Hi everyone!

I was going to move the S-Type to the bigger garage and replace the brake hoses but for the first time in 20 years it didn't start (excluding dead batteries, of course). There seems to be fuel in the tank. Adding more fuel resulted in the gauge reading to rise but only when I turned the engine on the starter motor for a short while. The level gauge is on the opposite side of the saddle tank to the filler, right?

I got 2 codes:
U1262 SCP J1850 - Communication Bus Fault
P1641 - Fuel pump primary circuit failure

I'm guessing the real problem is related to the fuel pumps. Maybe the right-hand pump module is working (level rise registered by the float on the LHS) but the transfer pump responsible for the fuel line pressure is not working? The pump fuse was blown but replacing it did not solve the problem. I swapped the relay for another one of the same type but that didn't help either.

Looking at the workshop manual, I believe I need to remove the rear seat and take a few measurements. I also need to relieve the fuel line pressure before taking anything else apart - how is that done? Or, if the pump is really dead, is there no pressure? Do I need special tools for this and disconnecting the pipe connectors?

Are the pumps the same on both sides?

Am I on the right track?

Am I missing something obvious?

Many thanks in advance ...

 

do you have a schrader valve on the rail?

 

May well have no pressure (but can check via OBD).

There are posts about changing pump(s), with pics I think.

 

Yes there is a small-diameter schrader valve and checking for pressure with the OBD reader is a good idea.

I have run through some of the pinpoint checks and looking at the resistance of the pump, 120 or so ohms, I'm expecting that this is the fault. I have to check the connection to the rear control module still but I haven't found it yet ...

EDIT: Got the resistance wrong. It is open so is really pointing to the pump. Pump on order, so we will see next week if I have struck lucky :>)

Also, the iCarSoft diagnostics box says that the rail pressure is around 100 and the tank pressure is around 1040. I guess that is in mBar so there shouldn't be any positive pressure in the line.

 

Update
I eventually solved this after making a wrong assumption sending me on a wild goose chase.

It was the pump and replacing it solved the problem. However, when I swapped out the pump a small non-return valve dropped out of the casing. The original pump doesn't have a ball-bearing type NRV on the outlet but the new one does. Without checking, I wrongly assumed that the lose NRV was not required with the new pump. However, without it, pressure doesn't build up in the fuel line. Repositioning the NRV, the car fired up after a few priming loops.

So when replacing a fuel pump, make sure that the NRV remains in place! If it falls out put it back into the vent recess above the pump outlet, round-hole side up.