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Garage => Mechanicals => Topic started by: EuroBenz on 01 July 2008, 05:04 PM

Title: Starting Problems -- Still happening
Post by: EuroBenz on 01 July 2008, 05:04 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.

(http://www.msprotege.com/members/KrayzieFox/Benz/DSC01608.JPG)

(http://www.msprotege.com/members/KrayzieFox/Benz/DSC01609.JPG)
Title: Re: Starting Problems -- Still happening
Post by: koan on 02 July 2008, 02:14 AM
Quote from: EuroBenz on 01 July 2008, 05:04 PM

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
Title: Re: Starting Problems -- Still happening
Post by: EuroBenz on 02 July 2008, 09:58 AM
Quote from: koan on 02 July 2008, 02:14 AM
Quote from: EuroBenz on 01 July 2008, 05:04 PM

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..
Title: Re: Starting Problems -- Still happening
Post by: koan on 02 July 2008, 08:27 PM
Quote from: EuroBenz on 02 July 2008, 09:58 AM

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
Title: Re: Starting Problems -- Still happening
Post by: Joe on 08 August 2008, 08:13 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.

Title: Re: Starting Problems -- Still happening
Post by: John Hubertz on 13 August 2008, 12:57 PM
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?
Title: Re: Starting Problems -- Still happening
Post by: Phuketguy on 25 September 2008, 01:53 AM
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.
Title: Re: Starting Problems -- Still happening
Post by: wonwon6 on 25 September 2008, 03:46 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 
Title: Re: Starting Problems -- Still happening
Post by: John Hubertz on 25 September 2008, 05:58 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.
Title: Re: Starting Problems -- Still happening
Post by: wbrian63 on 25 September 2008, 10:27 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.
Title: Re: Starting Problems -- Still happening
Post by: Phuketguy on 26 September 2008, 05:30 AM
Quote from: John Hubertz on 13 August 2008, 12:57 PM
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.
Title: Re: Starting Problems -- Still happening
Post by: TJ 450 on 26 September 2008, 09:20 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
Title: Re: Starting Problems -- Still happening
Post by: Phuketguy on 26 September 2008, 02:45 PM
Quote from: TJ 450 on 26 September 2008, 09:20 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

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.
Title: Re: Starting Problems -- Still happening
Post by: John Hubertz on 26 September 2008, 04:04 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.

Title: Re: Starting Problems -- Still happening
Post by: Phuketguy on 27 September 2008, 09:47 AM
Quote from: John Hubertz on 26 September 2008, 04:04 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.



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.
Title: Re: Starting Problems -- Still happening
Post by: WGB on 27 September 2008, 07:17 PM
Most cars in Thailand are Right Hand Drive  - is yours RHD or LHD.

It will make a difference to some parts including your ignition switch I would think.

Bill
Title: Re: Starting Problems -- Still happening
Post by: Paul Dellas on 27 September 2008, 07:25 PM
Hi to all,

What a great site, I am experiencing many of the same problems as listed in this discussion.

A friend has given me a 1979 280SEL that has a fuel pump problem. Initially the fuel pump was getting very hot and not running. I removed the fuel pump and found that it was seized. Replaced it with one that runs however now I have no voltage at the pump. Have checked fuses, all ok. My query is where is the fuel pump relay located. There is two metal can relays located in the fuse box. Is one of these relays the fueal pump relay? Also, is it possible to hard wire the fuel pump to battery to see if the car starts or will this cause any damage.

Paul   
Title: Re: Starting Problems -- Still happening
Post by: Phuketguy on 28 September 2008, 12:03 AM
Quote from: WGB on 27 September 2008, 07:17 PM
Most cars in Thailand are Right Hand Drive  - is yours RHD or LHD.

It will make a difference to some parts including your ignition switch I would think.

Bill

Yes, you're right, all cars in Thailand are RHD. You think that makes a difference on something like an ignition switch? 
Title: Re: Starting Problems -- Still happening
Post by: WGB on 28 September 2008, 12:22 AM
Quote from: Phuketguy on 28 September 2008, 12:03 AM
Quote from: WGB on 27 September 2008, 07:17 PM
Most cars in Thailand are Right Hand Drive  - is yours RHD or LHD.

