Author Topic: I have no spark (Read 9602 times)

G$ 993 · « **on:** April 28, 2018, 20:10:11 »

Hoping for some direction on how to tackle this problem. Was driving a few days ago with no problems and engine suddenly died and won't start. I check the distributor for the "blue arc" while cranking but there is none so I clearly have no spark. No electrical gremlins prior to this issue. The engine and wiring is completely new from a fresh restoration (not done locally) with about 750 miles on it. Inspection of the engine bay and wiring around the coil and surrounding relay reveals no obvious bad wiring or disconnects. The coil is new and distributor cap was verified as excellent during the restoration. All fuses appear intact.

I'm not really sure how to attack this. Ideas on how to best trouble shoot this problem?

Thanks!
Mark

doitwright · « **Reply #1 on:** April 28, 2018, 22:38:29 »

See if this flow chart helps.

Mike Hughes · « **Reply #2 on:** April 29, 2018, 00:03:00 »

If it was running well until it quit, the first thing I would check is the distributor points if you have an original points & condenser distributor. This happened to me during a short run down the GW Parkway a few years back, and I got the car home after opening up the points on the side of the road. Lucy was amazed - she was sure we were going to have to call Hagerty for a flatbed home! Those shiny tools in the tool roll are not just for show!

The rubbing block on the points can wear down quite rapidly in the absence of adequate lubrication and the points will close up resulting in no spark. If the rubbing block is not completely worn away you may be able to adjust the points enough to get the engine started again. If you can, wipe a dab of grease around the distributor rotor first!

A new set of points will last a good long while if the proper gap setting is maintained and adequate lubrication of the rotor and rubbing block is performed periodically. The grease on the rotor dries out when a vehicle sits in the garage for extended periods - like all winter long until all traces of road salt has been washed away!

cfm65@me.com · « **Reply #3 on:** April 29, 2018, 01:04:43 »

I have had that twice in forty years. Once in the 70s a rubbing block broke off in the middle of the night, in the middle of now where.
Then about two years ago my E Type rubbing block wore down faster than normal and closed the gap, loosing the spark in a few 100 miles.
It is quite common for a new rubbing block to wear off prematurely and then after a while, settle down and continue to last ‘for ever’
It could also be that the points arced and welded a little **** on the contact points.
Regards
Chris
Cape Town

Benz Dr. · « **Reply #4 on:** April 29, 2018, 01:11:37 »

Pull the distributor cap off and try turning the rotor. It should move slightly in one direction and then stop. If it continues to turn you just found your problem.

In this case the distributor slid up just enough to loose contact with the drive gear. Loosen the clamp a bit and turn the distributor rotor until it drops down into place. Time your ignition advance to 38 degrees at 3,000 RPM.

This happens than you might imagine and more often when everything was just apart.

G$ 993 · « **Reply #5 on:** April 29, 2018, 04:31:38 »

Thank you guy for the suggestions and direction. I will investigate!

G$ 993 · « **Reply #6 on:** April 29, 2018, 05:20:20 »

So trying to read about this int the technical manual and understand the vernacular of a distributor but am getting confused. So I popped of the cap and took a few pics. Anything appear out of sorts? Guidance on how to attack this?

The rotor does move slightly in one direction and then stop. There is no additional turn.

Pawel66 · « **Reply #7 on:** April 29, 2018, 09:10:06 »

The cam looks strange to me... but I may not remember correctly, if it is wrong, others will say. Maybe it is just the angle of the picture - two peaks look somehow different than the rest seen...

So there is no spark on no plug, correct? And plugs look nice and clean?

Do the points open and close as you turn the engine?

To be honest - the best way forward is, I think, the algorithm Frank posted (thank you Frank!). It is a quickiest and cheapest way - to go systematically along the potential causes if obvious cause is not seen (lose wire, lose screw etc.). Important moment there is "Spark from Coil" - did you check that? If you have spark after coil, you have:

condenser,
points
rotor
cap

To be honest again: I have all four in my bag in the car always with me (Well, recently I switched to 123, but that is another story). They are not thousands of dollars.
Rotor and cap - can be visually inspected. check if the coal connector is there in the cap. Check for cracks (thinner than hair). See if the connectors on rotor are clean. Sometimes it is just about replacing and trying. Buy rotor and cap from a good source, do not save money ( I had a very bad experience with Beru in M103, I buy from Mercedes now - easier to give back if there are issues).

