well im not the greatest with wiring diagrams or with electricity in general so i dont really understand much from the diagrams. i will go pull this wire tomorrow and see how it goes i will keep you guys posted. thanks for your advice HAILERS

 

Your figures are for a carb'd engine! EFI is very different. Fuel pressure should be ~37psi +/- manifold pressure. That means ~30psi at idle increasing to 45psi at 8psi boost. Less than that and you'll run lean.

Because then the engine will run richer than it's supposed to, except under high load when it'll run normally. Fuel consumption will increase noticeably, and power will drop slightly. You only need high fuel flow when the engine's under full load.
How can you hear the pump when it only runs when the engine's running?
How can you hear the relay while tapping the gas? It's in the engine bay. You must have really good ears...

 

haha, i thought you might ask such questions.

well, i don't see why we can't just run 13v all the time. after all, high fuel flow won't cause excesive gas usage, whereas, high pressure will. and now you're probably thinkin, if the pump is flowing more, then i'll have a higher pressure. in that case, the stock FPR isn't big enough, which i plan on replacing when i do the parallel fuel rail setup.

how can i hear the pump? it's a walbro pump. and it's loud as **** when running 13volts. and yes, i hear it when the car is running.

and lastly, how can i hear the relay switching? cause it's sitting next to the jack, along with the resistor. i did the re-wire. and the relay ticking is quite obvious.

 

You need to understand the relationship between flow and presusre. You can't change one with out changing the other. If you change the fuel pump voltage, then both flow and pressure will increase. Simple fluid dynamics. If you increase pump voltage without changing the ECU's fuel maps, it'll run richer than it should. Higher consumption, lower power.
The FPR has nothing to do with this. It only responds to manifold pressure, not upstream fuel pressure, so changing the FPR won't stop the fact that increasing the fuel pump voltage will affect mixtures. The FPR is only there to ensure constant pressure differential between the fuel rail and manifold as load changes.

If you don't believe me, ask Hailers. He tested it with a wide-band.

 

Hey ROTOR.........let me know what happen when the wire was disabled. The voltage SHOULD have gone up to 13 or so. But something sounds fishy about your car because that should have been happening everytime you did the smallest amount of boot. The ECU should have been taking the ground off that wre and making the pump get the full 13volts.

If the voltage does go up after disabling the wire, then I'd suspect that the boost/pressure sensor signal isn't getting to the ECU. That would not be a good thing to be happening.

IF the voltage stays low after disabling the wire....then I'd make suspect the relay in the Fuel Pump Resistor Relay package.......and maybe ask you if the *Fuel pump re-wire* has been done on your car. Maybe a step was missed in the re-wire??

 

No ive have never done the fuel pump rewire, because im afraid of messing something up. I have a spare relay/resistor pack that i can swap over, but i dont know if it worked either because i never tested it while my parts car was running. I want to let you know something HAILERS the only time i have ever looked at my ECU there was a wire spliced into one of the wires going into the ECU on the end of that wire was something that the previous owner rigged up i guess. It is a frickin WD-40 cap with some sort of electrical wiring in it and then it was taped up. i know it is hard to explain, so i gues i will take some pictures. i cant remember if it was spliced into 3D. and im afraid to take it off because i dont know what it is for, or why it was rigged like that. I will take some pictures for you guys today and maybe you can advice me what to do. While im in there i will also disable 3D and see how it goes. Oh BTW i tried to pull codes off my car and couldnt pull any, isnt that how you tell if your boost sensor is kaput?

 

I've took some pics of the contraption that is spliced into my ECU wiring. It is spliced into 3B, which is the starter switch. I'm going to pull 3D a little later to see if I can get 13v to my fuel pump at all! I will post my results in a few. Meanwhile maybe HAILERS or Icemark can figure out what the hell this thing is


Here are the pics of the contraption. I dont want to take it apart because i wont be able to put it back together.

http://www.cafes.net/rotory/pic/000_0055.JPG

http://www.cafes.net/rotory/pic/000_0056.JPG

 

I just got back from cutting 3D to see if i could get 12 or more volts. And just as HAILERS said i got 12.8v...yay! So im supposing that means my resistor/relay pack is bad right?

