Chris33ad

Jumpered the fuel pump relay, instantly the pump kicked in and runs steady continuosly. Is this normal? Does an electric fuel pump run constant while car is running? I have a no start situation and worried about burning out the pump.

Bill Ball

Yes. I only do this short term for testing. You are jumping constant 12V+ from the battery (pin 30) to the relay output (pin 87). Some people make a long jumper with a switch in it. Or you could jump a source of ignition switched power (15) to 87. Regardless, I wouldn't be too worried, as the pump runs constantly while you are driving, so it's not being harmed if run for a while.

Does it start with the relay socket jumpered?

Alan

Yes when the car is running the fuel pump runs constantly - however its not really very safe to run the car this way (on jumper) for any extended period - if you had an accident the fuel pump would continue to run - a 928 fuel pump will flow a huge amount of fuel if a line breaks - you want it to go off with the ignition and if the engine should stop.

This is a test mode only.

Alan

Rich9928p

With a no-start condition check for 12V at the 30 position and go ahead and jumper the LH and EZK relay sockets too. This removes all the control and switch issues from the no-start potential causes. If it starts, pull the jumpers one by one and put in a known good relay. When it doesn't start, you've found the problem circuit.

Rich
'93 GTS Cover girl
'87 S4
'79 rescue
'79 Euro track beast

Chris33ad

Agreed. It is a serious safety issue, only for testing. I'm actually jumping the Fuel Injection relay too. Both temporary...trying to get the car to start and can't believe a brand new relay would be defective but apparently so.

Chris33ad

Rich....that's a great idea! The LH would be the Fuel Injection relay, correct? I don't think my '81 euro has the EZK, does it??????

Rich9928p

I wasn't aware your 928 was an '81 Euro ... I thought it was an S4.

Your 928 has no LH or EZK modules so there are no associated relays. It is a CIS (continuous) injection system that uses K-Jetronic injection, same as from the first 1978 928. The fuel pump relay is turned on by the RPM signal from the TZS spark box.

You need to be sure the circuit from the spark box terminal 16 to central electric panel 07 to the fuel pump relay XVII socket position 31b is good. You also need to be sure that with ignition switch on, there is 12V at fuel pump relay socket position 15.

As long as there is spark and the fuel pump is running, there is no reason for the engine not to start unless there is a problem with the CIS fuel system. That CIS injection has a completely different set of diagnostics.

Rich

John Speake

Do you have a spark ?

Chris33ad

yes I do have spark....