Porsche Repair: 911sc wont start, fuel pump relay, trickle charge

Question
Dear Dave:
Thanks for your help.  I tested the  relay and heard the click;  I also used the jumper in the socket and heard the fuel pump whine.  

What should I check next?  I don't know if I mentioned earlier, but I had to charge the battery (I used a trickle charge) for a few days before it would turn the engine over.  Do you think that has any significance?

Thanks again
Rob
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Followup To

Question -
You answered someone's else's post that described my problem exactly(car won't start but will turn over with starter fluid, the car sat unused for several months)
you advised: "
You can test the relay and check to see if the pump is running at that location.  So...find the relay and verify it has terminal numbers 30, 85, 86, 87, and/or 87a.  If those numbers are there you can "jumper" the 30 and 87 relay "sockets"....."

I want to try this but don't understand how you jumper the sockets?

I read somewhere to replace the horn relay with the fuel pump relay and if the horn works, then the relay is ok, does that make sense?



Answer -
Hi Rob,

We seem to be having a rash of not starts lately.  

Let me explain what I was referring to regarding the "jumper" idea.

Additionally, there are three things to say about your questions:

1)  About the horn relay...it's true that 99% of the relays people find on their cars are "standardized"...meaning the "prongs" in certain locations are always associated with certain numbers.  These should be perfectly interchangeable.  That 1% is actually a BIG 1% because it includes fuel pump relays.  For Porsches and Mercedes, they are typically "not standard".  This is the reason they are so expen$$$ive.  You might be able to put the fuel pump relay in another slot, but I'd doubt it.

2)  So how do you test the relay?  Here's what you do.  Get two pieces of scrap wire and remove about 1/2 inch of the insulation of each.  So you have two wires with four exposed ends (let's say each wire is 24-36" long, but the length can be adjusted depending on the location of the battery).  This is because the next step is to take the wires and the fuel pump relay over to the battery and find a comfortable working space.  Perhaps a flat tray to hold things might be helpful.  First, attach one end of wire One to the negative terminal side of the battery (the grounded terminal).  Attach the other end of wire One to the 85 spade on the relay (if you have four hands you can just hold the wire against the spade).  Attach one end of wire Two to the positive battery terminal (12v+)...but before you do check the other end and make such it is not touching anything.  When ready, take that loose (and not touching anything) wire and brush it lightly against the 86 spade.  When the connection is made, you should hear an audible "click" inside the relay.  If you hear the click, the relay is fine.  Silence is bad.  Repeat the test til you are comfortable with the procedure and the results are confirmed.

3.  Take one of your "jumper wires" over to the relay's original location and find the 30 and 87 "sockets."  When I say sockets I mean the "hole" into which the relay spades (or prongs)  fit.  You can see the spades can only be inserted when the relay is pointing one way.  Your jumper wire should be inserted into the 30 socket while the other end should not be touching anything.  When ready, brush the other end of your jumper wire onto socket 87...at that point you should hear the fuel pump start running.  If you do not hear it, make the connection for a bit longer time...a couple seconds.  If you still can't hear it try the same procedure at the 87a socket.  (the reason there could be an 87 and an 87a is that many fuel pump relays ALSO provide power to another large component...often an A/C compressor).  Here again...if you hear the pump running, it's fine and the relay is suspect...that's because your jumper wire effectively did the job the relay is supposed to do.

Good luck and let me know how it goes.

Dave

Answer
Hi again,

If you have fuel, then the next thing to check is for spark.  First...measure the voltage at the coil's two side terminals with the ignition on.  There sould be battry voltage at each terminal.

To check for spark at the plugs, remove one and reattach it's wire.  Hold the plug on it's ceramic body with insulated pliers and put the working end very near a good ground...a chassis part, for example.  Have an assistant crank the starter just a few turns at most and watch the spark plug send an electric arc to your ground.  The little flash should be strong and brilliant.  If so, you'll next be checking for adequate fuel pressure.

Dave

P.S.  My Allexperts account will show me as on vacation soon...but I don't want you stranded...so e-mail me at daves356@yahoo.com.