560sl
 

I have been trying to get my 86 560sl started. The mechanic changed the ignition coil and timing chain. Ran for a couple of days. Then he changed the ignition module and coil. It ran for 1 day. Same problem changing the coil and module for the 3rd time. These replacement parts are used and wondering if the mechanic should have replaced with new parts specially the module.
Please help.

I'd concentrate on finding out why the car doesn't run, it may be fuel system or the ignition system.
Gilly

560sl
 

it sure sounds like the pickup on the flywheel that sends low voltage signals to the ignition module.these things have been bulletproof until a couple yrs ago now they are dropping like flies.could be worse though at least they give some warning before they go out completely.usual symptom is heat[high heat causes them to break down cool it off and car starts again] remember though [that when car stops] because fuel pump relay is kept on by td signal from module it's easy to condemn fuel supply if not checking spark first.

Good point, just wanted to make sure "we" aren't just throwing parts at a problem without being really sure of the cause. If it's the TD sensor, when it acts up the tach should also be dead. Not sure if it's dying on the road or just going out to the car at it doesn't start?? So if it's the TD sensor you'd evidently have no fuel OR spark?? Useful info there too I guess.....
Gilly

Gilly/David,

Could this also be the source of my problem...which I will describe.

Sometimes when I shut the car off and get out of it there is no power. The antenna will not go down and the interior lights don't come on. Turn the ignition key and it will not start...no power anywhere. After it cools down for awhile the antenna will retract. Open the door and the interior lights work just fine and it will start right up.

The only indication I have when driving the car that the above will play out is the ABS light comes on. I'm convinced the ABS is not the problem. The OVP relay has been replaced, pulled and replaced with another. Also recently went through a thrash with replacing the starter.

Also, what is this TD sensor called and where might it be located?

Thanks,

Nope, nothing to do with your problem, I wouldn't have suspected the OVP either. The OVP would cause the ABS light, but not "everything" goes through the OVP, just power to the items more subject to damage by overvoltages (hence the name), not things like light bulbs and antennas.
TD sensor is actually TDC sensor, it is like a crude version of a crank angle sensor, tells the things like the ignition system and the tach when the engine is at TDC (top dead center) on #1 cylinder, it's located up front facing the harmonic balancer, as it picks up the position on a small magnet on the balancer.
Not sure on you problem, would really need to study the electrical schematics, guessing some cobbled wiring or a loose connection in the fuse box.
Gilly

Thanks, Gilly. What caught my attention in David's post was the bit about heat. Whether my problem is heat related or not it mimics the fact that it could be.

My son is pretty sharp with electronics and he looked at the wiring diagram while home a couple weeks ago and determined most of the components come through fuses 5, 7 and 11. So he pulled those fuses and looked around in the fuse box, but saw no problems. I think I'll replace those fuses even though they look good.

My mechanic called the other day and suggested that it might be the neutral safety switch on the transmission. I've even thought of replacing the ignition switch just to see if that might be the problem.

Electrical problems sure can be aggravating...as we all know.

560sl
 

can i assume that you have checked the obvious? are both battery terminals clean and tight?

David,

Terminals are good and the battery cables have also been checked. It's perplexing.

560sl
 

ok you state that you are losing all power [no antenna,no int lites,etc] there would seem to be an interruption in the power from the trunk to the engine.under the hood is a big power bus in a plastic cover i think it's on pass side.check that connections are tight[one big wire from this bus goes to the starter]

David,

I found what I think you are referring to. It sits between the battery and the anti-freeze reservoir. I will have to take the battery out in order to get to it and check for tightness of the connections. Looks like there are four, maybe five, sets of wires that connect there. Unfortunately, I just had neck surgery a couple weeks ago and can't yet do any straining or heavy lifting. Getting the battery out could cause me some problems that I don't need.

We are going to meet our son and his family in Baton Rouge this weekend, but I haven't decided if I will drive the SL or the diesel. If I drive the SL, then it's something he can help check out. I'm concerned that if I put the SL on the road that it might just "fail to proceed" as a buddy of mine who once had a Rolls Royce said when his quit on him one day. I know that I wouldn't shut it off to fill up, but don't know if I want to test this particular problem to that extent. The wife would not be happy if we wound up sitting on the side of the road waiting for what seems like a 'reset' of the electrical system.

Anything else other than replacing the fuses mentioned previously that I might consider while I figure out how to con somebody into pulling that battery out for me?

Thanks!

The wires attach to the underside of the fusebox with phillips head machine screws, they can loosen up do to heat and vibration, make sure the affected fuses have tight screws underneath that attach to the power bus strips.
Gilly

560sl
 

wait a minute,hold the presses.........are you telling me that the battery is under the hood?because no self respecting us version 560sl had the battery anywhere else than in the trunk.give me the vin # of this car and letys find out which model we are dealing with.

Will do, Gilly. Probably won't do it today though. The humidity is a killer right now.

I've been very limited in what I could do the last six months and any exertion while outside immediately turns me into a dripping faucet. I'm glad to say though that I was told last Wednesday that I am cancer free. Just got some healing to do, regain some weight and get my strength back...and fix this problem with the SL!

Thanks,

560sl
 

it occurs to me that once you start the car that the battery is disconnecting from the main bus and that you have been running on the alternator it would sure explain a lot of things.