Talk Morgan

M3W Help wanted!

Posted By: Taffmog

M3W Help wanted! - 31/05/22 11:43 PM

Took the mistress out the weekend, 2013, 1700 miles with all upgrades, runs for 1/4 mile then cuts out, no warning, no coughing or spluttering, refuses to start for an hour or so then fires and process repeated 1/4 mile down the road. Turns over ok but refuses to fire. Idling and revving in garage it shows charge at 14.3 volts so I think the rectifier is ok. I don't suspect the fuel pump as cut out is instant, Factory suspect ECU and offered me a replacement to try. I do have a problem in that if I do a test drive and having to tow it home again I can't get it up my sloping drive into the garage 😫. Occasionally there's a smell of petrol when attempting to start ( an hour is a long time at the side of the road!) but plugs were dry and looked good. Last time it ran under load it did sound a bit rough, not exactly a misfire though, idling and revving it garage appears ok. Any thoughts Gents?
Posted By: truckin-on

Re: M3W Help wanted! - 01/06/22 01:27 AM

When it dies, and you go to try to re-start it, do you hear the fuel pump run for a few seconds when you turn the ignition on? I believe it always fires the pump, even if the lines are already pressurized. If you don't hear that - when it doesn't start - it's the pump. Would be my suspicion rather than the ECU.
Posted By: P964

Re: M3W Help wanted! - 01/06/22 03:18 AM

Faulty connection of the kill switch? Have been threads on this so suggest a quick search
Posted By: Chris99

Re: M3W Help wanted! - 01/06/22 07:18 AM

I'd suspect the fuel pump, particularly if the plugs are dry.

It will cut out suddenly if it loses fuel pressure and can restart after a while so that all fits. Check for 58psi at the Schrader valve near the injectors or, just replace with a Walbro anyway as this is a worthwhile upgrade.

The ECU is far less likely as there have been very few reported failures.
Posted By: LightSpeed

Re: M3W Help wanted! - 01/06/22 01:42 PM

My vote is for the fuel pump. Mine did that sort of activity before it died completely.
Posted By: Rog G

Re: M3W Help wanted! - 01/06/22 04:18 PM

Fuel pump. There was a M3W on our Cornish trip in March, the engine just stopped with no prior warning it would turn over with a slight hint that it was trying to fire but wouldn't , we changed the fuel pump at the side of the road and it started straight away. I believe it has done over 1000 miles since without a hint of any other issue.
Posted By: Jonathan G

Re: M3W Help wanted! - 01/06/22 04:40 PM

Fuel pump - I had the same problem!
Posted By: nippymog

Re: M3W Help wanted! - 01/06/22 06:35 PM

Something I have never done, and would only do with extreme caution ...
To prove its a fuel problem , how about taking the plugs out and squirting a small amount of fuel in each cylinder , put the plugs back and try it.
If it fires , it fuel.
Does this sound reasonable? and issues doing this ?
Posted By: MichaelS

Re: M3W Help wanted! - 01/06/22 08:40 PM

Ditto on likely fuel pump. As mentioned, when you turn on the key, if you don't hear the hum, that's it. Beware of false positives. If it does start, let it idle. If the pump is bad, it will die again soon enough. Sometimes it takes a few cycles to die completely. Mine failed at 2500 miles in my '17.
Posted By: Barrythebrave

Re: M3W Help wanted! - 02/06/22 07:39 AM

I had an intermittent issue like this, got myself a Fuel Injection Gauge Pressure Tester Test Kit from Ebay. Took the guess work out of it. Cost was around £25 at the time
Was the fuel pump BTW
Fuel Gauge
Posted By: Bunny

Re: M3W Help wanted! - 02/06/22 08:54 AM

This link takes you to FUEL PUMP REPLACEMENT GUIDE. It's a straight-forward DIY job but remember that there may be slight differences in the hardware used depending on what MMC had available at the time of manufacture.
Posted By: Taffmog

Re: M3W Help wanted! - 28/06/22 09:16 PM

Hi guys, thanks for all your input, done nothing as yet other than the purchase of a Walpro pump and also a US Pro fuel pump pressure testing kit off eBay, an absolute bargain at less than £25. The Factory are adamant that it is the Crank position sensor but have none in stock. My idea was to drive the car until it stopped then change the sensor at the side of the road as opposed to having to change the fuel pump. The sensor looks suspiciously like a Harley one, Anyone know? Thanks in advance.......
Posted By: Stevo666

Re: M3W Help wanted! - 29/06/22 05:44 AM

"The sensor looks suspiciously like a Harley one, Anyone know?"

