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  #1  
Old 05-29-2018, 10:38 AM
Hugin's Avatar
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W116 280SE -73 starting problem backfire

Hi

Some time back I bought a -73 280SE that used to belong to my wifes family. It is in very good shape, no rust at all. I drove it some 60 miles home, running smooth, pulling well.
Back in the garage I popped the hood and started looking over my new car, and I opened the distributor cap and had a look.
Put it back in place and started the car. It ran for a few sec and then died, restart, running a little while, then stop.
After a bit of checking, I found to my big surprise that the rotor was shoot, no connection from center to the tip. Never seen this...
Anyway, got a new rotor, new distributor cap, new plugs (BP6ES) and air filter.
Also got a new coil, a Flamethrower.
Now the car will barely start, sounds like 3 cyl, and I have to push hard on the pedal to get some fireing at all. And, I have a heavy backfire/fire out of intake.
Have not touched the timing at all.
Checked fuel pressure, was 1.8 bar, adjusted it to 2 bar.

Now I am stuck, can not see any reason for this behaviour.
Any advice will be highly appreciated.

Sorry if I get some expresions wrong, I'm Norwegian... ;-)
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1974 MB 230 4 cyl auto
1973 MB 280SE #12004
1970 MB 230/8 #53280
1970 MB 300SEL 6.3 #4509 sold
1968 MB 300SEL 6.3 #0335
1972 MB 280SE 4.5 75k miles sold
1971 MB 230/8 60k miles sold
1972 Volvo 142 60k miles sold
1969 Opel Rekord 1900 sold
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  #2  
Old 05-29-2018, 12:40 PM
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Location: Miami Beach, Florida
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It seems to me that you might have crossed or incorrectly installed one of the wires to the plugs when you installed your distributor cap.
This is a silly question but did you replace your plug wires one by one when you replaced your distributor cap and are your wires securely fastened to your plugs and distributor cap?
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1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT
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  #3  
Old 05-29-2018, 01:33 PM
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Definitely sounds like the order of plug wires is wrong after your cap replacement. Is the coil you're using compatible with your ignition system?
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  #4  
Old 05-29-2018, 01:37 PM
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Quote:
Originally Posted by Tomas7 View Post
It seems to me that you might have crossed or incorrectly installed one of the wires to the plugs when you installed your distributor cap.
This is a silly question but did you replace your plug wires one by one when you replaced your distributor cap and are your wires securely fastened to your plugs and distributor cap?
Hi

The thought did strike me, so I doublechecked everything ;-)
Unfortunatly, it was correct.

Tom
__________________
1974 MB 230 4 cyl auto
1973 MB 280SE #12004
1970 MB 230/8 #53280
1970 MB 300SEL 6.3 #4509 sold
1968 MB 300SEL 6.3 #0335
1972 MB 280SE 4.5 75k miles sold
1971 MB 230/8 60k miles sold
1972 Volvo 142 60k miles sold
1969 Opel Rekord 1900 sold
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  #5  
Old 05-29-2018, 01:40 PM
Hugin's Avatar
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Posts: 141
Quote:
Originally Posted by Diseasel300 View Post
Definitely sounds like the order of plug wires is wrong after your cap replacement. Is the coil you're using compatible with your ignition system?
I have swapped back to the original coil, same problem.
I use the Flamethrower with success on my w114, W115 and W109, it works great.
__________________
1974 MB 230 4 cyl auto
1973 MB 280SE #12004
1970 MB 230/8 #53280
1970 MB 300SEL 6.3 #4509 sold
1968 MB 300SEL 6.3 #0335
1972 MB 280SE 4.5 75k miles sold
1971 MB 230/8 60k miles sold
1972 Volvo 142 60k miles sold
1969 Opel Rekord 1900 sold
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  #6  
Old 05-29-2018, 02:43 PM
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Join Date: Feb 2011
Location: Modesto CA
Posts: 2,422
H:

Suggest that you place the old and the new distributor caps and rotors side by side. Carefully compare all dimensions, and in particular the location of the molded-in keys that orient the cap on the distributor body, and the rotor on the shaft. Bosch used the same diameter caps on different engine applications, but with different key locations. Rotors were supplied both with, and without a resistor between center and tip, and in versions that had a centrifugal grounding contact for RPM limitation.
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  #7  
Old 05-29-2018, 02:50 PM
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Posts: 141
Hi Frank

I have been staring at the rotors and the caps for a long time already, I can not see any difference. Will put engine in TDC tomorrow to check timing 100%
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  #8  
Old 05-30-2018, 07:59 AM
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Problem solved, and I shall not speak of it, ever ;-)

Now starts the job to convert to Pertronix.
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  #9  
Old 05-30-2018, 10:23 AM
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Quote:
Originally Posted by Hugin View Post
Problem solved, and I shall not speak of it, ever ;-)

Now starts the job to convert to Pertronix.
Please tells us so that WE will not do the same and learn from you.
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1976 280C
SLOWER DRIVERS KEEP TO THE RIGHT.
DRIVE RIGHT PASS LEFT
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  #10  
Old 05-31-2018, 03:49 AM
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Join Date: Apr 2005
Posts: 141
Ok, I will come clean ;-)
On the valvecover the firing order is stamped, in my hurry I mistook this for cylinder #, so the previous posts were right.

The car ran quite ok until almost warm engine, then it just died, and remained dead.

I just recently replaced the transistor ignition (silver box) and had 5,2 V on the coil + terminal.

Now I have 12,6 V and I suspect the box is broken, again.
Had a Pertronix ready, but it turned out that the adapter plate did not fit my dizzy, so I will have to wait for the correct one before I can bypass the silver box.
Shiiiit.
Any workaround the silver bix while I wait for the adapterplate?
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  #11  
Old 06-01-2018, 01:48 AM
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Posts: 141
Ok, took the green wire from points and fed it to Coil #1 (-), and unplugged the 4-way contact to the silver box, and voila, engine fired up.

Now it is time for finetuning the engine and enjoy the car.

Black with cognac leather, sunroof, rustfree. Daily driver for the icefree months.
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