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mercedes ml 320 1998
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5 Posts
Discussion Starter #1
:newbie::newbie:Hi Everyone
great forum you have here very useful :thumbsup:
i am need of your help
i have a 1998 ML320 71k lpg converted which i use for pulling my jetski
it has now developed a problem with the power running on petrol
and is misfiring as i have got the codes up for this
i have all the receipts for every part bought for this car from new
and in 2009 it had the fuel filter upgrade in august this year it had another new fuel filter and a MAF so i am pretty sure these are not causing the problem
also when the revs do go up they don't seem to go over 4500rpm its like there is a rev limiter on there
when putting it in drive it crawls along at about 2mph
but when switching to lpg there is is nothing wrong at all and runs lovely on lpg
but switch back to petrol and the problems start again and then engine stalls
i am thinking maybe this is a fuel pump problem it has been like this for ages now but not as bad as it has been the last few days but we are having cold weather -15 so this might be also contributing to the problem
i am used to driving v8's with a lot more power but even so i would of thought the 320 engine would have more than what i am getting
diesel vans are pulling ahead of me :banghead:

if it is the fuel pump that needs replacing
does any one have removel instructions i can use
thanks steve :newbie:
 

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ML320 2002
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1,600 Posts
Welcome to the forum. You can find the fuel pump DIY instructions on the sticky. But do not buy new parts before checking the fuel pressure on the fuel rail if you are suspecting fuel supply problems. Please reveal the codes for the experts on the forum. Can you explain why you replaced the fuel filter 1 year after the previous one.
 

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1999 ML320
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453 Posts
Is your CEL on all the time and what codes for misfiring are there?
If you pass 4500RPM and the CEL comes on in hard acceleration, I believe that is time to replace both oxygen sensors BEFORE the catalytic convertors. Showing only P03XX misfire codes for multiple cylinders.
Ben there, I haul cars ones a while and I was missing the top end power (RPM) but after replacement of injectors, plugs, wires, coils, MAF (all brand new oem) it was still there till I changed the O2 sensors out. Now I can race with anyone out there and the CEL dosn't want to come on even at 5500RPM.
Your rear reference sensors are the same as front monitoring ( all four Bosch 13782) try to swap them around using rear in the front and see what hapenes, this will not cost you anything, just 20 minutes of your time and you can keep them that way even if the problem consists.
Bernard
 

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mercedes ml 320 1998
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5 Posts
Discussion Starter #4
hi
thanks for your replies i have now found out it is not the fuel pump
the only codes i have now are p0170 and p0173
they was 10 codes in total but they have gone now after being erased and these are the only ones left and coming on
my engine fault light does not come on as the bulb has been removed by the people that fitted the gas conversion years ago
where are the 02 sensors located
thanks steve
 

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1999 ML320
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453 Posts
Hi Steve,
that code is for fuel trim but I belive it is controlled by feedback of oxygen sensor.
Maybe someone with more knowlidge then me will reply with their opinion. Main O2s are located on the exhaust pipe comming out of the engine right before catalytic converter, you can see them and get to them very easy from under the truck, running down on the side of transmission. Wiring harness is actually attached by plastic clips to the tranny.
Bernard
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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7,035 Posts
First, if you are trying to rev in neutral or park, yes a rev limiter cuts in.

Those specific codes for petrol system are for MAF - recheck the source/spec of that replacement MAF - have no idea if they tricked that out for the LP conversion or not.

If it was straight petrol system, then with those specific codes MAF replacement with genuine Bosch MAF would be indicated - and in the UK (like the US) replacement MAF's are suspect for rebuilt or non-brand short term part substitution by innocent or shady parts sources.

Keep the faith !
 
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