Another "crank no spark" question

[bobworkman]

Need some help with crank no start problem.
Vehicle is a 2WD 1986 Suburban 305 with a carb.
The ignition control module is a 5 pin version.

So I have:
verified power at dist cap B+
early test showed no blink at Tach terminal.

Multimeter probe of coil tests OK for both primary and secondary coils.
Multimeter probe of pickup coil tests OK.

This seems to say Ignition Control Module, and I have a replacement, but
I always like to confirm things.
I found a post on NastyZ28's site on how to bench test a 4 pin ICM
and articles on how to bypass the Electronic Spark Timing on several sites.

I set-up the test, 9v across B+ and ground, test light between B+ and tach,
jumper wire to B+ so I can apply momentary power to the 3 pin side.
I find that I get a flash on test light only when I apply a brief voltage
to the D terminal of the ICM (black wire).

While on a 4 pin this should happen when the green wire is temporarily given power.
Of course when I bypass the EST I get the flash when either Black and Green is
momentarily given power.

So my concern is... "is this behaviour normal" for a 5 pin module implying that
my module is OK and implying that the problem is in the EST?

Looking for my thermal paste... then a reassembly and test,
probably cap off center button test 1st.

 

[Charlie]

 

[smoothandlow84]

Did you check the fuel delivery...pump...clogged filter etc?

 

[bobworkman]

fuel is present, also originally tried ether and no fire.
Problem at this point is NO SPARK.

 

[1987 GMC Jimmy]

Don’t want to sound like I’m undermining your efforts here, but how far are you from a NAPA or someone who might be able to bench test? I like the machine because it tests different parameters and the module gets really hot, which helps simulate a common failure condition. My best advice with the module is one, clean up the old paste on the distributor. I had a premature failure for not taking the stuff seriously so now I clean everything up and smear one packet on the module and another on the distributor. No problems for six months and hopefully that turns into years. Also, the best brand is AC Delco if you can get it. I wouldn’t trust the fly-by-night house brands except as a backup when you’re in a pinch and while waiting for a new module.

 

[bobworkman]

thanks for the reply... tried 2 parts stores, NAPA & Partsource.. they looked at me like I was crazy.
Testing availability may be different here in Canada.
Also I have read mixed reviews on tests accuracy. Seems that if you get the trigger right and the test lamp flashes module should be good, just not sure which line should be trigger on a 5 pin module.

My replacement is a Standard Motors LX331. they are a well known brand.

Found my Thermal Grease just need to install everything and wait for my trusty helper to test again.

 

[1987 GMC Jimmy]

Wish I could be more help on the testing procedure. I’ve tried to do the same thing after hours on a suspected faulty five pin module, but I couldn’t find any literature. You should have looked at them like they were crazy! In my experience, the first test will sometimes show a good module, but once it’s scalding hot, a subsequent second or third test will show a faulty one. And that’s not all the time because I’ve had them show bad right off the bat. Oh well.

I just sent a Standard Motor Products TB injector back today because it didn’t work right at all. It was a substantially different design than OEM, and it dripped like a mother. I should have stuck to OEM, and I ended up having to get an AC Delco injector after all this anyway. I hope you have good results with your new module. Not trying to scare you, but this was literally my first experience with Standard Motor parts, and I am not happy. I also looked for reviews for the LX315 module, and while there were none I could find, the four pin version had high marks on Summit so maybe I just got unlucky...

 

[bobworkman]

I bought my module from Rock Auto... delivered to my door in 3 days for less than $20 CDN.
Tried 3 different sources and they all quoted me $145 CDN... I will take my chances on the one I got for that kind of price difference.

 

[1987 GMC Jimmy]

Yeah, I hear you.

 

[Snoots]

Check out this site. He has fantastic tech and testing tips.

https://easyautodiagnostics.com/