Hi Guys,

This is my first post here, so I hope this all makes sense.

I have an 86 Jap Spec FC3 RX7 13B Turbo and have an issue where my fuel pump is not turning on/powering up when you turn on the ignition.

Now, I understand that these cars have a Fuel Pump Resistor Relay which I believe is their to reduce voltage to the pump at idle and low revs - right? I also understand that if your Fuel Pump Resistor Relay was to die, there would be no power to the pump - right?

What I do NOT understand is I have heard that their is also a link between to the Air Flow Meter and the Fuel Pump Resistor Relay and that the AFM has the ability to ground the FPRR which essentially turns it on or off - is this right? why does it do this?

Could this be the cause of my pump getting no power?

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Here are some of the tests I have done so far and their results...

1) POWER WIRE CHECK
The first thing I tested was the actual blue power wire running from the fuel relay/resistor to the fuel pump. I did this two ways.

One was to run a long piece of wire from the fuel pump end of the power wire to the relay/resistor end at the front of the car. Then, using a voltmeter I tested for continuity - ALL GOOD.

I then ran a wire from my battery to the other side of the relay/resistor (essentially bypassing it) and the pump fired up - ALL GOOD.


2) FUEL PUMP RESISTOR CHECK
I removed the relay and resistor assembely and, as per the factory manual, checked the resistance and it was all within factory specs - ALL GOOD.


3) FUEL PUMP RELAY CHECK
This is where it gets a little technical and confusing for me.

When I turn the ignition on the Fuel Pump Relay makes a 'click' sound, which is a sign it should be working.

I went one step further and pulled the relay appart and did some more tests. I found that when the ignition is on one wire into the relay is supplying a constant 12v. But the thing is, NONE of the other wires are powering up - this makes me think the relay is stuffed? But then why does it still 'click' when the ignition is powered on?

I then fed a wire straight from my battery to one the wires on the relay which should normally feed 12v back out of the relay to the pump (essentially bypassing the relay) and the pump fired up.

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Now I know all these things point to a stuffed relay, but why does it still click?

Also, I am sure, that as mentioned at the start of the post, their is something else that links the Relay and AFM?

Thanks in advance for any help.

Here is a photo of the Fuel Pump Resistor Relay assembely:



Here is a photo of the actual relay pulled appart:

 

When I bought my car, there were many aftermarket things done to it
Went to the bathroom before I took it home
friend decided to play with all of the switches in the car
Wouldn't start
Same problem, pump wasn't turning on
Ran a wire to it and it worked
Soon found out that for some reason the pump was wired too the cruise control switch
Try pressing some buttons or switches

 

Ok the Fuel Pump Resistor is there to supply low voltage 8-10 volts to the fuel pump under non-boost times, then when the ECU sees a positive pressure it will activate the relay to increase the voltage and output of the fuel pump.

Now to test the fuel pump circuit there is a single double female connector on the middle lower of the passenger strut tower, this is the test port (It bypasses the Air Flow Meter, the Air Flow Meter switch inside of it is there so that the fuel pump will not run if the motor dies or isnt cranking, the Air Flow Meter only has to move a very small amount to turn the pump on) anyhow, if you jump this connector the fuel pump will turn on with the ignition switch.

If it doesnt run then it can be the Resistor (Check by ohm it out) or the relay. But there is another relay inside the car that controls the fuel pump also, if you are sitting in the drivers seat it is to the right of the steering wheel under the dash. Should have a 4 connector plug, this also controls power to the fuel pump.

 

This is just the write up I needed! I have an s4 GXL that will not fire up, I checked the compression in both rotors and they read 90psi. So that leads me to think fuel is not getting to the fuel injectors.

I checked for the fuel pump primer connector (should be yellow) but there is not one. So my next test is to spray carb fluid into the intake and see if the engine will fire up. Then my next test is to teat the fuel pump and fuel pump relay.

No matter how much I crank the ignition and pump the accelerator pedal I do not get any gas odor as in a sign of flooding.

 

The fuel check connector plug is Yellow but it is encased in a Black rubber boot. It is also part of the Emission harness and it usually lies hidden under that particular harness. Chances are very high that it is there. Also, the pump will not run if the 15 amp Engine fuse is bad so make sure to check that aspect of the fuel system. Lastly, jumpering the bottom two wires of the Circuit Opening Relay (relay under the dash and just to the right of the steering wheel column) is exactly equivalent to jumpering the fuel check connector.

 

You wouldn't have that resistor setup anyways as your car is N/A and never came with that part.

 

Doh!! I thought so and should know better, I was getting desperate for a solution ha ha .

I will be rebuilding my engine.

 

Instead of rebuilding, perhaps just check down the fuel pump supply circuit with a meter?

The wiring diagram is in the FSM.

The Factory Service Manuals for all years of RX-7 (and many other rotary cars) can be downloaded for free here: Foxed.ca - Mazda RX-7 Manuals . They contain all common service information information and more, and are an essential tool for any sort of service work that needs to be performed on these cars.

Additionally, the Haynes service manual for the 1986 thru 1991 RX-7 (both turbo and NA) can be found at most local auto parts stores or purchased from any good bookstore (ISBN number 1 56392 007 7). It is only about $25 and is a great quick reference for things like this. Not only does it contain most of the information in the FSM condensed into an easy to read format, but it includes full wiring diagrams as well.

