Misfire after switch over.

[57jam89]

Hi, what's good news your busy!
I will check gas pressure before it/as it switches over and report back.

Thanks.

[57jam89]

Hi all, my map pressure is the same when it misfires and when it's running fine. Its around the 20/30 with light throttle/town driving and around 90 on accelerating.

Could it still be injections?

[LPGC]

That's the manifold pressure reading and that would surely increase if it misfired at idle compared to normal idle....
But what are the gas pressure readings?

[57jam89]

Hi Simon, where do i find the gas pressure reads on software?
Map was the only one i could see.

Thanks

[Brian_H]

It should be shown as psys (the value to the right hand side of the map value you gave above if the software looks the same as the screenshot on the first page).

[57jam89]

Hi Simon, managed to get software running and recorded data but couldn't see any difference in vaporiser pressure with/without misfire.
A day later the misfire got worse and misfires all the time.

Thanks

[57jam89]

Update- had the software running again today and one by one switched each injector back to petrol/back to gas and I've got a faulty number 6 injector!

So which injectors did you fit Simon?
Do i reed to drill them out?

Thanks

[LPGC]

Hi Simon, managed to get software running and recorded data but couldn't see any difference in vaporiser pressure with/without misfire.
A day later the misfire got worse and misfires all the time.

Thanks

Hi Simon,

There can sometimes be a difference in Psys when an engine is misfiring because when a misfire occurs it causes the manifold pressure to increase, which in turn causes the reducer to increase gas pressure (since the reducer holds gas pressure relative to manifold pressure)... But that aspect wasn't what I was concerned with, I need to know what Psys is regardless of misfire or no misfire, constant or fluctuating pressure to know whether reducer pressure is high enough to probably prevent injector(s) from opening in certain conditions (especially when cold) - What is Psys?

Update- had the software running again today and one by one switched each injector back to petrol/back to gas and I've got a faulty number 6 injector!

So which injectors did you fit Simon?
Do i reed to drill them out?

Thanks

The injectors are discrete (singular) MagicJet. Been a while since we last spoke about this and I can't see your setup file on this laptop but if I remember correctly last time we discussed this I said it would be a good idea to drill the nozzles out to 3mm and turn reducer pressure down... But then it would need re-calibrating.

You could call me through the day, if I see a missed call I call the number back, haven't had any missed calls from you though?

Cheers, Simon

[57jam89]

Hi Simon, i will look at vaporiser pressure and come back to you.
Yes i drilled out injecters to 3m 2 years ago (maybe 3 years) over Christmas time and when bought it up to you for remapping on the 2nd of January.
Sorry i can't call, i work 11.5 days and no phones are allocated.

Thanks

[57jam89]

Just had a look at recorded data a vaporiser pressure stays around 1.20 ish all the time

[57jam89]

Well I'm confused!
After switching off injecter 6 yesterday and it running fine i thought i would run software and watch vaporiser pressure and when switch off number 6 again but turning turning injecter 6 off make no difference to the misfire! Also tried other injecters and made no difference.
It can't be run on gas with the misfire as it's just too bad.

Thanks.

[Brian_H]

Might be an intermittent fault - sticking injector likely given its worst when cold. Did you ever try injector cleaner? Or swap it for another injector to see if the problem cylinder moves with the injector?

[57jam89]

Might be an intermittent fault - sticking injector likely given its worst when cold. Did you ever try injector cleaner? Or swap it for another injector to see if the problem cylinder moves with the injector?

Hi, it misfires hot and cold engine.
No i haven't changed injecters (no one has stock at the moment).
Also not tried cleaner.
It's now done 91k since since simon fitted the system.

Thanks.

[Brian_H]

Was thinking more swap the injectors you have around to try and isolate it to an injector if possible? Seems fairly sure you have got that far anyway.

[LPGC]

Seems pressure is OK then so it's likely there is a problem with the injector on the misfiring cylinder.

Since the injectors are singular you could just buy one injector but it may be a better idea to buy/fit 6. You could re-use the nozzles you already have. Would be a good idea to check calibration again after changing injectors.

[57jam89]

Seems pressure is OK then so it's likely there is a problem with the injector on the misfiring cylinder.

Since the injectors are singular you could just buy one injector but it may be a better idea to buy/fit 6. You could re-use the nozzles you already have. Would be a good idea to check calibration again after changing injectors.

Hi Simon,
I will replace all 6 injectors and when bring it up to you.

My problem now is where to buy them from as one's got stock! Any ideas?

