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PostPosted: Mon Sep 09, 2013 6:55 pm 
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I wouldn't expect more than 0.2 bar under load.

Praps you missed the bit about filter and pipework.

We mentioned before about the idle MAP looking high, perhaps due to an air leak.

There should be two or four coil packs on this engine, depending on age. Do you have a boxy plenum or a bunch of bananas on top of the engine?

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PostPosted: Tue Sep 10, 2013 6:51 am 
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rossko wrote:
I wouldn't expect more than 0.2 bar under load.

Praps you missed the bit about filter and pipework.

We mentioned before about the idle MAP looking high, perhaps due to an air leak.

There should be two or four coil packs on this engine, depending on age. Do you have a boxy plenum or a bunch of bananas on top of the engine?


Hi, No I took note of the wet filter and pipework comment and will be checking and locating/changing this weekend when I can get the car inside out of the rain long enough to get underneath to have a good look.

So max of 0.2 bar would maintain over 1 bar at all times?

Its the GEMS engine with one bank of four coils. I replaced the whole bank, (four coils)

Had a quick look (due to the heavy rain) yesterday at the pressure sensor and pipe work. Looked ok, but again when I get it inside at weekend I will remove and inspect them all properly. (Just as a side note, the vacuum pipes come direct from the inlet manifold, not "T-d" off another hose).

Thanks for these point people, will get these jobs done and see how it goes...

Dan


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PostPosted: Tue Sep 10, 2013 9:06 am 
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I don't know where that "1 bar" comes from. Your zeta-S seems to be set up with an idle pressure circa 1.3 bar, that's fine.
I'd normally be looking that it does not droop below 1 bar on drag racing, or overshoot beyond 1.5 on fast overrun. It can only maintain output pressure with an adequate liquid inlet supply.

Afterthought; check the diaphragm and injector seat condition - run on gas then switch to petrol and allow to idle for ten minutes, then check the pressure has remained much the same as it was while idling on gas.

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PostPosted: Tue Sep 10, 2013 12:19 pm 
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rossko wrote:
I don't know where that "1 bar" comes from. Your zeta-S seems to be set up with an idle pressure circa 1.3 bar, that's fine.
I'd normally be looking that it does not droop below 1 bar on drag racing, or overshoot beyond 1.5 on fast overrun. It can only maintain output pressure with an adequate liquid inlet supply.

Afterthought; check the diaphragm and injector seat condition - run on gas then switch to petrol and allow to idle for ten minutes, then check the pressure has remained much the same as it was while idling on gas.


The 1 bar was because its running at 1.3 bar and you suggested that you wouldn't expect more than 0.2 bar drop.

The diaphragm and injector check.... after the ten minutes, do you mean the "press.gas" reading?

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PostPosted: Tue Sep 10, 2013 2:13 pm 
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That's right - it's a check to make sure gas isn't seeping away through a leaky diaphragm or injector.

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PostPosted: Tue Sep 10, 2013 3:29 pm 
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mat_fenwick wrote:
That's right - it's a check to make sure gas isn't seeping away through a leaky diaphragm or injector.


Ok cool, can do that one even if its raining :D

In the photo below, is this the solenoid and filter housing bolted onto the reducer? The solenoid being the blue piece?

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PostPosted: Tue Sep 10, 2013 6:48 pm 
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The blue part is the electrical coil that operates the solenoid innards. The brass lump it attaches to is the Valtek shutoff valve body. The round projection poking downwards from that in your photi is the filter bowl, the filter itself is under a round plate secured with a central bolt.
See "Valtek type 7" here
http://www.tinleytech.co.uk/acatalog/Fi ... ments.html

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PostPosted: Wed Sep 11, 2013 6:56 am 
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rossko wrote:
The blue part is the electrical coil that operates the solenoid innards. The brass lump it attaches to is the Valtek shutoff valve body. The round projection poking downwards from that in your photi is the filter bowl, the filter itself is under a round plate secured with a central bolt.
See "Valtek type 7" here
http://www.tinleytech.co.uk/acatalog/Fi ... ments.html



Hi, thank you. That's what I was hoping :D

Lets see if I cant get new filter ordered to be here for weekend replacement.

I done the ten minute gas pressure test last night ticking over on petrol and the gas pressure held at around 1.35 bar +/- 0.03 bar


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PostPosted: Wed Sep 11, 2013 7:00 am 
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Gilbertd wrote:
dangerousdan8 wrote:
Ok, here are a few photos... Only thing I can see is the lambda sensors are going up and down all over the place??
That's good, they are supposed to. You have the Titania sensors and 5V is a lean mixture with 0V being rich. The sensors will flip flop from one extreme to the other, if they stay at one end then you have a problem. The only thing I notice from that is that the Tinj petrol when idling on petrol is lower than it is when idling on gas. That shows that the mixture on gas is a bit on the weak side and the petrol ECU is increasing the pulse length to get the mixture correct.

