Relay / Rev blip / cut out

[SMerK]

Have an issue.  1400 Supersport on standard Rover ECU.  When running the relay situated underneath the ECU clicks and the revs fall from 1000 to 800 then up to 1600.  Occurs frequently with normal revs inbetween.  After a few clicks the rev change cause cut out.

Have done the following step by step.  Each time the issue reoccurred. so tried the next step.

- Swapped relay for new one

- Replaced original relay

- Swapped ECU for my spare (same Rover type for 1400 SS).

- New Battery Neutral Earth Lead.  Old ones ends not looking good.

- Lambda sensor loose in exhaust.  Tightened up.

- Lambda sensor connector not seated in full.  push together.

- All spark plus removed & checked.

Checked all other sensors / connectors looked OK (even if not sure what all do!)

Still going it! .   Any Ideas welcomed.  Thanks.

 

 

[Jonathan Kay]

Please let me know if you'd like a wiring diagram and the relay layout.

Jonathan

[revilla]

There are only two or three relays in the MFRU that are used, and one of them is for the starter motor so that should not be doing anything during idling.

One is the ECU main relay. That controls the whole electrical supply to most of the engine loom. If that dropped out the engine would stop immediately as no injectors or ignition. That is, if your car even has the main relay wired in - many cars don't and the supply is permanently live.

So that leaves the fuel pump relay. If that is dropping out intermittently, you'll lose fuel pressure, the mixture will go lean, the revs will probably drop off badly, the ECU will fight it first with ignition timing and then kick the IACV open, which will probably see the revs surge temporarily. Eventually if you touch the throttle you'll let in more air but no more fuel will be delivered so it will lean cut.

Does that sound like what's happening?

If so you need to prove that's what happening then we can work out why.

Can you rig up a 12V bulb between one of the terminals of the inertia cutoff switch (either one) and a decent earth? The inertia switch should remain connected, but alternatively you can unplug it, bridge the two terminals in the connector with a bit of wire and wire one to a bulb.

If you can, the bulb will light when the fuel pump is powered. See if the bulb goes out when the engine acts oddly.

Alternatively you can slip a fine needle alongside the rubber wire seal on the correct terminal on the MFRU (I'll look it up for you later, but it's easy to identify, it's the Yellow/Green wire on the larger connector) until it contacts the terminal and wire that either to a bulb or just a voltmeter (a bulb is just easier to monitor).

If that shows the fuel pump supply dropping out, then we can look at the signal from the ECU to the relay, the relay coil earth etc.

Let me know what you find!

[SMerK]

Thank you.  will do.

 

[SMerK]

Thanks Revilla

his kind of sound like it but often when I touched throttle it recovered.  Only some timed cutting out.

I will look into & let you know.....

 

[revilla]

I'm having a bit of difficulty keeping up with this thread. This time I don't think it's down to my age, the forum is playing up for me: See https://www.lotus7.club/forum/forum-bug-new-updated-replies-not-showing

 

If I don't respond and appear to be ignoring posts I might just have missed them so feel free to drop me a PM!

[SMerK]

Update.  The problem is fixed.

Turned out to be HT lead routed across the wiring loom where the gearbox sensor connector branch off.  Sensor removed, cleaned and the cable shielding and tape improved.  HT re routed away from loom. Issue resolved.  Apparently the subtle sensor signals are disrupted by the HT "field".

Thanks for the support.

[Jonathan Kay]

Thanks for posting the solution.

Jonathan