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Hey everybody,

I'm providing a description of my fuel pump problems, but you don't have to read the whole story if you don't want to. All I really need to know is where to start looking when troubleshooting the fuel pump wiring on a '71 Variant. It used to work fine giving me that two second buzz each time I turned the key half way, but today it pumped all by itself with no key in the ignition. Now it won't pump at all. Is it bad wiring?


Story Below:

I have been struggling with this car for a while now. I bought it the first weekend in October, and haven't had much time to work on it. In the time I have spent, the car hasn't started yet.

I've concluded that the car was left sitting so long ago because the fuel pump went out, evident by a secondary fuel pump in addition to the stock fuel pump, which a PO placed in the fuel lines that run from the transaxle back. This fuel pump was simply wired up to the coil.

I took apart and cleaned the old FP, and it seemed to work just fine upon reassembly, so I took the secondary one out.

Today, after replacing fuel injector seals, the pump wouldn't work at all.

That's when the man next door drove by on his tractor and inquired about the car I was working in. He said it was a beauty, and if I needed any parts, he had one just like it sitting down in the pasture.

Much to my surprise, he did! Except it was a 412. By the way, if anybody needs 412 gauges, door handles, head light bezels, or a driver side mirror, let me know. Everything else is probably crap. It is really really rusty. It had been sitting in water for a long time. Some parts might be good. Engine components are doubtful. Passenger side glass is still there.

Anyway, he picked the front end up with the tractor and I tore the fuel pump out.

Upon returning home to clean and inspect this newly-acquired very rusty fuel pump, I noticed my own car was making a whining noise. My fuel pump was running... non-stop. Maybe I left the key on. So, I opened the door and turned the key back. It was already off. Strange. So I took the key OUT. The fuel pump kept pumping. I quickly crawled under the car and unplugged the pump. It wasn't hot, and there's gas in the tank so it couldn't have burned up. Thank God for those easily removable wires!

I plugged the pump back in and it ran again without stopping. Then I (stupidly) decided that since the pump was opperational, maybe I would try to start the car and see if those fuel injection seals are the key to starting my enjine.

The engine didn't start, and after about five seconds of trying, I stopped because I realized that if a fuel line burst, my pump would just keep pumping gas all over my engine and I would probably have to crawl under a burning car to unplug that wire again. Bad.

Now the pump doesn't turn on at all when I turn the key. Before this week, everything was normal. I'm thinking it's got bad wiring. Any suggestions?

Ok...so the previous owner had a secondary fuel pump wired up to the coil....bad thing. But...what it shows is that somehow the previous owner also found the main wiring to the pump to be defective.

There are several things to check. First make absolutely sure that all of teh fuel injection system wires are correct to the ECU and that none of thwires have been "hacked" into to go elsewhere.

The next thing...is to make sure that all of the ignition wires at the key unit are correct and unhacked.

The thing this mostly seems to be is a relay that has either been omitted and wired direct, or has been fused due to rust or carbonized contacts. Find the fuel pump relay. Unplug the battery first, disconnect teh relay after checking and marking the wires....use a pair of diaginal cuttrs to remove the little crimps that hold the cover on the relay and pull the lid off. It can be fused, carbonized, full of water...or miswired. Check this and get back to us. Ray

I've pulled some sort of relay loose from under the dash. It's very corroded. I think brake fluid probably dripped down the wires under there and caused this. However, I don't know if this is the correct relay.

It has a 3 prong back, and it's VW part number ZVW225-546.

Horn, flashers, blinkers all worked fine, so I don't think this is a relay for those. Where would a fuel pump relay be found on the car? Pictures below:







This website has fuel pump relays for around $7. The picture provided, if it is the correct picture, looks completely different and has 4 prongs. Anybody want to describe to me what my fuel pump relay should look like?

(the relay for sale: http://replacement.dubautoparts.com/par ... l&dp=false )

RelayS. Now I see from the wiring diagram that there are two.

Yes, one of the pump relays is under the dash (but I believe it should have 4 connections). Is there any numbers on the connections of the relay? What colour were the wires to the relay?


/Lars

On the relay there are no numbers to indicate connections. Despite only having three prongs on the relay, there are four wires that go to its connector, but the plug-in side is very corroded. It could have had 3 or 4 female inlets. Perhaps one prong has corroded off of the relay. In the bundle of wires that go to the connector, one is red, one is light blue, another is red and very large diameter, and another is black and very large diameter. The connector is black and rubbery, and has DOR FLEX printed on the back. The wires that go to this connector are wrapped with electrical tape. I don't know if tape was used in Wolfsburg to put these cars together. This car also has dealer-installed AC, just so you know.

Running a google search of that part number only brings up a couple of matches. I can get a new relay like this one for $10. Also, I found a woman with a posting on the samba who had a beetle with electrical troubles. She had the same relay, but she didn't say what it was for. Eventually, she found that this relay wasn't her problem.

Checked my -70 411, yes the pump relay is situated next under the brake master cylinder at the steering column. It was a Bosh relay with 5 numbered connections. The metal cap looks a bit higher than yours. Wire colors dont match yours. Also all of the wires are thin.

The whole thing is a bit strange since this wiring diagram shows a 3-connector "Fuel injection cable relay"
http://www.type4.org/technology/wiring/ ... large.html

while this diagram
http://www.type4.org/technology/wiring/ ... large.html
shows a 5 connector Pump relay (no 10) which is what I found on my car.

Since a pair of the wires on your relay were thick I would guess it controls something more powerful than the fuel pump, possibly the AC.

/Lars

I think that the previous owner has cut a few wires back into the harness...or perhaps the wires going to that relay are not even the same ones. I would follow them back to the fuse block with a voltmeter to make sure they go to the right place.

The correct relays ae pretty common. This is the same relay that is the main fuel injection power relay. On variants it is mounted on top of the ECU under the armrest. On coupes its the first relay on the left in the engine bay. Type 3's have the same relays also.
This was pretty much a generic relay.

No, vw did not use any electrical tape. I would trace all the wires by the diagram. Ray

Yes, I have a relay directly under my master cylinder. For some reason I ruled that one out as a fuel pump relay because it was so big. I was looking for little square ones. It's hard to tell what things look like from the repair manual diagrams.

The one under the MC seems like it's in working order, but I haven't taken a very good look at it, or taken it apart. Almost anything under a leaky MC is destined to be crap.

I bet that other relay is for AC, because everything (except the fuel pump) worked last week. The engine hasn't been running, so I wouldn't know about the AC.

Ray, I'll check the one by the ECU. Is it identical to the one under my MC?

Yes, it is the same relay. It was pretty much used for power to anything in 68-73 types 3 and 4. Its a pretty basic relay and you should have little problems finding piles of them at most aircooled junkyards...or even in 1970's volvo's, saabs, mercedes etc. They were fuel pump and EFI power relays on many of the ACVW and many other European vehicles.
If you can't find one, look in the fuel injection manual section and you can generally find the diagram of the relay on the fuel injection wiring layout. If you take that to someplace like pep-boys and look at the general wiring and relay area....you can find matching aftermarket relays pretty easily. Ray