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v8 90 not running

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v8 90 3.5 efi , been stood a while but run up now and again,

to give a bit of back ground been run up a lot recently did about 70 miles yesterday , cut out when ideling but started again 2 mins later.

then did it again after about 20 mins of running , had to wait 10 mins to start then ,

filled it up as thought maybe fuel. got worst until the point it wouldnt start.

fuel tank is newish so ruled out carp in the fuel tank, plugs are dry as a bone ( only a few weeks old.

I had 10 mins today to look. getting nothing out the fuel pump no noise expected it to run a bit with ignition on when cranking.

getting clicks from the relays next to the ecu. took the pipe of the fuel pump nothing, sucked a bit thorugh to prime it , still nothing.

so im thinking its fuel pump/ wiring related . the pump has 2 wires on it are these + as presume its earthed via the tank,

any help will be great as this is a bit of a hybrid ecu behind the seat with 3 relays there , not sure what these do but one was clicking so presume a fuel pump relay.

I can see this beinga long process.

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The pump is self-priming and should run for a couple of seconds after turning on the ignition. No need for cranking to get it running.

The pump wires should be positive (controlled by the ECU via a relay) and earth.

Assuming you have checked and there is no fuel coming through the pipe in the engine bay when you turn on the ignition, then:

Check the pump wiring - that you have an earth on one wire and voltage for a second or two on the other when switching on. Move the wiring around to check for dodgy connections or internally broken or corroded wire.

If the above is ok then check the pump - hot-wire it (make sure you know which is power and which is earth first! If the pump runs but only for a short time then suspect a blocked filter or squashed pipe. When hot-wired, the pump should run continuously with fuel being circulated and returned to the tank - running in this manner will not damage or overheat the pump, in fact as a get-you-home measure it would be pretty effective in the event of pump relay failure, for example.

My personal suspicion, based on my experience, is that it may be sh!tty wiring around the pump. Mine was so badly corroded that it was hanging by a thread and all green and manky. I cut the insulation back trying to find fresh metal but the corrosion went right up the wire! I ended up replacing the last foot with fresh stuff.

Hope this helps :)


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thanks mate, i think your on the money with what you said, nothing out the pump at all.

i think its the earth as nothing on the meter, i will check it again today and do the hot wire.

will let you know

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got the fuel pump running and fuel is reaching to the injector rail and returning to the tank ok.

checked the earths on the back of the head and runa jump lead to them from the batt earth.

Presume what ever opens the injectors isnt. , is there anyway to by pass the air flow sensor . jump it with some wires . presume that will have some control over the injectors. before its ecu route.

will continue with wire checks on the relays etc. but anyone have any further ideas?

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will continue with wire checks on the relays etc. but anyone have any further ideas?

The injectors are controlled by the ECU in two banks but have a common lead which returns via a relay which should be alongside the fuel-pump relay and ECU. Might be worth checking the connections on that?

I think that now you have a working fuel pump (was it always working?) you are into ECU diagnostics, for which there is an excellent guide in the tech archive which I can never find - but it is there. You will have to wade through and find it... Each test is relatively simple - if you take it steady and work your way through you should find the problem :)


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plot thickens. getting only 8v tot he fuel pump feed. appears to be not enough to turn the pump.

going to try by passing the relay and see it that fires it up otherwise i think ecu maybe

The ECU should control the fuel pump relay - as long as the relay is clicking over then the ECU is doing it's job. Next thing to check is the voltage feeding into and out of the FP relay with the pump disconnected - they should be near as dammit battery voltage.

My money is even more on dirty or corroded contacts now... ;)


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you seem to be getting eratic / strange voltages etc at the fuel pump so to determine if the fuel pump is the actual problem.

how about

disconnect the fuel pump wires

then connect 12v (and earth) to the fuel pump using a new wire direct from the battery, so it'll be running

then crank it over :)

i did a similar thing on the p38 earlier this week, it wasn't running on petrol. so plumbed in a new petrol pump from a jerry can and it ran first time ! low and behold, after dropping the fuel tank out i found the discharge line from the pump had come off inside the tank...doh!



P.S. where are you located ?

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