As you don't have a problem at idle, then those screenshots don't show much. You need to get an assistant to either drive while you watch the computer or the other way round so you can see what happens when the problem occurs. Does the gas pressure drop? Do the lambdas sit at one end of the scale? Try accelerating while running on petrol and watch what the Tinj petrol shows and then see if it does the same when on gas.


Had a try of this last night, all I could really tell from driving and watching was that the gap between the 2 readings for Tinj petrol was much larger on gas than petrol??

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PostPosted: Wed Sep 11, 2013 5:58 pm 
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Once you get your head around how it works, then you can answer your own questions. The fuelling is controlled by the petrol ECU. It looks at the output from the lambda sensor(s) and adjusts the injector pulse length (the Tinj petrol) to keep the mixture correct. The gas injectors need to be open for slightly longer than the petrol injectors so the gas ECU adds a fiddle factor to the petrol injector pulse length and fires the gas injectors for this amount of time. The fiddle factor is the numbers on the map page that you showed us earlier. So, if the map is spot on, then when running on gas the petrol Tinj will not move at all from when running on petrol because the petrol ECU is not having to make any corrections. However, if the map causes it to run a bit lean, the petrol Tinj will increase to open the injectors for longer. Petrol Tinj plus the fiddle factor equals gas Tinj.

As you appear to have a poorly reducer, the pressure is dropping when you ask it for a bit more gas. That makes it run lean so the petrol ECU increases the petrol Tinj to try and get the mixture back where it should be. That is why you are seeing much more movement when on gas than when on petrol, the GEMS ECU is doing it's best to keep the lambda sensor reporting a correct mixture.

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PostPosted: Wed Sep 11, 2013 11:28 pm 
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Now, what I read he was looking at was the difference between the two reported Tinj-P figures for a vee-banked engine. On a healthy engine they should be similar, on average. Imbalance indicates a problem - air leaks, misfires, valve problems, exhaust leaks/blockages, or fuel supply affecting one engine bank more than the other.

Looking at the stills, it appears that there is an imbalance while running on petrol, which is exaggerated when running gas (par for the course). That would rule out fuel supply chain problems, pointing instead towards air leaks or dare I say ignition. But that makes two clues for air leak now. Or blowing manifold or blocked cat. You have to observe the wandering numbers over a few seconds really, to get the feel of the averages.

This is unconnected to failure to maintain pressure under load, which seems to be the more serious issue. It's not that suprising to find more than one issue when you closely at elderly cars.

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PostPosted: Thu Sep 12, 2013 6:55 am 
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rossko wrote:
Now, what I read he was looking at was the difference between the two reported Tinj-P figures for a vee-banked engine. On a healthy engine they should be similar, on average. Imbalance indicates a problem - air leaks, misfires, valve problems, exhaust leaks/blockages, or fuel supply affecting one engine bank more than the other.

Looking at the stills, it appears that there is an imbalance while running on petrol, which is exaggerated when running gas (par for the course). That would rule out fuel supply chain problems, pointing instead towards air leaks or dare I say ignition. But that makes two clues for air leak now. Or blowing manifold or blocked cat. You have to observe the wandering numbers over a few seconds really, to get the feel of the averages.

This is unconnected to failure to maintain pressure under load, which seems to be the more serious issue. It's not that suprising to find more than one issue when you closely at elderly cars.


Thanks for reply, I know you seem to think this whole problem is ignition, but as I asked previously and you never replied to was what else can I check on the ignition side?
I have replaced plugs, replaced leads (tried 2 sets), and new coil pack (complete bank of 4 coils)....

As for the air leak...are we talking of possible air leak from pipes and fittings or from the manifold, meaning removing inlet manifold and reseating with new gaskets etc?

Thanks for help


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PostPosted: Thu Sep 12, 2013 7:01 am 
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Gilbertd wrote:
Once you get your head around how it works, then you can answer your own questions. The fuelling is controlled by the petrol ECU. It looks at the output from the lambda sensor(s) and adjusts the injector pulse length (the Tinj petrol) to keep the mixture correct. The gas injectors need to be open for slightly longer than the petrol injectors so the gas ECU adds a fiddle factor to the petrol injector pulse length and fires the gas injectors for this amount of time. The fiddle factor is the numbers on the map page that you showed us earlier. So, if the map is spot on, then when running on gas the petrol Tinj will not move at all from when running on petrol because the petrol ECU is not having to make any corrections. However, if the map causes it to run a bit lean, the petrol Tinj will increase to open the injectors for longer. Petrol Tinj plus the fiddle factor equals gas Tinj.

