Trigger Points

Hi all,
I am a bit slow so please spell out your response like I was a 2 year old.

I am presently replacing the Trigger Points that I bought from Volker (in my 73 Merc 450 SLC) . I just wanted to check that all is ok before I put it back in the car ( I set the gap to app. 0.5 mm but it is hard to get it exactly 0.5 mm). I rotated the distributor checking with a multimeter and and marked on the top of the distributor the range when each of the 4 points were 'firing' when there was a circuit. Using a protractor I measured this time period as a degree.
1/. Is this time period when the contact points are closed / contacting / off the cam?
2/.My range was approximately Red 147 Dg, White 150 Dg, Green 150 Dg and Yellow 140 does this seem reasonable? MBGraham in this post Trigger Points Cleanup & Adjustment recommends that they should be between 100-120 degree??? What are your thoughts?
Regards
Peter

Hi Peter,

150° is a good value, 100-120° is small.< and I would not recommend setting that value. If you do so it means that you set cams closer than these famous 0,5 mm from rotating shaft. 0.5 mm is selected as the opening distance of shaft is 1.0 mm and thus we move in the middle. As we are not charging an ignition coil and as ECU only triggers on closing contacts, this value is not that important. What I do is that I put repaired trigger contacts on my ignition distributor test stand and align them to have SYMMETRIC closing angles and I also chack that they are 90° apart. Those 90° are most important.

Hi Volker, Hi Peter
- long closing time (150°) means :
- wide play between tool and fibre blocks
- points opening late, closing early
- small points-gap
not much reserve for fibre-blocks-wear.

- short closing time (100°) means:
- small play between tool and fibre blocks
- points opening early, closing late
- wide points-gap.
high reserve for fibre-blocks-wear, but maybe probs with fluttering points.

Consider adjusting using my tool... you will get reliable adjustments and the trigger points life will be as long as if they were new.

Regards
Norbert

Thank you for your information. It has cleared up my confusion about whether I was measuring the open or closed period on time. I used the tool to set the gap ( a rather stiff 0.5 mm). All of the 4 are now reading 143° so I'm pretty happy with that. Now to put it back in the car - Fingers crossed
Thank you both (again).
The information was clear and easy to understand.
Regards,
Peter

Sorry to be a pain,
I put the distributor back on and noticed that it was only running on 4 cylinders 2 pairs (1 and 5 and 4 and 8 are NOT working). It has spark - my fingers can testify this but I put a multimeter across the connection on the Trigger Point terminals using the black as the common- I got around 2.6 volts on the red and Green but next to nothing on the White and Yellow ( I'm pretty sure these are the banks not firing).
The question I have is this a Trigger point issue or an ECU issue or something else?
Regards
Peter

Hi Peter,
the wires of this kind of trigger-points-unit tend to break at the connector towards the housing. Maybe the grommet there is missing or defective... maybe you bended the cable some times. It's a problem that occurs quite often.

Disconnect the connection towards the D-Jet-harness and check boh the yellow and white wire for continuity against the black one.
If there is no continuity even if you let the engine turn, the wire will be broken.
Or check this after having removed the trigger-points-unit from the car.

Regards
Norbert

Hi Peter,

it is one of the reasons why I check repaired trigger contacts on an ignition distributor test stand. I am eager to see the symmetric 90° between all 4 contacts but also eliminate errors like

• contact issues like oil and dirt on contacts - I had to disasselble complete T.C. with transparent covers when I noticed a contact resistance. Since then I clean them before assemblng
• swapping upper and lower contacts erroneously while soldering them back to connector inside
• contact problems on connector outside and wires
• loose parts inside like rivets or screws so that t.c. can move
• This connector is especially often broken on grommet outside. I very seldom see a clean one.

So I feel much more confident when I do the live test. Of course I use Norbert's tool to pre-align them.

Hi all,
Just an update I went out and "mapped" the ignition points on the distributor to the opening/closing of the trigger points ( I don't think it has anything to do with my present problem) but all the ignition points (bar the green #14) are exactly the same as the closing (impulse) of the trigger contacts. I thought they had to be roughly 15° before spark??? I am wondering, and I'm not sure if this is possible, whether the guy who refurbished my distributor (and again I don't even know if it comes apart) may have split the shaft and put it back together out of its original alignment.???? I also checked the corresponding injector leads for voltage and there was none. I'm sorry about the quality of my drawing and the colours on it match the coloured wires at the trigger points. Someone replaced the original. I really am grateful for all the help you guys give and enjoy working on the old girl - bit like a 1000 piece jigsaw puzzle -sometimes with 1 piece missing .

Hi,

closing time of ignition contact determins dwell and thus charing of ignition coil. That is not the ignition timing. That is determined by rotor to cap.

Hi,

I do not want to open one of my T.C.s to verify color.

If your sequence does not fit, ECU will ignore contacts due to expecting them in right sequence.

Hi all,

I think I found the issue . The Yellow/Red wire in the connector from the ECU had broken off # 21 and I assume this effects its partner Yellow/Blue #22 as well ??? I haven't fixed it yet but I'm hoping all is good??? I'm wondering whether I shouldn't change the connector whilst I have it off??? Thanks you all for your input - although I don't understand every detail I like the learning experience.

Thanks
Peter

PS. All good except I found that #1 cylinder is not firing. Is it possible to have a faulty injector that still shows a resistance? O'h and I'll check the compression. leads and plug tomorrow. Enough for 1 day.
Thanks again.

Hi Peter,

if 1 contact does not fire then it can happen that the next following contact is ignored. ANd yes an injector can have resistance and still not open. Touch them while enigne runs and you will feel a tick if it operates.

Hi Peter,

I was just informed that you copy my pictures and parts of my articles elsewhere on the internet. Please be informed that you violate copyright by doing so. Please remove and leave a link to my articles / pictures instead.

Oh sorry. I didn't know this was a rule. I will do so immediately.