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Sun Apr 15, 2007 2:11 pm

I'm going to replace my tired electric fuel pump with this one http://www.cbperformance.com/catalog.asp?ProductID=577, and also would like to re-wire it so it's not powered off the coil. Can I get some recommendations on the best way to do this (or point to some Samba threads that contain such information)? I've heard of wiring it off the VR, and other's have said to hook it up somewhere else. Do I need the pump to be running as I'm cranking it, or just when it's running? Thanks for your advice!

Sun Apr 15, 2007 3:16 pm

you can use a 4 or 5 prong relay 30-40 amp and make a harness the 321 906 059C jetta relay has 5 pins, 15 to + side of coil. 31 to ground. 87 from battery. 30 to pump. and 31b to the - minus side of the coil. it will only start to pump when you crank the engine. there are other relays like a 4 prong that will work, but at the time i did mine was 16 yr's ago.i'm sure someone else here will chime in..

Sun Apr 15, 2007 3:28 pm

Forgive me for pointing to my own site, but it saves me from writing the same thing over and over again: Pump Power

I had that Carter pump for a while. Mount it underneath for safety.

Sun Apr 15, 2007 3:55 pm

Sweet... are those 40 amp 171 937 503 relays

Sun Apr 15, 2007 4:15 pm

Not sure, I think they may be 30A.
I'd look but it's raining like hell. :D

That pump runs at under 8A if memory serves so you don't need much in a relay for that purpose. When I found mine in a minivan, I spotted a Jaguar XJ with a nice block of 4 relays but it was too tough to remove.

The boneyards are full of lovely relays cheap.

Tue Apr 17, 2007 3:23 pm

Duncwarw wrote: Forgive me for pointing to my own site, but it saves me from writing the same thing over and over again: Pump Power

Just a quick question about this setup... wouldn't this also make the pump run while the key is in the start position, without the motor running, like it would when it's powered off the coil?

Tue Apr 17, 2007 3:40 pm

if you use a vw or audi fuel pump relay it is a bit simpler, only one relay and the pump will only run under cranking or when the engine is running.

the vw part number is 321 906 059 C. i think there are a few other number that interchange with this one. the relay gets a signal from the ignition coil but is not powered from the coil.

the relay looks like this:

http://germansupply.com/xcart/customer/product.php?productid=16928

the circuit diagram for installing this relay is here:

i have a link to a good page on installing it but it seems to be broken.

Thu Apr 16, 2009 1:41 pm

Scott,
I'm posting this question here for everyone's benefit. I just installed the german supply relay in conjunction with my Carter rotary pump. The pump only comes on when I begin cranking the engine, as expected. However, the pump will continue to run when the engine dies. I've tested this by killing the engine by dumping the clutch, and you can clearly hear the pump stay on.

Is this to be expected?

Thu Apr 16, 2009 3:27 pm

Just a follow up. Scott and I discussed this at length on the phone today and there's some speculation that since my bus has a Pertronix in place of the points that it may cause the relay to continue routing power to the pump after the engine stalls.

Are there any electrically-savvy folks out there who can offer advice on this?

Thu Apr 16, 2009 4:58 pm

Perhaps its because the relay is getting its signal from the coil? I'm no expert, but Paul Taylor's excellent diagram has the signal coming from the VR. I believe the VR in turn gets its signal from the alternator. If engine dies, alternator stops spinning, no more signal to VR, no more signal to relay and circuit opens.

Let me know if you need my diagramme...I thought I had it in my library, but it appears not :lol:

EDIT: Here's my version of Paul's excellent wiring diagramme. The colours of the wiring are just what I used. Hope it helps!

]

Thu Apr 16, 2009 5:14 pm

There's this one too.. same thing.

http://www.paultaylorimaging.com/Images/VW/Relays/Pump.jpg

Thu Apr 16, 2009 5:29 pm

Rubber Duck wrote: Perhaps its because the relay is getting its signal from the coil?

That's a nice diagram!

According to Scott, with this relay, it is getting it's signal from the negative side of the coil and should shut off if the engine dies. It doesn't though :x I'm beginning to wish I had just used the two relay set up.

Thu Apr 16, 2009 7:41 pm

i'm sure it's something simple that is making the pump stay running. the rabbit relay works perfectly, we've installed them and many customers have also and never had any issues.

Fri Apr 17, 2009 4:12 pm

Following up, it seems I might have a defective relay. Once the engine dies the relay continues to click loudly and the pump stays running. Actually, it once quit 10 seconds after killing the engine, but I couldn't get it to do it again.

As for german supply, Scott has been super helpful and has agreed to send another relay free of charge. I don't think you could find better customer service from any aircooled parts house.

In the mean time, I'll be controlling the pump with a single relay triggered off of the voltage regulator. With dual carbs there's enough fuel in the float bowls to start the bus without needing a second relay from the starter. That is, of course, as long as I don't run it out of gas!

Fri May 01, 2009 8:02 pm

To close this out, I received the new relay from Scott today. Installed and found it to work flawlessly. Once I simulate an engine dying the pump stays on for about two seconds and then shuts right off. You can hear the relay click a couple times first before it secures power to the pump.

Thanks again to Scott for such great customer service and helping me trouble shoot this issue. I'll send the defective relay back first thing next week.

Sat May 02, 2009 2:08 pm

I prefer to get one of those internal switches that replaces the oil sending unit. They are about 8 bucks and can be mounted with the original sending unit with a T. Then, I can run my fuel pump off the coil and have automatic shut down for disaster or some boob running my bus without oil. Also, I don't know of it matters, yet I get a short delay before fuel pressure untill the oil pressure comes up. Seems like it might be a little easier on start up wear even tho the fuel in the bowls is still doing the starting.

Just a thought, Mark

Thu Feb 17, 2011 7:50 am

germansupplyscott wrote: i'm sure it's something simple that is making the pump stay running. the rabbit relay works perfectly, we've installed them and many customers have also and never had any issues.

Scott or anyone else. I came across this thread and talked my friend into running the single "Rabbit" relay to power his electric fuel pump. He has a '74 bus with dual Kadrons. This set up has worked great except for two small issues. The relay he bought has a blade style fuse integrated into the relay. The relay came with a 15 amp fuse. A couple months ago he was traveling on the highway and the fuse blew. We figured it out and replaced it with another 15 amp fuse. Just last night, he blew his second 15 amp fuse. This time he put a 20 amp in there.

My question is...is this a common occurrence using this style relay, or should he be running a larger rated fuse.

BTW, the relay is powering a German made rotary pump made for carbs.

Thu Feb 17, 2011 8:20 am

Your buddy has some serious issues if a pump is blowing a 15a fuse, is the pump designed for a bypass system and is currently deadheaded by any chance?

Thu Feb 17, 2011 8:24 am

busdaddy wrote: Your buddy has some serious issues if a pump is blowing a 15a fuse, is the pump designed for a bypass system and is currently deadheaded by any chance?

By a bypass system, I assume you are talking about what a late bay FI system runs with a FPR.

Dead heading I assume would be using a pump to push into a regulator that then dumps straight to carbs with no return line.

I honestly don't have the answer to your question. I know he bought the pump at a reputable German/European parts supplier. I believe he was told it was for use with carbs. I specifically told him no facet pumps, and he followed those instructions.

How would one know if a pump is made for by pass or deadheading?

Thu Feb 17, 2011 8:57 am

make sure you make a jumper so if your charging system dies your not stranded