1990 (G) 300te wont start

ig_Al_300te

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'90 209k W124 300TE on LPG
Hi There All.

Well where do i start?
Prior to the old girl just giving up she was a bit lazy starting and the abs light was on ( did come on before but went out a few days later)
Then one morning she just didnt want to know a few splutters but nothing. So after some probing I checked I had a spark, Fuel to and from metering head (non at injectors) so as shes on gas also managed to start it with easy start and with a rev get her to kick into gas so I could go to the breakers in LEEK, Staffs. (what helpful chaps they are) After finding out my fuel pump relay was shot replaced that and also the OVP relay (to cure the abs light ect problem) whilst I was there we checked the ICU, pressure actuator and ECU still with no joy:(

When I had a further look today I have found that there was no feed to the cold start valve so If i bridge pins 87v and 30 on the fel pump relay the car will start:) but with any revs dies again:( So Im thinking it must be fuel and electrical related
As you can imagine Im at my wits end:mad: and dont want to start replacing parts willy nilly because Ive had different advice (fuel distributor, fuel pressure regulator, metering head.....blah..blah..blah)
Its the Bosch KE jetronic system fitted.

Like I say It will run fine on LPG just wont start (unless 87v and 30 are bridged) on Petrol.

Any advice will be a great help as Im pulling my hair out here!!

Thanks Alex.
 

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I will take a look later in the day and post back
 

shayes

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How modern is your LPG system out of interest?
 
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ig_Al_300te

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How modern is your LPG system out of interest?

Hi Stuart.
The LPG system was fitted 9k ago back in 2004 by D&N autogas in somerset prior to me buying the car.
Its a Romano Sir system with the torpedol tank fitted in the wheel space/well.
Alex.
 

shayes

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Was the Fuel pump relay replaced with a brand new one?
What is its reference number?
My curiosity ove rthe LPG is that I didn't think Cars can start from cold on LG, but my own is a single point and therefore dated. You have a multi presumeably, and you used cold start is that squirted into the air intake?
 
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ig_Al_300te

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Was the Fuel pump relay replaced with a brand new one?
What is its reference number?
My curiosity ove rthe LPG is that I didn't think Cars can start from cold on LG, but my own is a single point and therefore dated. You have a multi presumeably, and you used cold start is that squirted into the air intake?

Hi Stuart,
No the fuel pump relay came off a running car ref # 003 545 24 05
And as for the LPG question my system will start as soon as the revs are high enough to switch over (I presume its based on tacho settings) and as long as the switch is set to gas
And yes it was squirted easy start into the intake after removing the air filter and holding open the flap and giving it a good dose and full revs it flicks to gas then it will run OK:confused:
So it has to be fuel related right?
But since then i have followed a thread about bridging pins
87v ( to the cold star valve) and pin 30 (12v) at the fuel pump relay and give gentle revs ill go to aprox 2500rpm then i can kick it into running on gas.
Thanks for the reply
Alex.
 

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Just sounds like the replacement fuel pump relay is faulty, as it stands do you hear the fuel pump prime when you turn the ignition lights on?
 
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ig_Al_300te

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Just sounds like the replacement fuel pump relay is faulty, as it stands do you hear the fuel pump prime when you turn the ignition lights on?

Hi There Rob,

Yes You can hear the fuel pump once you turn the ignition on but it doesn't turn off once upto pressure if thats what you want to know I wasn't sure as some cars shut off once at pressure others will just pump away.

Hope his helps
Alex.
 

shayes

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After a vexing time with my last car, (500SEL) after replacement of various fuel related parts etc, it turned out to be a faulty Fuel Pump relay.

I overlooked that your car will be a straight six whereas my car was a V8, so the spare Relays I have and know to be sound will be no good to you to double check. Sorry, but if you are certain that the replacement is OK then its irrelevant.

Hope someone else will be able to help.
 

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Hi ig_Al_300te,


While I'm not too conversant with the Merc set-up in particular
(IE: I've played around with many a motor of this error - years back now )

I wouldn't swear to it ( but IIRC ) Doesn't the K-jetronic system have an Ign feed ( pin-15 ) on the fuel pump circuit in some form or other ?
My reasoning being < While cranking it will get a feed > but once it fires - It sounds like it's not being latched to stay on ? ( another relay isn't working ??? blown fuse ?? etc )
Can you get hold of a circuit diagram ? and suss what's required ?

Also - One test ( worth trying ) comes to mind
Remove the Intake duct from the from the Air-Flow metering unit and ( with Ign ON ) Push the flap down and check if fuel gets pumped to the injectors ( ie: listen for a change in the noise re- fuel system )

note - The central plate ( in the middle of the Air Flow meter ) Should move smoothly with a slight feel of resistance on the down stroke ( as if pushing against a steady back-pressure )
Lift your finger away fast ( once it's reached it's full travel ) and the flap should return in a smooth delayed motion - any thing different and there's sumit wrong !

