S14 Fuel Pump Relay Buzzing

[fliprayzin240sx]

K, trying to figure this out on my S14. Car was running fine, came home for lunch, car suddenly doesnt wanna start. Turn the ignition on and the fuel pump relay would start buzzing. I'm getting 11v on the black/white wires, pin 2 and 3 on the relay. Only getting 8v on the black/pink wire and only getting 4v on the black/yellow wires. I know the black/yellow is whats hooked up to the fuel pump. I'm thinking a bad ground but no clue where to start. I know as far as the dash harness you have a grounding ring in both kick panel.

Also, my PFC commander is stuck on the Apexi logo...for the love of god, I hope its not fried. Opened up the PFC, didnt see anything burnt out.

[fliprayzin240sx]

K, I already tried swapping with a known good relay, still does it.

I'm debating on using the hardwire/relayed mod for the pump. Question is, what did you use for the trigger for the relay? Do I just jump the relay in the kick panel (Black/Yellow wires), then use the fuel pump 12v (same Black/Yellow) for the switch?

Also, I was reading some stuff last night that kinda got me worried. Does the black/pink wire from the relay go to the ECU? I vaguely remember somebody saying that wire is a ground wire that the ECU uses to control the relay, is that true? If it is, almost sounds like my damn ECU isnt grounding out the signal, so the relay would stay on...which would mean, fuck me beautiful, my RB25 PFC might be fried.

[Mikester]

^^Dude... That would be some serious suckage. Do you have a WS harness? If so, give Yuri a call... I bet he'd know(?)

Did you happen to meter power right at your battery just to see if it has a full charge? Maybe there's not enough power to fire the system up. Yea, I know... long shot but figured I'd ask. ANYTHING is better than a cooked RB25 PFC.

[cotbu]

There are a few things needed to work before the ecu will control the fuel pump.
CAS, MAFS, ECT, Ignition switch and the ECU. I usually work backward from the pump, it's rare that the ign, ect ,mafs and the CAS are faulty. Most likely cause is the ECU or the wiring from there to the relay or to the pump.
Yes the ecu triggers the relay via ground. pink and black for s13, so I'll assume s14 as well.
Your ?'s: There are a few ways you can trigger the pump.
1. if your ecu and wiring is good use the ecu to trigger the relay, (stock with hot wire mod).
2. jumping the relay, one of the 12v ign pins on the relay to the 12v out to fuel pump pin on relay. (12v to hot wire,ign on).key on pump runs.

3. Manually trigger the relay ground with a switch.

I could go on, the one thing these have in common are, a working relay socket to fuel pump wiring.

You need to determine if the ecu, or wiring to the relay is bad. I'm thinking the ecu, based on your description.

I think I covered everything, i'll sub to this to try and help if you like.
HTMS

[fliprayzin240sx]

Only thing I'm hoping for is a bad ground. So im busting out the wire brush and running it on both kick panel dash harness grounding points to see if that helps my situation.

JSpec Sam is saying its also possible its the alternator. I've read couple of folks who had this issue with clicking relays and their alternator ground was bad. I just dont understand how the car was running fine, all of a sudden it wont fire up.

[jr_ss]

Flip, I think the typical way to run a new relay is to use the factory power wire to the pump as your switched source from the existing relay to new one and use heavier gauge wire to the pump from there. I'm not familiar with the "hot-wire mod" so I can't comment on that end.

Have you checked resistance/continuity on the wires that run to said relay?

[cotbu]

Your car should still start, with out an alternator. If that's what you think it might be. Charge the battery, remove alternator wires and secure. See If you get 12v instead of the 11v. My car used to be able to start w/ 10.6v now I need at least 11.6v, also with the charge the pfc might boot up all the way. So maybe try a full charge before, starting. Even If you don't remove the alternator out of the equation. I know from experience that pfc's are finicky about proper voltage. I'm leaning towards that conclusion as I type. Try reseating the eccs, relay as well.
Can you swap the pfc witn friend or different car?

