Computer Elimination

[WTFestiva]

Wow. A lot of this is becoming WAY over my head here, but I'll try to answer a few questions I saw.

- I tested the fuel pump, it works fine when jumped it with a tester.
- Battery is not dead, I charged it as well as hooked another newer battery to it.
- As for the emmisions controls... yeah our car isnt leagal anyways on that...

The car is a bit out of my reach now so I can only tell you what I already know from here on. Worst case scenario we're just gonna replace the computer and such, if our guy can't figure out or decide what he's going to do. I'll keep you guys posted on what is going on though and see if I can get my buddy to join here and read all this, right now i've been a sort of middle man...

[Bert]

How long does the pump run when you turn the key on? Can you make a Youtube video of it?

The initial electric pump motor sound is only momentary (1/10 sec?) as you turn the key and I figured it was due to air in the lines, but a year later the sound is still there. One day I'll get a better pump that also doesn't sound like a hive of bees under the back seat.

[MasterTec]

The computer does not ground the FP relay. The VAF switch does that. The FP relay is also energized (a separate pulldown) by the starter circuit.

I stand corrected. I don't have a whole lot of experience with VAF systems and my Festy is carbed. Most newer cars are grounded by the engine computer.

Regardless the problem has nothing to do with the computer so I don't quite see how bypassing it (if it were possible) would fix anything...

[georgeb]

He needs to jump the fuel pump tester then test for voltage.

[DON SVO]

Dumb question but, I noticed the jumper box on the battery... could the fuel pump be getting mediocre voltage because the battery is dead? The battery supplies power when cranking or just KOEO. If the battery has lost a few cells, the jumper box might not be able to power the system up.

Yes it would suck if a dead battery was the root cause but I've seen stranger.

[Damkid]

^^not my fuel pump mine has a custom circuit with an 8 gauge wire powering the pump

[georgeb]

Yeah I'm a bit confused as well. The computer controls the fuel side of things so without it the engine won't run.

Also you mentioned only 3v is getting to the fuel pump. This has nothing at all to do with the computer. The computer is responsible for grounding the relay to send power to the pump but it does not power the pump directly. Being that you have voltage at all then you have a wiring problem, bad VAF or a bad fuel pump relay. If the computer was at fault here then you'd have no power at all to the pump.

It is possible to eliminate the fuel pump circuit from the computer. It could be wired so that the pump gets power all the time by grounding the circuit that the computer normally grounds but this wouldn't be bypassing the computer entirely.. instead only the fuel pump circuit would be bypassed (the computer still needs to function to pulse the ground circuit of the injectors).

I should also add that even if it were possible to eliminate the computer entirely doing so is against Federal Law. I know there are no Emissions Inspections in Salem, MO but that doesn't make bypassing emissions control devices legal - and yes the engine computer is considered an emissions control device. Whether you're likely to get caught or not.. well that's another story altogether.

The computer does not ground the FP relay. The VAF switch does that. The FP relay is also energized (a separate pulldown) by the starter circuit.

[MasterTec]

Yeah I'm a bit confused as well. The computer controls the fuel side of things so without it the engine won't run.

Also you mentioned only 3v is getting to the fuel pump. This has nothing at all to do with the computer. The computer is responsible for grounding the relay to send power to the pump but it does not power the pump directly. Being that you have voltage at all then you have a wiring problem, bad VAF or a bad fuel pump relay. If the computer was at fault here then you'd have no power at all to the pump.

It is possible to eliminate the fuel pump circuit from the computer. It could be wired so that the pump gets power all the time by grounding the circuit that the computer normally grounds but this wouldn't be bypassing the computer entirely.. instead only the fuel pump circuit would be bypassed (the computer still needs to function to pulse the ground circuit of the injectors).

I should also add that even if it were possible to eliminate the computer entirely doing so is against Federal Law. I know there are no Emissions Inspections in Salem, MO but that doesn't make bypassing emissions control devices legal - and yes the engine computer is considered an emissions control device. Whether you're likely to get caught or not.. well that's another story altogether.

[Damkid]

^^I'm with stupid JK brad

[bhazard]

Lol you guys are funny.

[gauge_half_inch]

All that ground wire does is disable the timing advance. For even our very basic efi system removing the computer is impossible, the ecu(computer) grounds the injectors causing them to pulse. Without the ecu the injectors will be dead. Maybe on a late 80s computer controled carb its possible, maybe even a tbi(throttle body injected) system it could be possible but not likely.

[WmWatt]

All cars are supposed to run without the computer. I think it's a safety feature. But you wont' get the same fuel economy or low emissions. When checking the timing on my car I have to ground one of the wires which I think disables the computer. If so all you need to disable the computer is to ground that one wire. I could be wrong about that part.

[georgeb]

The starter motor is grounded through the trans/eng which is grounded by the neg batt cable. Also you can't just "eliminate" the ECU. It controls ign and injector timing. You're going to take it back to the guy who fried your coil?

[gauge_half_inch]

Did you just remove the Vaf for the pics? The Vaf signal controls the fuel pump kick on, and the generally basic job of a standard Throttle position sensor. The vehicle will NOT run at all with out it connected properly. Seems kinda obvious, but it seems at this point that's where your problem is. right there in front of you. After fighting and fighting, its always a simple fix. Best of luck.

[Prafeston]

3.) basic tune job to get it running for October 6 in Watkins Mill MO

Fixed that for you