These manuals will answer 99% of service related questions for the car and if you intend to do your own repair work, you will need at least one of them. Preferably both, since the FSM is a free download. The Haynes is a good quick reference covering 99% of questions, while the FSMs show complete and detailed procedures.

The pump circuit is very simple and can be checked in about 10 minute with a volt meter.

If you get voltage at the pump, but the pump doesn't run, it's dead. Common issue if the car has been sitting.

 

You are correct that the AFM too plays a roll in the fuel pump wiring of 86-88 cars. There's a relay under the driver's side dash by the steering column that gets signal from the AFM. If no valid signal is received, the pump will not run. As mentioned, you can find this diagram in the FSM.

 

the fuel pump relay can still click even when its bad, start replacing parts from the bottom to top, but double check everything first.

I am thinking relay but cant guarantee you that. see if a friend or someone parting there 7 and yank whatever you need..


oh a trick that might help disconnect the start cut relay under the steering and give it a go once it starts to go put it back on

 

Thank you all for your advice, I did spray some carb cleaner into the throttle body and got the engine to start for a few seconds then it shut off (I did not reconnect the intake tube during the start). I will check the fuel pump relay as you all have described. Also I noticed the previous owner butt connected all the wires for the AFM which makes me think there could be a disconnect here. I will be working on my car this weekend and hopefully will have good news.

Here is a video I took last weekend:

 

If you do not have the air flow meter hooked up then the car will start up and die.
It needs to see Air,and that happens once the car is starting to suck air through the AFM, opening the flapper on the AFM(which will turn the fuel pump ON.)

 

The wires that are butt connected on the afm harness forces me to believe the wires could possibly not be connected. I will try spray the carb cleaner again, re install the intake tube and see if the engine starts and runs. I will check everything fuel and air related.

 

Update: I sprayed more carb cleaner into the throttle body and put the intake tube back on. The engine started for a few seconds and died again. I repeated the carb cleaner procedure again the engine started and idled high, I pushed the gas pedal and the engine died.

I checked fuel injection, egi and main meter fuses, they are all good. I found the yellow fuel pump check connector and connected a wire between the two terminals. I turned on the ignition, and did not hear the fuel pump wine. I played with the wire on the fuel pump check connector and I could hear the relay box click.

Attached is a picture of the wire job that was done to the air meter. It looks like a different air flow meter connector was used because the colors of the wires before and after the butt connectors do not match. Is the air meter connected the right one?

 

I don't know if this will help or not because I have an s5 and the s4 may be different but the only time the fuel pump comes on in my car per factory setup is when the AFM actually feels air coming through it. IE: no fuel in the on position but fuel while the car is cranking. To test my pump I went to the trunk, disconnected the feed line to the pump and had a helper crank the car and while they were cranking the fuel sprayed.

 

The Circuit Opening Relay, located under the dash and to the right of the steering wheel column (Yellow and Black colored relay). The Blue wire carries voltage to the fuel pump thus this wire can be checked to show that the pump is either properly powered or not. It would have voltage w/key to on and fuel check connector jumpered, key to start, and AFM flapper door opened w/key to on.

 

There is a black IGN wire located in this relay harness. Identify it with a meter (IIRC there are a couple BK and BK/W wires) and jump it to your blue wire to see if the pump runs. If you're not getting IGN on the supply wire or if you jump it and nothing happens, you now have a point from which to start your troubleshoot.

 

Thank you for your advices, I will try all your suggested methods and hope to find a solution. It would be so great if the AFM, or fuel pump is the problem the engine wont start. Because the car has not been started, or driven since 2002.

 

Ok, so today I ran two test on my fuel pump. First I ran an in car test running wires directly from my battery to the fuel pump. I did not hear the fuel pump running so I removed the fuel pump from the tank and performed the same test. And still the fuel pump did not run. So is it safe to say the fuel pump is dead???

 

Check online and you can get an upgraded fuel pump for the same price as factory or less. I bought my aeromotive 340 glh for $68 on eBay. Yes the pump is dead

 

There's a very good change you've identified your issue. I'd suggest first doing a resistance test from the harness to the posts on the inside of the pump lid. Over the years the soft metal gets very brittle and can cause problems.

 

Ok, I will check E bay for a good quality fuel pump to buy and install.

 

Today I installed a good fuel pump and I connected a jumper wire to prime the fuel system. I cranked the ignition and the engine started for 10 seconds then died. I cranked the ignition again the engine started, I disconnected the jumper wire and the engine and fuel pump both died.

Is the afm causing the fuel pump to shut off?

 

You might have flooded the car. Like I said before, the AFM turns the pump on when it sees air coming through. Meaning while your turning the car over. So as previously stated the in car test of the pump is to have someone crank the car with the feed line off and see if fuel comes out. With your jumper on you were feeding the car fuel constantly and on the off chance you have leaky injectors you could have flooded it. If you get no fuel go back and check your pump. If that pans out then we now know you have an electrical issue with the AFM getting the power on signal to the fuel pump

 

If the engine dies as a result of the fuel check connector jumper being pulled then the fuel switch found within the AFM is likely your problem.