Well, I found out what happens if the limp mode relay is actuated through the accessory switch (correct) but the “B” "VRef" pin (correct) is hooked to the relays’ “87A” pin by mistake (NOT Correct) instead of pin "87". In other words the "Ref" signal is honked up. The the engine will try to run for half a second, every 2 seconds. But it will try to run terribly. You’ll know something is wrong. But it’s hard to find out "What" is wrong. It may even kick back against the starter, HARD. This may damage the flywheel starter ring. Yepper, mine broke. Heck, it even RAN BACKWARDS for about 2 seconds on the fuel that had been dumped into the exhaust. Boy, did it sound funny and loud, as it spit fresh fuel vapor everywhere!
Probably most people won't ever need or read this, this is just in case someone does have this terrible starting issue. It took me a long time to find it as I "Knew" I did everything correctly. And the schematics make it look like the timing would have just been advanced too far. Well, not so. Anyway, don't do what I did.
Holl
8 pin HEI Limp mode relay
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0). For tuning/troubleshooting questions, please attached a datalog and your MSQ file to your post.
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
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Bernard Fife
- Master Squirter
- Posts: 475
- Joined: Thu Oct 29, 2009 12:54 pm
Re: 8 pin HEI Limp mode relay
Holl,
Yeah, too much advance is a killer on starters. On my application (406cid SBC) anything more than 12 degrees advance while cranking would crack the aluminum nose housing on the OEM 'big block' starter. This allowed enough play that the teeth wouldn't engage properly, putting even more stress on them, and it was all downhill from there.
I had a pile of 8 or 9 of them at one time - all brand new, with just a few miles on them, but broken off due to too much cranking advance. Luckily the ring gear wasn't damaged by these events.
Eventually I ended up buying a bullet-proof aftermarket gear reduction starter, and setting the cranking advance to very near TDC, and haven't had any problems since.
Lance.
Yeah, too much advance is a killer on starters. On my application (406cid SBC) anything more than 12 degrees advance while cranking would crack the aluminum nose housing on the OEM 'big block' starter. This allowed enough play that the teeth wouldn't engage properly, putting even more stress on them, and it was all downhill from there.
I had a pile of 8 or 9 of them at one time - all brand new, with just a few miles on them, but broken off due to too much cranking advance. Luckily the ring gear wasn't damaged by these events.
Eventually I ended up buying a bullet-proof aftermarket gear reduction starter, and setting the cranking advance to very near TDC, and haven't had any problems since.
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it.” - George Bernard Shaw