No power to Fuel Cut Relay

Starting issues with a Gen5 VFR.

Symptoms: Key on, no fault lights, power to everything except fuel pump. No normal fuel pump priming noise. Engine cranks over but no signs of starting.

Fault testing: Charged battery 12.9V. Earth points all cleaned and dielectric greased. Continuity of all wiring to Fuel cut relay, ECM, BAS, ESR good - zero to very low resistance on all. FCR, ESR relays checked - functioning as normal. If I jump the FCR to power the relay - fuel pump runs continuously - i.e. does not shut off after fuel prime. When fuel pump is running I get a few pops of ignition, but not enough to start the engine.
Just tested point A5 of ECM. I have continuity from A5 to FCR (brown/black). Key off - zero voltage from A5 to earth. Key on - zero voltage from A5 to earth.

Can anyone confirm that with ignition ON that there should be (I am assuming) 12V supplied from ECM A5 to FCR? Or am I missing something between fuel pressure regulator/ECM/ESR/ECM??

If there is no signal under Ignition On to A5 - is this indicating a fried ECM?

Help always appreciated.

 

our man GRUM is the nearest to an electrickal wizard we have here.

r u sure the battery is fully up to snuff at least 12.6 v ?

 

Yeah, tried sending a couple of PMs to him directly. Either out of contact at the moment or is ignoring me.

 

The brown/black wire should reach to earth through the ECM if it is trying to power the pump, so assume you'll get 3 seconds continuitiy to earth at the brown/black at the FCR when the ignition is first powered on. The black/white at the FCR should show 12v when the ignition is on and the ESR is energised.

 

Definitely. 12.9V which for an AGM should be fully charged

Diagram above sure helps the logic - thinking the way thru. And a few more tests to be done.

"From the diagram - the next part of the control must be feed back from the fuel pressure regulator. I am guessing that on initial startup the low fuel pressure allows the ECM to make the contact across the FCR coil. And then when fuel pressure gets up to specified it interrupts that connection - and fuel pump stops."
NOPE! That was my initial thinking - but the fuel pressure regulator is purely mechanical.
So...FCR energises on Ign ON for 3 seconds to allow priming. Then switches off - until engine starts - then is energised constantly (or intermittantly??) while engine is running to maintain fuel supply.

I am determined to get my head around the logics of how this works!

 

Hi again Kiwi.
The Fuel Pump "logic" is simple.
- The ECM receives no feedback from the FPR.
- At switch on the ECM is supplying the Ground (Brown/Black wire) to energise the FCR and runs the Fuel Pump for 2 to 3 secs. then removes the Ground.
- As soon as the ECM receives crankshaft rotation pulses (even during start cranking) the Ground is again enabled to energise the FCR permanently running the pump while crank pulses are recieved.

If you measure 12v on the Black/White wire of the FCR at Switch On, then you Don't have a problem with the ESR, BAS or Kill Switch,

Make sure the electrical connector is clean and making good contact to the FP connector. Sounds like you might have an ECM Ground issue. Make sure all ECM Grounds have good continuity back to the battery Negative. Have a close inspection of the Orange Ground block located above the chain guard, this is a high failure rate item and is the cause of many issue including Fuel Pump ops.
Let's know how you get on.
AND if you decide to do the FCR bypass to run the pump for testing, Make Sure you get the connections correct otherwise you can Destroy your ECM. Place 12v on the ECM Brown/Black wire and your ECM is Killed!

 

Ahh sorry Kiwi, not recieved any PM's regards Fuel Pump issues!

 

When probing A5 the Brown/Black (FCR control Ground) place your meter Black lead on this wire and Red lead to Battery Positive you should measure 12v. At switch On the 12v should remain for 2 to 3 secs then disappear. Once cranking the 12v should reappear,

If the FCR is energizing for the 2 to 3 secs at switch On then there is no need to do the above check!

 

I had the same issue... turned out to be a bad connection on the ESR... only found it by moving the plugs by hand with the ignition on. As i moved the plug the pump primed... as i looked on the back of the plug one of the wires had parted company with the connector so check that area... just because there is no power on top doesnt mean its not getting to it underneath so check at the back of the plug. If you suspect your relay may be faulty there are 2 near the headlights you can use that fit.