- Pump Runs when given 12V.
- Wires to pump are OK.
- Power up to FP Relay Socket in Fuse Box is good.
What is (under normal conditions) triggering the FP Relay to 'trigger' and run power out to the Pump?
So another issue popped up today. We finally got the sciRATco to spark, fire, & run but....., the fuel pump doesn't work like it should w/ the relay. The relay tested good, the pump works fine when "jumped", just doesn't work when the relay is plugged in. WTF?!?!?!? I guess I should mention, for those who haven't seen any of my prior posts pertaining to this car, it's equipped w/ a carbed ABA running off the stock ICM.
No, don't do that. Defeats the safety function of the fuel pump relay (unless you're planning on rigging in a proper fuel pump relay, instead of a standard 4-pin...)
Don't overthink it (which it sounds like you may be doing.) There's only 5 pins (wires) to deal with here:
87 (relay output, to fuel pumps)
85 & 86 (relay coil power (via ignition switch) & ground (*note: I may have these reversed (Bentley not on hand))
1 (tach signal, from coil negative.)
Depending on what you jumpered to 87 (was it B+, or ignition power?), you've already checked two (if not three) of the circuits.
Quick check for all but tach signal: swap your horn relay (marked with 53) into the fuel pump relay socket. Pumps work? Move on to checking the tach input:
Take relay out. Install jumper wire between 15 and 87. Start engine. Check for presense of a tach signal (using a DVOM with a tach function) at the relay socket.
If that's also OK, replace fuel pump relay.
Does your tach work?
Both the tach (obvoiusly) and the fuel pump relay both need an engine speed (tach) signal. This comes from coil negative (in German (DIN) parlance, "terminal 1")
You hooked up all of the wires at the coil, right?1 (tach signal, from coil negative.)
There's a (should be) black wire, that runs from coil (-), to fusebox D26. This is the tach signal, for the fuel pump relay, and the tach.
Is the wire OK (read: no corrosion or breaks), and hooked up to the coil?
Ah ha! So, when everything was still OEM that's what the 2nd black wire on the coil was....that I'm actuall missing right now!?!?? Yea most of the, what I thought would no longer be needed, wiring was removed to clean things up when I did my swap. Obviously there was a critical wire that should not have been removed.
So basically I need to find D26 pin in my fuse/relay panel via bentley wiring diagrams & run a wire from there to negative coil?
Last edited by microdub98; 05-27-2012 at 08:51 PM.
You absolutely need that wire for the fuel pumps to run. No tach signal = no worky.
This should help, too (remember it - or, bookmark it!)
Fusebox connector layout is at the top of the page.
Finding the necessary pin is easy - the connectors are labelled. 'tis tiny type, yes; but, the numbers are cast into the plug housings.
Um, you sure about that?
I double-checked the wiring diagram in my Bentley, and.... the E connector is "rear lighting harness." (D is one of the two engine bay harness connections.)
E14 is the pump relay output - it feeds both pumps (and, if you still had CIS, also feeds the control pressure regulator, and aux. air valve.)
D26 is (should be) the tach signal input (coil negative) to the relay plate.
In the relay plate, it leads to B19 (dash harness, tach connection for instrument cluster), as well as to fuel pump relay socket, pin 5.
Yup. I hooked D26 to the neg coil & got nada. Looked that diagram over again, found the E14 "plug" on the back of the fuse panel....it had the RD/WHT & RD/Y running in it....hooked it up & got fuel pump. Can't say I got the tach yet though. The carbs & timing still need dialed in a bit so getting it fired yesterday to check the tach didn't happen.
So, that makes me really need to ask:
What did you hook up to the wires at E14? Simply plug it in? (methinks not, seeing as you had previously sucessfully jumpered the pumps into operation....) Or, did you jumper something to there?
That terminal is the pump relay output - Red/Yellow feeds the main pump; Red/White feeds the transfer pump, CPR, and AAR.
If all you did is jumper, say, ignition power to that terminal... you're running without a pump relay at all. Or a fuse on that circuit, either.
I think I might be understanding things a bit better tho. D26 is primarily tach so that needs the negative coil hooked to it. But what about the fuel pump? When I originally hooked D26 up, the fuel pump wasn't coming on when the ignition was switched to "on".
Last edited by microdub98; 05-30-2012 at 10:20 PM.
From the sound of that, you connected ignition power to the T1b connector in front of the fuse box. It being "unused" makes sense in your case - that's where the CPR and AAR got power from. Since you pullled them (and their wiring), the connector is now unused.
As to simply putting a fuse on that line:
That will give you circuit safety (read: short-circuit / overload protection); but, it still doesn't give you operational safety (pump shutdown if engine stops. This feature is for crash safety.)
Let's go back to basics.....
Let's see if the four main circuits really are working properly. And, this is a quick test!
Step 1: verify that your horn relay works (read: horns function?)
Step 2: take horn relay, swap it to the fuel pump relay socket.
Step 3: turn key on. Pumps work yes/no?
Report back with results.
I thought you already did that!
Yeah, get that done. It needs done sooner or later....
And, it's not just for the tach. The pump relay gets engine speed from there, too (and, again, ir needs that to work at all!)
