Sup guy, ok,, i cant get the fuel pump to work without connecting the yellow bybass connector... Any ideas why???? S5 90 gxl.

 

could be that your AFM isn't functioning or is stuck closed.

 

Whats a AFM?

 

Air Fuel Meter. Located just under and a part of the air filter assy. Plug is on the left side. Near the radiator hose. A little lower than the hose. Pulls straight off and back on. No screws or bolts.

Download the factory service manual from http://www.iluvmyrx7.com Just the Fuel section for the info you want in this post. Ring out the circuit in the afm per the manual.

 

S5 AFM isn't connected to the fuel pump. only the S4 is. so one of your relays or some wiring is disconected / not working.

 

Well phoohey. I missed that mention of a nintey model. I have no wiring diagram. This jpg is the best I could come up with.
JPG:

 

This is a better jpg: I'd say its the circuit opening relay. It only seems to make a circuit to the fuel pump if you put a ground on that relay and pull that set of contacts up which makes a Different circuit than thru what looks like some kind of resistor at the bottom of the circuit opening relay.

 

Ring the plug out to this chart: I'm guessing you have no resistance b/t pins C AND D on the resistor relay if I'm reading that right. Its late.

 

Scott: but the fuel pump won't run if the AFM is closed.

 

SonicRaT

I'm not sure what SonicRat is getting at. Do you mean the series five does indeed have a switch in the afm for the fuel pump circuit?????? If you have a series five schematic (anybody), please post it. I don't have one myself. The jpg's I posted indicated that there is none, but I wouldn't bet any money on it.

Hmmmmm. Nows my big chance to open my old HAYNES manual and see if it reflects anything useful.

EDIT: No. Its still useless. Shows a 88 circuit and says later models similar. Not good enough for me. Common??????sense says the later models must have some have a circuit thru the air flow meter like the earlier models to cut the fuel off in case of an accident.

A manual without schematics is, welllllllll, not too effective.

EDIT: It would be the circuit opening relay that would disable the fuel pump. Not a wire running thru the afm to the fuel pump.

 

Hard wire that son if a bitch with a toggle switch just to get you down the road is all i can say

 

Hailers: I don't believe it has an actually 'trigger' inside the AFM, however I do know that if the AFM is extremely defective, or jammed, that they relay will not kick on thus, the fuel pump remains off, which is what I was getting at, starting simple I guess, as I've had it happen before. I believe the relay's located right in front of the AFM in the silver box bolted to the radiator panel.

 

AFM - AIR FLOW METER..

 

So if the air flow meter is bad then this is why the the fuel pump gets kicked off???.

 

It happened to me, but I can't gaurantee it for you, it could be a number of things! Have you checked the 'motor' fuse under the driver side kick panel? I've also had my fuel pump not work because that fuse was blown I'm just saying what I went through and suggesting to look at it if all else fails

 

Do not hardwire the fuel pump. This could be insanely dangerous in the event of an accident.

When you try to start the car, does the relay under the dash click? That is the fuel pump relay. If not, then you are more then likely looking at an AFM problem.

 

Looking at the jpg that I attached its apparent that what makes the fuel pump work AFTER you let the key go from START to just ON, is a ground signal from the ECU at pin K. When you jumper the yellow plug, you are doing what pin K on the ECU should be doing. I don't have a series five manual with schematics. I assume it still has something to do with the afm. Perhaps when the cone of the afm moves back, the ECU senses this and then put a ground on pin 3K of the ECU which pulls the relay in and makes the fuel pump circuit work full time.

I'd suggest making sure the afm's plug is on good. Then take the filter off and shove the cone of the afm back and forth a couple of times. Then try to start the car without the jumper in the car.

I think I'll be able to look at a series five manual and schematics tomorrow sometime, and if I come up with something else, I'll let you know.

Do your best to stay out of accidents if your jumpering the yellow plug. At least turn the key off before you passout from your injuries.humor

 

Here's another idea. Go to https://www.rx7club.com/forum/attach...postid=1341017 See the jpg and that chart with the back of the plug just to the left?? The chart is telling you, that if you put your meters positive lead to the socket called Fp, and the other lead to a good ground, and then,with the key to ON, shove the cone in the afm back. You should now see 12v on the meter. Release the cone and let it return to its spring loaded position, and the voltage should go to zero. That should tell you if the afm is good or not.

 

HAILERS: You're right about pushing the cone back and the AFM having the ECU trigger the relay, you can just have the car in the ON position and push it open and hear the fuel pump turn on, I had a bad afm that wouldn't cause it to click, if I forced it to run the car would run (like crap) but it never would make the relay click, so I replaced it and it worked just fine. Just something to check

 

The S5 ECU won't open the circuit opening relay unless the AFM reading is above zero airflow. This gives the same effect as the S4's AFM switch.

 

It's your AFM. Part of its function is to shut off the fuel pump if the cars on and its not sucking any air. That part is screwed, so just get a new AFM and you'll be all good.

Later,
Matt Ford