99 W202 C240 Won't start

[mintyish]

Help! About 2 weeks, the car wouldn't start. Out the blue one morning engine turns over no problems, but not a hint of running.
Checked all the fuses, and found the rear fuses near the battery and the location of the fuel pump relay - and searched the web.
Found the crank position sensor discussions and found the sensor on the flywheel housing and wiggled the wires. Also disconnected the battery for 10 minutes and then reconnected - and hey presto - engine starts.

Now tonight the very same thing. Only problem being that I don't know how I fixed it last time!

The engine has been running fine with no issues - so I'm hesitant to blame the crank sensor - no rough idle or stalling at all.

Could the fuel pump relay at the rear fuse box be at fault?

Any ideas?

Thanks

John

 

[roofless]

welcome & good morning....if it's a fuel pump related problem the easy check to do is turn on the ignition & if you can hear the pump run for a few secs then it's not at fault . the relay is No 65 http://www.detali.ru/cat/oem_mb2.as...GM=716.626&CT=F&cat=45H&SID=54&SGR=045&SGN=05

 

[mintyish]

Update

Update - there is definately a spark - I pulled a plug lead and it sparked away against the cylinder head. Could I change the fuel pump relay for another one - or are relays voltage/load specific?

Thanks for the link to the russian site.

I can't hear the fuel pump with the ignition on - which made me look at the relay last time. However, I read on another forum that the pump starts on command from the engine ecu so may not necessarily run just with the ignition on.

I'll carry on but it's dark outside - I'm in New Zealand! And I was going to watch the F1 - but it's turned into a parade, so not missing much!

John

 

[roofless]

as far as i know it runs for a few seconds to prime the system prior to starting . it could be caused by the immobiliser if fitted but i would be looking at the relay first

 

[mintyish]

Success.

I swapped the fuel pump and fuel return pump relays and it started - just like normal.

Off to work in the morning - and I can get a new relay at lunchtime. Only question is will I have to go full throttle all the way to use all the fuel, so the engine doesn't flood without a fuel return pump :lol:

John

 

[mattkh]

........ and fuel return pump relays and it started

Hi
What number on the diagram is the fuel return pump relay ?

 

[mintyish]

The fuse pump relay is number 65

 

[mintyish]

What was wrong with carb, a distributor and a set of points?

Got in the car this morning, and back to not starting - so after running last night no problems, the fault is obviously not the fuel pump relay.

How does the MAF fail? Could it be intermittent? I might have to call out the AA at this rate...

John

 

[roofless]

i don't think the maff is at fault it would cause poor running but if you remove the relay & put it back in & it runs seems odd .i would get the fault codes read to see what it says

 

[television]

Yes the MAF has nothing to do with starting, or when cold

 

[mattkh]

I swapped the fuel pump and fuel return pump relays
John

Hi
Am I misreading the above post?
How many relays did you swap? One or two.
Did you also change the fuel pump? If so, which fuel pump did you change?

 

[mintyish]

There were two identical relays side by side - part number 0025421913 - from the parts list one is for the fuel pump and the other for the fuel return flow pump - so I swapped them over - and the car started last night.

I've not checked the fuel pump itself yet - as I was assuming last night that I'd fixed the problem.

I'm off to the dealer now to chat to them and see what they say.

John

 

[mintyish]

So - Went to the dealer on Monday and they said they would need to plug in the diagnostics to find out what was wrong. Only trouble being how to get the car to the dealer. Anyway, miracle of miracles, it started first turn of the key on Tuesday morning and I drove straight there.
The dealer couldn't find anything wrong - no fault codes stored - and none recorded when the fuel pump relay was removed!
They do think it's the fuel pump though - as the tech said he thought it noisier than normal - though it's not by any means load at all.
The interesting part - NZ$931 for a new pump and NZ$220 for a fuel filter! $1200 or about GBP450 - just for the parts.
Local independent can do the parts for half that....just not sure I want to spend all that money on a hunch...

John

 

[mintyish]

So - 3 weeks later and the car's been running fine until Saturday afternoon - won't start. Turns over fine but won't run. Now that I've got the fault, I pulled the fuel pump fuse whilst cranking and no current. Which suggests the relay. After reading all afternoon about relays on the web, I decided to go buy a replacement - and got one for $16 - GBP9 or so. Fitted it this morning and car is back to normal.
I pulled the old relay apart hoping to find black and burned contacts, they looked as good as the day they came out the Siemens factory...

 

[horgantrevor]

lets hope this fixes it also make sure the electrical connectors on the relay position in the car are clean you can get a spray but a quick spray of wd40 and with the engine off , plug the relay in and out a few times that will wear of the and dirt if any

 

[furto]

I am going to bring this ancient thread back from the dead and ask what type of relay did you buy? Im sure that if i buy one from Mercedes it will cost heaps. Is there some sort of model number or relay type i should look for because i have the 100% EXACT same problem.

 

[jasonyw]

Plug in the STAR to ascertain, no guess work.

 

[Alex Crow]

furto, can you hearthe fuel pump run for a second when you turn the ignition on? what about about when it WILL start, can you hear it then? does the engine always turn over OK? is it just a starting problem? does it happen when cold/hot or both?

 

[furto]

Well the problem seemed to be completely random, although it did sort of stop happening for a year or so, the last couple of days however, it started up again real bad.

So a few hours ago I pulled the fuel pump relay out, opened it up and used some emery paper (fine grit sand paper) to clean the relay contacts up which looked a bit dirty.

Now it starts first go every time! It looks like it was definately that relay and I cant thank you guys enough for this thread! I have had this issue for 3 years lol

 

[sparky_jay]

same problem 98 W202 C240

I have had exactly the same problem of not starting for a couple of years now!
I can turn the engine over all day and it doesn't start....
Whenever it happens now (once a month or so) I pop out, open the boot, lift the floor, tap the relay with my hand,drop the floor back, close the boot, get back in, start the car and drive away - EVERY TIME!
Got to be either the relay or the holder. One day I will get around to buying a new relay!