No Voltage At Fuel Pump

[govich]

Hey guys,

I've got an R33 GTS25t, and i've got no voltage on the positive wire for the fuel pump, as tested just outside the tank. The relay and fuse in the boot are fine, along with the fuel pump. I drove it home by exposing a bit of the fuel pump wiring and connecting a line direct from battery positive. Any ideas on where to look in the stock wiring? If i can't figure it out i might just set up my own relay..

Cheers

edit: FIXED! Guide is here: http://www.skylinesaustralia.com/forums/in...t&p=3382664 . Also read the rest of the thread for more helpful input.

Edited March 14, 2008 by govich

[BHDave]

Isn't the fuel pump relay and fuse under the bonnet? It's common for s13's to pop fuses when they upgrade the pump, i'd say it's the prime suspect here as well.

I can't remember how low your car is but it's worth checking that you haven't eaten into the wiring in the inner guards.

Then it's just a matter of checking the wiring, make sure the trigger for the fuel pump relay is ok, that the relay has power to it, that it has power going to the pump at that end.

A rewire is worthwhile to maintain voltage to the pump, but you still want to trigger it off the ecu so the pump will stop if you have an acco, rather than keep running if it's straight off the ignition.

[govich]

Thanks for the reply Dave.

The story goes, it's a Walbro pump and has been in the car for a long time (4-5months now), including track days and all. Then the other day the car just died, turns out the relay was shagged and was blowing fuses. So got a relay and fuse and it worked fine for about an hour's worth of driving, and then stopped again, except this time it's not blowing fuses and the same relay is fine.

I'm a bit stumped, i guess i'll have to trace the wiring back.

Oh and R33s have a relay in the boot, apparently there's another one next to the ECU which i'm about to look into.

Edited September 27, 2007 by govich

[BHDave]

That really sounds like a short has killed the fuse and relay in the first place, to me anyway. in order to pop a fuse you have to pull too much current through it, same thing kills relays.

Do the checks to see what is still working, getting power etc, then rewire accordingly.

Edited September 27, 2007 by BHDave

[govich]

The relay in the boot is definitely not getting a switching signal. It has perfect voltage from the battery and i just confirmed the relay itself is working. Fuel pump fuse is fine.

I'm pulling the interior apart now to get at the wires.

Cheers

[govich]

OK i've found out the hard way that R33 GTST only uses Pin 104 on the ECU, as opposed to Pin 18 on some other models, and sends a signal to the FPCM through 104. Would anyone be so kind as to tell me where i can find the control module? Is it stashed above the fuel tank with the HICAS computer? The engine manual has nothing.

edit: I've had it with the stock wiring, way too complicated, i'm just going to splice the wire coming from Pin 104 on the ECU and use it for my own relay setup. Might post pics in the DIY section when i get around to it.

For the more electrically inclined people, please let me know if there's any problems with this proposed setup:

- Use a 12V 4pin relay rated to 30A (standard)

- ECU signal from pin 104 to Relay pin 1 (inductor in)

- Relay pin 2 (inductor out) to ground

- Relay pin 3 (switched link in) to battery positive

- Relay pin 4 (switched link out) to fuel pump positive

- 15A fuse between battery positive and relay pin 3

Edited September 28, 2007 by govich

[govich]

Just for the sake of those in future who are going to have this problem, i'm going to keep posting progress.

I've canned the relay idea, since the ECU grounds the inductor in the relay as opposed to providing power to it. (ie. you'd need to provide a really low voltage supply to the relay in order to set up your own working relay)

I've narrowed my problem down to the "A/T Controller" fuse (2nd from the top on the right column of the fuse box under the dash) blowing intermittently (This fuse is on the power link to the inductor in the fuel pump relay), regardless of what size fuse i put in (15A blows just as readily as 10A). This makes me think that this wire is shorting on the chassis (etc) somewhere. It also blows at seemingly random intervals, meaning this theory is even more likely. I'm going to cut both ends and join them with a new wire outside the car to see if it still keeps blowing this fuse.

