Trigger Points & 4 fuel injectors/seals

Hi all,

Thanks for the advise so far. Brought the '75 450 SEL I bought to my independent guy and he said I need new trigger points and at least 4 new fuel injectors and seals. Possibly a new ignition module. Gave me a ballpark price of $1500-$2000 installed.

This is waaaay more than I want to spend on the car. If its the case, I'll sell it for what I can get.

Can anybody give me some feedback? Is any of this too difficult to try to DIY? I don't have much experience with the gassers, but I have a desire to learn and I sure love these old cars.

Wondering if I sould try to clean the trigger points. Is that possible?

Thanks in advance.

[kpb]

You should get a bunch of responses on this. In my short time of MB gasser ownership I have learned the trigger points are readily accessible once the distributor is pulled but you must NOT use any abrasive to clean them as they are platinum and you will scour the precious metal right off. Fortunately, I did not learn this the hard way but rather from the collective wisdom of this assemblage. If you run a search at the bottom of this page and put in "trigger points" I bet you'll get some very helpful info. Hope you can hold on to your ride

kpb

Thanks for the info! Need to find a local MB buddy who can show me the ropes on my old girl!

[Tomguy]

The trigger points new cost about $200. Involves dizzy removal and replacement, then re-timing. No more than 2 hours for the dumbest and most incompetent mechanic.

The injector seals are about $1 each. you only need to replace the "lowers." Once again, 2 hours for the most incompetent mechanic.

Go back to him, laugh in his face, and tell him it'd be cheaper for you to do it yourself, take 3 weeks, and screw it up 4 times.

Gonna tackle the car this weekend. Please know I am by no means mechanically inclined, but I love these old cars and want to keep this big beast running, so hopefully that counts for something~!

Here are my symptoms:

She will begin to skip, sputter, hiccup, etc. Especially when going up hills. Fuel economy plummets. Sounds as if maybe a cylinder isn't firing...hesitation as well. I suspect something in the fuel delivery/injection sysytem. Previous owner thought was ignition related and replaced plugs, wires, distributor, cap etc but couldn't solve.

I plan to:
1. Replace fuel filter.
2. Clean Trigger points with LPS electronics cleaner.
3. Replace fuel injector lower seals.
4. Run some fuel injection cleaner in the tank.

If this doesn't help, I will:

1. Look at replacing with Pertronix ignition (although the ignition module was just replaced -newly rebuilt.
2. Look to replace the fuel injectors themselves.
3. Any other ideas?

I have a couple of specific questions:

My car is a '75 non-calif 450 SEL. Knowing that, can anybody tell me which type of fuel filter and lower injector seals I should buy. On the fastlane parts site, they have many different options.

Anything else I should be thinking of to solve this problem?

Thanks very much!

[psfred]

Replace the ignition points. If they foul again, replace the coil and get a Pertronix or Crane ignition to replace the breaker points and the factory transistor unit.

Peter

Thanks very much Peter.

a couple of things:

1. The PO said he replaced the coil and yes, it looks new.
2. When you say breaker points, you mean trigger points?
3. Is one better than the other--Crane or Pertronix?

Since the PO says replaced the ignition module recently, does that mean anything?

Thanks a lot. I have a long way to go as you can see.

[ctaylor738]

Peter usually says this, but also closely examine all of the vacuum lines to make sure they are connected, and replace all the rubber connectors. Make sure that your cabin vacuum is tight, and if it isn't, block the connector at the back of the manifold.

Check the spark by pulling a wire off a plug and holding it an inch from ground while someone cranks the engine - if it's nice and blue, don't worry about ignition just yet.

If it makes any difference, the vaccuum locks do work, albeit s-l-o-w-l-y and the door lock post does not go all the way down, but just enough to engage the locks.

if the car sits for a few days, the vaccuum is lost and won't work.

[psfred]

You have ignition points, too -- this is a breaker point transistorized ignition, with the points acting a a logic switch, main coil current is handled by the switching unit.

The problem is that when the dizzy gets worn, you get too much oil vapor in there and the ignition points get dirty, causing problems with spark. Pry off the white plastic cover and run a bit of clean paper between the points. If it tears, they are shot, replace. If it slides, but comes out filthy, you will have to clean them periodically until you either re-bush the dizzy or replace them with a Pertronix or Crane system.

I have no evidence that Crane is better than Pertronix, take a look at both and see what you think. Pertronix is easier to install, I think.

Other things to check are the vac line to the MAP (on the firewall) and the MAP itself -- must hold vac. The line is a problem, it's a metric size and you must get the next SMALLER SAE size hose to replace it, or you have a big vac leak (and rich running).

If the mixture doesn't change when you adjust the MAP, it's dead and must be replaced ($$$).

Peter

talked again to my mechanic--he said my fuel injectors were leaking. I said I wanted to replace the lower seal and he admonished me not to--said could have "big problems".

Sheesh-starting to appreciate more my 300SD. no spark plugs, no distributor, no trigger points, and yeah--no power!

[ctaylor738]

1972 450SL hot start and injectors

[Tomguy]

Originally posted by GoWolfpack
talked again to my mechanic--he said my fuel injectors were leaking. I said I wanted to replace the lower seal and he admonished me not to--said could have "big problems".

Sheesh-starting to appreciate more my 300SD. no spark plugs, no distributor, no trigger points, and yeah--no power!

Replacing the lower injector seals can do NO harm, and if anything, would do good.
Unless your mechanic pulled ALL 8 INJECTORS (with them still on the fuel rails) and tested them for leaks by EXAMINING the tips on EACH ONE with the system FULLY pressurized, he cannot honestly tell you any injector is leaking.

I don't have one single leaky injector.
Pull all 8 off the rails and soak them overnight in carb cleaner or similar. You can do what I did if you don't mind - I put my vac pump on the ends of the hose (with an adapter included) and pumped to 25" of vac, then put the nozzle in rubbing alcohol and opened it (be careful of sparks near the alcohol, a remote switch is more ideal). I let 1" of alcohol flow into the long clear tube, then I took it off, put the injector on a towel (tip-side down) and pulsed it a few times. I then leak-tested them with the vac pump.

And I just notice that he suggested a new ignition module. If the car runs, it's good. I don't think there's an "In-between" with these, they either work or they don't work. And since it was "replaced recently" there is NO need to do anything with it. I think most of us here are still on our original unit! (Note: I'm not - I'm on an original unit from another car, a '71!)

[psfred]

the body of the injector can crack and cause leaks, in which case they must be replaced. Not cheap.

Seals are easy, and what looks like a dripping injector can easily be a vac leak on several others, with the CO set at the tailpipe -- the ones NOT leaking air from bad seals will show up rich on the plugs as though they were leaking.

Leaking hoses can be replaced (see the kit on FastLane).

Ignition points full of crud will cause misfire, but if you start and run, the switchbox is OK. Bad primary resistors, on the other hand, will cause weak spark from low current flow to the coil -- check the resistance and replace any corroded or cracked resistors -- on the W108 they are on the driver's side innner fender near the rad, don't know where they are on the W116.

Peter

[Tomguy]

Peter: Same location in the 116, right in front of/below the coil, two (a 0.6 and 0.4 ohm).