Points - gap should be checked and dwell. See if the screw holding the points is tight (the slotted one under the black wire on your pic). Cleaning the points with very fine sand paper may help as well. Bosch had a produciton lot of these points with fault - there were many cases here that new points stopped working. I am not suggesting this is your case, but it was a lot of headache for a couple of us here until they admitted that.

Condenser - may check the resistance. Otherwise I would replace it and try. You have an old condesner as much as I cen see.

Unless more educated fellow Members see anything on the pictures - do not shoot from the hip, go systematically through what Frank sent.

Tyler S · « **Reply #8 on:** April 29, 2018, 14:11:42 »

The spade terminal for the points lead looks dangerously close to the advance detent ball cover. If it is touching, the coil will load but never fire.

Jonny B · « **Reply #9 on:** April 29, 2018, 14:17:23 »

Does your car have the transistorized ignition? The factory one, with the transistorized module located below the battery tray. Sometimes a wire has been added to allow for checking of dwell. The wire would be coming from under the battery tray and then in the wheel well, or taped in place. The wire may make contact, or intermittent contact with ground, through the chassis. It can stop the car dead. It can be as simple as a frayed wire. It happened to me, and was just like an on/off switch.

Ditto on the comment about the condenser being an issue.

G$ 993 · « **Reply #10 on:** April 29, 2018, 19:20:38 »

Thank you guys for all the great suggestions. I have followed the very helpful spreadsheet and I have no voltage at the coil so I don't think its a distributor issue. There is only one wire that has any "blemish" in it that I can find. You can see in the first pic there is a partially uninsulated wire adjacent to the terminal lug and marked with a red arrow. All other wires appear sound. I have removed the battery and tray and inspected the wires there as well. All appears tidy (to my untrained eyes) but please see attached pics. Jonny B I am not sure about my ignition but I do not see this wire you speak of.

Thoughts?

Thank you!

G$ 993 · « **Reply #11 on:** April 29, 2018, 19:23:14 »

I should add that there is no voltage at this resistor where the possible wire in question is. I have been unable to check for voltage proximal to this as I had to remove the battery just to get to the wires! Ughh.

Pawel66 · « **Reply #12 on:** April 29, 2018, 21:32:27 »

I think this may be a serious wire. Is it cut (looks like it on the picture)? It is either the wire from transistor unit to resistor or from resistor to coil. If it shorted, that was not good for the unit and the car would not run, I think.

You have the description of transistorized ignition in the Tech Manual. There is a simple test of the module. I would check if the wire is not cut, solder it together if it is, insulate it, put all back together and then do the test from tech Manual. Simply hook the voltmeter to connector 15 on the coil and ground. Turn the engine so that you see in the distributor that the ponts are closed. Voltmeter should read around 3V. When points are open, voltage should be zero (like you said you had). If you do not get voltage when the points are closed (and the other resistor has indeed 0.4 Ohms) probably the unit is broken...

If I had this, I would be tempted to check if the car is running when you bypass the unit. But you have a blue coil probably. So do not try it unless someone confirms it makes sense as a test. I have never done it, so I am not sure if it is ok.

G$ 993 · « **Reply #13 on:** April 30, 2018, 04:54:30 »

Thank you Pawel66. I will investigate this unit more tomorrow. I have established continuity throughout the system from fuse 2 through the ignition coil. I will reapply voltage tomorrow to see if I can further isolate. Thanks!

450sl · « **Reply #14 on:** April 30, 2018, 08:59:50 »

you should have 12V at the coil ; if not suspect the ignition keyswitch .

Pawel66 · « **Reply #15 on:** April 30, 2018, 10:16:29 »

Quote from: 450sl on April 30, 2018, 08:59:50

you should have 12V at the coil ; if not suspect the ignition keyswitch .

Normally it is 12V, but this is transistorized ignition.

