Hello everyone
I have a strange one. So I have a 1998 VP L the previous owner had what he believed was a bad pump and had a mechanic install an external one.
then I got the car. It ran fine fofine couple of days but then started getting stuttering with lack of power. No codes.
So I decided to replace the pump in the tank and bypass the external.
Well I can't get the tank pump to start. The car just turns over. But if I hook up the external it starts right away.
What do I need to check for the tank fuel pump.
Both pumps powered from the same wire in the trunk.
Checked inside tank wired they looked okay no burnt or fraying wires or connectors.
thanks.

 

Is the Fuel pump relay working in the trunk fusebox? Does it have both voltages and does ecu control it?

 

So I will try jumping the relay but I did exchange a couple of relays around to see if this would help but it did not.
also I was thinking if I'm getting power to the external fuel pump from the same spliced power wire that should power the pump inside the tank then it would be working.

 

So the external pump turns on when ecm turns it on and it is connected to the wires what takes the electricity to the in tank pump. How about in tank fuel pump earth lead ?

 

There is a fuse for the power that passes through the fuel pump relay and a 2nd fuse that controls the relay by way of a ground provided by the engine ECU

this 2nd fuse is shared by other systems in the car one being the OBD 2 port that someone found bent pins in shorting out the fuse



In my case on the inline 6 X300 a connector was bad on the way to the engine ECU

In the engine starting sequence the fuel pump will only run for 3 seconds then off by a safety deign

When the engine ECU sees engine rotation by the crankshaft position sensor the pump will come back on for the duration of your drive

There have been problems ith the CKPS enable where the single signal the CKPS provides is good enough for your tach and ignition timing but not good enough to be seen for fuel pump enable and gives no CEL code of P0335

There is a inertia / crash switch that can be reset or jumpered that trips for no reason and this shuts off the fuel pump by design until reset

 

Thanks for the helpe everyone but if I can get power to the external from the same power lead as the internal pump would that suggest that the relays are okay. The car start up immediately on the external. I think I saw a red connector or something like one attached at the bottom of the tank close to where the pump sits . Am I just imaging it.

 

If you put a meter on the # 5 power out socket of the # 1 fuel pump relay to the unknown connector

The # 3 socket is hot at all times

If you had the supercharged engine, you have 2 fuel pump motors in the same location above the fuel tank flange each with their own 2 wire connector

The # 2 connector has a seperate # 2 fuel pump relay controlled by coming on at 4000 RPM by the ECU / CKPS

the # 1 fuel pump is the Brown / Blue wire

the # 2 is the Blue / Red wire

 

I have encountered high resistance and open circuits from the lid on top of the tank. I’ve also forgotten to plug in the electrical connector on the underside of that lid. The wiring harness from the underside of the lid going to the fuel pump can also be open circuit. Some replacement fuel pumps require a different connector to be added and where it’s spliced into the old harness can be a poor connection. These are just some ideas to think about. If you have an ohm meter, you can unplug the electrical connector on top of the tank and probe the 2 pins for the fuel pump and see if you have continuity before you go any further.

 

There was a little black box noise suppressor on the wiring harness to the fuel pumps on some X308s

Sorry to say but some new fuel pumps are bad off the shelf

And the check valve in the pump can be bad off the shelf which is a different issue , where you able to hear your new in tank pump run ?

The original in tank pump as it failed can burn the sockets in the fuel pump connector along with the power contacts inside the original fuel pump relay so it is recommended to at least change the relay on pump replacement and observe the connector on the pump

This would limit the current to properly run your new pump even though you may see a full 12 volts on the pump connector

When I received M' Lady Penelope from the previous owner with a bad connector running up to the ECU they had wired the pump to a different relay that worked ( auxiliary / trailer ) and this was on a X300 which has a different relay box