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Old 14th March 2011, 20:55   #1261
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by star_aqua View Post
Yeah it is JUST a fuel pump issue. But how will you detect it in a CRDE vehicle?? it will show in the scanner as rail pressure buildup error or min max deviation error.
But is that not enough for engineer's to figure it out. Am not one

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Now tell me what will be the behaviour of non-crde engine for the same problem?
It would still run, with a sputter or two?

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And do you think both crde and non-crde will behave same for this problem?
Nope

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what will you think when all of a sudden the engine shuts off with MIL ON??
GULP!

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Originally Posted by Sutripta View Post
Hi,
Was the filler cap very difficult to remove? Was there a hiss while removing it?
Oh yeah i get that sometimes in most of my cars, but i thought it was more of environment thingie but somehow ensures vapor lock situation from not building up.

Oh by the way, being BS IV how are they allowing fuel fume vent to atmosphere? Am confused now.
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Old 14th March 2011, 21:11   #1262
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by robinson.s View Post
You are absolutely right. But never expected such issues in the first few thousand Kms.

And to add further, the response from the M&M team was really poor.
Is the breather hole on the Thar's fuel tank incorporated into the cap? For vehicles with larger fuel tanks, you can see the breather pipe, with a flexible plastic tube to let the fuel overflow/vapour out.

In the Thar it could have happened for any number of reasons. I know in 1999, there were quite a few fuel tank collapses for Mahindra Jeeps and it was traced back to a manufacturing issue with the supplier. It may be quite possible that one can get the breather hole plugged with dirt and other stuff during OTRs. Since these vehicles use a fuel pump which I believe is quite powerful, the chances of a collapsed fuel tank is high. And these fuel tanks are not as robust as the cylindrical ones that we see on trucks. Anyway if the fuel tank did not collapse, then the damage would have been borne by some other component - I am not sure which one.

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Originally Posted by svsantosh View Post
I think Biju's point relates to Vikram's headers experience 'Sir - Did you drive around without fuel' - i think what the mech meant was did you bring it to a dry/low fuel condition -

So, does the CrDe engine/fuel system have a known issue when driven with low fuel and air gets sucked in?

Should be a cause for concern because
(1) OTRs cause the vehicle to be at very steep angles and thus cause the vacuum situation.

(2) Even on highways - the owner should be concerned that the last 10odd liters is useless and can cause a air lock.
...
Steep gradients combined with low fuel can lead to air locks. That will not lead to fuel tank being collapsed. But then as Tanveer pointed out, the manual pump and level ground should solve the problem.

So checking that the fuel breather pipe/vent is open for Jeeps/OTR vehciles is a must.

Last edited by pjbiju : 14th March 2011 at 21:16.
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Old 14th March 2011, 21:14   #1263
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Sutripta View Post
Hi,
Was the filler cap very difficult to remove? Was there a hiss while removing it?

Regards
Sutripta
Hi,
Not sure. All i concluded was presupply was ok but not adequate for the full load, the reason for stalling and MIL coming ON. it used to crank immediately with key OFF ON on flat road but required key on for long time and then crank, on slopes. Couldn't spend more time as we had to leave for the OTR and i suggested owner to completely check the fuel tank and low pressure fuel lines. later i came to know today that it was due to breather pipe blocking.

it seems to be an after effect of the last OTR for getting into the slush which made the existing problem more worse.
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Old 14th March 2011, 21:28   #1264
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Jaggu View Post
...
Oh yeah i get that sometimes in most of my cars, but i thought it was more of environment thingie but somehow ensures vapor lock situation from not building up.

Oh by the way, being BS IV how are they allowing fuel fume vent to atmosphere? Am confused now.
In petrols you are not allowed to vent. Carbon cannisters and all. Vapour pressure takes care of internal pressure. However, if you run dry, you might not even be able to remove the fuel filler cap!

Could be wrong, but because HSD is far less volatile, maybe the strict rules regarding venting to atmosphere don't hold. Vapour pressure at ambient would be negligible.

As others have mentioned, there is a difference between running dry, and not being able to draw fuel.

Regards
Sutripta
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Old 14th March 2011, 21:53   #1265
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Sutripta View Post

As others have mentioned, there is a difference between running dry, and not being able to draw fuel.
Little OT , anyone aware of cotton waste syndrome ? , its a garage story I heard at least 3 times by different mechs .

People tie a piece of cloth on the mouth of tank ,specially when a job related to tank rubber hose ( filler ) is in progress . or when the cap is lost & to avoid anything entering , now accidentally the cloth goes in & plugs the fuel out ,

sounds weird but true

this is possible when any piece of packaging plastic ( that comes with a new tank , as wrapping ) gets inside .

