TII: Judgement Day

Just out of curiosity, I wanted someone to explain what the fuel pump resistor relay is responsible for and how it works.

As well as I would like to know where the resistor pack is located on a S4 Turbo II. i.e. the item responsible for the resistance in the injector electrical lines.

James

MountainTurbo

It is there to save wear on your fuel pump under cruising/light throttle conditions. Essentially it cuts down the voltage your fuel pump sees when there's not as much demand on it, the theory being that this will help prolong the life of your pump, and may also help with gas mileage.

On the S4 TII cars it's located on the passenger side under where the stock airbox resides, just behind the headlight.

TII: Judgement Day

Thanks! Just what I needed to know.

And... can someone post a picture of what the resistor pack looks like?

HAILERS

On a early 87 turboii there are two items. One item is the Solenoid Resistor. It is a package of resistors inline with the input voltage of the fuel injectors and is only used on cars with low impedence injectors. It's located below the air fliter assy and attached to the fender with two bolts. It's a aluminum covered outfit with one large electrical plug with five wires.

Then there is the Fuel Pump Resistor and Relay located in front of the airbox and on about the same level. At very low boost and less than boost conditions it limits the voltage to the fuel pump to approx 9-10 vdc to save wear on the pump. When in boost, the ground signal from the ECU to the Fuel Pump Resistor and Relay drops out and the contacts in the relay supply a full battery voltage/alternator voltage to the pump.

I only butted in because there seemed to be some confusion in your mind about which is which?

The Solenoid Resistor is NOT shown in the online fsm because that fsm is for cars made after mid 1987.

HAILERS

I have a picture of the Solenoid Resistor that is used on early 87models here: http://www.teamfc3s.org/forum/showth...threadid=33353

Here's that part installed: https://www.rx7club.com/forum/showth...resistor+relay

The Fuel Pump Resistor and Relay looks like a picture attached to the following thread, that came out of the fsm: https://www.rx7club.com/forum/showth...resistor+relay

TII: Judgement Day

Awesome! This is truly helping me out a lot.

So here's a story you should hear:

I get my 88 Turbo II a year ago...

I find out later that it has a N332 ECU & low impedance injectors. So that seemed wrong to me considering that my year should have a N333 ECu and high impendance injectors. Now thanks to you guys, I see that a resistor pack was installed in my car to make the original stuff that was in it work. Well I currently now have high impedance injectors & a N333 ECU like I should of had.

I need to remove this resistor pack now to make everything work. What is the proper way to remove it and put everything back the way it's supposed to be?

HAILERS

So what you have is the 88 car but have a Early 87 Emissions harness in the car. That's the harness with the Solenoid Resistor package.

And now you have the high resistance resistors. You can't just remove the Solenoid Resistor because the 12vdc for the injectors passes throught it.

So what you can do, is what I suggested in one of the jpgs I attached to one of those posts I attached above.

You need to either pull the Solenoid Resistor off and put it on the shelf, then somehow jumper ALL FIVE of the pins in the harness plug (the plug the solenoid resistor attached to).

OR you can take that Solenoid Resistor and cut it's harness about half way b/t the plug and the resistor. Then put the resistor half on the shelf in the garage. Now take the plug with the five wires and solder or crimp ALL FIVE TOGETHER. Now reattach the plug to the harness and start the engine.

I have done this myself. Cut the Solenoid Resistor harness in half......stripped and spliced all five wires together and reattached the plug to the harness. Works just fine. I have a great pair of wire crimpers and that's what I used. If you decide to solder all five together make sure you protect the bare wires with shrink tubing and convoluted tubing or???? whatever.

Cut this harness halfway b/t its plug and resistors: http://www.teamfc3s.org/forum/showth...threadid=33353

TII: Judgement Day

It took me awhile to understand all of this, but I got it down now.

Thanks a million. So if I do exactly as you say correctly, this is a guaranteed fix for the resistance issue?

TII '87

maybe a bit off topic but...

do I need these to resistor box if I use an aftermarket EMS????

TII: Judgement Day

I did what you said HAILERS. Thanks a lot, I owe you one.

HAILERS

*********It took me awhile to understand all of this, but I got it down now.

Thanks a million. So if I do exactly as you say correctly, this is a guaranteed fix for the resistance issue?************

I only understand ten percent of what I write.

By the way, either ECU should work just fine no matter what the configuration of the injecotors is. Whether they are all high or all low, the ECU itself is not a factor (almost a true statement).

The driving factor is that the ECU (either ECU) needs to see around 10ohms resistance on the feed wire before the ECU. That's done either using low resistance injectors of about 2.1 ohms and the resistor in the solenoid resistor OR no solenoid resistor but an injector with a resistance of 10-12 ohms.

If either ECU does not have that impedence on the injector feed line, then sooner or later the injector driver in the ECU will go kaput and strand you out in the middle of nowhere.

IF for some reason you decide to go back to the low impedence injectors, you can splice all five of the wires you just cut, back to their original wires and plug the solenoid resistor back into the harness.

TII: Judgement Day

Yeah, I completely see the advantage in keeping the resistors around. Good idea. I may need a major upgrade in injectors soon so I will eventually get 720cc or higher for my secondaries at least which I am sure I will probably only find them in a low impedance version.

BlaCkPlaGUE

Honestly HAILERS, and I mean no offence when I say this but

what the **** is that supposed to mean??@? lol

HAILERS

It means that it's all about the big *I*, the most important part. I don't understand the other part.

Syonyk

Back on topic, the other (primary?) reason for the resistor pack on the fuel pump is not flowing insane amounts of fuel at idle/low throttle situations. The TII fuel pump flows more than the NA pump, and if it's running at it's full output the fuel pressure regulator & return lines aren't quite large enough to return all the fuel, and the fuel line pressure rises, screwing up idle & low throttle. I guess it was cheaper/more effective to put in a resistor pack than to enlarge the fuel pressure regulator & return lines.

-=Russ=-

HAILERS

IF your at idle, and have a turboii with the Fuel Pump Resistor Relay, and are watching a wideband afr gauge, you'll see about .1 to .2 drop in afr if you disconnect the ground wire from 3D on the ECU.

Or put another way, if 3D is disconnected on a series four at IDLE, then if the afr at idle was 13.0, it will now be 12.8/9. Been there....done that on a 1987 series four turboII.

Just in case: JUDGEMENTSDAY's problem was not with the Fuel Pump Relay and Resistor, it was with the Solenoid Resistor which is a completley different thing and is only found on 86 to mid 1987 cars. Just in case someone out there is confused.

HAILERS

A jpg of the two:

TII '87

since nobody listens to me, I' m gonna ask my question again

Do I need those with a standalone ( microtech LT8 if it matters )??

cuz I removed them and I dont wanna bullshit my gas system