Radio interference suppression relay '93 940

Eric Kropp · Post by **Eric Kropp** » 15 Sep 2010, 23:27

Hi, I was reading an old posting (August 28, 2010) about a radio frequency suppression relay. I am struggling to find it on our '93 940 non turbo. I found one relay up by the coolant fill tank. According to the wiring diagram, this should not be it as it does not have a gray, black, red and blue/yellow wire. So according the reply made on the August 28 post, this should be the cooling fan relay. I have been searching hi and low and can't find another relay. Any Ideas?

Eric

Post by **billofdurham** » 16 Sep 2010, 11:46

Usually the radio suppression and coolant fan relays are next to each other but that, apparently, isn't set in stone.

The attached shows the location of the radio suppression relay. My wiring diagram shows it as having blue/yellow; black; green/red and red wires to it.

940 Radio suppression relay.pdf: (293.9 KiB) Downloaded 1803 times

Bill.

Eric Kropp · Post by **Eric Kropp** » 16 Sep 2010, 16:15

Well....armed with that, then I might be looking at it by the coolant tank as there was all those colored wires on the pig-tail. The diagram that I saw for this car did not show the green/red wire combo, but the relay I changed definitely had that combo. I would say the wire colors are not set in stone!!!!

Eric

Post by **billofdurham** » 17 Sep 2010, 11:39

I have found many differences in wiring colours when looking at more than one diagram for the same part. It's probably a ploy to keep us on our toes.

Bill.

Eric Kropp · Post by **Eric Kropp** » 20 Sep 2010, 14:53

OK, this has taken a long time but....I have positively identified the Radio Frequency Suppression( RFS) Relay. It is the one by the coolant tank on the passenger side of the engine compartment. The cooling fan relay is behine the left head light on the passenger side of the engine compartment. The relay for the cooling fan is not the same one as the RFS relay. This explains why I could not find two of the same relay...'cause they are not the same. So I have eliminated that from reasons it won't start. Here is what I know and what I've done.
1. Fuel pressure is good to the fuel rail when it won't start
2. Replaced crank position sensor
3. Replaced coil
4. Replaced ignition amplifer modual
5 Replaced radio frequency suppression relay

One day when it was throwing a starting fit, one of my sons buddies un hooked the air intake down stream from the mass air sensor and sprayed some starting fluid in the hose and it fired right up. Must be either week spark or week fuel supply out of the injectors. 40 psig in the fuel rail though.a

Any Ideas?

Post by **billofdurham** » 21 Sep 2010, 11:56

You have replaced some of the ignition parts but have you checked the spark?

To check for a spark remove one of the plugs and put it back onto the end of the plug lead. Hold the plug lead with insulated pliers and find a spot on the engine that is a good and easily accessible earthing (grounding point). Any exposed metal, including the engine itself, will do. Now touch the threaded portion of the spark plug to the earthing point. Have somebody crank the engine with the key, and look for a bright blue spark to jump across the spark plug gap. If you see a nice, bright spark (clearly visible in daylight) you have the required spark.

To test the injectors you need an ohmmeter and the attached:

240 injector test..pdf: (96.79 KiB) Downloaded 420 times

Bill.

Eric Kropp · Post by **Eric Kropp** » 21 Sep 2010, 13:15

On and off I have had spark from the coil wire to the valve cover. Have not checked it at the plug yet

Post by **billofdurham** » 21 Sep 2010, 15:28

You have replaced the coil so should get a good spark from the coil wire. However, you need to check the spark from the distributor to the plugs. Have you had the distributor cap off to check for cracks/tracking and how long is it since you checked/changed the rotor arm?

Bill.

Eric Kropp · Post by **Eric Kropp** » 22 Sep 2010, 21:17

I have to admit, I have not had the distributor cap off because it looks like it would really suck to remove...back against the fire wall and all...guess that is next

Eric

Post by **billofdurham** » 24 Sep 2010, 11:42

The distributor cap isn't too bad to get off.

The screws are captive so you shouldn't drop any.

Using a cranked screwdriver helps.

Bill.