire it using the regular fiero relay. all you need to do is run the fuel pump turnon from the pcm to the relay, and dont wire in any of the fuel pump resistor stuff.
does the fuel pump care if it is running at high speed all the time?
Maybe a more reassuring way to think of this is not in terms of either a "high speed" OR a "low speed," but simply the ONLY speed the Walbro fuel pump (you mentioned elsewhere you'll be using) was designed for. In other words, after it's installed in your Fiero, the Walbro fuel pump should run at the speed it was designed to run at, a single speed.
Remember, the idea of the two-speed factory fuel pump design which GM had was simply an "economy measure" of sorts (by slowing the fuel pump's speed after starting the car, wear on the pump is reduced), something that sounds like MUCH less fun than the added power likely to result from your supercharged GTP engine swap.
Good luck with your project!
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11:05 AM
AJxtcman Member
Posts: 1098 From: Rock Hill SC Registered: Nov 2006
Fuel Pump Relay VIN 1 When the ignition switch is first turned on, and before engaging the starter, the PCM energizes the fuel pump relay which applies power to the fuel pump control module (VIN 1). The PCM sends a signal based on the engine fuel demand to the fuel pump control module in order to change the control module's voltage output. The fuel pump will then pressurize the fuel system. The fuel pump relay remains on as long as the engine is running or cranking and the PCM is receiving reference pulses. If reference pulses are not present, the PCM de-energizes the fuel pump relay within 2 seconds of the ignition turning on. During high engine load situations the PCM commands the fuel pump to run at high speed. Refer to Fuel Pump Electrical Circuit Diagnosis for further description and diagnosis of the fuel pump electrical circuit.
Fuel Pump Control Module (VIN 1 only)
The L67 supercharged engine utilizes a 2-speed fuel pump control module. The fuel pump control module is located on the wheel house flange in the trunk. The fuel pump control module controls the fuel pump output depending on the MAP sensor input received by the PCM.
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04:04 PM
AJxtcman Member
Posts: 1098 From: Rock Hill SC Registered: Nov 2006
Run the two speed fuel pump or you will hurt performance.
Because it is a performance-oriented, or "high capacity" fuel pump, I can understand why the Walbro fuel pump might be criticized by some as being too noisy for their tastes, or even unnecessary with some engine applications. However, I think this is the first time I've ever heard the Walbro fuel pump being criticized for being able to HURT performance.
It sounds counterintuitive to me, but if true, that criticism presumably should be of great interest to many on this forum.
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06:25 PM
May 29th, 2007
AJxtcman Member
Posts: 1098 From: Rock Hill SC Registered: Nov 2006
The stock pump is a Walbro correct? The majority of the GM pumps are Walbro's! The last pump I replace was not and it was in a CTS. I have a LS1 Camaro pump Walbro............Leaks down I have an 04 Escalade ESV pump Walbro....Plastic line rubbed through in tank I have an 00 S10 pump Walbro.................Misdiagnosed I have an 05 Escalade ESV pump Walbro....Placstic line rubbed through in tank I have another 02 Camaro SS pump Walbro.....Tank unit Damaged in accident. . The First LS1 and the 04 ESV use the big pump that they say to install in turbo cars (syclones, GN) I have not checked the 02 Camaro and the 05 ESV to see if the # are the same. . . . If the car is running the stock PCM and calibration the fuel trim will be way off. Even if the fuel pressure Reg can handle the extra volume. The rise and fall of pressure in the rail as the injectors fire will change. If you run a small non SC pump in full boost the fuel pressure will drop off. If you run a larger volume pump and slow it down under non boost then set a calibration and set the injector pulse for this, but then under boost crank up the volume you can control fuel trim and injector pulse better in WOT.
Yeah, you guys (AJxtcman and Project34) are helping me with my question. The original Fiero fuel pump would never feed the SC 3800, so I plan on using a Walbro 255, High Pressure pump (I can't recall the PN, F something ...169, I think). Anyhow, did I understand AJxtcman to say 1) This would be the correct pump? 2) I should use the two speed control? Also, one of you included a drawing of a speed control that apparently mounts in the trunk. The manuals for the 2000 GTP that this engine came from show an 'Underhood Accessory Wiring Junction Block' that appears to be mounted to the right strut tower. It has one relay that provides power to the pump, driven by a signal from C2, pin 3, and another relay that controls the speed, based on a ground signal from C1, pin 39. If I should use this control, then I need to come up with this 'juction block/relay' deal. I do appreciate you guys help, please overlook my ignorance of this aspect of the project. Thanks, John
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10:31 PM
May 31st, 2007
darkhorizon Member
Posts: 12279 From: Flint Michigan Registered: Jan 2006
Please disregard the 2speed pump control unless your looking to get super extended life out of your pump. All the second speed does for you is it runs the main power of the fuel pump through a resistor, that slows the pump down, while cruising.
