1985 vw quantum, bad relay or fuel pump?

I have been trying to get my '85 VW Quantum running, after blowing a couple of relays that operate the fuel pump. I put a new relay in place and I now get the humming of the fuel pump for a second or two and then nothing. The car does not start. I tried using a jumper relay (87-30-86-85) and that relay lets power continue to the fuel pump, but the car still does not start.

From this description, can we conclude that the fuel pump is bad?

You get the humming for a second or two when you jump the relay or when you put the new relay in and turn on the ignition? The fuel pump should prime when you key on, but it won't run continuously if the engine is not running. To rule out the fuel pump you should measure the fuel pressure while jumping the fuel pump to run continuously. I am not sure what you mean by a jumper relay? Did you short Pins 30&87 so that you bypass the relay?

Thanks for your reply.

You asked: "You get the humming for a second or two when you jump the relay or when you put the new relay in and turn on the ignition?"  The fuel pump hums for a couple of seconds with the new relay (spades marked 87, 30, 15, 31, and 1), There is current with the key on at spades 30 and 15.

With the jumper relay, the fuel pump keeps humming. The jumper relay is one used for the x contact. It has spades 87, 30. 85. and 86.

There is probably a pressure switch on the fuel line.  When the pressure is low, the pump turns on to get to the desired pressure.  The jumper relay is keeping the pump on full time. 

From the other Quantum thread.... If the KAE relay, the pump is ONLY on when pulses are present present - was it 31b to the ignition coil -ve? But there might be an initial turnon by the internal relay module upon power up.

Look at another reason for it to fail. Your description of the fuel pump sounds about right. Time to borrow the VAG com.

It is expected for the fuel pump to come on for a few seconds (referred to as prime) and then shut down if the engine is not running. You have confirmed this behavior. What about when you crank the engine, does the fuel pump turn back on? If it does the the power circuit feeding your fuel pump should be fine and working as expected. You mentioned it still doesn't start with the fuel pump relay jumped so I would continue on to the next trouble shooting point. Either measure the fuel pressure or check for spark. Is that engine PFI? TBI? I am not familiar at all with it.

awdeclipse wrote: It is expected for the fuel pump to come on for a few seconds (referred to as prime) and then shut down if the engine is not running. You have confirmed this behavior. What about when you crank the engine, does the fuel pump turn back on? >No, with the correct relay in place, it does not. If it does the the power circuit feeding your fuel pump should be fine and working as expected. > Since power is "interrupted" or shut off, what should I look for? Voltage regulator issues? You mentioned it still doesn't start with the fuel pump relay jumped so I would continue on to the next trouble shooting point. Either measure the fuel pressure or check for spark. > Yep, I tried to find spark, but could not see it. A friend is going to double check me on that tomorrow. I did find power on both sides of the coil when the key is in the on position. And there is power to the fuel pump relay slots that would be occupied by spades 30 and 15.  Is that engine PFI? TBI? I am not familiar at all with it.

> It is called Jetronic, as used by BMW, Volvo, Audi, even Ferrari in the 80's :)

The alternator is new to me, taken from a '92 VW Golf. I did miswire it when I installed it about 3 weeks ago: I had connected the blue wire that goes to the alternator light to the body of the alternator instead of to the D+ terminal. I can't remember what symptoms told me something was wrong, but I corrected the error after talking with a Bosch rep. After that the car operated just fine. Then two weeks ago, it just quit.

Thanks for your questions!

oldspark wrote: From the other Quantum thread.... If the KAE relay, the pump is ONLY on when pulses are present present - was it 31b to the ignition coil -ve? But there might be an initial turnon by the internal relay module upon power up.

Hello again! On the new KAE relay, the spade that was marked 31b on the relay that was in the car when it quit is marked 1. That corresponds to the schematic in my Bentley manual, connecting right to a #1 post on the coil. There is continuity between those points..

Here we go with the usual catch-all answer to VAG problems...POS engine management