MSD Tech Support Forums

Go Back   MSD Tech Support Forums > MSD Ignition Forums > Trouble-Shooting

Trouble-Shooting Diagnose your ignition

Reply
 
Thread Tools
  #1  
Old 04-18-2012, 01:14 PM
FONC FONC is offline
Junior Member
 
Join Date: Dec 2011
Posts: 12
Question Msd-7ml-2

G'day Fellas,
We have a MSD-7ML-2 fitted in a circuit race boat. With MSD Pro Power HVC. The motor is SBC 363ci SB2.2 (6ltr Carby eng).
Motor rpm range upto 8500.
Recently we had an ignition problem. Backfiring and ignition cutting out completely for several minutes and would then restart. After a short run time would do the same thing.
Replaced igniton coil still had same problem. Checked all wiring no fault found. Checked MSD Pro Billet Distributor pick up sensor, cap, rotor and leads all okay. Replaced battery as we run a total loss system (no alternator). Same problem existed still.
Tested the complete ignition system with MSD Ignition test unit. Ran system at 15,000 rpm for 10 minutes with no problems.
Put boat back in water to run under race conditions same problem existed.
Replaced MSD-7ML-2 with a spare unit and this solved the problem.
The faulty unit was sent for repairs to Rocket Industries. Unit was returned and we were told no fault was found.
Unit was refitted to boat and under race conditions failed by breaking down (misfiring) as if running on rev limiter. Removed Rev limiter chip same problem.
I have since opened unit up it was very dirty inside unit as well as a lot of rust on a coil unit inside.
Long story I know and a frustrating problem can anybody help with a diagnosis here please?
Thanks in advance for any advice or assistance.
Reply With Quote
  #2  
Old 04-18-2012, 03:04 PM
msdtech1955's Avatar
msdtech1955 msdtech1955 is offline
Senior Member
 
Join Date: Jan 2008
Posts: 8,692
Default

1)whats a carby?

2) where is everything grounded too?
Reply With Quote
  #3  
Old 04-18-2012, 06:25 PM
FONC FONC is offline
Junior Member
 
Join Date: Dec 2011
Posts: 12
Thumbs up

G'day MSDTech1955,

1. A carby is a carburettor. The carb we run is a Holley Dominator 1150 cfm. In saying this we do not have a fuel problem.

2. All earths (grounds) are direct to battery earth (negative) terminal. We run no alternator. We do keep the battery fully charged. Maximum running time including warm up time and race time is 6-8 minutes.

We are still running nearly the same system wired exactly the same way as the MSD wiring diagram.
The only thing that has changed is the current unit we are running is a MSD-7AL-2 instead of the MSD-7ML-2.

As stated earlier the MSD-7ML-2 will run perfectly all day on a MSD Ignition Test Unit at 10-15000 rpm. As soon as it is fitted to an engine very similar to a old style NASCAR engine SBC with SB2.2 cyl heads 12.5:1 comp ratio runing on Avgas 100 under a proper engine load condition the unit fails to fire the engine. To fix the problem we simply put a new unit in place of the old one and the problem is solved.
My question is what is wrong with the unit that won't run when connected to the engine. It has been tested by the Australian authorised repair facility who gave the unit a clean bill of health. No problems found with unit. Yet it has exactly the same problem as it did when we sent it away for testing after it failed.
Thanks again for any input.
Reply With Quote
  #4  
Old 04-19-2012, 08:49 AM
msdtech1955's Avatar
msdtech1955 msdtech1955 is offline
Senior Member
 
Join Date: Jan 2008
Posts: 8,692
Default

is the battery grounded to the heads ..motor plate ..?
Reply With Quote
  #5  
Old 04-20-2012, 04:10 AM
FONC FONC is offline
Junior Member
 
Join Date: Dec 2011
Posts: 12
Smile

G'day MSDTech1955,

There are several earthing cables. The main cable is battery (-) to aluminium (non anodised) flywheel cover. Attached via a 3/8" UNC bolt through cover into the cast iron cylinder block. The battery cable is a 1/2" tinned copper core with soldered terminals each end 12" in length.
There is a seperate earth cable to the HCV base. Two earth straps to the MSD-7ML-2 unit. One is the negative battery cable (black wire). The other cable is attached to the "ground" terminal on the MSD-7ML-2 unit.
All earth cables are direct connections to the negative battery terminal.

I am not sure why you need to know these facts when if we just replace the MSD-7 unit and make no other changes at all to anything mechanical or electrical and the problem is gone.

The unit (MSD-7) removed ran successfully for years then failed. Was sent away for repairs as stated previously. The repairer stated there was no problem with the unit. It worked just fine. Yet once it is fitted into the application it fails to operate correctly. As stated previously reconnect a new unit (MSD-7) exactly the same way as Faulty MSD-7 and all problems are corrected (gone).

From what I have looked at inside the unit there is 3 circuit boards, 1 Capacitor, 1 red epoxy sealed unit with 3 wires (red, yellow and black) attached to the main circuit board, 1 coil (very rusty), and possibly a couple of diodes.

I believe the old unit is faulty and breaks down under severe load conditions but I am not sure what is actually causing the fault.

Please try to understand we can fix the problems we have by fitting a new MSD-7AL-2 unit without changing anything else at all.

Thank you again for all of your responses. I apologise for any language barriers. We are based in Australia and sometimes there seems to be a bit of confusion with descriptions or meanings of words.
Reply With Quote
  #6  
Old 04-24-2012, 08:37 PM
FONC FONC is offline
Junior Member
 
Join Date: Dec 2011
Posts: 12
Question

So do you have any ideas on what is the possible cause of MSD-7ML-2 breaking down under engine load?
Reply With Quote
  #7  
Old 04-28-2012, 01:27 AM
FONC FONC is offline
Junior Member
 
Join Date: Dec 2011
Posts: 12
Exclamation

Hello?????
Reply With Quote
  #8  
Old 05-02-2012, 04:19 AM
FONC FONC is offline
Junior Member
 
Join Date: Dec 2011
Posts: 12
Question MSDTech1955

Quote:
Originally Posted by msdtech1955 View Post
is the battery grounded to the heads ..motor plate ..?
I am taking it that your solution to our Ignition problem is just buy a new unit everytime our "repairable" unit fails.

I am offended with your lack of replys. Did you even read my posts? I have answered all of your 2 questions.

Are you associated with MSD?

Are you actually a technician for MSD?

Is there any reason as to why your are not even making any suggestions as to what the problem could be?
Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 01:21 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
2011 MSD Performance