And, it's quite likely. They usually don't give any warning of impending failure - they simply JustStop. (be happy it was at home! )
Want to verify, before you get a pump relay (and, this will check your wiring work, too)?
Have DVOM with a tach function (or, can you borrow one?)
Take the relay back out. Jumper terminals 15 & 87 (pins 4 & 3.) Connect DVOM (in 'tach' mode) to terminal 1 (pin 5.)
Start engine. See speed? Wiring's OK; pump relay isn't. Get a new one.
Not exactly sure if my Fluke has tach capabilities , guess I'll find out. It'll be tough tho right now to check to see if all wiring is legitimate. The car is having firing issues again, prolly bad fuel....have'nt diagnosed the issue yet. I will report back when I have good info.
Eh, could always just do a simple continuity check between the coil, and the relay socket, too.
(nothing says "it works!", though, quite like actually measuring engine speed there.)
Nothing to report, yet......just a question. Since a standard style relay such as the horn relay worked, could I just roll w/ one of them as a replacement? I have $hit loads of them laying around LOL. Or does it have to be specifically a "fuel pump relay" specific piece? Cuz I did notice it has the odd ball tiny 5th pin.
I'm an 8v, four-pin FP Relay kinds guy, so I went searching for more info into what the 5 pin is for... (I had seen them before but couldn't recall what purpose a fifth pin on the relay served.)
Golf II & Jetta II - the 5 pin fuel pump relay??
Fuel Pump Relay (5-pin) Diagnostic NeededThe early CIS models used a rev limiter built into the relay, the extra pin is for the tach feed. You should be able to use a standard relay as long as you don't mind no rev limiter, oh and if your car has an accident the fuel pump won't ever shut off so it may cause a fire (fuel lines cut=engine dead=fp relay switches off).
Testing a 5 pin RelayIt's actually rather simple how it works - it's just a standard 4-pin 'Bosch-type' relay, plus a little logic controller, with an extra pin (which leads to coil terminal 1 (negative) as an input to the logic in it.)
Dats just from some 5 mins of searching but helps fill in the cracks in my knowledge. (Special kudos to the Cuppster btw)The relay works as follows:
IF ground is on pin 31 WHEN power is applied to 15 THEN close for 3 seconds.
IF ground is on pin 31 AND power is applied to 15 AND a square wave is applied to pin 31B THEN close.
The idea is to not pump gasoline all over the ground when you've crashed and your engine isn't running. It requires a signal on the hall sensor. However, if you apply battery to 15 and ground to 31, then apply battery to 31b you should see the relay close then open again.
Of course, since I found all this on the Intewebs, It Must Be True...
Indeed, the interwebz never lies ! Yea, after posting that last post is when my think sponge decided to work. Holy $hit, that's sig worthy BAWHAWHAWHAW. Anyway, the 5th pin is all the above. Most importantly the rev limiter/shut off factor. If what I was reading was correct, the 5th pin shuts the pump down at 6400 rpm's.
Yeah, you pretty much got it.
As to the rev cutoff - that varies from relay to relay.
As the years went on, the cutoff speed increased. And, IIRC, there's a certain Fox relay that has no rev limiter in it...
Nope, wrong one - that would be for a Digi Fox. There, the Digi box controls the pump relay (therefore, no tach signal to the relay.)
It's for certain (I can't find exactly which ones) CIS Foxes. TT sells it for $35:
But, a little more Googling (of Vortex posts) has it that people just use a 5cyl Audi CIS pump relay, too. Since the 5cyl has a redline of ~6,000rpm (and, IIRC, my QSW has a 6200rpm redline) , on a 4cyl that translates (in ignition events) to >7500rpm.
Part# is 321 906 059F
From AutohausAZ, it's on backorder; GAP, though, shows them in stock. $25.
UPDATE ....... got her firing up regularly now. Ordered a new fuel pump relay from NAPA, should be here monday. Now for the latest head scratcher, D26 hooked up as previously suggested KILLS my ignition spark. Disconnect it & spark comes back. Honestly right now the tach working is the least of my problems. I think a compression test may be in order for the motor & my carbs may be in need of a serious freshening up. So....., this thread may sit at idle for the time being till those issues are addressed.
If hooking up D26 kills the car, then that circuit is shorted to either ground or B+.
Only three places it can be:
- relay plate
- dash harness
- instrument cluster (tach, oil warning board, circuit foil.)
Try unplugging the instrument cluster, hooking D26 back up, and rechecking.
Just remembered item #4. Upshift light relay. Pull that, too. Car work?
Last edited by cuppie; 06-09-2012 at 08:06 AM.
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You said that the car runs, unless you connect the coil (-) wire to D26 on the fuse/relay plate. Correct?
If the wire itself is shorted to B- (ground) (or to B+ - either will kill the ignition system), then the car would still fail to run, even with the wire disconnected.
That it fails to run only with that wire connected to the relay plate, says that the short is either in the relay plate itself, or farther 'downstream' than that.
Where found it be? well.... (I did mention these before)
- relay plate
- dash harness
- instrument cluster (tach, oil pressure warning board)
- upshift warning lamp relay
Here's what I would do:
Reconnect wire at D26. Pull the upshift light relay.
Car start yes/no? If no, unplug instrument cluster. Check again. Car start yes/no?