Fuel Pump Resistor Relay Woes
 

I have an issue I've been chasing and I think I finally narrowed it down and need some advice. when I took delivery of the car she was idling, but occasionally I would hear a loud clicking and then it would die.

Well fast forward a few weeks and I dumped all the emissions, cleaned up the vacuum hoses, new fuel lines, rewired some old wiring etc and get her to start. She was running and then suddenly I hear the clicking again and she dies. On restart attempt, I would hear a clicking so I cycle the key and then it starts. happens pretty frequent. While I had her running I start searching for the clicking and find out I could hear it faintly while running under the passenger head light. Turns out it's this Fuel Pump Resistor garbage that steps voltage down to the fuel pump.

Now I looked at the FSM and tested my voltages.

Specs should be:
A-B 0 ohm
C-D 68-92 ohm
E-F 0.64 ohm

I get:
A-B .2
C-D 75
E-F 0.8 - 0.9

So she doesn't seem to be too far out of spec, but I def hear her clicking like a mofo. So, the next question is, these look like the relay may not be great but is this the symptom or the cause? Ie could something else have caused her to bounce around like that? What is the ECU basing low load off of to switch the relay?

Now, it's hard to find a lot on this fella. I've seen some folks say they bypass it. based on my mods and long term goals I'm wondering if that makes sense. As the car sits:

She has Rtek 1.8
4x720
Walbro 255

Long term plans will be ultimately be aftermarket FPR, standalone ECU, parallel Fuel system, bigger injectors and bigger turbo.

I want to take baby steps towards the long term goal. Any advice or information about what I have said above is appreciated

Adam

I didn't see it documented, but did you check voltage back at the actual pump? Kudos for checking the FSM and trying to spec it out, but do yourself a favor and eliminate the resistor/relay. Search for the procedure, run new wiring with a relay from the battery, and re-evaluate your issue afterwards. At 25+ years old these things are a known issue, especially in a performance application now. Let us know how it goes.

So I have seen folks say remove it all together and it just runs a little rich in cruise. I'm running the RTEK with 720s, and worry like I heard at least one member mention I'll get some stumble at tip in? Or am I over thinking?

I suppose I should just go for the rewire and battery relocation at the same time. It's super hard nor is it expensive. But right now the FC is on the ground and the FD is blocked up on the 4post. I gotta get her to run long enough to swap positions.

I ran an RTEK with 725/1000 at first, did not rewire the pump at the time. I didn't have stumbling issues, but the RTEK is VERY basic and limited so I can understand where some may experience issue. For the mods you have planned, rewiring the pump will be critical so I still recommend doing it despite the possible stumble. When you're ready for your standalone, look into an Adaptronic PnP, you will never look back.

The voltage for the relay is supplied by the main relay. The trigger for the relay comes from the ECU. Either of these could be the issue or perhaps it is just the relay itself regardless of the extraneous inputs. The ECU senses load from the TPS, boost sensor and AFM.

I think you're conflating the S4 resistor pack and the S5 fuel pump voltage resistor...they are different things.

You NEED the resistor pack for the injectors so the ECU gets the proper signal/voltage(?)...this is basic hardware, not a performance/emissions enhancement.
The S5 voltage regulator on the other hand is an attempt to mitigate fuel consumption by varying voltage to the pump but the pump works just fine if it's deleted.

Yes, I'm def talking about the relay resistor verying voltage to my pump. I know the other resistor for low impedence inectors is right next to it and stays as I'm an '87 with low impede. After depinning the ECU ground she now has stopped clicking and I'm one step closer to running well.

After lots of searching I found someone experiencing some of my similar issues: https://www.rx7club.com/2nd-generati...estion-772752/

So, I'll be adding rewiring of my Fuel pump to my list of TODOs. At least she runs long enough to swap spots on the lift. I'm still chasing gremlins. She will idle for a good 5 minutes at 1500 and then just die with no warning but at least this isn't part of the problem anymore. I gotta check the TPS and CAS as well as my coils I suppose.

Thanks, I just discovered at lunch my boost sensor connector is falling apart. I'll test it, tps, and afm here next. Before I removed the green/red signal wire I put the resistor back in and pinned the fuel pump trigger and gave it power. She just clicked like mad so I'm pretty sure she was part of the problem. I just want to ensure it wasn't a symptom of something else.