M43 Fuel pump / relay woes

[Tom_B]

Hi All,

This might be a familiar story, but here goes:

After a couple of years in storage our 1.9 now won't start:- it cranks and has spark (runs on easystart) but has no pressure at the fuel rail. Prior to be dry stored it ran and drove fine.
This isn't too much of a surprise as the fuel pump evidently isn't running, and so far I've found the following:

- The 5 fuses in the ECU box all get 12v with ign on (I think this meant the DME powers up ok)
- Fuse 18 in main underbonnet box has permanent 12v
- Fuse 13 gets 12v with ign on ( I think/guess/hope this means that the EWS is seeing the key and the DME is happy?)

The fuel pump relay does not click when ignition is switched on, but pin 30 has 12v and pin 86 has 12v with ign on. However, pin 85 (I think should be a DME switched earth) has 0v with ign off, but goes to +4.25v once ign on. I assume this is why the relay does not attempt to energise, but I'm at a total loss to understand why this positive voltage appears

(In addition, I'm fairly sure I also have a failed fuel pump as well - if I connect a jumper between pins 30 & 87 on the relay base you can't hear the pump run and there's no pressure at the rail).

Any thoughts or tips very much appreciated!!

Tom

 

[colb]

Similar situation to you on a Z3M, fuses and relays checked out, ran on easystart so attention turned to the pump in the tank. Sure enough the pump had died. Car had been in store for a prolonged period. New pump fitted and that resolved the issue.

 

[Tom_B]

Thank you for the reply - very encouraging!
I'll replace the fuel pump and see what happens. The part that makes me uneasy is the 4v on the relay switched earth, which I really don't understand but perhaps is something complicated to do with the way the DME controls the earthing..

 

[Nodzed]

Similar situation to you on a Z3M, fuses and relays checked out, ran on easystart so attention turned to the pump in the tank. Sure enough the pump had died. Car had been in store for a prolonged period. New pump fitted and that resolved the issue.

The Zed in question was mine, Colin and me chased this for ages, my advice get the pump out and check / change it, its a simple removal just remove the drivers seat first it will save a lot of agro

Edit: And drain the tank of fuel

 

[Tom_B]

Thank you guys, I'll get on with replacing the pump and try to stop over-thinking the relay coil voltage!

 

[Stevo7682]

Do you get voltage at the pump in prime and crank situations.
Stephen.

 

[Tom_B]

That's a good question - I've not yet had the carpet up to access the top of the tank.
Fingers crossed it's got power though - I imagine replacing the pump is a lot easier than finding a break somewhere in the supply?

 

[Stevo7682]

Move drivers seat forward.
Behind seat you will see carpet partially cut then cut the remaing bits to make the 3/4 circle fold open behind it you will see a plate remove it pump behind it .
Stephen.

 

[Stevo7682]

Lower 2 pins are pump live and earth

Left earth
Live right

2 upper wires are level sender unit .

Stephen.

 

[Tom_B]

Perfect, thank you!
Will keep you posted on progress

 

[Tom_B]

After a very long delay I've finally had a chance to make a bit of progress - but quite possibly several steps backwards...
Having followed the really useful advise above I bought a new pump and set about stripping the old one. Before pulling the old pump out I've disconnected the electrical plug and stuck it on the new pump, sat inside the car.
Now when I key-on I can hear the new pump run - BUT it only runs for about half a second, whereas I'd expect at least a couple of seconds to prime the system?
I've swapped out the pump relay and replaced fuse 18 as a precaution but this has made no difference.
Feeling pretty close to defeated now...

 

[colb]

Y understanding is that when installed in the tank and connected up it will turn on and prime when ignition turned on. It will only prime for a short period. When you turn to start the pump will be energised and pump fuel. Near in mind since the fuel line has been disconnected they will nne dry. Best cycle the key a good few times to prime and fill the line then turn to start and see if the car fires and runs. Did this on an M car successfuly.

 

[Stevo7682]

Does the pump run on crank

Stephen.

 

[Tom_B]

Hi Stephen - good question: guess it ought to run continuously when the crank sensor sees rotation.
I've not tried this yet!
Tom

 

[Stevo7682]

It will only prime a second or so on ignition turn on depending on system pressure.
But should start to run on engine crank ( but possibly only if pressure drops)
If runs on crank but no start various other checks still to do as could be a block somewhere amongst other things.
Stephen

 

[Stevo7682]

Wouldn't do any harm to replace the fuel filter under the floor.
Stephen

 

[Duncodin]

Hi All,

This might be a familiar story, but here goes:

After a couple of years in storage our 1.9 now won't start:- it cranks and has spark (runs on easystart) but has no pressure at the fuel rail. Prior to be dry stored it ran and drove fine.
This isn't too much of a surprise as the fuel pump evidently isn't running, and so far I've found the following:

- The 5 fuses in the ECU box all get 12v with ign on (I think this meant the DME powers up ok)
- Fuse 18 in main underbonnet box has permanent 12v
- Fuse 13 gets 12v with ign on ( I think/guess/hope this means that the EWS is seeing the key and the DME is happy?)

The fuel pump relay does not click when ignition is switched on, but pin 30 has 12v and pin 86 has 12v with ign on. However, pin 85 (I think should be a DME switched earth) has 0v with ign off, but goes to +4.25v once ign on. I assume this is why the relay does not attempt to energise, but I'm at a total loss to understand why this positive voltage appears

(In addition, I'm fairly sure I also have a failed fuel pump as well - if I connect a jumper between pins 30 & 87 on the relay base you can't hear the pump run and there's no pressure at the rail).

Any thoughts or tips very much appreciated!!

Tom

With the relay removed and you're measuring pin 85 that isn't directly tied to the chassis 0v. It goes through electrical thingy-m-bobs and, because it's not connected to the relay, it's kinda floating.

To test the pump. Remove the relay and bridge pins 30 to 87. With ignition on the pump should run continuously. I use that method to empty my tank when doing stuff with pumps etc.

 

[Tom_B]

Thanks Stephen - you were absolutely right!
With the pump out of the tank it did run continuously while cranking, so I went ahead and installed properly, and then tried repeatedly keying on & off to get some fuel pressure.
After 15 cycles I then got decent pressure at the Schraeder valve - so I'm feeling optimistic that it'll now start.
Just need to get rid of all the old petrol I took out of the tank & refill first...