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Old 01-01-2018, 03:03 PM   #1
andyh1956
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Need RamJet Help

Happy New Year!
I need a little RamJet help today. I've been looking for a service manual for my engine, part# 12486611 but it is outta print. I most immediately need a wiring diagram for it. My engine is an MEFI 3.
If anyone can help I appreciate it!
Thanks!
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Old 01-01-2018, 03:30 PM   #2
Bigdav160
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Re: Need RamJet Help

I found these online.GM used that controller on it's marine engines also. Hopefully these will help.



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Old 01-01-2018, 04:40 PM   #3
oldusafmsgt
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Re: Need RamJet Help

I got mine from Jegs.

http://www.jegs.com/p/Chevrolet-Perf...06363/10002/-1
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Old 01-01-2018, 05:54 PM   #4
andyh1956
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Re: Need RamJet Help

Thanks Guys.
I have the Mercruiser Diagrams & while some parts are the same the distributor & hookup is different. Also the way the fuel pump driver works is different. But now that I think about it I prolly can use the info in these to make just the repairs I need!
oldusafmsgt that is an MEFI 4 book. I bet the wiring diagram for the 502 would be that same.
I had the wiring in a big box up in the barn & my neighbors horse tore the fence down so he could come visit our horse. He knocked the box over & stomped / chewed the wires...rowdy ass horse...
On another note Yall still using the MEFI 3 & 4 controllers or gone to something more modern?

Last edited by andyh1956; 01-01-2018 at 06:13 PM.
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Old 01-07-2018, 01:57 AM   #5
andyh1956
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Re: Need RamJet Help

OK Chevy Performance is giving me the run a round on this. No $ being spent so they blow me off.
There are a couple of places out in California that deal with the electronics on these engines & they have what I need but won't let me have it without me spending a bunch of money on "ECM Upgrades" & crap.
I'll pull this injection manifold off & chuck into the creek & put a carb on it before I let somebody strong arm me into buying something I don't need just to get a wiring diagram.
I'm starting to think I have a White Elephant.
If any Yall know of a bud who has one of these engines I would really appreciate an inquire to them about a diagram.
Thanks
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Old 01-07-2018, 10:40 AM   #6
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Re: Need RamJet Help

I am going to post these pictures again. I am not sure what happened to the linked pictures. I think there are a lot of items in the marine diagram that can simply be ignored for car application. I don't think the fuel pump and distributor wiring are insurmountable.

My ski boat has a Mercruiser Black Scorpion and, being a '96 model, likely has one of these controllers. It uses a GM small cap distributor also.

I have a similar port injected engine in my Suburban but since it is all homebrewed I went with a Microsquirt controller.
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Old 01-08-2018, 01:53 PM   #7
andyh1956
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Re: Need RamJet Help

Thanks a lot. I took some photos of the snow & a couple turned blue when I saved them, I dunno.
I have printed your diagrams out & have them in a folder.
I have ID the knock sensor wire & repaired it.
From your diagram I can tell the wire to the fuel pump should be signal to a relay.
Likewise the ignition circuit from keyed voltage.
The coil circuit I have ID by matching color, now just to determine what coil I'm gonna use & terminate the wires..
With your help I think I'm close to recovery here.
Working towards getting this baby on the test stand later this week.
Thanks Again!
Interesting to note on these Mercruiser diagrams that the voltage for the injectors & fuel pump relay come from keyed voltage, thru the inj & fpr then to ground inside the ecm, instead of coming FROM the ecm to the inj & fpr. I woulda never figured this out before I burned something up.

Last edited by andyh1956; 01-08-2018 at 02:42 PM.
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