Has anyone ever hot wired the fuel pump on a 98? What're the bad things about doing it?
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
98 Mustang Fuel Pump Hot Wiring
- Thread starter BottleFed98
- Start date
Anyone?
Do you think that will help with the nitrous/fuel rail issue?The 98 has the variable voltage fuel pump "basket in a tub" pump set up.A safer method would be to swap in an 03-04 Cobra tank pump set up.I believe it also has dual pumps and baffles,some have hacked up the basket in the 98's as a way to meet increased demand for fuel.
As far as the pros and con of the hot wiring the pump Mark Olson is the man PM him.He is a Guru when it comes to the electronics of our cars,he knows more about that stuff than the"engineers" that built them.
Here is a write up on what one guy did on his 98 fuel system.
http://www.modularfords.com/threads/130219-Let-s-talk-return-style-fuel-systems?p=1345896&viewfull=1
Goggle 1998 mustang cobra fuel system,there is quite a bit written on why its called a bastard year with regards to the fuel system.
As far as the pros and con of the hot wiring the pump Mark Olson is the man PM him.He is a Guru when it comes to the electronics of our cars,he knows more about that stuff than the"engineers" that built them.
Here is a write up on what one guy did on his 98 fuel system.
http://www.modularfords.com/threads/130219-Let-s-talk-return-style-fuel-systems?p=1345896&viewfull=1
Goggle 1998 mustang cobra fuel system,there is quite a bit written on why its called a bastard year with regards to the fuel system.
It is not clear to me exactly what you mean by "hot wiring" the fuel pump.
I hot wire them to test them all the time. What I mean by that is I wire them straight to battery voltage to ensure that they are working.
Our fuel pumps are driven by a two stage power system controlled by the PCM. At low RPMs, the power to the fuel pump is run through a current limiting resistor that reduces the power that flows to the pump. With lower power, the pump flows less fuel, which is ok because the engine is at low RPM. Once you hit the RPM threshold set in the tune, the PCM activates a relay that shorts across the current limiting resistor, which lets full power go to the fuel pump, which causes it to flow at its maximum rate.
The PCM monitors the voltage after the relay to ensure that the two stage power system is working correctly. If it sees the wrong voltage, it should set a DTC. It is not 100% clear to me what happens if it sees a low voltage at high RPM, when it expects full fuel pump flow. I was once having problems with my engine simply shutting off when it hit the fuel pump threshold. I suspected that the PCM was protecting the engine from going lean. I wound up replacing the CCRM and the problem went away.
One key bit of information is what happens when you put a BAP into the circuit. The BAP will increase the voltage to 12 to 17V depending on where you set the knob. That also increases the current flow to the pump which increases the fuel flow. The interesting thing is that the BAP increases the voltage to its preset level regardless of which stage the fuel pump power is in.
Personally, I don't particularly like the two stage system. I have seen AFR glitches when the high stage kicks in on some cars, and I don't like that. But there are a couple of benefits to running it. They both come from the fact that the low flow stage prevents a large amount of fuel from flowing through the FPR and back to the tank through the return line. When the fuel does that, it tends to heat up a lot, which tends to add load to the evap system, increasing emissions. And I don't think hot fuel helps much when it comes to trying to prevent detonation. But I am ambivalent as to how much benefit those things are. I would not hesitate to run my fuel pump at full battery voltage, and have run it all the time at 17V when my BAP was in the car.
You can turn the two stage fuel system off in the tune, BTW.
I would not know how to wire a Terminator pump (a returnless system) into an older return style fuel system. I know the Terminator pump was designed to be driven by an FPDM controlled by the PCM. I would be curious to know how that is done if people do it.
Probably more than you wanted to know...
I hot wire them to test them all the time. What I mean by that is I wire them straight to battery voltage to ensure that they are working.
Our fuel pumps are driven by a two stage power system controlled by the PCM. At low RPMs, the power to the fuel pump is run through a current limiting resistor that reduces the power that flows to the pump. With lower power, the pump flows less fuel, which is ok because the engine is at low RPM. Once you hit the RPM threshold set in the tune, the PCM activates a relay that shorts across the current limiting resistor, which lets full power go to the fuel pump, which causes it to flow at its maximum rate.
The PCM monitors the voltage after the relay to ensure that the two stage power system is working correctly. If it sees the wrong voltage, it should set a DTC. It is not 100% clear to me what happens if it sees a low voltage at high RPM, when it expects full fuel pump flow. I was once having problems with my engine simply shutting off when it hit the fuel pump threshold. I suspected that the PCM was protecting the engine from going lean. I wound up replacing the CCRM and the problem went away.
One key bit of information is what happens when you put a BAP into the circuit. The BAP will increase the voltage to 12 to 17V depending on where you set the knob. That also increases the current flow to the pump which increases the fuel flow. The interesting thing is that the BAP increases the voltage to its preset level regardless of which stage the fuel pump power is in.
Personally, I don't particularly like the two stage system. I have seen AFR glitches when the high stage kicks in on some cars, and I don't like that. But there are a couple of benefits to running it. They both come from the fact that the low flow stage prevents a large amount of fuel from flowing through the FPR and back to the tank through the return line. When the fuel does that, it tends to heat up a lot, which tends to add load to the evap system, increasing emissions. And I don't think hot fuel helps much when it comes to trying to prevent detonation. But I am ambivalent as to how much benefit those things are. I would not hesitate to run my fuel pump at full battery voltage, and have run it all the time at 17V when my BAP was in the car.
You can turn the two stage fuel system off in the tune, BTW.
I would not know how to wire a Terminator pump (a returnless system) into an older return style fuel system. I know the Terminator pump was designed to be driven by an FPDM controlled by the PCM. I would be curious to know how that is done if people do it.
Probably more than you wanted to know...
Last edited:
Users who are viewing this thread
Total: 2 (members: 0, guests: 2)