As you appear to have a poorly reducer, the pressure is dropping when you ask it for a bit more gas. That makes it run lean so the petrol ECU increases the petrol Tinj to try and get the mixture back where it should be. That is why you are seeing much more movement when on gas than when on petrol, the GEMS ECU is doing it's best to keep the lambda sensor reporting a correct mixture.


Thanks for reply, this helps get me head round things.
Will change liquid stage filter and go over all the air hoses etc and inspect them see if there is then any improvement.
Im willing to put money on that the liquid filter has never been changed looking at the condition of the housing and how much or a pain its going to be to get to.
Cheers


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PostPosted: Thu Sep 12, 2013 8:08 am 
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It's doubtful you've got a manifold leak, there's enough bolts holding it down and I would have expected a leak there to affect petrol running too. Carefully check all of the pipes and hoses for the gas system and the breathers too, they have a habit of going a bit soft and squashy.

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PostPosted: Thu Sep 12, 2013 8:46 am 
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Gilbertd wrote:
As you appear to have a poorly reducer

I'd just add that (unless I've missed something) it may just be the filter...hopefully at least. It's surprising the number of people (not directed at yourself) who only think the LPG system needs a service when it doesn't work correctly!

From my understanding I'd expect a clogged filter to be OK up to a certain demand, at which point a significant pressure drop is seen. Compared to a tired reducer which would be generally unstable. Not sure which best fits your symptoms but agree that changing the filter should be the first step. Ross also mentioned the possibility of a squashed feed pipe; worth a check too especially if it has been used off road.

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PostPosted: Thu Sep 12, 2013 9:23 am 
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Do make that liquid filter your priority.

My worry about ignition is that a set of brand new chinese or second-hand coils aren't necessarily any better than what came out. Unfortunately GEMS isn't smart enough to log misfires per cyl, for a solid clue.

There's a simple misfire detector, hold a postcard close at the tailpipe ... misses give it a good thwap noticeable over the general buzz. Won't tell you why or which cyl.

Minor air leaks are indeed more likely to be from perished hoses than the manifold itself.

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PostPosted: Thu Sep 12, 2013 9:40 am 
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Thank you guys.

Well my first jobs are the air, breather pipes etc and filter see how that goes.

If it didn't run so perfect/smooth on petrol I could believe it being ignition but I'm not ruling it out and will try anything to get this sorted... I will try your simple card test see if I can notice anything.

Wouldn't any miss fire code show up on diagnostics? I know rossko said "Unfortunately GEMS isn't smart enough to log misfires per cyl, for a solid clue." but wouldn't something show to say it generally was not right?

Again thanks everyone...


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PostPosted: Thu Sep 12, 2013 9:53 am 
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dangerousdan8 wrote:
but wouldn't something show to say it generally was not right?
Afraid not. Cars fitted with the GEMS engine are before EOBD became mandatory so although they have the 16 pin socket and most code readers will connect and talk to them, you don't get all the information. You will only get misfire reports on the later Bosch controlled Thor as that is fully EOBD compliant. I had a big chunk of head gasket missing so no compression, and no firing, on 2 cylinders but no faults were logged. With yours (and mine) what you get is an indication of something not right but even then it often makes no sense. As an example, I've got an iffy lambda sensor on my car and the fault codes it throws up are lambda heater short circuit, lambda heater high resistance and lambda heater open circuit. It could be any 2 out of the three but not all of them unless the wires were flapping about all over the place and doing something silly, which they aren't.

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PostPosted: Sat Sep 21, 2013 8:34 pm 
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As Rossko said, Map figure is high at idle. So are the TinjP times, I expect Bosch P38s to run around 0.4bar Map and 4.0ms at idle. I'm wondering if the car was in drive, they are the sort of figures I'd expect when the car is in drive.

I scanned through this thread so sorry if I missed anything. Is this the Bosch or Gems engine? Is fuel injection type set to full group or sequential? I hope it's sequential due to the figures...

High bank to bank trims seem to be a common thing with Rover V8's, This could maybe be dialled out with the bank trim feature? if the bank trim is high and the same way on petrol, though, I'd be looking at the engine itself. If high bank to bank trims are high only on gas I'd swap the rails over then try equalising the pipe lengths to rails etc. This is unlikely to fix the issues but could give insight into injector problems etc.

I'm sure someone will already have suggested looking at plugs and plug leads.

Simon
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PostPosted: Mon Oct 28, 2013 1:30 pm 
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Taken a while to get round to posting due to one thing or another... anyhow

Changed the liquid filter which made a slight difference but nothing major so I've decided to get me other car on the road on the 1st of November and strip the V8 down and give it a overhaul as don't need to tow anything till the spring now.


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