Edited September 29, 2007 by govich

[SevenAngryPenguins]

I rewired mine with a new relay in the boot so the pump is supplied straight from the battery the old relay is still in place I just use that to trigger my new relay. I read somewhere that the stock wiring cant handle the current draw from the bigger pump and also that the voltage can fall as low as 10V through the stock wiring.

[govich]

I read somewhere that the stock wiring cant handle the current draw from the bigger pump and also that the voltage can fall as low as 10V through the stock wiring.

I now think this is a bunch of bs spread by a lot of people (no offence intended). The stock wiring is fine (to a point, obviously), but R33 GTS25ts come with a little thing called the Fuel Pressure Control Module, which is basically a variable ground for the fuel pump, and the ECU varies the voltage across the pump through the FPCM according to the load on the engine so that the amount of fuel recirculated to the tank is minimised. Obviously this is meant for a stock setup, so that it might not be an ideal method of operation for an upgraded engine or upgraded fuel pump.

Grounding the negative terminal of the pump directly, as is often done, bypasses the operation of the FPCM by providing a constant healthy ground at all times. However this also means that the pump is working 100% all of the time, and a lot of fuel is recirculated by the fuel pressure regulator, meaning it gets hotter (from passing by the hot motor), which has consequences.

Edited September 29, 2007 by govich

[SevenAngryPenguins]

I'm no expert but I'm not so sure its a good idea to run the walbro pump at an under voltage as it will decrease the life of the pump something about running at lower voltage will cause the pump to draw more current and heat up feel free to correct me I'm all for learning.

[govich]

I don't see why that would be the case, since the current drawn by the pump (from a DC supply) is proportional to the voltage across it. I've already got the negative terminal grounded anyway. That has nothing to do with my current problem though, since it's a different circuit.

I bought plenty of 25A-rated wire today and will probably get stuck into finishing this off tomorrow.

[dangerman4]

I don't see why that would be the case, since the current drawn by the pump (from a DC supply) is proportional to the voltage across it. I've already got the negative terminal grounded anyway. That has nothing to do with my current problem though, since it's a different circuit.

I bought plenty of 25A-rated wire today and will probably get stuck into finishing this off tomorrow.

ive got the same issue so once you solve it can you pm me your findings.

my car keeps blowing the engine control fuse under the steering wheel.

so i ran a new fused + feed from the battery to the stock fuel relay and it all works perfectly.

i cannot find anything else thats been effected by the EC fuse been blown.

i hope that helps.

[govich]

Hey guys,

Well i've finally solved my problem. I'll make this post comprehensive so that anyone who has this problem can follow and hopefully diagnose their problem.

First here's a mspaint sketch of the fuel pump control system in an R33 GTS25t.

From the diagram above you can extrapolate what you need to test if your fuel pump is getting no power or you're getting no priming when you turn the key to ignition on. The following are possible if you have such a problem:

1) Blown fuse. Check the Fuel pump fuse in the boot (15A). This fuse is on the battery-to-relay link. Note: DO NOT try giving the pump a live link direct from the battery under any circumstances here.

2) Blown/bad relay. Check the Fuel pump relay (next to the row of blade fuses in the boot) by replacing it with another, i recommend the air con relay in the fuse panel under the bonnet.

3) Blown A/T Control fuse, possibly the wire from the fuse panel to relay grounding on the chassis. Check the "A/T Control" fuse (10A) in the dash fuse panel, replace and see if it blows again. If it does, you probably have the wire shorting. Follow what i did below.

4) Check the fuel pump works, by exposing some of the fuel pump positive wire (stock wire is light blue with silver bars), and connecting a direct link from battery positive to this exposed bit of wire. I don't recommend driving the car around like this, as the link is not fused, but it could be used to get you home, just BE CAREFUL! If it doesn't do anything or primes but very weakly, try giving it a good ground by exposing the fuel pump negative wire and connecting it directly to a good grounding point (suggest battery negative). If this still doesn't work, have a look at the in-tank wiring or fuel pump itself.

