W126 500 won't run - help!

[Bellow]

How would i check for a blockage?

Remove trunking at air filter and see that it's clear all the way to where air enters.

Seems unlikely anyway as after sorting the vaccum issues it was idling really nicely and has been driven all of 10 metres before this issue occured

Stray plastic bags, bird nests, etc, etc - all manner of things have been found in air inlets!

 

[grober]

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12minutes on explains how a faulty warm up regulator would cause excessive fuelling

 

[alabbasi]

Press down on the plate and see if there's any pressure. Plunger may be stuck

 

[DaimlerBenz29]

Remove trunking at air filter and see that it's clear all the way to where air enters.

Stray plastic bags, bird nests, etc, etc - all manner of things have been found in air inlets!

Ah ok, yeh there's no blockages. Like I said, vacuum system is in great shape - not like i sucked in a plastic bag whilst driving on the street for 30 seconds.

 

[Bellow]

Ah ok, yeh there's no blockages. Like I said, vacuum system is in great shape - not like i sucked in a plastic bag whilst driving on the street for 30 seconds.

The vacuum and induction system are not the same thing. No matter, the induction system is now known to be clear so resources can be thrown at the fuelling system without fear of that being a colossal waste had it later transpired that a squirrel had selected your air filter housing as its preferred location for its nest.

 

[DaimlerBenz29]

The vacuum and induction system are not the same thing. No matter, the induction system is now known to be clear so resources can be thrown at the fuelling system without fear of that being a colossal waste had it later transpired that a squirrel had selected your air filter housing as its preferred location for its nest.

Yes sorry i was thinking of it as the 'air' system as a whole

 

[DaimlerBenz29]

Does anyone know much about the ignition module (EZL). I just followed a test from the workshop manual where you are supposed to be able to see battery voltage reading from one of the pins to ground - mine shows zero.

The manual says that means it's fauly and needs replaced but before chucking money at it, i wonder if there's any other electrical issue that could also cause that result.

 

[grober]

THIRD (3rd) 300-24 EZL failure in 1 year | Engine

Hello All, This is a request for any ideas on what might be the cause of the THIRD (yes, 3rd) EZL failure in 12 months. My son and I will start some electrical diagnosis this morning but I would much appreciate any input from the clever chaps out there. Relevant information includes...

forums.mbclub.co.uk

Wayback Machine

 

[grober]

Normally how these systems work is the primary winding of the ignition coil is continuously powered and should have a constant 12 supply--- the coil is "fired" by collapsing the 12 V supply by a switching power transistor thus inducing a voltage in the high tension secondary winding producing an HT pulse to the main distributor lead. Usually what happens is the switching power transistor burns out-- this may be the reason you're not seeing 12 V on that EZL PIN? The EZL UNITS are heatsinked to the chassis via a heat transfer compound this dries out over the years causing the unit to overheat unfortunately they are sealed units and can't be repaired unlike later HFM ecus

 

[DaimlerBenz29]

Normally how these systems work is the primary winding of the ignition coil is continuously powered and should have a constant 12 supply--- the coil is "fired" by collapsing the 12 V supply by a switching power transistor thus inducing a voltage in the high tension secondary winding producing an HT pulse to the main distributor lead. Usually what happens is the switching power transistor burns out-- this may be the reason you're not seeing 12 V on that EZL PIN? The EZL UNITS are heatsinked to the chassis via a heat transfer compound this dries out over the years causing the unit to overheat unfortunately they are sealed units and can't be repaired unlike later HFM ecus

Thanks for the info. It's interesting that you mention the contact with the chassis as right now the module is unbolted and loose for testing. The car will still start eventually as long as the cables are plugged in so it must be doing something. That said, I dont know the failure modes of the module so perhaps it's on the way out but not quite dead.

 

[grober]

Thanks for the info. It's interesting that you mention the contact with the chassis as right now the module is unbolted and loose for testing. The car will still start eventually as long as the cables are plugged in so it must be doing something. That said, I dont know the failure modes of the module so perhaps it's on the way out but not quite dead.

When the EZLs are on the way out they can often work for a short time till that power transistor overheats. Let it cool down and it will work again-- but eventually it will fail completely

 

[DaimlerBenz29]

I've made some progress. Before sorting out the idle issue, I had to drain the tank as the car had been sitting for a long time. By doing so, I may have inadvertently clogged the fuel filter. I had dismissed this initially as the filter was so new and didn't think it could clog so easily.
Anyway... changed the filter today and the car now fires up and doesn't die when I touch the gas. However, it revs horribly; hard to explain but sort of judders a couple of times before actually doing its job. It's still a big improvement so now I want to look at the fuel tank screen but that requires the tank to be drained....

Any ideas how to tackle this without clogging the filter again?