The Harley sensors are shorter so will not fit....its a bespoke S&S part....

If it was a sudden engine cut then I would also agree to faulty crank sensor (which will also give symptoms of a faulty fuel pump) but change the fuel pump regardless as it is worthwhile doing so.
Posted By: britmog

Re: M3W Help wanted! - 29/06/22 02:02 PM

Originally Posted by Stevo666
If it was a sudden engine cut then I would also agree to faulty crank sensor (which will also give symptoms of a faulty fuel pump) but change the fuel pump regardless as it is worthwhile doing so.


I agree change the fuel pump or you will regret not doing so.
Posted By: Taffmog

Re: M3W Help wanted! - 29/06/22 11:35 PM

Thanks for that Stevo666
Posted By: MOR404

Re: M3W Help wanted! - 02/07/22 06:32 PM

I had the same problem on and after replacing many parts it turned out to be the Crank Position Sensor. It is a different engine to yours but when I went to the agent of the engine to order the part he asked me for Euros200 but I bought the same part by the same manufacturer for euros40. Very often these sensors are used on different cars so it might be worth checking that. If I am not mistaken I think there is a thread with a list of parts on Talkmorgan where you can find the same replacement part and the car it is used on. I spent a lot of time and money to fix the fault but at least I now know my trike much better. Phase sensor faults could be intermittent and could prove very dangerous on the road
Posted By: IMHO

Re: M3W Help wanted! - 02/07/22 10:04 PM

Originally Posted by Taffmog
Hi guys, thanks for all your input, done nothing as yet other than the purchase of a Walpro pump and also a US Pro fuel pump pressure testing kit off eBay, an absolute bargain at less than £25. The Factory are adamant that it is the Crank position sensor but have none in stock. My idea was to drive the car until it stopped then change the sensor at the side of the road as opposed to having to change the fuel pump. The sensor looks suspiciously like a Harley one, Anyone know? Thanks in advance.......


I have the same pressure testing kit, mine didn’t come with the right size Schraeder adaptor, did you manage to locate one?
Posted By: Black Adder

Re: M3W Help wanted! - 03/07/22 02:31 PM

Originally Posted by MOR404
I had the same problem on and after replacing many parts it turned out to be the Crank Position Sensor. It is a different engine to yours but when I went to the agent of the engine to order the part he asked me for Euros200 but I bought the same part by the same manufacturer for euros40. Very often these sensors are used on different cars so it might be worth checking that. If I am not mistaken I think there is a thread with a list of parts on Talkmorgan where you can find the same replacement part and the car it is used on. I spent a lot of time and money to fix the fault but at least I now know my trike much better. Phase sensor faults could be intermittent and could prove very dangerous on the road


If anyone has a source or a compatible alternative part for an X-Wedge Crank Position sensor then please let me know, as I have need of one.
Posted By: MOR404

Re: M3W Help wanted! - 04/07/22 05:47 AM

Probably it’s the same one used by Harley Davidson. If you go on eBay I am sure you will find the required part
Posted By: Bunny

Re: M3W Help wanted! - 04/07/22 10:03 AM

Originally Posted by MOR404
Probably it’s the same one used by Harley Davidson. If you go on eBay I am sure you will find the required part
I would love to be proved wrong but I think in this case the CPS is unique to the X-Wedge. The Harley ones unfortunately won't fit because they are around 10mm too short. I'll start a new thread to see if we can track down an alternative.
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