No Fuel, bad relay? but pump can be made to run?

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naki

New Member
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80
Location
nr Tiverton/Exe Valley, Devon
hi guys, this is a 1990 3.9 V8, with no cats/ or Lambdas.
i have been looking into getting the engine started. it was working fine up until a few days ago and gets used once a week or so.
basically turning over fine, but no fuel is getting through.
i found the fuel pump relay under the driver seat, jumped the connector and made the fuel pump run and fuel squirted out, when i had disconnected the pipe in the engine bay.
but the fuel pump will not run, by turning the key. there is 12v present at the fuel pump relay base, but i think it needs a constant live and switched live??? correct me if i am wrong?
i checked and changed the fuel pump 10a fuse but it made no difference.
so now this is where am at. there is no 12v present at the fuse connector base. the reading shows 0.12v

(also, checked the inertia switch is not tripped).

i have looked at the wiring diagram, but i am struggling to work out what other component is not working to give the fuel pump fuse 12v.
basically i am guessing that another relay or sensor needs to send a signal to the fuel pump fuse, but am not sure which one?
any ideas, any common fails. anyone had this before?

strangely i have a similar issues on a jag too, so hopefully i may be able to kill two birds here?

about a year back i had a similar issue on a jag, and it was a poor faulty "heated oxygen sensor relay", tat need to send a signal to the fuel pump relay, but this rangie will not have that.
 
When you turn the ignition on you should hear at least two relays energise - these will be the main EFI relay and the fuel pump relay. If you have ABS you'll also hear the ABS power relay energise (and the ABS pump run if system not up to pressure).

There was a similar thread a while back, I'll see if I can find it.
 
O.K. you need to do a bit of research. Get over to the V8 section then search. If you do a search for "fuel pump relay" you'll get a list of threads that talk about issues involving all sorts of maladies.

You didn't say if you have got a spark. The problem may be your ignition system. Do the search you'll see what I mean.
 
classic kev said:
O.K. you need to do a bit of research. Get over to the V8 section then search. If you do a search for "fuel pump relay" you'll get a list of threads that talk about issues involving all sorts of maladies.

You didn't say if you have got a spark. The problem may be your ignition system. Do the search you'll see what I mean.
Click to expand...

Ok, I hear two relays, but they are in the front footwells, left and right.
The abs pump goes as normal.
I have a good spark from the king lead.
Swapped the two tin relays around under the drivers seat.
Still no joy. They appear to have good very clean connections.
Wiring looks ok.

Will get on to read the V8 section see what I can find.
 
opened the relays to check the points, see if they were furred up, only very slightly. cleaned the contact points.
also bridged the connector made the fuel pump run, but still will not start, even with spark and fuel pump running.
i am starting to think its the ECU somehow
 
naki said:
hi guys, this is a 1990 3.9 V8, with no cats/ or Lambdas.
i have been looking into getting the engine started. it was working fine up until a few days ago and gets used once a week or so.
basically turning over fine, but no fuel is getting through.
i found the fuel pump relay under the driver seat, jumped the connector and made the fuel pump run and fuel squirted out, when i had disconnected the pipe in the engine bay.
but the fuel pump will not run, by turning the key. there is 12v present at the fuel pump relay base, but i think it needs a constant live and switched live??? correct me if i am wrong?
i checked and changed the fuel pump 10a fuse but it made no difference.
so now this is where am at. there is no 12v present at the fuse connector base. the reading shows 0.12v

(also, checked the inertia switch is not tripped).

i have looked at the wiring diagram, but i am struggling to work out what other component is not working to give the fuel pump fuse 12v.
basically i am guessing that another relay or sensor needs to send a signal to the fuel pump fuse, but am not sure which one?
any ideas, any common fails. anyone had this before?

strangely i have a similar issues on a jag too, so hopefully i may be able to kill two birds here?

about a year back i had a similar issue on a jag, and it was a poor faulty "heated oxygen sensor relay", tat need to send a signal to the fuel pump relay, but this rangie will not have that.
Click to expand...

Dodgy ign amplifier will give wrong earth signal to ecu -check the coil voltage and switching with multi meter
 
ImageUploadedByTapatalk1372201600.484743.jpg this is it !
 
early ignition amps were on distributor, there was a **** aluminium lucas block or the amplifier was remote mounted next to coil because of heat issues.
 
The engine ECU takes a signal from the coil through a resistor to let it know the engine is running, if this resistor or wire to/from is bust, the engine ECU will not fire the injectors as it won't know the ignition coil is firing!

Maybe off the mark, but I had similar issues and this was one thing I checked for.....
 
Saint.V8 said:
The engine ECU takes a signal from the coil through a resistor to let it know the engine is running, if this resistor or wire to/from is bust, the engine ECU will not fire the injectors as it won't know the ignition coil is firing!

Maybe off the mark, but I had similar issues and this was one thing I checked for.....
Click to expand...

thats sounds very plausible considering the symptoms. am pretty sure the injectors are not firing. i dont have anyone to help me, so cant crank and listen for the injectors simultaneously at the moment.
where would i find this resistor to test? which wire is it on?
 
any advance on this ? can you make a self cranking control by fitting croc clips to each end of a cable with a momentary push to make switch in the middle , linking the battery to the starter spade , thus being able to crank single handed ?
 
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