Sent from my Galaxy SIII using Xparent Red Tapatalk 2

[fliprayzin240sx]

K, I cleaned up the grounding points for the dash harness and battery ground (relocated in the trunk), checked alternator connections, everything is good. Turned the car on, same thing, relay clicking, PFC commander stuck on the intro logo. I decided to try to jump the car, the clicking on the relay is still there but it seems to have slowed down, check engine light is blinking with the clicking but the PFC commander actually cycled thru and I saw that the ECU is only seeing 6V on the commander. Any suggestion on which pin to check to make sure the PFC IS getting 12V? This is on an RB25.

Now the interesting part. I put in the stock RB25 ECU just to see if the fuel pump will prime and if the relay would stop clicking. Well, turned it on, pump primed up and everything is normal. No clicking or anything. For shits and giggles, I started the car and it fired right up. Now, here's the WTF moment...its a stock RB ECU but I have Nismo 500s and Z32 MAF, how the hell is the car running normal with these on? AFR is slightly rich, 10.5 on idle while cold but got sat about 12.5-13.0 once warmed up. I even took the car out for a quick spin and it pulled all the way up to redline and AFR stayed around 12.

[oni jake]

It could be the Power F/C itself or possibly the harness wires. Take your Power F/C apart and inspect the circuit board for any damage or burns. As a said note, you should call Apex'I and talk to their representative about the problem. I've called them before and they're actually really helpful. (We had a problem with the fuel pump ECU ground not shutting off)

A stock ECU should idle about the same as your tuned Power F/C. Z32 and RB25 mafs are similar enough in voltage readings, and 550cc isn't that big of an increase to cause terrible idle problems. If you start putting a load on the motor then you'll notice the difference, and probably cause some serious motor damage along the way.

With all this said, I wouldn't be surprised if its a wiring problem. Possibly 2 wires are grounding each other out and tripping the Power F/C from loading correctly.

[oni jake]

Also, do you have a voltmeter? I would start by tracing the ignition wires. (They are intertwined with the ECU harness relays.)

Find the FSM for that info, I can't recall the correct pin locations. :(

[Mikester]

PM returned.

[oni jake]

This might help you or someone else, so worth a post for later searches.

This is a fuel pump relay design in a stock zenki S14. The F3 (sometimes known as F4) plug remains the same. The only thing that changed is the pin number to your ECU.



http://img716.imageshack.us/img716/2778/fuelpumpd.jpg

[fliprayzin240sx]

Jake, where exactly is the ECCS relay for the ECU? I've been scouring the FSM trying to find the damn thing. I want to verify that I'm getting 12v across it when the relay is on. From what I've read, the ECU grounds out the trigger to turn the relay on and power the switched 12v to itself. I just wan to verify thats whats happening and the voltage is good across it.

I opened up the PFC, didnt see any burnt up resistor. But right when the 2 12v pin goes into the PFC, there is a resistor on there. I will double check the resistance thru it and verify it matches what it's rated for.

[jr_ss]

It's typically in the passenger side foot well. Usually tucked into that recess behind the factory ECU.

[oni jake]

The ECCS relay is located on the ECU harness. So you'll have to look at the specific FSM to the RB25 rather than chassis stuff. I haven't done wiring on a RB25 yet so I'm going to assume they're comparable to SR stuff, at least in terms of the F4 plug.

You should have 2 or 3 relay's located on the ECU harness close to the ECU plug. They get their power through separate fuses coming from the battery source. The power feeding to the relays must remain constant as they also feed to ECU memory. When the IGN signal wire is activated, (traces directly back to the IGN column) the ECU gets the command to boot and opens grounds to activate the various relays, ECCS and Fuel Pump relay included.

When Power F/Cs don't have enough voltage to maintain an open ground for relays it sometimes go hay-wire and acts funny. Similar to how you're describing your problems. Power F/Cs do not have a fail-safe option built in, like stock ECUs, so if the most minor thing goes wrong, everything stops. Its best to call Apex'I with the exact details as they could give you a better diagnostics on your glitched boot screen.

