[Mark1971]

Hopefully someone can help shed some light  on a problem I'm facing with my beloved classic 500.  A couple of weeks ago my bike was juddering on the way to work and I thought it was due to the air filter element being wet due to rain. I changed the air filter for a new one and all seemed good for a short while. A couple of days ago the bike started juddering again, feeling hesitant and stuttering then picking up as normal. Today it got worse and the MIL light illuminated on the way home from work and the bike was lurching then picking up again. I nursed it home and checked the MIL for any code's. If I switch the ignition key to on, the light stays illuminated but if I ground the MIL wire out the light extinguishes after a couple of seconds. It's not flashing at all. Am I missing something? The bikes a 2020 model with 3700 miles on it, I don't feel confident riding the bike again until I get to the bottom of the issue as I'm worried its going to die on the side of a road any time soon. I'm not sure the  dealer will help as I've completed all the servicing myself so it might have voided the warranty even though I've documented everything I've done and kept receipts for everything I've bought.

[Richard230]

Perhaps you have water in your fuel tank.  That would likely result in engine shuddering and juddering. The first thing I would do is to drain your fuel tank and check for water. Then dump the old fuel into your car's gas tank and put fresh fuel in your classic's tank. I bet that will solve your problem and you won't have to visit your dealer so that he can tell you "They all do that, Sir". 

[Haggis]

You have to ground the ecu check wire first, before turning on the ignition.
Any misfire will result in an overly rich mixture which can foul the plug.
A new plug would be my first try.
Also disconnect the side stand switch if you have not already done so, as it can cause the same fault especially in the wet.

[Antipodean Andrew]

You could also check your earth connection and the battery terminal connections.

[Mark1971]

Thanks for the pointers guys. I've just removed the side stand switch and checked the plug. Spark plug looks fine, but I gave it a quick clean up anyway and the side stand switch now lives on the shelf labelled "stuff I don't need, but I'll keep just in case". I did check the small earth wire the other day by disconnecting it at its connector socket and spraying some contact cleaner into plug. It's got heat shrink around the cable at the battery connector end, is it worth removing it and using a ring connector instead. I had previously read about this earth cable issue,  is it just this small bit to the battery that causes the issues?
I had earthed the MIL wire before switching the ignition on which extinguished the MIL light a couple of seconds after ignition on which is the normal start up sequence I think. If I don't connect the MIL wire to anything the light stays illuminated with ignition on, only going off if I start the bike up. The MIL light hasn't flashed any codes at me when it was earthed out but it was illuminated for about 4 miles when I was riding home then it went off briefly then back on again.
I'm going to have some more investigation time over the weekend.

[Richard230]

Did you also drain your fuel tank to make sure that water didn't get into the tank? You said that your air filter was damaged by riding in the rain. Perhaps at the same time water entered your fuel while filling up during the rainy weather.

[axman88]

Rainy weather misfiring always has me suspecting ignition system leakage.  This is a regular thing here in Chicago, where salt is used to melt ice and snow during winter.  An invisibly thin layer of ion bearing salt deposit, on the distributor cap and high tension wires, plus a little moisture to free up the ions, creates a path for high voltage to leak off to ground, or to adjacent spark wires on multi-cylinder machines.

I've experienced misfiring on many rainy or foggy days, and fixed it with five minutes of attention to my wires and distributor cap with a clean damp rag.

[Mark1971]

Fiddled with some stuff this morning then went for a test ride. It seems to take about 10 minutes of riding before the symptoms start. It will pull ok,  but when you let off the throttle that's when the lurching and stuttering happens. It also has the same symptoms at about 30mph on a light throttle. I'm totally stumped now. I don't think it's water in the tank as its taking 10 minutes to start acting up.

[Mark1971]

Finally the MIL light has revealed the error code. 4 long flashes and 1 short = fuel pump circuit. The various stuttering rather than continuous would make me think dodgy wire perhaps? I can only see the wire off the bottom of the fuel pump which has 2 wires in it. Is there a chance a relay could be the Culprit?

[heloego]

Disconnect and clean the contacts in the connectors (male AND female) for the pump.
Re-connect and ride.
Fixed or same problem?
If not fixed check voltage at the relay with ignition ON. If relay is working, the pump is the problem.IIRC my C5 had a Keihin pump. Too damned expensive so I replaced with a Quantum through Amazon. Works good and I expect it to last a long time.
I hope simply cleaning the connectors solves the issue.

[Mark1971]

Fixed it. I cleaned out the connectors as described. I then decided to swap the relays over as the C5 only has the two and they are the same, my thinking was see if the problem stopped. I started the bike and then touched the power relay and the bike died. I removed the relay holders from their mounting bracket and discovered one of the pins wasn't secure in the block on the power relay. I guess it was making contact but vibration was making it lose contact at certain revs. I've pushed it right back in onto the relay and after a 30 mile ride it hasn't missed a beat.
Thank you for all the suggestions, I now know the bike a little better after all the tinkering.
Now I just need to find the post on here regarding what to do to clear the fault code, as the MIL light only extinguishes when you start the bike, rather than after a couple of seconds like it used to.

Thanks again guys
Mark

[Haggis]

1. Ground diagnostic wire (the single wire with a female bullet connector
next to the ECU) to a clean part of the chassis, or to the Negative side of
the battery.
2. Set the kill switch to the run position.
3. Hold the throttle fully open.
4. Turn the key on. MIL light will illuminate for a few seconds.
5. As soon as the MIL light goes out (NOT before), and before the MIL
comes on again, release the throttle.
6. There will be a couple fast blinks after that to let you know the code(s)
are cleared.
Now run the engine. If no Codes are present ride the bike and monitor
the MIL for any further codes. The MIL will illuminate and remain steady
if any further faults appear.

[Mark1971]

Reset procedure did as it should, however the code reappeared. 4 long then 1 short. I'll just ignore it and see what happens.

[Haggis]

If its a real, 4 long and 1 short, the engine will turn over but not start.

[wildbill]

common problen with euro4 bikes and 650 interceptor is- a fair batch of bikes sold in 019/020 were fitted with not what one would call good factory relays. i was stopped in both bikes.
i had such problem in trials model. i bought two relays off hitchcocks uk and solved the drama. had the same issue in the 019 plate interceptor...swapped out those too. bike worked fine
dont buy from a bike shop as you'll get the old relay stock! hitchcocks relays are resin filled with some kind of stuff.
plus you could do this too.
pull out the fuel pump connector and spray it with auto electrical cleaner. also check all 3 sensors either side of the injector. just on side of motor. do a press fit and see if all are all snug and secure. ive been stopped by that alone.
check out the battery too. just because its a 2020 means not much in enfield country. id do a check on it anyway.
your bike would have the new position battery terminals so i can't see battery leads breaking there. not like the old days much better sorted there now.
this shouldnt b an issue but you probably know turn the gas cap to just first click only.
in most cases its the simple things which stop these bikes. ones easily over-looked