News:

The Org - Serving W116 Enthusiasts since 2004!

Main Menu

not starting

Started by Pete49, 05 July 2018, 10:42 PM

Pete49

Today I went to start the 1978 450SEL and nothing. It has fuel ( I checked  :D) and spark to the cylinders (checked via timing light) but not a cough. In desperation I gave it a squirt of start ya bastard and it didn't even cough. (my wife turned the key and I squirted the stuff). Is there a relay or something that may be out? It was running a couple days ago, bit hard to start but did fire up and ran ok and with less tappet rattle. :) Just puzzling me.
Pete
What this country needs are more unemployed politicians.
Edward Langley,  Artist (1928-1995)

polymathman

Any chance someone put diesel fuel in it?
190sl 1957 rusting away
250S 1968 long gone
280SE 1976 got hit, parts
280SE 1979 running fine
C320 4Matic 2005 for wife -Mercedes after MIT

Max-NL

Do you hear the fuel pump running?
1971 R107 350 SL
1972 W108 280 SEL 3.5
1975 W116 280 S
1975 W116 450 SEL 6.9 #140
1977 W123 230
1992 W124 230 CE
2001 Ducati Monster S4

Pete49

defiantly no diesel in there.
mmm I'll check that on the weekend didn't think of the fuel pumps.
Pete
What this country needs are more unemployed politicians.
Edward Langley,  Artist (1928-1995)

daantjie

Check battery for full charge, as well as good grounding on the chassis.  Remove battery and check below the tray that all connections on the terminal block are clean and tight.  Also pull your voltage regulator from the back of the alternator, this is a very common culprit.  Next move to distributor cap and rotor, check if all is well there, no burnt connections.  Starter relay is in the engine bay fuse box, maybe swap that out too and see if there is any difference.
Daniel
1977 450 SEL 6.9 - Astralsilber

Pete49

Further to this problem I checked the fuse box and all are good and all are copper. I have put new fuel in and still no go. In the fuse box there are some relays (4 or 5) but I don't know if they are the problem or even how to test them. The fuel pumps are good. The only things not working on the dash are the clock and fuel gauge but can't see that being the problem as they didn't work before either.
Finding a suitable manual is also proving difficult. Where would I find out if the motor is original or replaced in this car and if it is a '78 motor or an earlier one.
Losing more hair daily,
Pete
What this country needs are more unemployed politicians.
Edward Langley,  Artist (1928-1995)

Randys01

The fact there was no response to the qik start squirt suggests the issue resides with the spark.

I wouldn't be satisfied that the spark is good enuff by relying on the timing light method. Remove a spark plug at random, ensure it is earthed  and see if it  sparks boldly when cranked. [u might need a helper ]

While u r at it, does the plug look sooty/black. is the gap ok?  If it looks pretty manky then changing them all out for new would be a good start.
One of the irritating quirks of K Jetronic is that repeated cold starts/short garage moves etc loads the plugs up and one day it just wont start.
I suspect your day has arrived.
Repeated cranking exacerbates the problem.

Only when you have a really good spark can u move on.

Assuming you have 100% guaranteed good spark u need to revisit the start spray technique. Make sure the throttle is depressed as the engine is cranked as the spray is injected. with K jetronic, just spraying it into the air damper box with the throttle plate closed is often not enuff.
Get the thing going with the spay and then wonder about why it won't start under its own steam.

  **Care needs to be exercised that the engine does not get fuel overload as the injection is working as well as the squirt spray. it is possible the perfect storm arises where the fuel mixture is flooded/too rich and it wont start, meanwhile the plugs are fouling up, partic if they are crappy.



Pete49

Thanks for the tip Randy I'll check it out on the weekend and report back.
What this country needs are more unemployed politicians.
Edward Langley,  Artist (1928-1995)

Pete49

Mystery solved. When I removed the tappet cover I had to remove a hose and cable on the mudguard that came from a pump? to the back of the motor and the electrical plug wasn't pushed right in. While checking all connections I found it and made sure it fitted properly and hey presto it runs. Still have a tappet noise but a lot quieter than it was so back to it later.
Pete
What this country needs are more unemployed politicians.
Edward Langley,  Artist (1928-1995)

TJ 450

Excellent work. With the tappet noise, did you look closely at the cam oiler tubes and the plastic fittings? If any of those are loose fitting you will lose oil pressure in the tube and the cams may be starved of oil. Also, the holes in the tube may also be blocked. The fittings are available cheaply and should be replaced every decade or so.

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

raueda1

Quote from: TJ 450 on 16 July 2018, 03:30 AM
Excellent work. With the tappet noise, did you look closely at the cam oiler tubes and the plastic fittings? If any of those are loose fitting you will lose oil pressure in the tube and the cams may be starved of oil. Also, the holes in the tube may also be blocked. The fittings are available cheaply and should be replaced every decade or so.

Tim
Does that also apply to 6.9?
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

Quote from: raueda1 on 16 July 2018, 01:43 PM
Quote from: TJ 450 on 16 July 2018, 03:30 AM
Excellent work. With the tappet noise, did you look closely at the cam oiler tubes and the plastic fittings? If any of those are loose fitting you will lose oil pressure in the tube and the cams may be starved of oil. Also, the holes in the tube may also be blocked. The fittings are available cheaply and should be replaced every decade or so.

Tim
Does that also apply to 6.9?

6.9 has metal fittings but still good idea to make sure the holes in the tube are clear.
Daniel
1977 450 SEL 6.9 - Astralsilber