M110 Engine In Sickbay

[nobby]

I put the 1983 280SL away last November running great.

I ran the car up to operating temerature twice during the winter.

The third time running this early spring it idled fine. The maiden voyage it started chugging and bucking, a bit.


Pulled the plugs to check, and in doing so two ignition wires came apart in my hands.
6 years old so I replaced them with new.
Plugs, cap and rotor were new last June and have about 5K on them. Cap and rotor appear to still be good. Inside cap is clean.

New wires on....car runs great again.

For 2 trips. One trip 20 miles and second trip 60 miles.

Back to the chugging on the return trip of 60 miles.
I had it running at speeds of 55-70 MPH but it seemed that some combustion was taking place in the exhaust system.
In fact, I would have bet money on a running on 5 cylinder scenario.

However, pulling the plugs today was "disappointing"....they are all uniform.

Have a look.

[DieselPaul]

Sticking injectors?

[RadioTek]

Nobby,

Could you have 'stale fuel' issues? Possibly a can of Seafoam could be in order?

Otherwise:

Basic tune-up checks, timing, condition of new parts, check for vacuum leaks.

Could you have lost a sensor over the winter, or one of the vacuum valves they control?

Possible dead wombat in the works somewhere? (I know the Canadian ones are extra furry, and cause more problems:-) )

Scott

[nobby]

I ran 2 bottles of Techron with a half a tank of the TREATED winter gas.
I then filled up with fresh premium....currently at $1.50 a litre. Ouchy.

I have new plugs coming tomorrow.......I'm going to check the coil / ignition mounting and wiring....I have a known good used cap and rotor....I will check for vacuum leaks.

But it really sounds like poor ignition.



How do you bench test a coil or ignition module? I hate changing expensive things on spec....

[jdhill]

For the coil, you need to know the resistance specs for yours. Connect an ohm meter across the pos. and neg. terminals for the primary curcuit and compare, then the pos. terminal to the secondary (center tower) for the secondary curcuit and compare. Then pos. terminal to a good ground, reading should be infinite. This is of course with all leads disconnected.

[nobby]

Originally Posted by jdhill

For the coil, you need to know the resistance specs for yours. Connect an ohm meter across the pos. and neg. terminals for the primary curcuit and compare, then the pos. terminal to the secondary (center tower) for the secondary curcuit and compare. Then pos. terminal to a good ground, reading should be infinite. This is of course with all leads disconnected.

Thank you.................but I took the easy way out and ordered a new one.
the old one is 20+ years old.
I should everything assembled for Saturday morning which, incidentally, is my first availability time wise.

[nobby]

Well after following the troubleshooting path in the M110 manual......looks like I need an Ignition Control Module.

Between $700-$1000.


But!!.....I bought a clone made by Hueco from ********z AZ for $59.00 on sale.


We'll see how that works out when it shows up.

[nobby]

Well the new ICM cured the problem.............partially.

I am now only getting the misfire over 4200rpms.

Back to sickbay.

[280EZRider]

Have you checked your plug connectors? It's rare that OE wires go bad, but the connectors are another story. Also make sure your plugs are non-resistor plugs. The connectors have resistors in them, so if you use resistor plugs, you are going to have way to much resistance at the plugs.

[nobby]

I had a brand new set of Magnecor wires on there to replace an old set of BERUs that were stiff, tired and falling apart.
It didn't solve the problem so I went chasing my tail for 2 weeks thinking it can't be the wires...they're new!.

I had the original set of BERUs that came with the car (when I bought it) stored away and I finally threw those on as a Hail Mary fix and lo and behold it fixed the problem.

Seems simple, now.