If you were to be making consistant 100+mile trips where the fuel pump would be running full out all the time, I would consider it, but even then I think I would just plan on testing walbro's 2 year failure warrentee.
I plan on using a Walbro 255, High Pressure pump....This would be the correct pump?
The Walbro 255 is a "high capacity" fuel pump that should be quite adequate for your 3800 SC engine swap.
This pump, and more specifically, even its use with the 3800 SC engine swap, are discussed at some length in the thread, "Higher Capacity Fuel Pumps": https://www.fiero.nl/forum/Forum2/HTML/081196.html
Reading that thread should reassure you about the Walbro 255 fuel pump. You'll see that it had been criticized by some in that thread as being too noisy for their tastes or even unnecessary for a 3800 SC engine swap, but NOBODY criticized it as being the wrong pump to use with a 3800 SC engine swap.
In contrast to those on the Walbro 255, the opinions regarding the use of other fuel pumps with a 3800 SC engine swap were not so unanimous.
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05:22 AM
PFF
System Bot
AJxtcman Member
Posts: 1098 From: Rock Hill SC Registered: Nov 2006
97 Buick Regal. . . . Circuit Description When the Ignition switch is first turned ON, the PCM energizes the fuel pump relay which applies power to the fuel pump through the high speed circuit (controlled by the fuel pump speed control relay). The fuel pump relay will remain ON as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present, the PCM de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped. The fuel pump delivers fuel to the fuel rail and injectors, then to the fuel pressure regulator. The fuel pressure regulator controls fuel pressure by allowing excess fuel to be returned to the fuel tank. With the engine stopped, the fuel pump can be turn ON by using the scan tool output controls function.
The PCM alters fuel pump speed by energizing the fuel pump speed control relay Under normal conditions, the fuel pump control speed control relay is energized (normal fuel pump speed). The applied voltage to the fuel pump is controlled by a resistor assembly. When higher fuel volume is required due to increased engine load (MAP sensor value over 90 kPa). the PCM de-energizes the fuel pump speed control relay circuit. The increased voltage to the in-tank fuel pump allows a higher volume of fuel to be delivered to the fuel rail. The PCM also compensates for low system voltage by energizing the fuel pump speed control relay.
Fuel Pump (VIN K)
A high pressure gerotor fuel pump is mounted to the fuel sender inside the fuel tank. The fuel is pumped to the engine at a specified flow and pressure through the fuel pump. Excess fuel is returned to the fuel tank by a return pipe. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers.
The electric fuel pump operation is controlled by the Powertrain Control Module (PCM) through a fuel pump relay. Refer to Fuel Pump Electrical Circuit Diagnosis .
Fuel Pump (VIN 1)
A high pressure rollervane fuel pump is mounted to the fuel sender inside the fuel tank. The fuel is pumped to the engine at a specified flow and pressure through the fuel pump. Excess fuel is returned to the fuel tank by a return pipe. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers.
The electric fuel pump operation is controlled by the Powertrain Control Module (PCM) through a fuel pump relay. Refer to Fuel Pump Electrical Circuit Diagnosis .
. (1) Fuel Pump Fuse (2) Fuel Pump Relay (3) Under Hood Electrical Center (4) Powertrain Control Module (PCM) (5) Fuel Pump Relay Control (6) Fuel Pump Speed Control Relay Control (7) Fuel Tank (8) Fuel Pump (9) Fuel Pump Resistor (10) Fuel Pump Speed Control Relay
The L67 engine utilizes a two speed fuel pump speed control relay. When the ignition switch is first turned ON, the PCM energizes the fuel pump relay which applies power to the fuel pump through the fuel pump speed control relay. The fuel pump relay will remain ON as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present, the PCM de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped. The fuel pump delivers fuel to the fuel rail and injectors, then to the fuel pressure regulator. The fuel pressure regulator controls fuel pressure by allowing excess fuel to be returned to the fuel tank. With the engine stopped, the fuel pump can be turned ON by using the scan tool output controls function.
