Cleaned EFI Points 1974 450 SEL - Won't run now!

[EthanH]

Okay, I know this is well-trodden ground, but I decided to clean my EFI points today in hopes of curing a rough-running when cold condition, and now the blasted thing won't start at all (or it will, then sputter, then rapidly die). For what it's worth, I used an electronic parts cleaner.

I figured that maybe I was off a tooth when reinstalling the distributor, so I pulled the valve cover off of the left (passenger) side, and made sure that I was at TDC on the compression stroke of cylinder 1 before realigning the rotor with the mark on the distributor. It's perfectly in alignment when at rest, but can be pushed past the mark maybe 1/4", which I figure is for the vacuum advance, right?

The only other thing I can think to mention is that the bakelite surrounding the 4 wires going to the EFI points (on the outside of the distributor) cracked up and fell off during the removal and reinstallation process. I didn't see any arcing or anything, though.

I didn't reset the points because I didn't loosen them, and I haven't dynamically timed it because I can't get it to run long enough. Am I missing something obvious? Thanks in advance! This car's been a bit of a headache so far, but that's to be expected with a 35 year old car that didn't see much use. Once I get through the teething process here, it'll be a joy to drive for a long time....
Ethan

[Gurunutkins]

first time I did mine I had a similar problem, the two "legs" of the points have to sit between the dimples at the back of the distributor to get them aligned. even if its out of true you can put the screws in and do it up but you don't get any signal. check that first and see if it helps
cheers
barri

[ja17]

Hello Ethan,

Most likely your timing is off as you suspected. You can do a static timing setting with 12v test light or an ohm meter. Turn the engine by hand. When it comes to 0 TDC compression stroke, adjust the distributor (turning closckwise) so that the reading on the meter or the light changes, (indicating the ignition points opening.) This should be enough to get you started. Finish timing adjustment with car running.

[meltedpanda]

Check what Barri mentioned and if OK , another way to time is to keep the distributor loose and have another start it while you make quick ( but small) adjustments, just keep your fingers and hair out of the way.

[EthanH]

I guess there are advantages to being bald! I will try these suggestions today and report back. Thanks again for all the help!
E.

[EthanH]

Okay, so after pulling everything apart again and checking, it's running just as bad as before. Seems like it's missing on a few cylinders. The trigger points and distributor were installed correctly. I even moved the distributor one tooth each way from what I thought correct was, and it wouldn't start at all, so I'm sure that's right, now. When I put it back where it belonged, the car would start (barely) and stumble for a little bit before quitting.
Since the bakelite over the trigger point wires (where they enter the distributor) cracked up on me, I'm wondering if it's not just shorting out. I'm thinking of just getting new trigger points and going from there....thoughts?

E.

[Tomguy]

Rule out the trigger points easily:

"Screwdriver test" with the engine running. See if they all fire. Hold a screwdriver against each injector and listen with your ear. I use a rubber heater hose since I'm deaf and can't hear w/a screwdriver personally. If any are missing you may have bad points, a bad harness, or bad injectors. If all 8 fire, then it's ignition. If any miss, it's bad trigger points if the pairs that miss are:
1 and 5
4 and 8
5 and 3
7 ans 2
Otherwise it's bad injectors. If none miss, look ignition. If ignition is fine, they may be clicking but have a poor (or non-existent) spray.

[meltedpanda]

I always go back to where I started when my result is worse than before I started and trace my steps. On my 220 rebuild after setting points and new condenser - would not start, two days later traced my work and found a short

[EthanH]

Okay, new trigger points cured the "not running" problem, which I expected. Given the way the wiring harness and connectors crumbled when I pulled the old ones out, I figured new points would be a good idea.

However....although it's moving under it's own power again, it's still not running particularly smoothly. I guess I'll check the grounding wires next....

Ethan

[meltedpanda]

in what way now? Here is a check list
Misses and Hesitates under a load
1. Fuel pressure incorrect:
2. Fuel injector clogged:
3. Control Plunger Binding:
4. Incorrect ignition timing or faulty ignition system:
5. Clogged Fuel Filter:
6. Faulty injector:
7. Vacuum leaks:
8. Fuel Pump not working:
9. Warm Control Pressure too high:
10. Warm Control Pressure to low:

[Tomguy]

Originally Posted by EthanH

Okay, new trigger points cured the "not running" problem, which I expected. Given the way the wiring harness and connectors crumbled when I pulled the old ones out, I figured new points would be a good idea.

However....although it's moving under it's own power again, it's still not running particularly smoothly. I guess I'll check the grounding wires next....

Don't put the cart before the horse. Find out which injectors aren't firing (if any), then find out why. Common mistake shadetree mechanics make. This way you know which trigger point wire(s) and/or ground(s) are affected.

[bwostosh]

My cheap trick is to allow the engine to cool, or start the next morning.

Idle for about 1 minute and touch the exhaust manifolds one at a time near the head to check for temperature hot=firing, cold= not (duh)

They can electrically fire (do the click) (listen with shop vac hose stethoscope) but ignition not spark correctly. hot=firing, cold= not

This is tracking down and isolation, to determine source of failure.

This motor can be diagnosed and tuned by ears and logic.
Just a few bits of experience too.

[EthanH]

Thanks for the tips, guys! I'll start eliminating suspects tonight, starting with ignition timing and dwell, checking the injectors, etc. When I bought it a few weeks ago it ran brilliantly, and has since started acting up, so I can't imagine it's anything too serious. It was a one-owner car with 95k miles on it that was always garaged, so I imagine almost everything that's wrong with it is down to not having been used enough....
E.

[EthanH]

Narrowing things down, but still not quite there. Based on how flawlessly the car ran when I got it a few weeks ago, I'm convinced that the ignition timing is the primary issue at this point (especially since the trigger points are brand new).

I checked the dwell yesterday and it was at around 13 degrees, so I reset it to 32. The factory setting is something like 30-35. That improved things somewhat, but when I set the ignition timing to 5 degrees ATDC per the manual, the car was totally gutless, missing all over the place, and barely made it up the hill out of my neighborhood. I reset it to about 5 degrees BTDC and it improved somewhat, but still seems to be missing under load. (For what it's worth, the vacuum is fine). It idles nicely, though. I'm going to try to advance it another 5 degrees and see what happens. 10 degrees BTDC is about as advanced as I want to go though; I don't want to risk any more than that. I'll keep you all posted.

E.

[Gurunutkins]

Hi Ethan
I have a 450sl same year but our engines should be pretty similar. remember that when the vacuum is connected it works backwards to normal. best way to do the timing is get it running then set it to 30 deg BTDC at 3000rpm.
cheers
barri