I have a habit of thoroughly cleaning the tank with air hose & diesel, & also checking with battery light before fitting on any vehicle .

Sudarshan

Last edited by Sudarshan : 14th March 2011 at 22:04.
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Old 14th March 2011, 22:08   #1266
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Default Re: Mahindra Thar : Test Drive & Review

^^^
Hi,
Not only does it sound logical, it happens!

Also, two of my most difficult (ie took a long time) to diagnose problems were fuel feed related. (XDP, not CRDIs) One was a slight leakage at the fuel filter. Would draw in a bit of air, resulting in erratic running. Other was the pipe from the tank would collapse resulting in lack of power. Would idle perfectly. Was on the verge of sending the FIP for repairs!

Regards
Sutripta
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Old 14th March 2011, 22:14   #1267
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Default Re: Mahindra Thar : Test Drive & Review

^^^ Pipe collapse is a harrassment , the worst thing to diagnose for any ' serious minded ' mech because most of the time we forget to look at the smaller obvious cause . Happened to me .
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Old 14th March 2011, 22:45   #1268
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Sutripta View Post
In petrols you are not allowed to vent. Carbon cannisters and all. Vapour pressure takes care of internal pressure. However, if you run dry, you might not even be able to remove the fuel filler cap!
I assume that excludes motorcycles.
The tank has a lot of fuel and the vent is between our legs.
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Old 15th March 2011, 08:25   #1269
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Default Re: Mahindra Thar : Test Drive & Review

My THAR after the 1st OTR and some basic Mods...
Ownership review, Let the experts speak...
For me Mahindra has given what i was looking for.
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Old 15th March 2011, 10:20   #1270
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Default Re: Mahindra Thar : Test Drive & Review

Congratz Pain in U. Really handsome vehicle, alloys planned? Looking forward to the review and participation in otr's. Once again all the very best.

@Sutripta: Diesels also have this closed system, i can talk from my car experience. It does give out woosh's sometimes, especially when fuel refill happens at less than half mark and in summer time.
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Old 15th March 2011, 11:11   #1271
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Sutripta View Post
In petrols you are not allowed to vent. Carbon cannisters and all. Vapour pressure takes care of internal pressure. However, if you run dry, you might not even be able to remove the fuel filler cap!
Cannot figure that out. As fuel is consumed, the volume it occupied has to be replaced, and that is just air off the atmosphere. That is the role of the vent in the fuel cap. In case the air cannot enter the tank, you will have vacuum building up slowly, which will ultimately collapse the fuel tank, if the pump is powerful enough to keep extracting the fuel.

To prevent venting fuel directly to atmosphere you have to install a sophisticated one way valve, which would let the air in, but prevent fuel vapours escaping. I have yet to see such a valve in our vehicles.
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Old 15th March 2011, 11:24   #1272
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To prevent venting fuel directly to atmosphere you have to install a sophisticated one way valve, which would let the air in, but prevent fuel vapours escaping. I have yet to see such a valve in our vehicles.
This IS

Sir I have serviced ( cleaned/overhauled ) such cap , on my Friends Land Rover Defender 1989 model . it had a very small valve mechanism , that I found dirty & clogged up .

I sorted out issues in fuel supply , so the diesel supply pressure rose by 25 % .

This vehicle had similar ' Under power ' kind of problems ,

Sudarshan
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Old 15th March 2011, 11:53   #1273
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Sudarshan View Post
This IS

Sir I have serviced ( cleaned/overhauled ) such cap , on my Friends Land Rover Defender 1989 model . it had a very small valve mechanism , that I found dirty & clogged up .
Point noted, but such valves are still lacking on the passenger vehicles sold in India. I believe that some earth moving machinery have them, and it is mandatory in underground mining environment (to prevent explosions).

Of all the things vapour lock happened in my Jawa once on a hot 45+ Delhi summer day.

Last edited by Aroy : 15th March 2011 at 11:55.
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Old 15th March 2011, 15:35   #1274
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Default Re: Mahindra Thar : Test Drive & Review

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Originally Posted by Pain_in_U View Post
My THAR after the 1st OTR and some basic Mods...For me Mahindra has given what i was looking for.
Just curious if you got the AC installed? And also if you got some music player installed - if yes where were the speakers installed.

By the way very nice looking jeep

Cheers
Carrot
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Old 15th March 2011, 20:15   #1275
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Default Re: Mahindra Thar : Test Drive & Review

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@Sutripta: Diesels also have this closed system, i can talk from my car experience. It does give out woosh's sometimes, especially when fuel refill happens at less than half mark and in summer time.
so for Thar, as a preventive mechanism, can we say it is safer to fill up when below half way mark?
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