Also the flap has to be perfectly central ( ie: so it has a tiny - even - gap ) all the way around the 'cone' it sits in ( measured in "thou" )
Any fowling of said plate - will cause it to require way too much 'Air-flow' pressure ( ie: being sucked down ) before it can move - hence a lack of enough fuel being delivered ( Metered - whatever )

Hope this makes some sort of sense ( ?? )

Regards M.G.

Note - To Mods < Would this thread be better off in Technical - D.I.Y - Engine - Fuel > etc ??
 
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ig_Al_300te

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Hi There M.G,
Thanks for your reply and to answer you questions....Ive checked the fuel pump relay..results as follows...
PIN 31 (BRN) -30 AT REST -30 AT IGN ON -30 AT CRANK
PIN 15 (PINK/RED)-30 AT REST -30 AT IGN ON +30 AT CRANK
PIN87 (BLK/WHT/YEL) N/A AT REST +30 AT IGN ON +30 AT CRANK
PIN 87h (BLK/RED/WHT) N/A AT REST N/A AT IGN +30* AT CRANK
PIN 50 (VIO/WHT) -30 AT REST -30 AT IGN +30* AT CRANK
PIN td (GRN/YEL) N/A AT REST +30 AT IGN PULSES AT CRANK (+30/-30)
PIN 30 (RED) +30 AT REST +30 AT IGN +30 AT CRANK
PIN 87k N/A AT REST N/A AT IGN +30 AT CRANK
PIN 87v 30 AT REST -30 AT IGN +30 AT CRANK
PIN tf -30 AT REST -30 AT IGN -30 AT CRANK

As for the fuel Yes with the IGN on i can hear the fuel being pumped (and if I crack off the lines to the injectors fuel is present)

Also upon removing the plug to the unit http://www.automotive-tradition.de/en/teile/media/Product_profil_Contact_housing.pdf the car seemed to run OK (would rev) but this was short lived :mad:

And to follow on from the central plate on the metering head I'm presuming that this is OK as once It runs on gas (LPG) the It is fine throughout the rev range.:confused:

Thanks for the ideas M.G
As I said before any help is better than none!!

I think I'm at the stage to test the fuel pressure (operating should be 5.3-5.5 bar) and delivery pressure should be 2-4 bar to see if this is the problem here.


thanks again Alex.:)
 
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ig_Al_300te

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After a vexing time with my last car, (500SEL) after replacement of various fuel related parts etc, it turned out to be a faulty Fuel Pump relay.

I overlooked that your car will be a straight six whereas my car was a V8, so the spare Relays I have and know to be sound will be no good to you to double check. Sorry, but if you are certain that the replacement is OK then its irrelevant.

Hope someone else will be able to help.

Hi there Stuart,
Ive replaced the fuel pump relay as the one that was on I'm surprised it worked at all as It looked like It had lived In the bilges of a boat:eek: and the new one looks like new inside.

And Ive also replaced the OVP relay as per the ABS light fault with a new one (that cured the problem with that)

And I can't thank people like yourself enough that are willing to help total strangers that share only a common interest in there cars! :)

WHY is it always just the bad press about pedophiles and the like that always echo regarding the internet? and very little about genuine people that are willing to help out others (like the people on this forum) in your spare time?

I couldn't without the internet it's a great tool for information (just gotta find it first):)

Thanks Alex.
 

shayes

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I've been on many forums and IMO this Mercedes site is without doubt the most enjoyable, knowledgeable and (dare I say) respectable (if we ignore the thread with the "f***cking " I just noticed. YOU KNOW WHO YOU ARE!! LOL

Not sure about your engine. Recall when I had a 230TE the Cold Start Valve was a part I needed to replace at great cost. It was a long time ago but I seem to recall car wouldn't start.

I am presuming that the LPG is direct fed and does not flow through it and so you are able to run on gas without a problem.

Just mentioning this for someone more knowledgeable to discount as a possible cause.
 

M.G.

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Hi There M.G,
Thanks for your reply and to answer you questions....Ive checked the fuel pump relay..results as follows...
PIN 31 (BRN) -30 AT REST -30 AT IGN ON -30 AT CRANK
PIN 15 (PINK/RED)-30 AT REST -30 AT IGN ON +30 AT CRANK
PIN87 (BLK/WHT/YEL) N/A AT REST +30 AT IGN ON +30 AT CRANK
PIN 87h (BLK/RED/WHT) N/A AT REST N/A AT IGN +30* AT CRANK
PIN 50 (VIO/WHT) -30 AT REST -30 AT IGN +30* AT CRANK
PIN td (GRN/YEL) N/A AT REST +30 AT IGN PULSES AT CRANK (+30/-30)
PIN 30 (RED) +30 AT REST +30 AT IGN +30 AT CRANK
PIN 87k N/A AT REST N/A AT IGN +30 AT CRANK
PIN 87v 30 AT REST -30 AT IGN +30 AT CRANK
PIN tf -30 AT REST -30 AT IGN -30 AT CRANK

