Author Topic: Starting Problems -- Still happening  (Read 4995 times)

EuroBenz

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Starting Problems -- Still happening
« on: 01 July 2008, 03:04 PM »
Hey everyone,

I joined this forum so I could hopefully fix my grandpa's '78 Benz 280SE but I'm still having problems. I posted about the starting issues in another thread when I first joined and I made some progress, but not too much.

The progress is that the car starts now, it fires right up actually, but it then dies immediately after. It only works for about a second and even under full throttle it still dies immediately. I'm not sure which engine is in the car, so I've attached a few photos. Also, what's under the cap where all the fuel injectors come from? I'm thinking that might be the source of the problem because fuel is being delivered up to that point, but I'm not sure if it's under enough pressure to make it through the injectors and inside the engine.

Thank you in advance for all your help.




koan

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Re: Starting Problems -- Still happening
« Reply #1 on: 02 July 2008, 12:14 AM »

The progress is that the car starts now, it fires right up actually, but it then dies immediately after. It only works for about a second and even under full throttle it still dies immediately,


Sounds like it could be a stuffed fuel pump relay. The injection system has a safety circuit to prevent the fuel pump running if the engine isn't, this needs a relay to allow the engine to be started initially.

In your second photo, just below and slightly to the left of what you refer to as "the cap where all  fuel injectors come from" is a blue electrical plug.  Pull this plug from the connector(might need to wiggle and squeeze/stretch the wire clip) and try to start and run the engine again. If now runs properly you most likely have a faulty fuel pump relay.

Quote

what's under the cap where all the fuel injectors come from?


That's the fuel distributor, doubt if its the problem if the engine fires up even if it's only for a second.

koan
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EuroBenz

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Re: Starting Problems -- Still happening
« Reply #2 on: 02 July 2008, 07:58 AM »

The progress is that the car starts now, it fires right up actually, but it then dies immediately after. It only works for about a second and even under full throttle it still dies immediately,


Sounds like it could be a stuffed fuel pump relay. The injection system has a safety circuit to prevent the fuel pump running if the engine isn't, this needs a relay to allow the engine to be started initially.

In your second photo, just below and slightly to the left of what you refer to as "the cap where all  fuel injectors come from" is a blue electrical plug.  Pull this plug from the connector(might need to wiggle and squeeze/stretch the wire clip) and try to start and run the engine again. If now runs properly you most likely have a faulty fuel pump relay.

Quote

what's under the cap where all the fuel injectors come from?


That's the fuel distributor, doubt if its the problem if the engine fires up even if it's only for a second.

koan
I removed the plug and it wouldn't start at all now. I tried the other plug as well, and both removed and all yielded the same result. Not starting at all..

koan

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Re: Starting Problems -- Still happening
« Reply #3 on: 02 July 2008, 06:27 PM »

I removed the plug and it wouldn't start at all now. I tried the other plug as well, and both removed and all yielded the same result. Not starting at all.


That's very odd because removing the plug allows the fuel pump to run all the time.

Can you hear the fuel pump running under any condition, ignition on, cranking, both with plug on and off?

koan
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Joe

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Re: Starting Problems -- Still happening
« Reply #4 on: 08 August 2008, 06:13 AM »
Hi

Not sure if you have sorted out your problem or not but  I have the exact same thing playing up with my car  I have a  79  450 SEL .

If you have sorted it out please let me know as to what it was.I am getting the warm up regulator reconditioned, as a new one cost $3200.oo a bit expensive.

Any advise would be greatly appreciated.


John Hubertz

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Re: Starting Problems -- Still happening
« Reply #5 on: 13 August 2008, 10:57 AM »
Mine did that, till I discovered that the contact points in the ignition switch are very very wear-sensitive.

I've got to "baby" my ignition switch when starting (not hard - a habit I don't even think about) as if I just let it pop back like I normally used to with cars it will start, then die due to the ignition shutting off even in the "run" position.  Mines a smidge touchy on cold days too - until it "arcs" a new contact point while running it sometimes will die if I hit a big bump even.   I bet I'm even losing some power as that partially compromised electrical circuit has GOT to produce some voltage drop.

Have you guys tried not fully letting the key snap back, but just disengaging the starter while holding the key against the spring a smidge?
« Last Edit: 13 August 2008, 11:00 AM by John Hubertz »
John Hubertz
"When the going gets weird, the weird turn pro."
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1977 450SEL (Max Headroom)

Phuketguy

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Re: Starting Problems -- Still happening
« Reply #6 on: 24 September 2008, 11:53 PM »
Hi everyone,

I too have a 1980 280se w116 with starting problems.  I recently replaced the spark plugs, had a new fuel filter installed and had the accelerator assembly cleaned and serviced because it was sticky.  It runs fine apart from idling a little rough.

However, when the car has been sitting for a day or two, it is extremely difficult to start.  It just turns over fine but won't catch and start.  I thought it might be a fuel pump problem, but if I pump the pedal, I can smell gas so assume it's flooding and fuel pump is not the problem?  The ignition switch discussion might be interesting.  John, do you have any additional info on that?

It is true that eventually, when it kicks over, it is because I have released the key a little early and it just seems to kick in.  If I run the car around for awhile, it starts fine.  It's only when it sits for awhile that it has this problem?