In my case, the problem was the car constantly blowing the A/T Control fuse in the dash fuse box. I checked that the ECU was grounding pin 18 and that was working fine. I then replaced the 10A A/T Control fuse with a 15A fuse to get a better idea of the problem, and the 15A fuse blew straight away, suggesting the fusebox-to-relay wire was grounding on the chassis. The culprit wire is blue with white stripes and silver bars (see below).

First i cut this wire at the relay and attached my own wire:

Then on the back of the fuse panel:

After doing this (and obviously soldering the connections and insulating with electrical tape) i idled the car for a fair while and it hasn't blown the A/T control fuse again yet, so unless i come back on here with profanities within the next few days, that was my problem. The car now works fine.

As a bonus, i also found that very annoying beeper for when you have the driver's side door open and the key in the barrell. edit: actually found it this time, here's a photo from below. (thanks to SevenAngryPenguins for helping me locate this)

Hope this helps someone.

Edited February 25, 2008 by govich

[dk_fabiosantos]

I'm happy that you have your car running man, I have some question for you:

In your mspaint sketch you have 4 wirings but on your fuel pump relay real pic I see 5 wirings, so can you tell me where they coming from?

color--strip

black/pink?

blue/black?

blue silver pin?

blue/white?

blue?

and what about the fpcm?Have you found it?Can you tell the wirings for that?

I really aprecciate if you can tell me it, cause I'm about to finish my project just missing the fuel wiring to run the car as I have all the wiring cutted right before the driver's seat so any info in wirings going from the driver's seat back to the trunk will make me happy!

Thank you very much!

[govich]

Sorry i should have made it clearer, i cut the blue/white wire and replaced it with the blue wire in that photo.

Personally i think you shouldn't bother with the FPCM, just connect the negative terminal of the fuel pump to a chassis ground.

Also for the last part of my post, if you remove the beeper the power window switches stop operating, so it looks like it'll have to stay in a little longer while i figure out how to get around this.

Cheers

[SevenAngryPenguins]

good to hear you fixed the problem, so how/where is the fpcm connected/wired i would have thought that it would have varied the positive supply voltage to the pump I gather from what you are saying is that it alters a resistive load in series before it goes to earth. Just curious as I'm still using the ecu triggered ground.

With the beepers I have disconnected mine also however my windows still work if you have a look under the dash where you disconnected the plug there is a smaller plastic box just behind it with 2 small wires connected to it that is actauly the beeper, If you unplugged the one in front with the rather large wires to it then yes it kills the beeper and the window switches and who knows what else

Edited October 1, 2007 by SevenAngryPenguins

[govich]

With the beepers I have disconnected mine also however my windows still work if you have a look under the dash where you disconnected the plug there is a smaller plastic box just behind it with 2 small wires connected to it that is actauly the beeper, If you unplugged the one in front with the rather large wires to it then yes it kills the beeper and the window switches and who knows what else

LOL i just disconnected whatever made it shut up. Thanks for that, i've updated the post above with a photo of the actual beeper (and the windows still work!).

[SevenAngryPenguins]

yeah i did the same thing, it's seriously annoying if your doing any work on the car

[govich]

good to hear you fixed the problem, so how/where is the fpcm connected/wired i would have thought that it would have varied the positive supply voltage to the pump I gather from what you are saying is that it alters a resistive load in series before it goes to earth. Just curious as I'm still using the ecu triggered ground.

I didn't actually find the FPCM. I've grounded the negative terminal of the fuel pump just outside the tank and this bypasses all the varying ground shenanigans and gives the full voltage at all times. I looked for it for about 30minutes before realising i didn't have to anyway.

edit: and yeah it is just basically a variable resistor

Edited October 1, 2007 by govich

[SevenAngryPenguins]

actually i did ground my pump as well I just forgot........ i did some research on fpcm for other cars and came up with some interesting facts one was that its linked to the oil sender pressure sensor so no oil pressure no fuel pressure, another was that some are linked to a restraint control module so if your in a crash stops fuel and one more was that they normally operate in 2 ranges hi and low, anyhoo thought you might find it interesting to know some reasons why they are there.