Fuel pump resistor relay?
 

While my '91 GXL is running, it's running extremely rich, black smoke, about a 1/4 of a tank burned in less than 20 minutes at idle and of course, no power whatsoever. I found a distinct rapid shorting out sound right behind the pass. side headlight, under a stethescope there's no where else the clicking sound could be coming from other than the fuel pump resistor relay.

I have a volt-meter, but it needs new needles, and either way I can't find the write-up that I read a long time ago about testing this particular part. Should I just skip trying to test it and spring for a new/used one? Mazda dealership wants $199.94 for this part so my budget is leaning towards buying a used one here on the forum.

Anyone?

88.5 to 91's have high impedance (or is it low) injectors. You don't have the fuel solenoid resistor and it wouldn't have anything to do with it anyway.

More likely a bad AFM (nearby) and you may need to adjust your variable resistor (the one with the screw that the factory epoxies so you don't screw with it) mounted near the boost sensor. Search "sensor pictures reference" I took pictures of all that stuff including fuel pump jumper connector I referred to in another thread.

Really, then what's this?

https://www.rx7club.com/attachment.p...1&d=1190406637

Fuel Pump Resistor Relay.

If it's clicking, then pull the small plug off the ECU and see if it stops. It should. The ECU puts a gnd on that relay when there's no load on the engine as sensed by the boost/pressure sensor. Pull the small ECU plug off and it can not click/pull in.

It's also possible the boost sensor is inputing a wrong signal to the ECU and causing the relay to pull in/click. Make sure the vacuum line is on the boost sensor.

I thought 88.5's didn't have the fuel inj. resistor because of the change in injectors. Is this something else? Doesn't look anything like the one's I've seen in the earlier cars. Please comment. In the meantime, I'll check the 89-91 FSM so I don't look like a fool next time.

uhh the fuel pump resistor relay is not the fuel injector resistor pack. they are not the same things.

And I thought only turbo IIs had a resistor relay for the fuel pump, unless they changed it for s5's or something

Harbor Freight has a nice cheap DVM fo $4.99.
You want to check the fuel pump voltage near the pump anyway.
That will tell if ther are any connector problems.

My 91NA used to toggle the voltage some during warmup, so a temp sensor could also be suspect.

Also, if the FPR hose is pinched or off, you will go rich.

Wasn't it 87.5+

dupe.. please delete.

indeed.

why would u make a .5

stupid

there should be a way to test it in the factory service manual. I took mine out. it's pretty useless and I'd prefer my fuel pump to be running at full power all the time anyway, just to be safe. there is a write up on how to get rid of it on www.1300cc.com.

The fuel pump resistor relay is only on Turbo models. It says you have a GXL so i doubt you have it.

All series five have the Fuel Pump Resistor Relay. Check it out.

If you wanted it to run with full 12vdc all the time all you had to do is clip/remove the green/red wire that runs from the relay to the ECU. Explanation is in the online FSM. Fuel section.

^one more thing to know and not like about S5. :P

Funny you should mention that, I did just do a silicone vacuum hose cleanup on my FC a few months back, and one of the hoses I replaced was the FPR hose on the primary rail to the rat's nest. I replaced it with 4MM hose, should I have used 6MM instead? I couldn't tell what the original size was since the hose was so deformed, cracked and bloated from 17 years of age so I assumed it was 4MM, didn't know it could even make a difference like this.

I have replaced the water thermosensor already so it shouldn't be the problem. It even floods when trying to crank, it's like a hit and miss when starting, sometimes it will, sometimes it won't, and when it does crank it runs so rich that it won't idle on it's own.

Any help is appreciated.

Im not very sure what the picture is. But have you noticed the problem seens you replaced the hoses. If you have a fuel pressure gauge you can see what its reading. if you dfont have one i think you rent one from autozone. im guessing you should check the fsm but i think its around 25-30psi.

I think this whole problem started around when I did the silicone lines, but before I tear it apart tomorrow I want to see if anybody knows if the FPR vacuum hose is a 4MM ID or a 6MM ID. I'm thinking it calls for 6MM and the 4MM is shooting the pressure sky high and causing all of this. I don't have a fuel pressure gauge, but that will be one of my next steps.

Upon teardown of the UIM, TB and DC, I see that I used 3.5MM for the fuel pressure regulator vacuum hose. Does anyone know what the factory calls for on this specific line? 3.5MM, 4MM or 6MM?