The PCM alters fuel pump speed by energizing the fuel pump speed control relay. Under most conditions, the fuel pump speed control relay is energized. The applied voltage to the fuel pump is controlled by a resistor assembly. When higher fuel volume is required due to increased engine load (MAP sensor value over 90 kPa), the PCM de-energizes the fuel pump speed control relay circuit. The increased voltage to the in tank fuel pump allows a higher volume of fuel to be delivered to the fuel rail. The PCM also compensates for low system voltage by de-energizing the fuel pump speed control relay circuit.
. . Resistor. (it looks like a Caddy DRL resistor) .
[This message has been edited by AJxtcman (edited 05-31-2007).]
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07:18 AM
AJxtcman Member
Posts: 1098 From: Rock Hill SC Registered: Nov 2006
I just grabbed the old LS1 pump. IT IS NOT A Walbro. It is an AC and is a Vane type. I had thought I had this in my hand as I was talking to one of the body shop guy's. He needed a pump in his Syclone and every thing he read said to install a Walbro. I grabbed a pump labled 5.7 LS1 and showed him it was a Walbro from the factory.
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07:34 AM
darkhorizon Member
Posts: 12279 From: Flint Michigan Registered: Jan 2006
The only pump proven to handle even lightly modded 3800SC's using fiero wiring, is the walbro.
The old vette pump has been proven time and time again, to be a very boarder line pump, with a very decent chance of it being in addiquate in common non perfect conditions.
Why are you guys so interested in this 2speed deal? It didnt make my fuel pump on my GTP last any longer, it died at 144k miles. There is no performance issues here, IMO its a heck of a lot of wiring, for a performance decreasing setup, as sudden WOT bursts could cause fuel pump pressure drop spikes from the fact the fuel pump is in "run like crap mode" all the time untill you see near boost pressures. I disabled the low speed system on my GTP after I put the new pump in.
I disabled the low speed system on my GTP after I put the new pump in.
I agree with the path darkhorizon took.
In my opinion, whatever wear-and-tear "advantage" that might occur from employing two speeds in a fuel pump for a 3800 SC engine swap in a Fiero probably is more than offset by the downside risk of running an engine that could become too lean --- even if only momentarily.
To me, employing two fuel pump speeds is "false economy," because however small the risk of a lean condition occurring, it would take a LOT more money to replace a 3800 SC engine that ran too lean, than it would to simply replace a worn-out fuel pump.
As I mentioned earlier, the Walbro 255 fuel pump is a "high capacity" fuel pump that should be quite adequate for bc12dJohn's 3800 SC engine swap, and the thread I referenced in my previous post to the present one backs that up.
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10:24 AM
Jun 1st, 2007
AJxtcman Member
Posts: 1098 From: Rock Hill SC Registered: Nov 2006
I must be a rocket scientist. I built a rocket. This must be over your heads. . If the factory pump is a Walbro 255 and the fuel pressure line is 3/8ths and the pump is ran at one speed. What is the disadvantages? . The pump module on the 2000 bon looks expensive! If GM could save a dollar they would. Why do they use it?
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06:41 AM
LFiero67 Member
Posts: 882 From: Lethbridge, Alberta, Canada Registered: Jun 2002
They use it because running at low speed reduces pump noise. It is not to make them last longer, in fact if you run too little power to the pump it will actually burn out faster. Ford had a problem with that in their pickups.(tank switch dropping voltage) The two speed operation is a customer pleasing thing. The stock pump is "too noisy" for the every day person. Reducing the speed reduces the noise of the pump until the throttle is opened.
I think you would have a hard time finding anybody on ClubGP that runs the 2 speed resistor if their car is modded, or after the resistor burns out and leaves them stranded on the side of the road which happens fairly regularly it seems.
------------------ 11.806 @115.07 Best 60' 1.569 seconds 3800 S/C 4T65E
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12:46 PM
Jun 11th, 2007
bc12dJohn Member
Posts: 84 From: Jackson, Michigan Registered: May 2007
OK guys, this is what I needed to know. I don't need the two speed relay and resistor stuff for my Walbro fuel pump. In fact, it sounds like it is another potential problem. And, man I don't need to create any more of them for myself!! Thanks, John
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01:29 PM
PFF
System Bot
Will Member
Posts: 14278 From: Where you least expect me Registered: Jun 2000
Please disregard the 2speed pump control unless your looking to get super extended life out of your pump. All the second speed does for you is it runs the main power of the fuel pump through a resistor, that slows the pump down, while cruising.
If you were to be making consistant 100+mile trips where the fuel pump would be running full out all the time, I would consider it, but even then I think I would just plan on testing walbro's 2 year failure warrentee.
Typical lifespan of a factory pump is over 100,000 miles. I hope a Walbro lasts more than 2 years...
