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Britain Smith
Well, I had a shitty day and to add to it my car decided that it was a good day to have issues. I was driving to the doctors office for my bum wrist and on a high speed onramp the car started to go slower and die. I coasted up the onramp and stopped right in the path of cars going 60mph. I was able to turn over the motor with it in gear to move it forward and then pushed it back out of the way. A tow truck guy who said he was a 914 guy, ended up pushing me off the highway using his rubber push bumper (I was a bit nervous).

I spent the better half of a hour on the phone with Brad try to determine what the hell happened. The car would turn over and it smelled like gas. It started up a couple of time for a few seconds and died immediately. To make matters worse, I had no tools on me and was in nice clothes. After going through every connection, switching the injectors around, looking for broken wires, checking EVERYTHING, I began to start switching out the relays in the engine bay. When I switched out the second one, the car fired up and ran like nothing happened.

So, my first question...what does the middle relay do on an early car? Also, what is the failure mechanism for relays? Do they die immediately or are they intermitant? Is there anything else I should check? The funny thing is, I just picked up the 1.7 injectors that lmcchesney sent me...thanks man! Unfortunately, I had no tools...that won't happen again.

-Britain
mightyohm
The middle relay is the fuel pump relay. I've never had a relay die, but I have had problems with broken wires in the harness that connects to the relay board. The relay board also has a tendency to get flakey because the rivets inside will oxidize and cause bad connections. The solution is to rebuild the board by stripping off the tar on the backside and soldering all the connections.
ArtechnikA
QUOTE(Britain Smith @ May 20 2004, 10:41 PM)
Also, what is the failure mechanism for relays? Do they die immediately or are they intermitant?

varies all over the map; this makes troubleshooting them so much fun !

a break in the coil wire will kill them instantly. unless there is an internal short or the break is inside the coil somewhere and decides to make contact again depending on the temperature, the size of the last pothole you just ran over, the humidity, the phase of the moon, and how late you are for the meeting you're trying to attend...

crappy contacts where they plug in can help them go intermittent. a common failure mode is that the switch contacts inside the relay (which i know you know is just a remote-control switch, but i'm mentioning it for those just learning...) get dirty from environmental factors, or pitted, from many thousands of little current arcs. those then work 'sometimes'...

or the coil develops high internal resistance just from age, and sometimes pulls the armature in 'almost' far enough. or makes contact and then gets tired and falls out in operation. or the little spring that's supposed to hold the contacts open when not energised gets tired or breaks and then it mostly won't turn off...

(i once chased a CIS-KE problem for two years and it turned out to be a tricko VW special dual relay...)

everything on a 30 year old car is suspect unless you personally have replaced it - electromechanical stuff doubly so ...
lmcchesney
Replace them at $20 each or get one as a diagnostic replacement. Hope the injectors help you.
L. McC
Demick
Britain

30 year old relays die fairly regularly. Every 914 owner should carry a couple extras around in the car. I usually pick up a handfull at the swap meets for $1 each or so. About half of them end up being bad (but that means that the good ones only cost $2 each). Cut open a bad one and you can usually find the problem. Common failure method is that they rust inside.

Demick

P.S. when your car dies like that, the first thing to check is the fuel pump to see if it runs (for a second or so) when you turn on the key. Unless you are in a noisy place, you can hear it turn on and then off when you turn on the key. You can also usually hear the relay click on and off. No relay click means the relay has failed (or something upstream of the relay). If you can hear the relay click but the pump doesn't run, then the problem is either the wiring to the pump or the pump itself. I'm surprised that's not the first thing Brad had you check.
Trekkor
I believe, if you got in a bind, you could snake a relay from either side of the headlight motor assymblies up front under the hood.
Demick
Yep. In addition, the frontmost and rearmost relay sockets on the relay plate are not necessary for driving the car. The rearmost relay is for the heater blower motor, and the frontmost is for the rear window defroster. Most cars do not have the defroster, so that relay plug is a perfect place to keep a spare. So if you get in a bind, either of those relays are handy to swap out with important ones.

Demick
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