 

NO, NO, NO, NO! Just the opposite. The relay package is good. The problem MUST be in the signal from the Boot/Pressure sensor to the ECU.

I gotta go back and see what your car is sometime. I took it for a turboii without strange modifications.

The way it works is .......the boost sensor sends a signal to the ECU. If that signal indicates boost...the ECU kills the ground it's been sending to the fuel relay package.

I'd be showing a little concern about the boost sensor. Its signal can be monitored on pin 2B on a series four car. Just for grins you might backprobe that pin 2B and go for a drive. The volts should be approx 2.3 to 2.7 volts at idle (WITH THE PRESSURE SENSOR VAC HOSE OFF AND PLUGGED).

As you get into boost.....the voltage will hit about 3.65v when you are boosting around 7psi (memory here), unless you have a FCD then it'll stop climbing at about 3.50 or whereever the FCD has the clamp voltage.

I'm guessing your boost sensor ain't a showing any voltage change when boosting. Time to go for a drive and see.

OH! When you go for the drive...make SURE the boost sensor is connected to the vacuum hose 100percent and the plug is connected. YOu only take the vac hose off to read the volts at pin 2B when at idle.

 

OOOps. My bad. I did not read everything above. About the bottle cap and whatever. I'm in a rush right now, and I'll look later.
https://www.rx7club.com/forum/attach...postid=1291996

 

damn and i just put all that crap back together...are a 87 and 88 boost sensor interchangeable? Because it would be easier for me to go swap only a boost sensor and see if the fuel pump voltage will switch up to 13v. I have a spare 87 TII boost sensor but my car is an 88 TII are the boost sensors swappable is my main question now i guess

 

Yes, the turbo ones are the same. The non turbo ones WILL NOT work right. See the diagram I just added to my above post??? Is there anything in 2B???? Its the center plug and 2B is bottom row, far right when looking into the wire end of the plug with the plug connected. Gotta hurry now, I'm late, I'm late, I'm late..........

 

man just go we will figure this out later...i dont want you to be late...but no there is nothing weird about 2B its just a wire going into it like normal

 

Since this is a "89 GTU TurboII conversion", what ECU are you using? Is it the stock NA one or has the TII ECU and harness been swapped in?

 

In the pictures it say N333. Guess I'll go to the search and look it up to see what it belongs to.

EDIT:This site says its for a 88turbo. https://www.rx7club.com/showthread.p...highlight=n333

EDIT: OOPS, another mistake I erased.

So....I think I see what NZ is getting at. I *think* the pinouts for a 88 would be different than a 89. Soooooo, what color is the wire in 2B would be my question since I'm not near a manual. I'll be looking online while I wait for an answer. I'll look at a 89fsm maybe.

EDIT: I just looked at the 89fsm online. Ooops. The pinouts are different. 2B on a 89 is for the afm. This is not a good sign if you have a N333 and its true that that is for a 88 model. Anyone care to elaborate????

 

And I just looked at the 89fsm again. It seems on a 89 the pin 3D is a constant ground whereas on a 88 pin 3D is a ground that comes and goes depending on boost/no boot situation.

That explains everything. You've got the wrong ECU in the car. You need a N350 (memory again) or get the pinouts for the two model ECU/cars and swap a lot of pins in the existing harness.

I bet this car is not a smooth running affair. I'd opt to swap pins in the plugs....but if you've never done that before it might be....well interesting at the least to do that.

Right now it appears that the boost sensor signal is going to 2H which on a 88 car/ECU would be the pin for the atmospheric pressure sensor. Giggle, giggle. Funny.