Any ideas?

Thanks for any help.
« Last Edit: 25 September 2008, 12:25 AM by Phuketguy »

wonwon6

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Re: Starting Problems -- Still happening
« Reply #7 on: 25 September 2008, 01:46 AM »
I must agree with Koan- Gollum my 77 280se did exactly the same thing and it turned out to be the relay...also check the fuel filter- if it is clogged, that can also stuff up things. mine was restricting the fuel which can stuff up the relay eventually (according to my mechanic) then just go ahead and and put in new injectors  ;D 
77 280se For Sale
76 450se
96 S500 Coupe

John Hubertz

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Re: Starting Problems -- Still happening
« Reply #8 on: 25 September 2008, 03:58 PM »
pump operation is so easy to test - low pump volume or a plugged filter could easily be the cause.  Your pressure regulator might likely be allowing a good pressure to build, thus allowing the start/stall condition as the pump can't keep up.

Get a tin and turn on your key after removing the high pressure line, and let it run for 15 seconds.  There is a standard for how much should be flowing per minute - I can't recall it right now.

I can't recall the volume required, anyone know?  These bosch pumps are expensive new and super cheap used as they were also fitted to volvos etc.

The relays/ignition circuits are always suspect - hotwire the d*mn pump if you aren't sure.  Then start it and see if it stays running.
John Hubertz
"When the going gets weird, the weird turn pro."
(Hunter S. Thompson) 

1977 450SEL (Max Headroom)

wbrian63

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Re: Starting Problems -- Still happening
« Reply #9 on: 25 September 2008, 08:27 PM »
I'm new to 116's, having just recently purchased a 1976 Euro 6.9. According to the CIS Diagnosis Manual for 1976-1979 cars, the volume spec is 1 litre in 30 seconds with at least 1/2 tank of gas and 11.5v minimum volts at the pump. Also indicates that the gas cap should be open during the test.
W. Brian Fogarty

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'76 450SEL 6.9 Euro #521
'02 S55 AMG (W220) - sold
'76 450SEL 6.9 Euro #1164 - parted out

"Bond reflected that good Americans were fine people, and most of them seemed to come from Texas..." Casino Royale, Chapter V

Phuketguy

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Re: Starting Problems -- Still happening
« Reply #10 on: 26 September 2008, 03:30 AM »
Mine did that, till I discovered that the contact points in the ignition switch are very very wear-sensitive.

I've got to "baby" my ignition switch when starting (not hard - a habit I don't even think about) as if I just let it pop back like I normally used to with cars it will start, then die due to the ignition shutting off even in the "run" position.  Mines a smidge touchy on cold days too - until it "arcs" a new contact point while running it sometimes will die if I hit a big bump even.   I bet I'm even losing some power as that partially compromised electrical circuit has GOT to produce some voltage drop.

Have you guys tried not fully letting the key snap back, but just disengaging the starter while holding the key against the spring a smidge?

Yeah, I think I have determined it is the ignition switch which has gotten fussy with age.  I just release it quickly after it starts cranking and the engine catches right away.  I suppose I can use this work around for awhile, but is the fix for this replacing the ignition switch?  If so, does anyone know if other Mercedes switches are interchangeable, as I imagine it would be very hard to find one.

TJ 450

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Re: Starting Problems -- Still happening
« Reply #11 on: 26 September 2008, 07:20 AM »
Regarding ignition switches, they are all the same on petrol W116's at least. I would say it was highly likely that W123's and 107's have the same part. It is fiddly to get at, but not really that difficult to replace unless you drop a screw down the chasm! The switch on my 6.9 failed such that it would not release from the start position... ouch ! :o

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Phuketguy

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Re: Starting Problems -- Still happening
« Reply #12 on: 26 September 2008, 12:45 PM »
Regarding ignition switches, they are all the same on petrol W116's at least. I would say it was highly likely that W123's and 107's have the same part. It is fiddly to get at, but not really that difficult to replace unless you drop a screw down the chasm! The switch on my 6.9 failed such that it would not release from the start position... ouch ! :o

Tim

Thanks Tim.  However, all W116 parts are hard to obtain where I live, in the south of Thailand.  I'll let you all know how it turns out. 

Cheers.

John Hubertz

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Re: Starting Problems -- Still happening
« Reply #13 on: 26 September 2008, 02:04 PM »
mr ph, If used parts aren't an issue across your borders I'd be happy to post you anything you need from American junkyards - always wanted to make a friend in your part of the world.

Let me know if I can help and I'll try.

John Hubertz
"When the going gets weird, the weird turn pro."
(Hunter S. Thompson) 

1977 450SEL (Max Headroom)

Phuketguy

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Re: Starting Problems -- Still happening
« Reply #14 on: 27 September 2008, 07:47 AM »
mr ph, If used parts aren't an issue across your borders I'd be happy to post you anything you need from American junkyards - always wanted to make a friend in your part of the world.

Let me know if I can help and I'll try.



Hey John, man what a nice guy.  Yeah, I may ask you to source this, but will first look around the parts dealers in Bangkok.  I'm also an American but lived so many years here.  I will be in touch soon, or in any event will advise if I found the ignition switch and how much it cost me.  This is really a great forum.