450sl · « **Reply #16 on:** April 30, 2018, 13:09:57 »

still need 12v

Tyler S · « **Reply #17 on:** April 30, 2018, 13:22:35 »

Havent seen if you have checked the fuses. If they all look intact try spinning them in their holders to remove any corrosion

G$ 993 · « **Reply #18 on:** April 30, 2018, 20:12:08 »

Thank you guys. Fuses are good.

I have been checking voltage across all points in the circuit using the #2 fuse. I now have 12V everywhere except I have no voltage at what I believe is the 4 Ohm resistor (#40 on the wiring diagram). I don't understand how I could have no voltage there but voltage at the coil. I have attached a pic of the resistor in question.

Pawel66 · « **Reply #19 on:** April 30, 2018, 20:38:14 »

You have no voltage on 0.4ohm resistor on the power supply side (ignition side)? Or the trnasistor modue side? Sure you measure correctly? This is the only way power gets there when you are not cranking the engine. Have you checked the resistance of that resistor?

Maybe someone has already bypassed the transistor gear? You would do that by connecting ignition switch wire with the other resistor and the other end of the other resistor with connector 15 on the coil. Maybe also the blue coil should be replaced (not sure).

Can't get it either...

Pawel66 · « **Reply #20 on:** April 30, 2018, 20:41:39 »

Quote from: 450sl on April 30, 2018, 13:09:57

still need 12v

Ok, thank you. My experience with transistorized ignition is limited to just one car some time ago. We were checking that voltage, but I do not remember how many volts were there. I would have thought I was comparing it with Tech Manual that says around 3V, but I may be wrong. Thank you for straightening it out.

Tyler S · « **Reply #21 on:** April 30, 2018, 22:36:12 »

Quote

I have been checking voltage across all points in the circuit using the #2 fuse.

How are you checking voltage?
Using a test light or a multimeter, you need to ground the black lead. Preferably on the battery. Then use the red lead or test light probe to check for voltage all along the circuit. A test light is preferable because a voltage drop could exist and a meter wont pick it up if the circuit is not loaded. Do your checks with everything connected and the key on.

G$ 993 · « **Reply #22 on:** April 30, 2018, 23:34:32 »

I think I have figured out the issue with the car. I had a poor ground before. This has been resolved.

Let me explain and see if you guys agree. So to summarize, I checked continuity throughout the system and found no issues. I then removed the battery and then connected the battery to the terminals in the car via jumper cables. I then checked voltage at all points beginning at the #2 fuse followed by the 0,4 Ohm resistor, the #15 wire on the transistorized ignition, the 0,6 ohm resistor and finally the coil.

I was able to find voltage through the #15 wire however there was no voltage at the 0,6 ohm resistor, I then created a paper clip jump from #15 -> #16 wire on this terminal (see pic below) and established voltage at the 0,6 ohm resistor and the coil. Thus I think the transistorized ignition module (MB Part No. 000 545 18 32) has failed. From my reading it appears the entire unit would need to be replaced.

You guys agree?

Tyler S · « **Reply #23 on:** May 01, 2018, 00:01:48 »

If the points happen to be open at the time of your check then no, you will not see voltage at pin 16 or the coil. Verify the points are closed and working by checking for ground on pin 7. You can also hook a test light aligator clip to battery + and use the probe to check for a pulsating ground while cranking the engine. This will verify the points and condensor are ok.
Additionally, you can check if the transistorized unit is functioning properly by supplying it your own momentary ground with a jumper wire to pin 7

Pawel66 · « **Reply #24 on:** May 01, 2018, 17:19:31 »

As Tyler is saying: you do not get voltage on 0.6 Ohm resistor and coil when the points are open. You get voltage only when the points are closed. Verify that before concluding. Also: what Tyler says about providing ground "manually" to connector 7 - by manually providing ground there you perform the function of points. You should get voltage on 0.6 resistor and coil as well.

If you do not get voltage on 0.6 resistor and coil when the points are closed, but you get voltage when you supply ground "manually" - there is something wrong with the points.

If you do not get voltage on 0.6 resistor/coil with points closed or with ground provided manually - this indicates the unit is broken.

News:

Author Topic: I have no spark (Read 9602 times)

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