Thanks

Would a magic jet fx injectors be ok?

[Brian_H]

Are these any good?
https://www.lpgshop.co.uk/magic-jet-fx- ... cng-spare/

They list a very similar one at £14.99 but no stock on those currently

[57jam89]

Are these any good?
https://www.lpgshop.co.uk/magic-jet-fx- ... cng-spare/

They list a very similar one at £14.99 but no stock on those currently

That's the ones i have the 14.99 one, just wondering if i can fit the fx model one as a replacement without messing up the settings.

[LPGC]

Are these any good?
https://www.lpgshop.co.uk/magic-jet-fx- ... cng-spare/

They list a very similar one at £14.99 but no stock on those currently

That's the ones i have the 14.99 one, just wondering if i can fit the fx model one as a replacement without messing up the settings.

No, If it has the full size MJ injectors and you're just replacing one it would need to be a full size MJ injector, can't have 5 full size and 1 FX. You could replace them all with FX but it would definitely need recalibrating then. The full size and smaller FX MJ injectors look very similar but have quite different response at low pulse duration, at low to medium pressures and when warm the FX are a bit more linear at low ginj than the full size injectors but this is reversed at higher pressures and when cold, while for any given nozzle size the full size MJ injector flows around 7% more than the FX at longer pulse durations.

I believe that the rail type and the singular type are both the same injector, just that they have a different gas feed adapter screwed into the side of them. So if you can't get hold of any singular full size MJ's it should be possible to buy a rail (of 3 or 4) MJ's, tap out the 2 expansion pins that secure the feed to the rail (I've used a narrow drill bit of around 1.5mm>2mm as a drift for this), so now you have removed the MJ injector with rail type adapter attached from it's rail, then unscrew the adapter from the new injector, unscrew the long pipetail adapter from your old singular injector and swap the adapters over... So you'd be fitting the pipetail adapter from your old singular MJ to the new MJ.

It may be a good idea to run the 'injectors test' facility built into the software. First save settings ('Menu', 'Save settings'), then go into 'installation' > 'corrections' and click on 'banks'. In the banks pop-up screen click on 'standard'. Then close the 'banks' pop-up screen and go into 'installation' > 'Basic' and change 'delay after valve opening' to 10 seconds. Then go into 'diagnostics' > 'injectors test' and click on 'start'. The software then does a bleed down test on injectors... It opens the gas solenoids and waits the 10 seconds we just set (which will allow time for the reducer filter solenoid to completely bleed up), then closes gas solenoids and begins to pulse an injector, it continues to pulse the injector until gas pressure falls to around 0.4bar and then records a value that is a calculated flow rate for that injector (based on time it takes for pressure to fall to 0.4bar). It repeats this for every injector and this is a rudimental way of comparing the performance of all the individual injectors. At the bottom of the screen the software makes a bar chart showing how each injector's flow compares to other injectors with the calculated flow rate above each bar on the chart (a bar with the number above it will appear on the chart immediately after testing of each individual injector). We know that yours will misfire when it gets to cylinder 6... The misfire will throw off the rest of the results so make a note of the number at the top of each bar on the chart as each bar appears (because those bars are going to look very different when the misfire on cyl 6 causes them all to change, the misfire on cyl6 will change the scale of the chart).

In theory the software allows you to select which injectors to check and if that facility worked properly you would be able to deselect cylinder 6 but the facility to select/deselect which injectors are tested doesn't work properly and causes the results to be be messed up anyway.

The injectors test facility is by no means definitive or 100% accurate and sometimes external factors (such as if the filter solenoid internal volume is quite large) can mess up the results, or one engine bank breathing a bit more air and therefore needing more fuel than the other bank can be reflected in the results as 3 injectors having greater flow rate than the other 3. Since the test is only done at idle the results are only at best relevant to idle, further up the load range the injectors might flow quiet equally. But the injectors test facility is another tool in the box, I always run it after bedding in new injectors but I run other tests and sometimes even disregard results of this test if other factors don't agree with the results of this test.

Run the injectors test a few times and keep notes of all the sets of numbers it produces. The results may be helpful in deciding whether it would be a good idea to change all 6 injectors or just the one. Considering they're not easy to access and it's just as much work to dig into the engine to change 1 as it is to change 6 I would probably change all 6 if they've done a lot of mileage?

[57jam89]

Cheers for info Simon, I've order 2no 3 rail magic jet injecters and do the mod you talked above above. Thanks