Look at page F1-80 of the online 89fsm and you'll see the pinouts for the 89ECU. Then go look at a 86-88fsm and compare the pinouts. EEEEEEEEEEKKKKK! SCARY!

 

Well, I sacred myself if nobody else. I got to looking and that car would not even start is the harness didn't match the ECU. There must have been a harness change along with the ECU. Got me. Only way I could tell would be to compare wire colors on the harness with the the schematic.

So...back to the question. What color is the wire at pin 2B. That should tell us a lot.

 

I'm aware of fluid dynamics, however, i wasn't aware of exactly how our FPR's worked. I thought the FPR's were set at a particular static fuel pressure, say 35psi no matter what the fuel flow is. The FPR will try it's damndest to hold 35psi. I understand that when boost is applied, fuel pressure will increase at a rate proportional to the boost increase. What I don't understand is, why won't the FPR try and hold the set "35psi"?

 

If it helps any the N333 is definitely an 88 T2 ECU. I pulled one from a stock AE turbo.

Don't know if the plugs will fit in the different years. Hope you don't have an S5 harness with that S4 ECU--that might be a real mess.

Scott

 

No, it's only the difference between the fuel rail pressure and manifold pressure that the FPR is trying to keep constant. It's only input is manifold pressure and that's all it responds to. All it is is a variable restriction that closes (increasing fuel pressure) as manifold pressure increases.
Because that's not what it's there for. It doesn't matter whether the engine's turbo'd or not, at low load (small throttle opening) there is high vacuum in the manifold, and at high load (large throttle opening) there is low vacuum or even positive pressure in the manifold. Since the fuel is being pushed through the injector into the manifold, the higher the pressure is in the manifold, the harder you need to push the fuel to get the same flow rate. The FPR keeps the pressure difference constant so that no matter what the engine load is, fuel flows through the injector at the same rate.

Contrary to popular belief, fuel pressure doesn't increase to push more fuel in, it increases so that the same amount of fuel is pushed in. Adding more fuel as load increases is done by increasing the injector opening time. NA FPR 's and turbo FPR's work exactly the same way, the only difference is that fuel rail pressure keeps increasing as boost increases instead of stopping when manifold pressure reaches astmospheric.

FC's have a static fuel pressure of ~37psi. That means when the FPR keeps fuel pressure ~37psi above whatever manifold pressure is. At idle (say 16inHg vacuum which is -8psig) fuel pressure should be ~29psi, at zero manifold pressure (WOT on a NA) it'll be ~37psi and at 10psi boost it'll be ~47psi.

I hope that clears that up for ya.

 

guys guys everyone calm down...MY CAR ISNT THE GTU TURBO CONVERSION that was the guy who started the thread. i hijacked this thread because he never came back! My car is a bone stock 88 TURBO 2. except for that weird wiring **** on my ecu. Sorry i went to a LAN party and couldnt reply back for a while. and as an update i changed my boost sensor and my fuel pump still wont get the full 13v so tomorrow im going to change out the relay/resistor pack. Sorry for the mix up!!

 

No. It CANNOT be relay resistor package. You cut/disconnected the wire at 3D. This removed the ground that was pulling in the relay which in turn keeps the voltage LOW.

The problem lies in the ECU or the pressure sensor. The fuel pump relay is working as designed.......i.e. no ground equals fully battery voltage. The ground is controlled by the boost sensor signal to the ECU and then the ECU making the decision to remove the ground from pin 3D.

 

well i have a spare 87 ECU i could swap in but im afraid i will burn it up because im not sure what that wiring job is on my ECU or if it will fry my 87 ECU

 

so why couldnt it be the relay...tell me this. IF the boost sensor indicates boost and the ECU does remove the ground but the voltage still doesnt jump then couldnt that be the relay?

 

If the ECU had been removing the ground from the relay ....then yes I'd say its the relay. But from what I read you never got full voltage until you cut/disabled the wire a pn 3D. That indicates to me that the ECU has not been removing the ground from the relay.