It will make a difference to some parts including your ignition switch I would think.

Bill

Yes, you're right, all cars in Thailand are RHD. You think that makes a difference on something like an ignition switch? 

Not sure about the electrical part of the ignition switch - likely to be the same for both -  but I would check before buying anything.

Some of us here have a copy of the EPC (Electronic Parts Catalogue) and next time I am going through it I will look it up.

Either post your VIN or PM it to me and I can look up the correct number for it and whether it is "Handed" or not.

It also may be possible to remove your own switch, dismantle it and clean the contacts. Most Bosch switches are not designed to be serviceable but come apart with some gentle persuasion and care and are quite repairable.

Quote from: Paul Dellas on 27 September 2008, 07:25 PM
Initially the fuel pump was getting very hot and not running. I removed the fuel pump and found that it was seized. Replaced it with one that runs however now I have no voltage at the pump. Have checked fuses, all ok. My query is where is the fuel pump relay located. There is two metal can relays located in the fuse box. Is one of these relays the fueal pump relay? Also, is it possible to hard wire the fuel pump to battery to see if the car starts or will this cause any damage.

Paul  

Sounds like you have either burnt out your relay or more likely blown the fuse. Have you checked the fuse?

I do not know what country version your car is but assume it is Euro/UK/Aus in which case there are two relays in the fuse box. US Models have three.

It should be numbered on the harness as No 1 but it may not be easy to see and you may need to detach the socket from the holder to see it.

The following photo is a description of the numbering system for relays.

(http://i257.photobucket.com/albums/hh219/WGB_album/M-BTechnicalDataJan1980-relaydata.jpg)

And yes you can jump the terminals to test it without damaging anything but all the safeguards will of course be removed.

Bill

Title: Re: Starting Problems -- Still happening
Post by: Paul Dellas on 09 November 2008, 09:54 PM
Hi to all.....

Around september I post a problem with my 280 SEL not starting. Just got back into it. Have replaced the fuel pump and the new one is running fine. Have plenty of sparks at the plugs, have fuel pouring out of the fuel line at the rear of the fuel distributor when I crack it. Still cant get the engine to kick! What am I missing???? There is another fuel line on the side of the fuel distributor.... Is this a return line to the tank and should there be fuel circulating? I have poured some fuel down the air intake.... No kick. Do I need to bleed the fuel lines to the cylinders? Any help most appreciated.

Paul
Title: Re: Starting Problems -- Still happening
Post by: WGB on 10 November 2008, 07:49 AM
Isn't there some form of cut off switch built into the back of the K-jet unit.

Bill
Title: Re: Starting Problems -- Still happening
Post by: koan on 10 November 2008, 09:00 AM

The  line into the fuel distributor is the front most one, the other is the return, and yes, fuel does circulate.

Pressure in the tank will force fuel forward so remove the filler cap before investigating fuel supply.

If it doesn't fire with fuel poured in and you have spark, maybe the spark is not happening at the right time, either timing is off or the plug leads out of order.

No need to bleed injector lines.

koan
Title: Re: Starting Problems -- Still happening
Post by: Paul Dellas on 19 November 2008, 01:39 AM
Hi again all......

Have to report I am a pretty happy camper, the motor is purring away nicely. Amazing what a new set of plugs and new fuel will do.

After replacing the siezed fuel pump, draining the fuel tank and replacing the plugs the beast fired up straight away. Have yet to take it on a run to blow the engine out. Apart from a slight exhaust leak from either the flange or manifold it runs very nicely.

Anyone had any experience with injector cleaner additives? Am thinking I might ad a bottle to clean the system out.

Paul


Title: Re: Starting Problems -- Still happening
Post by: Phuketguy on 05 January 2009, 08:24 PM
Quote from: John Hubertz on 26 September 2008, 04:04 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, I'll take you up on your offer.  Actually, my son lives in Denver and will be coming to Thailand in about 3 weeks.  Do you think you could find one and work it out with him?  Let me know and we'll exchange PMs with details.  thanks very much.