It first started as a no start after driving for awhile. I suspected fuel system, but then the car won't start at all, hot or cold. Traced the problem to a no spark condition from the coil. Coil resistance is in spec and I have all the proper voltages per service manual. Distributior resistances are also within spec. Fault by elimination is leading me to the ignition control module. Has there been problems with the control modules, and could this have been causing the no start after hot soak isuue? Thanks for any help!

you may have 2 problems. very likely with an old car. 1-the no start when hot is probably the accumulator and/or the fuel pump check valve. 2-constant cranking, trying to fire a low pressure fuel system, likely took out the ignition control unit. there's a specific checkout for both. the first requires a dedicated pressure test and tester for the fuel system on the car, not a generic 1. the 2nd has a trouble tree which i don't have right now. but, the ignition has to see specific things in order to work. it wouldn't suprise me if you had both problems. seen it a few times over the years. you have to buy the fuel tester and i have to find both tests. lemme know, chuck.

I went through the tests in the mercedes service manual (I have it on CD-ROM), and it didn't exactly say that the module was bad, but everything else was in spec or passed the tests. After reading many posts on here, I am definately looking at a new accumulator. If you have any other tests, it would be great. I really appreciate all the help! Thanks!

Before you go replacing the fuel accumulator or other fuel parts you should do a fuel system pressure check.

I have a 78 450sl and I had problem starting, "went away" and returned again. I replaced several fuel parts before I went out and get a fuel pressure tester for my car; the thread is below; ~$100 with shipping, but worth it to diagnose properly.

Where to purchase a fuel pressure gauge - 78 450SL CIS

What I've found: Fuel pressure is excellent; 6 bars as should be. What the problem likely is for me - auxiliary air valve; it probably sticking/not sliding and hence replicating having a broken vacuum line and hence not starting.

I'm gonna work with/replace the auxiliary air valve when I next get a chance, but here is another post on aux air valves

1976 280E Hot Idle Problem

In any case, I suggest getting the fuel pressure tester to resolve its not a fuel problem.