BRC Sequent 32 LPG Issues ...

[Probs]

First off, LPGC knows all about this one It's attached to a Subaru Legacy Spec-B JDM (2.0 Turbo)

Ok so for months things have been 'Ok' no worse than usual. However today on gas the car stutters and hesitates like there is some sort of ignition/fuel/boost cut. I am assuming the easlier two as boost cut is pretty brutal and it feels softer when it cuts in. Car is un-drivable unless you slowly increase the revs, if you need to pull out in a hurry you are done.

Non of this occurs running on petrol.

Folks have suggest coil packs or plugs. Which figures, but they are a shocker to get to (2Hr job at least) also they are iridium plugs and only done a year or so ago. Which leaves coil packs, which I have no idea how to test

Checked the diagnostic codes using FreeSSM ... nothing. Creates a dump of this happening using the BRC software. Anyone fancy telling me whats going on?

https://photos.app.goo.gl/MPtw61sj3uBfNqdj8

Uploading a video so you can hear it ...

https://youtu.be/e8SnWV3z8hU

Thanks,

Probs

[Brian_H]

To test coil packs, its either a case of put spark testers on them to compare difference between cylinders - example of the ones i've got > https://www.amazon.co.uk/Laser-2780-Ign ... 003AN1VPW/

Or hope that the obd gives you a sign of which cylinder is the problem and swap for a known good one. Alternatively swap a good one about until you find a difference if they are the type that don't come as a single unit. Given you have no fault codes, the other option you might have (though I'd suspect not on a BRC ecu) is to swap cylinders between fuels to see if you can find one cylinder more problematic than the rest.

I would wonder though, if your having a supply of fuel problem rather than ignition problems - You'd usually get popping from the exhaust under hard acceleration if it was ignition and coil pack related, you don't mention that so I'd suspect you aren't getting that?

If its been getting gradually worse, I'd be suspecting either gummed up injectors (Simon's bound to ask if he doesn't already know, does the car have the BRC lube system fitted with the injectors having the lube going through them?) or a restriction in the supply - debris in the solenoid usually a good place to start on that.

Don't think the BRC system has a pressure sensor fitted (can't see any sign of a value for it on your screenshot) but if it does, any idea what it shows?

[Probs]

Hi Brian,

So no problems at all for quite some time. Nothing has got any worse, it's been pretty consistent for a good few months. ODB isn't telling me much, I did knock off an injector at a time with Injector 2 probably feeling the worst but it would be a guess as OBD tells me nowt.

System has flash lube and is working (I also ran diagnostics on that)

Have a listen to the vid (It's not amazing) but you can hear a little bit of a pop/stutter however it doesn't bang.

Are injectors something you can take to bits yourself

[Brian_H]

Some you can and some you can't (or you can, but they won't work well if at all once you do).

Is it flash lube rather than the brc system (where do the pipes from the flashlube join the manifold - upstream of the injectors or directly into the manifold?)

If you suspect injector 2 to be the problem, swapping the cable and hose between it and a suspected to be ok injector might allow you to narrrow it down to the cylinder or injector, in which case might be worth trying to swap that coil pack?

They do tend to go bad suddenly from what I've found - twice I've been driving along and felt them fail, the most recent one i had seemed to gradually start to fail - noticablely more on Gas when it fully went. I had suspected it to be a calibration issue of some sort and had got Simon to have a look at it, he did suspect it was ignition related, changed plugs and leads expecting that to sort it, which it seemed to for about 100 miles then got much worse to the point of being noticable at idle on gas although petrol was fine. Spark plug testers showed just enough that cylinders 1&4 were occasionally missing a spark (or at least weren't so bright) which pointed to the coil pack in my case.

[Brian_H]

Just listened to the vid (wasn't there on the first post when i started replying) and that doesn't sound like a miss to me, sounds more like a lack of fuel on one cylinder intermittently.

On the injectors question, I won't know but others might if you tell us which injectors your using? (I'd guess BRC ones of some type). The usual clue is if you can find a rebuild kit for them you stand a good chance of being able to do something with them.

[Probs]

Hi Brian, they are BRC 'Yellow' injectors. I lift off a few times in the vid and accelerate slowly so that might be why it sounds like that. Every time I WOT it stutters ...

Another observation just quickly, I ran through the injector diagnostics where I can turn off an injector at a time. I started by turning them all off and turning one on at a time and doing the same run. Each time the car felt like it was stuttering but did get up to speed. Pretty much the same with each injector.

Not sure how valid a 'test' it was (My assumption was the car should run like that but whether it runs well is something else)

Would that be normal behaviour for that sort of test do you think? Should it run like a bit of a dog with only one injector on LPG and the other three on petrol?

[Brian_H]

Nope, if the calibration is right and the components in good order it should be the same as all on gas or all on petrol.

I think you either need to rule out an ignition problem - Can you get to any of the coil packs easily? (I assume this is either a coil pack per plug or pair of plugs rather than a single unit with leads you have?)

