Megajolt problems after alternator failier

General Topics for configuring, operating and tuning the Megajolt. Also see the <a href="http://www.autosportlabs.net/MJLJ_V4_Operation_Guide">Operation Guide</a>

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snapperpaul
Posts: 13
Joined: Mon May 02, 2005 9:43 am

Megajolt problems after alternator failier

Post by snapperpaul »

Past SVA, got registration etc then went for some short runs, the car had been started and run for almost a year but had net been on the road.

Previous 7.5 amp fuse failure put down to magajolt and edis from same feed so upped fuse to 10 amp no problem since

after running the car on the road for about 60 miles the volt meter went from 13.5V to 11V and falling, i charged the battery and ran the car for a further 20 miles before coming to a halt.

re-charged the battery and tried to start but no spark
Replaced alternator, car would not start.
Changed coil and EDIS but no spark seen

Checked wiring for connections and continuity

Checked for spark again and found very weak occasional spark

connected computer and cranked, V2 megajolt on MAP, displays 0 revs, 80 to 96 Kpa vacuum, 37 degs of advance at cranking, map shows yellow dot @ 0 Kpa, 0 revs, 14 deg advance bin, also shows red dot at 80 to 96 Kpa @ 5000 revs, 37 degs of advance.

Some advise on how to proceed please, just got the car on the road and am gutted that i cant drive it,

brentp
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Post by brentp »

Hello-


While cranking:

What voltage are you reading at the coil (the common +) connection? Also, what voltage do you read at the +12V supply of the EDIS module?

While observing the configuration software, do you ever see the "timeout" error message at the bottom while cranking?
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snapperpaul
Posts: 13
Joined: Mon May 02, 2005 9:43 am

Post by snapperpaul »

I get 12V at common feed to coil and 12V at feed to EDIS

No time out message while cranking

I have a spare coil pack and EDIS, i have swapped both out and have eliminated these as a faulty

brentp
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Post by brentp »

With two different EDIS modules tested and the MJLJ seemingly functional, it seems at this point you should treat the alternator failure strictly as 'coincidence' and re-validate your whole installation.

That is- check all of your wiring (understood you've done much of that already). In addition to what you've done already, double check all of the ground connections, especially at the EDIS module. (this might be the cause of the weak spark) If you suspect your ground, run a temporary wire from the EDIS ground connection straight to the (-) of your battery. You can even temporarily run + and - straight to your battery for the coil pack, EDIS and MJLJ to eliminate variables.

Also check your VR sensor signal- while cranking watch for a voltage on this signal. Also check your VR sensor for misalignment/gaps.

Let us know what you find out.
Brent Picasso
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snapperpaul
Posts: 13
Joined: Mon May 02, 2005 9:43 am

Post by snapperpaul »

My conclusion is that the problem was Me leaping to conclusions.
A weak or seemingly weak spark was the cause of myself and my friend trying to eliminate electrical problems when there were none or at least a few minor ones.
We did find some anomalies in the main wiring loom for the EDIS and the Megajolt, TPS power wire connected when i am on MAP and some shielding wires not earthed.
I did also find that the VR sensor had slipped and was quite some distance from the trigger wheel, all this was corrected Sunday afternoon but still the engine would not fire up, some weak sparks were seen when tested and the spark plugs were checked for gap and condition. Power to all the right places and battery fully charged
Back to basics I thought, fuel should be OK as i brimmed it last week and have not used it since, fuel guage said 3/4 full.
Popped the fuel pressure guage plug and cranked, oops no fuel, check pump, it pumps, check fuel tank with stick not 3/4 thats for sure, add gallon of fuel, it fires and runs.
Embaressed or what.
SVA fuel filler restrictor had turned all the way round so when you fill by the pump it blocks the filler tube and fuel squirts out of the breather holes, that why i thought i had brimmed it, new replacement Telemetrics guage reads empty when full and full when empty when connected to the ancient sender provided with the kit.

Sorry to all those that replied and lessons learned for me, start with Spark, Fuel, Air, then investigate further.

Oh i don't have a capacitor fitted to the EDIS power feed, do i need this? if so what size?

DannyP
Posts: 417
Joined: Sun Apr 09, 2006 3:48 pm

Post by DannyP »

Paul, capacitor not needed, glad you figured it out. I've had a few of those moments in my life, sometimes you just want to smack yourself with a hammer!

brentp
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Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

Simple problem, simple resolution- good!

With that still a fresh experience, you should especially enjoy this story. :)
http://www.damninteresting.com/?p=744
Brent Picasso
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