no COR or fuel pump resistor on conversion, issue?

[jimGTS]

having a nose around the other day on my converted car, i noticed these items missing from the engine bay.
i believe the COR controls the 9-12v feed to the pump (as well as cuts fuel when car stalls), but some folks wire to run the pump constantly at 12v, (aparently a good mod?) i assume this is what has happened here.
but the resistor missing also unless its sitting somewhere else?
im not 100% sure what the resistor does?

car runs fine and has done for years, just expected theyd be there.


question is, is this an issue?

[MRturboTom]

I thought it was the resistor that did that. Don't know what cor means?

But it's fine like that

[jimGTS]

Sorry, circuit opening relay.

[shinny]

Circuit opening relay is in the fuse box, no?

I think you're taking about the fuel pump relay and resistor, which is no great loss to be without

Sent from my Flux Capacitor using Mr Fusion Home Energy Reactor

[stuMR2lee]

I think it's the fuel pump relay that's missing.

Edit: Shinny beat me to it!

[stuMR2lee]

From mr2.com:

As for the fuel pump resistor and relay on the turbo's, use the resistor is to reduce current to the pump to slow it down when fuel demand is low. This helps retain (or increase) the life of the pump. The relay that the turbo's use does not however turn on the pump, it only acts as a switch to determine which way the pump receives power, If the relay either sends the power directly to the pump or to the pump through the resistor pack. If that relay goes bad, the pump will still work, just it will be stuck in one speed operation since that relay is just a selector switch and not the main power feed. The main power feed is the COR (Circuit Open Relay) just like the N/A's.

[jimGTS]

Yes sorry your correct, the COR is indeed in the fuse box!
Things are slowly coming back to me, thanks for that.
Arh ok if just fuel pump relay that's missing, no biggy I guess.
I can't even find the redundant plugs for them both!

Cleaner bay for it I guess!
I will be removing canister and doing the coolant bypass on the tb soon as well to clear the unnecessary bits.

[MR2DI4]

Ok what the Relay does on a Rev 2 turbo at least is to SHORT OUT or bypass the resistor pack on cold start and also it comes in again over a few thousand rpm and this is controlled by the ECU.

If you have a fuel pressure guage you can see it in operation. During cold start the relay also operates to short out the resistor and increase your fuel pressure for about 10 seconds.

You really need both the resistor and the relay to be working or you are also upsetting your fuel pressure by about 4 psi.

I had quite a bit to do with this section when I boosted the Voltage to my fuel pump to about 17.5V using a DC-DC converter and as the Voltage was adjustable it turned into a electronic FPR that allows me to run 32psi at idle with the vac line to the FPR connected. The stock range is 27psi to 31psi but you have no control over it so you get what you get and it drops off the older the fuel pump becomes.

There is no "Mod" here that is going to increase your power but what you do want is fuel pressure at the top end of the spec if your trying to run 17psi.

The reason I went electronic is that it was easier than fitting an adjustable FPR or changing my fuel pump which had dropped in pressure to 26psi .....perfect for blowing up your engine when running more than stock boost.

[jimGTS]

All it is doing is running full pressure 100% of the time.
Maybe likely to reduce life of the pump slightly.

Reading up on why people would do this on an mr2 at least seems to be down to smoothing out the power curve and response when that transition happens. That switch over can upset afrs, so running full pressure all the time means you avoid it.
Doesn't net you power, just makes things a little smoother where that switch over point was.

I am currently running a wideband and can safely say there is plenty of fuel.

[sinjen]

Ok what the Relay does on a Rev 2 turbo at least is to SHORT OUT or bypass the resistor pack on cold start and also it comes in again over a few thousand rpm and this is controlled by the ECU.

If you have a fuel pressure guage you can see it in operation. During cold start the relay also operates to short out the resistor and increase your fuel pressure for about 10 seconds.

You really need both the resistor and the relay to be working or you are also upsetting your fuel pressure by about 4 psi.

I had quite a bit to do with this section when I boosted the Voltage to my fuel pump to about 17.5V using a DC-DC converter and as the Voltage was adjustable it turned into a electronic FPR that allows me to run 32psi at idle with the vac line to the FPR connected. The stock range is 27psi to 31psi but you have no control over it so you get what you get and it drops off the older the fuel pump becomes.

There is no "Mod" here that is going to increase your power but what you do want is fuel pressure at the top end of the spec if your trying to run 17psi.

The reason I went electronic is that it was easier than fitting an adjustable FPR or changing my fuel pump which had dropped in pressure to 26psi .....perfect for blowing up your engine when running more than stock boost.

That's interesting, I know that on the Gen 4 if you don't earth the fuel pump resistor it'll start, run for about 10 seconds then stop.

[MRturboTom]

I need to look into this. Mine is stuck on low possibly. Put a walbro pump in and its still lean when cold and on boost. Everything on the car has been replaced only thing left!
Wonder how I can bridge it to full volts without cutting out the resistor

[jimGTS]

I have a fuel pressure gauge Tom if you wona borrow it?
Just a mechanical one that you'd need to cut into the fuel line off the fuel filter.
You'd have to find a joiner to mate the now 2 pipes back together thou.

[MR2DI4]

I have no problems when the relay switches over.

Increasing the fuel pressure highlighted a 10 year old problem in the car had however as the car hesitated and sometimes stalled when I activated the alarm and the turbo timer would try and come on for a minute.

What was happening is that on switchover the power was cut to the ECU for 20ms or the time it took for the relay contacts to switch over and this was long enough for the ECU to go through the cold start again. The sudden increase in fuel pressure (38psi) killed the hot engine at idle. I added a couple of electrolytic caps at the input of the ECU power and this holds up the supply long enough to remove the problem.

The MR2 is very old technology now, I'm sure they would have just moved the PWM Voltage control to the pump to control the speed and use a fuel pressure sensor for feedback to the controller to get the perfect fuel pressure over the life of the car.

[MRturboTom]

Thanks Jim I'll keep that in mind.
I will be getting an adjustable fpr which I have a gauge for.

There's certainly no way I'd up the voltage on an old weak pump. Its certainly going to kill it. They're not designed to run over 14v. Disaster waiting to happen.

I know on the gt4 its a lot easier to bridge the connector to bypass the resistor.
They run full fuel pump voltage all the time.

Apparently its only idle the voltage drops it runs full volts the rest of the time.

Its just like most electrical drains are reduced at idle to help with alternator strain which also helps idle