Hi Alex,

Not sure what your chart shows ( the -30's / + 30's ) :confused:
So am guessing it relates to a voltage being present ??
With this in mind - I would have expected to see <Pin 15 > as a '+' when set to 'Ign' on
So this could well be linked to your fault (imo)

As for the fuel Yes with the IGN on i can hear the fuel being pumped (and if I crack off the lines to the injectors fuel is present) ----
I think I'm at the stage to test the fuel pressure

Yep agreed - Deffo time for a pressure gauge reading me thinks ( an old V12-XJS caught me on this one - sounded fine but just didn't have sufficient pressure when actually tested )

And to follow on from the central plate on the metering head I'm presuming that this is OK as once It runs on gas (LPG) the It is fine throughout the rev range.:confused:

Eeer - I'd disagree ( although admit -I know very little re- Gas set-ups )
But < Doesn't the gas get regulated / metered by it's own device > ??
AFAIK the metering device mentioned is for normal Fuel ( ie: petrol ) <<< see below quote >>>
Stuart said:
I am presuming that the LPG is direct fed and does not flow through it and so you are able to run on gas without a problem.
Hence I'm with Stuart on this one

Good luck ;)

Regards M.G.

PS - Unfortunatley I no longer have any of my old Bosch service manuals to hand :(
( so much of this info is off the top of my head ) :lol:
 
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ig_Al_300te

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Just done a pressure test...
over 6 bar at fuel in at metering head
just under 0.5 bar at fuel return from pressure regulator.
5.5 bar at top of metering head
5.5 bar at bottom of metering head
all the info I have says that this is OK and within the tolerances. :mad:
Could the metering head be at fault?? or any of its components??

Ive also put on a new fuel filter as the old one seemed to be on the wrong way round arrow pointing towards the rear of the car and not towards the banjo bolt!:eek:
That was also full of dirty fuel (could this have blocked the injectors) ???

Sorry about the (+30's and -30's) that's how we used to write them at work and +15 was ign live:Oops:
But the +30 denotes LIVE and -30 denotes Negative.

I don't know what to try next:(

maybe a pin out test at the ECU?? to see if i have crank angle sensor signal
ect (so any tests required for testing the electrical components that could cause a non-starting problem would be a great help)
I know my way around a multi-meter and have had 10years experience fitting car audio and alarms so I'm not numb to what signals to look for and precautions to take.

Im sure this is going to be something daft that I've over looked but I'm giving serious thought to giving it to M/B to do a diagnostic check but Ive read on here that they can be vague and still not cure the problem:(


thanks again for all the help
Alex.
 

M.G.

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Alex said:
Sorry about the (+30's and -30's) that's how we used to write them at work and +15 was ign live
But the +30 denotes LIVE and -30 denotes Negative.

Hi Alex,

Exactly what I was trying to say chap ;)

30 = 12v live ( or more accurately Batt voltage )
15 = Ign feed - live supply
31 = Earth potential etc
50 = Crank circuit
87 = Output voltage ( in some form or another )
I'm sure there's loads I've forgotten :Oops:

Have you a circuit diagram of the fuel layout ?
One thing worth trying ( with regards my suspicions of no Ign feed on < pin 15 > after releasing the starter switch position ) is to link a feed directly to the appropriate destination terminal ( where ever that may be ? )

Sounds like you have a reasonable knowledge of the mysterious electron trail :lol:
and would suggest an Oscilloscope is probably your next line of attack ( to check your crank sensor signal etc )

Try to source the 'Bosch' service docs for your system - as they had a pretty extensive test procedure listed for fault diagnoses

Keep at it

M.G.

PS - Double check the polarity of the actual fuel pump ! ( I've seen that before as well ) :rolleyes:
 
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ig_Al_300te

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SHE IVES ON!


Well I feel a little stupid but in my frustration prior to fitting a new fuel pump relay messed up the CO adjustment screw and with a little time with my dwell meter and some major adjustment to where I totaly screwed up messing with the setup of the metering head She's running!!:Oops:

Just gotta get it setup on a 4 gas machine to make sure what Ive set it up to is correct and were laughing!:D

Thanks once again to everyone that has helped with info/ideas and support..

.Just so glad i didn't follow my instinct to get a new metering head (at the cost of £150 + VAT and exchange)
And persevered to get it sorted!

The smile on my face when she fired and kept running......Priceless!

Thanks All and thanks Mercedesclub Members :)
Alex.
 

M.G.

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:p

Well done chap for sticking with it ;)

Glad your sorted

Regards M.G.
 

Alex Crow

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if this is a '90 car it doesn't have a lambda sensor. shame, because you can set these up without a gas analyser. just tweak the meetering head adjustment screw until the car goes into closed loop (voltage at sensor varying 0.1v to 0.8v or thereabouts) then keep adjusting till the voltage at the EHA is in the region +30mv at idle or thereabouts.

just read all this thread and was going to suggest the backfire scenario where the lpg sytem backfires and blows off the idle circuit hose from the flap body. guess not though, and as has been said this set up is probably the lpg with individual injectors. used to see that all the time though with k-jet systems, not always with gas.
 

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