Fuel relay

green944 · 01-12-2003, 07:11 PM

Anyone know where/how I would check to see if this is working? Is this a common problem?

Dantilla · 01-12-2003, 07:52 PM

If the car starts, it's working.

If the car doesn't start, try a new one. It's about $30. If that's not the problem, keep it in the glove box for a spare.

Relatively common.

green944 · 01-12-2003, 07:55 PM

Thanks. Any other ideas why the fuel pump might not be working? It is only a few months old. Is there anything else that could cause this?

951carter · 01-12-2003, 11:03 PM

Check the fuse.

Make sure that the gas is not too old.

I once burnt up 3 pumps before I wisened up and drained the fuel =(

coupe · 01-13-2003, 05:14 AM

You can look at the electric diagram on the side of the relay. There are 2 coils and two sets of contacts.
You can use a 12v DC power supply to drive one coil at a time and use a multi-meter to check for a closed/open contact.

You can always run 2 leads to your battery for power supply to the coil of the relay, for this check.

Do one coil one contact at a time., I had a simular fault with my relay, and i noticed that although the coil was enegizing, the contact wan't closing. I looked carefully at the solder joints and found 2 dry solder joints, I re-soldered and away it went.

green944 · 01-13-2003, 08:04 AM

Awesome, thanks guys. Found out it was the relay. In the Haynes Manual, it says which connections to complete it bypass the relay. Did that and the pump fired right up. Going to replace today.

SoCal Driver · SoCal Driver's Garage

Not so fast!

The DME relay is a two stage device. The first coil/contacts are closed with just turning on the key. These provide current to the DME brain and to the injectors. You should be able to find battery current at the connectors to the injectors. This will tell you that the first part of the coil is working. Note: The first contact has to be closed to provide current to the fuel pump contacts -- read further.

To run the fuel pump -- closing the second stage coil/contacts -- three things are required:

First: The first set of contacts must close (see first paragraph).

Second during the cranking the current to the starter also goes to the DME brain and then to the DME relay to run the fuel pump to charge the fuel system.

Finally when the engine fires and the starter is disengaged, the speed sensor on the engine tells the DME brain to keep the fuel pump running.

So check the coil and the injectors for battery voltage with the key on. The coil gets it's juice directly from the key while the injectors get current after the first set of contacts close.

With current on both of these devices crank the car with someone listening under the right rear wheel for the fuel pump to run. If it is running with the car cranking then the DME relay works and your non starting problem lies else where (that's another post).

PS: Most of the time it is the DME relay and it is advised that you do keep a working spare in your car. I do.

coupe · 01-13-2003, 08:52 AM

Hey SoCal, I have a question for you.. I can hear a sound coming from the rear of my car, when I sit at the drivers seat.I don't think that it was there a month a go. It sounds like an anoying bass note. Could this be my fuel pump on the way out?

Any ideas?

SoCal Driver · SoCal Driver's Garage

Besides the fuel pump there is a filter screen that goes into the tank and the one way valve at the outlet of the pump.

You could have a clogged filter screen causing the pump to strain. You could also have a plugged filter forcing the pump to strain.

I would get a pump and filter then run the tank almost empty, drain the tank and remove the screen filter. Clean it and start putting all the new stuff back on. I've had a fuel pump failure. It's not fun in traffic and miles from the tools in my garage.