[LPGC]

Best clarify a few points... I believe the following is true but please correct me if I'm wrong (could be a different person/car I'm thinking of)...
When Probs has said 'OK / no worse than usual' I don't think he meant usual was great under all driving conditions
There's been a long standing (since new) issue of hesitation/misfire on acceleration when the boost starts to come in
Several BRC installers and BRC's tech support guy have made attempts at sorting the long standing issue. I've also seen the car, I made some changes including positioning spuds lower in the manifold, shortened injector pipes, looked at calibration. I identified that the long standing issue seems at least in part due to the Seq32 not having a runtime map sensor to measure actual runtime manifold pressure in real time, instead of having a runtime manifold pressure it learns manifold pressure at calibration time based on rpm versus pinj versus map whilst a calibration time map sensor is plugged in - but at the onset of boost the learned/assumed map pressure is incorrect (it would never get time to learn how map pressure responds at the onset of boost even if it's rpm versus pinj versus map table has enough resolution), which means delta pressure (the measured gas pressure minus manifold pressure) is incorrect because the assumed manifold pressure is incorrect, which means pressure compensation for ginj is incorrect, which means fuelling is incorrect.

The effects of issues/shortfalls I've mentioned above aren't usually noticeable in normal driving but become apparent if the car is accelerated from low rpm (around 1000) in conditions such as (owners example to me iirc) accelerating between speed bumps in high gear.

Other than that, any new symptoms could be due to plug / coilpacks, wouldn't expect the BRC injectors to be at fault, iirc the lube system isn't the type that pushes lube fluid through LPG injectors and BRC injectors are at least usually reliable.

Some engines / petrol ECU's don't like running on some cylinders on petrol while others are running on gas... or at least not with certain LPG ECU's, and no engine will run as well with some cylinders on petrol some on LPG if LPG calibration isn't close to correct.

[Probs]

Assuming at the moment that LPG wise nothing has changed I've ordered some new iridium plugs one stage colder than normal pre gapped to 0.61mm

I'll.try those first as frankly I've exhausted the basic LPG checks and it all seems fine. Fine being in the context of this system as it was a day or two ago.

LPGC is correct it had some low speed drivability issues but I've sorted most of those now since I got access to the software. Runs better than ever but still not perfect.

However the problems I have now with misfiring are new and not the ones LPGC saw. The new problem is very dramatic where as the others were quite slight ....

Keep you all posted!

[Probs]

So plugs swapped. No difference. Pulls great on petrol no hesitation(In fact pulls a bit better) if be shocked if it was coil packs ....

All plugs looked evenly worn and gaps are as they were when they went in.

It feels like when you ask a lot of has to turn up it just can't deliver it. Like getting an imaginary wall. Anyway of confirming coil failure before swapping?

[LPGC]

There's usually a way of confirming before buying new coil packs... swap positions and see if misfire codes move with coil packs... but no easy way of confirming coil failure before swapping positions.

What did you change in calibration?

[Probs]

Hi Si,

No codes, no errors only a very 'slight' lumpyness on idle. Hard to pin point which bank let alone which cylinder at the mo (If any)

[Probs]

Oh and calibration I change percentage tip-in/out a few months back.

It's not perfect but it's as good as it's going to get I think.

[Brian_H]

Hi Si,

No codes, no errors only a very 'slight' lumpyness on idle. Hard to pin point which bank let alone which cylinder at the mo (If any)

I've found at idle, and hard acceleration is where your most likely to see a coil pack starting to fail when on gas, and i've had 3 that appear fine on petrol, but miss on gas over a few cars . Lumpyness at idle is a fair description from what I've seen as well, probably where its most consistent.

Of course, a bad supply can cause issues as well - I had a short circuit between the wires on the rpm pickup on one of mine a few years ago from a poorly done install, that went all of a sudden as well and wasn't the easiest to locate what was going on at the time, and again it was far more noticable on gas.

[LPGC]

Is it any lumpier specifically during fuel changeover than it was before (we know it's lumpier overal, but in relevant terms)? And, if so, have you moved injector plugs? What I'm getting at is that such symptoms could be due to incorrect input channel / output channel routing.

[Probs]

On gas it does not pull past 3k, stutters like it hits a fuel cut. I've not physically moved anything under the hood as it were. It feels fine on change over.

Also plugs and coil packs changed. Has made no difference whatsoever ....

Any ideas?

[Brian_H]

Can you get to the wiring where the petrol injectors is, and check what colour wires go to each injector, and either match them against which colour or labeled gas injector goes to the same cylinder? (so trace the wires to where the soldered joint is on the cars loom, and follow the same cylinder to see which injector is connected to it, and what wires go to that injector).

That will answer Simon's point above, as you will either be able to compare it to the wiring diagram, or post the info here and then that can be compared to the wiring diagram by someone who has access to it.

[Probs]

I can but talk me through your thinking it sounds like you are going on assumption one of the injectors have been switched over?

[Brian_H]

I would guess Simon's thinking is more along the lines of its always been wrong rather than it suddenly being swapped over? But hopefully he will reply.

[Probs]

Found the issue. BRC P1 MAP T piece broken so small boost leak on petroleum which wasn’t noticeable. Obviously no MAP data. On gas so ... Joy.

I need an LPG install training course or something so I can do this stuff myself in the future