4200 - Vapour canister purge valve

TimR

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Might seem like a stupid question but I want to know what it is & where ....
Anyone know the part number at all...?

Cheers
 

Gp79

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Behind the ABS module, mounted on a rubber mount on bulk head.

I’ll see if I can find number but it’s on ES
 

TimR

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It’s not what they’re calling a “washing valve” is it...?
Not sure which of the fiche drawings depicts it tbh...! :sad:
 

Gp79

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Why are you looking to replace?
I fit a new one to mine even though it was fine to avoid future problems after hearing if one failing and causing running issues.
 

TimR

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Why are you looking to replace?
I fit a new one to mine even though it was fine to avoid future problems after hearing if one failing and causing running issues.
I have a so called "hot start'issue. Actually, it is very erratic having, thus far, not occurred after refueling, as is typical of the purge valve failure, apparently. The only thing I can say is the start issue never occurs when the car is stone cold ( not ambient cold but running temp cold, if that makes sense?)
Anyway...a new coolant temp sensor didnt fix it despite giving poor readings...Next up the crank/speed sensor but Im also thinking bung a purge valve in as they're cheap enough..( I would have expected to smell a flooded engine that failed to start but ?) I think it runs a little lumpy at times too....
If that dont get it, I'll have to think about Lambdas I guess, After 15 years, a wideband sensor is likely fairly used up but Im no expert. Im sure they can be tested but whether the software allows for it Im not certain....

Thanks for the info !
 

Zep

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The lambda sensors are checked by the ECU, they have a cycle time. The mixture cycles from slightly rich to slightly lean on opposing cycles and the response time from the sensor should be around 1 cycle per second. If the cycle time extends to more than 1.5 seconds then you get a check engine light I have been told. On my GS I was told that the cycle time was in the 1.2 second range and so decided to change the sensor before the CEL point and it did make a difference to the idle quality and the throttle response.
 

Oneball

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When you say hot start issue, I assume you mean difficult to start when hot?

If so it won’t be lambda sensors. When you start a car the sensors are in open loop for a period of time and the ECU takes no feed back from them. They won’t make it hard to start.

If you’ve got an code reader a lot of them give live data and you’ll be able to see how they don’t cycle at start up and then do as Zep says after a while.

Does the 4200 have more than one temp sensor? A lot of cars have two sensors one for the ECU and one for the gauge.
 

Zep

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Agree with Oneball, lumpiness / roughness could be lambdas, if the long term fuel trim is high due to the lambdas it might be overfueling on start up. If not you might well be on to something with the purge valve. Has the canister itself been renewed? If it is saturated then this would lead to an excess of fuel vapour on start up, giving hard starting, but, as you say, this would exhibit more often than not when you refuel. You could also look at the condition of the spark plugs.
 

Gp79

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I also suffered the hot start issue, only once, the ambient temp was cold but engine hot / warm.
Stinking of fuel from exhaust when turning engine over and radiator fan running at high speed with just ignition on.
After this problem I replaced the temp sensor and thermostat and not had issue again.... yet

O2 sensors had already been done only 6 months prior and fan control resistor replaced also.
 

TimR

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Looking at an SD2 printout...looks like the cycle times are marginally over the sec interval ( 1.008 & 1.01 No units given however. ( If thats correct, its impressive after 12years and 60Kmiles ) Maserati say change them every 4 years I believe..
Trying to find some more info on how to interpret printout data but looks like I have to pay up the Maserati TechInfo subscription...
Unless there is anything online which would offer insight to the uninitiated..?
 

Oneball

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The rule of thumb is cycle time of less than a second. You also need the max and min voltage to see what the mixture is actually doing. Have you got a trace? It should go from ~0.1v to ~0.9v and in the space of a second cross the midway point 3 times, ie one cycle.

Remember that the lambda sensors are just that, a sensor, so issues with mixture and cycle time may indicate faults other than the lambda sensors.
 

TimR

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What I have is a static snapshot I believe...
I should stress the technician @ McGrath Maserati tells me he sees nothing to indicate the lambdas are not functioning properly..( I wasnt present)
Voltages stated as fr 1.45 rr 0.75 followed by o2 sensor values given ( bank RH under 1 )
it goes on the give values for o2 sensors again throughout ( @ 1 or marginally below)
Perhaps I havent understood what was meant by "snapshot"....?