How good is the rest of the wiring on the car? Nothing is rubbed through? Everything is soldered correctly? No way water can get close to the ECU? etc.?

[fliprayzin240sx]

Its a bad ECCS relay. WS harness added a generic relay in and basically doesnt plugged into the OEM relay behind the ECU. Forgot about it since I had it stashed up behind the heater core until I asked Yury about it a couple days ago. I managed to test the PFC on a buddy's car and it worked fine. Decided to check the relay on the harness, held it on my hand and turned the key on with the PFC on. Barely felt the relay click on. Grabbed another relay off my HIDs, swapped them and that one clicked audibly when turned on. Car started right up. Thing I cant figure out is, the "bad" relay is good. Tossed it on my HID and works fine. I never thought a bad relay can have 12v going into it and only push 6v out. Always figured it as an ON/OFF switch.

[Mikester]

Its a bad ECCS relay. WS harness added a generic relay in and basically doesnt plugged into the OEM relay behind the ECU. Forgot about it since I had it stashed up behind the heater core until I asked Yury about it a couple days ago. I managed to test the PFC on a buddy's car and it worked fine. Decided to check the relay on the harness, held it on my hand and turned the key on with the PFC on. Barely felt the relay click on. Grabbed another relay off my HIDs, swapped them and that one clicked audibly when turned on. Car started right up. Thing I cant figure out is, the "bad" relay is good. Tossed it on my HID and works fine. I never thought a bad relay can have 12v going into it and only push 6v out. Always figured it as an ON/OFF switch.

That's exactly what a relay is. If there are 12v going in and 6v coming out; it's only a matter of time before it fails completely. Glad you solved it Ray!

[fliprayzin240sx]

That was the thing Mike, I had a very generic multimeter. Not baller enough to have a fucking Fluke, which I should have borrowed from work. I couldnt tell exactly why the voltage was dropping. In my head, it was pointing to a resistance issue.

[dragtheater]

same thing happened to me, last sunday.. while driving, check engine light turned on, then the engine shuts down..
im using the powerFC for more than a year, until this happened last sunday..

where exactly is the ECCS relay? what are the colors of the wires connected to it?

on the fuel pump relay,
i measured the input, its 11.8v-12v
the out put is 2.8v-3v

so does that mean, i have a busted fuel pump relay?

but i put on another good relay, then i measured it, the output is 2.8v-3v.. same as the old one..

[Mikester]

Get an aftermarket relay & wire it directly to the battery on an ignition-powered circuit (preferably the existing fuel pump wiring as it's closest and easiest since you'll be cutting those wires anyway).

You realize this thread is over 2yrs old right?

[dragtheater]

btw, my car is an s14 SR20det (jdm) camelback..

i really dont know where to find the eccs relay..

@mikester: yes its old but i find this thread the closest for my situation right now..
ill try putting on a bosch relay later.. thanks..

[dbeiler]

on the fuel pump relay,
i measured the input, its 11.8v-12v
the out put is 2.8v-3v


But did you actually activate the relay? During normal operation, Terminal 2 of the relay is grounded by the ECU. If I remember correctly, the ECU will do so for only a few seconds (after ignition key is turned to 'ON') to build fuel pressure. Then it will shut off the pump until someone attempts to start the engine. If you're testing the relay, you need to ground Terminal 2 or do the testing during those first few seconds when the ECU grounds Terminal 2.

The ECCS relays are located a few inches from the ECU. They are connected to the ECU/engine harness in the passenger footwell.

[dragtheater]

just an update.. checked all the relays.. working fine except for the eccs relay which gave an output of 6.4V.. did try to swap 3 new relays, still gave a 6.4v output...

so i clean the battery terminals, saw a busted fuse that says EGI and replaced it..

after that, the car is normal again..