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Posted by: brooks944 Dec 24 2014, 12:29 PM

The annoying fuel pump noise isn't coming on when the key is turned on. I tried a couple of times to see if it would start, no luck. The car has a new fuel pump relay. What do I need to check first?

BTW, the FP noise is really nice when the car is running....

Thanks,
Rick

Posted by: Mike Bellis Dec 24 2014, 12:43 PM

You need to check for power at the fuse, relay and at the fuel pump.

Posted by: Steve Snyder Dec 24 2014, 01:13 PM

Assuming that you replaced the relay after the pump stopped working, I agree with Mike, although I would check the actual fuse first, then start with a meter at the pump itself (power reading while jumping across the pump terminals would indicate a failed pump, no voltage read across terminals but read from either pump terminal to ground point would imply pump grounding issue, etc.).

Posted by: poorsche914 Dec 24 2014, 01:39 PM

Rick,

Hot wire the fuel pump to be sure it is working. Then go from there.

steve

Posted by: brooks944 Dec 24 2014, 01:40 PM

Tanks guys. Where is the fuse? The relay was replaced before it stopped working. My car is a 75 1.8 with original FI.

Posted by: dlee6204 Dec 24 2014, 03:14 PM

And that is very helpful information. Original fuel injection for a 1.8l is L-Jet and you Should NOT hear the fuel pump with the key turned on. For L-Jet the fuel pump only runs when cranking or running.

What relay did you replace? The dual relay by the battery?

Posted by: brooks944 Dec 24 2014, 03:38 PM

Thanks, but the pump has run whenever the key has been turned since I got it. Is something wired wrong? Haven't had the car that long so not sure what it's supposed to do.

Is there a separate fuse for the pump or only the relay?

Posted by: colingreene Dec 24 2014, 03:40 PM

before i got carried away id check for voltage at the pump key on and cranking.
Then work my way back rather than hot wire stuff.
That could cause damage...

Posted by: brooks944 Dec 24 2014, 03:40 PM

Yes it was the relay by the battery, sorry didn't answer the question!

Rick

Posted by: dlee6204 Dec 24 2014, 04:14 PM

So did the fuel pump run all the time that the key was turned on? If so it sounds like someone hot wired the fuel pump. This is common for carburator cars but for FI it shows there is an issue with the wiring and/or FI System.

A lot of people hot wire the fuel pump to run directly off the coil. Do you notice any homemade wiring in the engine bay?

The best way though is to trace the wires from the fuel pump and see where they go and compare it to a factory wiring diagram since it sounds like there is some "custom" wiring.

If you could care less about the custom repairs and simply want it to run then you should see if you have 12V+ at the terminals on the fuel pump. That will at least tell you if you have a bad fuel pump.

Posted by: dlee6204 Dec 24 2014, 04:16 PM

Also if you want to do some reading on the correct way the fuel pump gets its power, then this great thread talks in detail about that dual relay you replaced by the battery.

http://www.thesamba.com/vw/forum/viewtopic.php?t=334340

Posted by: brooks944 Dec 24 2014, 05:48 PM

Thanks Doug. I will check that link. Noticed you have a Mars Hill address. I am a '77 graduate from there, but it was a college and not a university in the old days.

Merry Christmas,
Rick

Posted by: Mike Bellis Dec 24 2014, 05:57 PM

Here is the factory relay board with fuel pump relay...

Posted by: brooks944 Dec 25 2014, 09:10 AM

Steve, is there a separate fuse for the fuel pump? If so, where is it located?

Thanks,
Rick

Posted by: dflesburg Dec 25 2014, 09:14 AM

if you wire it backwards it wont run.

Posted by: brooks944 Dec 25 2014, 09:33 AM

I haven't had the pump disconnected so haven't messed with any wiring. Do you know if there is a separate fuse for the pump and where it's located?

Thanks,
Rick

Posted by: dlee6204 Dec 25 2014, 09:40 AM

On the relay board in the engine bay there are two fuses. The rearward one should be a 25A and it is the fuse for the fuel pump.

Posted by: rhodyguy Dec 25 2014, 09:41 AM

what year is your car? has the fuel pump been moved from the stock location? i've never quite understood how the fuel pumps get powered when moved from the rear to the front and utilize the stock circuitry.

Posted by: brooks944 Dec 25 2014, 09:48 AM

My car is a 75 with the 1.8L, so the fuel pump is already in the front trunk. Is there a way to check the fuses on the relay board? Really appreciate the help.

Rick

Posted by: dlee6204 Dec 25 2014, 09:57 AM

You should be able to visually look at the fuse and see if it's blown. I usually twist it back and forth a little bit in case it's making poor contact in its holder.

Posted by: timothy_nd28 Dec 25 2014, 10:21 AM

Relay board is irrelevant, power comes from the dual relay, which comes from the battery. Here's the question, do you want the fuel pump wired and working like the original, or do you want it to be activated with the key on?

Posted by: brooks944 Dec 25 2014, 10:45 AM

I'm just trying to get my car reliable and originality isn't a big deal to me unless that results in the best reliability. My car will never be a concours vehicle.

I pulled all the fuses from the board, there was what looked like corrosion which I cleaned and put them back, still no power to the pump. Is there a way to test the relay, it's probably about a month old!

Thanks,
Rick

Posted by: timothy_nd28 Dec 25 2014, 11:02 AM

Post some pics of what you have. If the pump was wired by the PO to be on with the key, it's hard to speculate what he did or where he tied in to get power for your fuel pump. The relay board has nothing to do with the fuel pump, unless the PO tied into it somehow. For what it is worth, I think the oem wiring setup is the best way to go. Otherwise you are drawing excessive current thru the ignition switch, which wasn't designed for the extra load of the fuel pump.

Posted by: brooks944 Dec 25 2014, 03:25 PM

Thanks to all for the advice, the problem turned out to be bad wires at the pump on the positive side. Easy fix and cheap!

Happy Holidays to all,
Rick