Temp sensor ( therees only one...and so it tells the dash and the ECU) was changed because invalid signal ( 3000 miles ago) and says the same thing again ( invalid signal - so there's that !!)
 

doodlebug

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A few years ago I had exactly the same intermittent problem over a period of a couple of years. The car would occasionally not start when the engine was hot and the radiator fan would be on full speed when starting the car even if it was Pearl Harbor outside.

The temperature sensor was changed (twice) but the hot-start problem reappeared after a couple of months each time. A few months later the temperature gauge stopped reading normal engine temperature, staying down the bottom quarter of the gauge. I suspected a faulty thermostat which was replaced but the gauge still didn't read engine temperature correctly. Eventually the cause was traced to a faulty gauge control unit, which is located under the top of the dash.
 

Oneball

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I’d except a snapshot to be the sensor values at a specific point in time. An example from my old v8 BMW is below.

Left column is bank 1, right is bank 2

Lambda Sensor is pre cat and is the one that should cycle between 0.1v and 0.9v if it’s fixed at 0.45v it’s in open loop and no adjustments are being made.

Post cat is the lambda after the cat this should be constant if the cats are working properly

The others are fuel trims which is the ECU adjusting the mixture.

55482

As I’ve said before if it’s a starting issue it definitely won’t be lambda sensor related. They dont do anything during start up.
 

TimR

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929
Nope ..but poor/rough running in low load scenario ( eg 30mph, 4th gear, town pootling) if it were corroborated by rich trim values ( i thought indicated by report at PPI stage a year ago) ...you might want to look at lambda function..?
Lambdas seem fine however...Fans have raced only once ( febuary heat wave and car at full operating temp) and I think it sensible to get more time in the seat before concluding that the engine is under performing...

Crank sensor changed.( It was pushed out of its natural resting place by corrosion. was a pig to remove and this was distorting the gap between the sensor and the marker..so we had reason to hope it might help...) Purge valve replaced. We certainly havent made it worse or broken the bank...
Id suspect something coolant temp sensor related having learned that the error is stored, again, following a new sensor last year. Cabin gauge is plausible and always functions...

Could also be less of an issue than an irritation...?
It has never failed to start ( did I just say that out loud..? That was silly !!!)

:rolleyes::D
 

TimR

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A few years ago I had exactly the same intermittent problem over a period of a couple of years. The car would occasionally not start when the engine was hot and the radiator fan would be on full speed when starting the car even if it was Pearl Harbor outside.

The temperature sensor was changed (twice) but the hot-start problem reappeared after a couple of months each time. A few months later the temperature gauge stopped reading normal engine temperature, staying down the bottom quarter of the gauge. I suspected a faulty thermostat which was replaced but the gauge still didn't read engine temperature correctly. Eventually the cause was traced to a faulty gauge control unit, which is located under the top of the dash.
Are you saying the gauge control unit failure was responsible for the starting issue..?
Does the sensor tell the gauge, only then the ECU? That seems unlikely somehow...
 

doodlebug

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Are you saying the gauge control unit failure was responsible for the starting issue..?
Does the sensor tell the gauge, only then the ECU? That seems unlikely somehow...
This is from memory of what was recounted to me by Roberto Grimaldi at Grimaldi's so I can't vouch for it's accuracy.

The signal from the engine temperature sensor goes to the Gauge Controller, either directly or communicated via CAN from the main ECU. The Gauge Controller was not driving the temperature gauge correctly. The radiator fan was getting a signal (either from the ECU or the gauge controller, can't remember) to turn the fan on full, even if the engine was cold and it was freezing outside. It is probably a safety thing in case of a dodgy temperature sensor.

The ECU relies on getting an accurate engine temperature and if it is reading cold when it is in fact warm the car will be over-fueled, which was exactly the symptom I was experiencing. On warm starts there was a very strong smell of petrol.

I had this intermittent warm-start fault for about 2 to 3 years. The car is a daily driver and it would happen 2 or 3 times a month. Bill McGrath tried to fix it, Grimaldi's and Lancaster's each tried twice and none were successful. I decided to put up with it and plan journeys minimising the chance of a restart being required.

After a while, the fault to the temperature gauge appeared, so I got Roberto to have another look. He originally thought it was the thermostat, so he changed it but the gauge still didn't register the engine temperature properly. That's when he substituted the gauge controller and the car has been fine ever since.
 

Oneball

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1,261
A simple code reader should be able to tell you what engine temp the ECU is being told it’s running at as the obd2 port gets its data from the ECU.