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Boat 502
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Discussion Starter #1
My current set up is 7ml-2 ignition box, hvc-2 coil, start retard box, and billet pro dizzy(locked out). I lost spark and thought it was the box had it tested by MSD and it checked out. I guess you need a special tester because they say a multi meter won't tell you if the box is working properly ?? Doesn't make sense to me but..... So, I tested the coil, then I put in a new pickup. Everything tested out ok, but boat will not start ? I pulled the coil wire, set near ground, cranked it over and I get "single spark" then its dead. So, I put a different coil in the boat and it did the same thing. I can crank it over for 5-6 seconds and I get nothing, just initial spark ????? I have heard of no spark, but " one spark " then nothing ?? Could this be the key switch going bad ? I do have the acc. on the key switch powering quite a few things but the boat has worked like this all season long.Thanks for any help.
 

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It really sounds like a bad ground...I would be curious to see what a jumper does though...The dizzy does turn right (stupid question I know)..

GT
 

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Boat 502
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Discussion Starter #4
I would jump the little red to hot feed and see what happens. Bet your on to something with the key.
Forgot to mention, but that was the last thing I tried before I had to go to work. Same thing, single spark then nothing. I'm wondering if this key switch is just going bad or if I have it doing to much work. It powers quite a bit, acc sends pwr to : gauges, pwrs kill switch, pwrs n20 purge(switch), pwrs arming switch for n2o system. Then, starts the boat w/ the next click. But.....its worked all season ???
 

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Cantard
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5,017 Posts
Forgot to mention, but that was the last thing I tried before I had to go to work. Same thing, single spark then nothing. I'm wondering if this key switch is just going bad or if I have it doing to much work. It powers quite a bit, acc sends pwr to : gauges, pwrs kill switch, pwrs n20 purge(switch), pwrs arming switch for n2o system. Then, starts the boat w/ the next click. But.....its worked all season ???
Can you disconect the spark retard?
 

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Boat 502
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Discussion Starter #6
It really sounds like a bad ground...I would be curious to see what a jumper does though...The dizzy does turn right (stupid question I know)..

GT

Yep, its turning. The ground on the box goes straight to the block and its got 12.5 volts. When the motor is cranking it drops to 10 volts, but it has always been that way.
 

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It is true that you cant test the box with a volt/ohm meter. Typical electronic ignition testing has always been to eliminate any problems in distributor/coil/wiring and if all are good "replace ignition module with known good unit".

As for the "single spark" issue, that is something I have generally found relates to a distributor that is not turning and, therefore, not sending a signal to the module. Being I'm an import tech, the usual cause would be a broken t-belt which was generally obvious by the sound of no compression while cranking. Since you replaced the pickup, I assume you verified the distributor actually turns while cranking? You may want to check the resistance of both the old and new pickups. Spec should be available on MSD's website.Do a visual on the harness and connections between distributor and MSD box. The test 71Hallett
suggests is a good idea as well.
 

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Boat 502
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Discussion Starter #9
Can you disconect the spark retard?
I could, but I tested it w/ the jumper wire test that msd's web page recommends and it sparked like crazy, and its conected to the 7al box which is grounded to the block. It also really helps the boat start because it pulls 10* of timing when cranking (locked out timing). :)st
 

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Yep, its turning. The ground on the box goes straight to the block and its got 12.5 volts. When the motor is cranking it drops to 10 volts, but it has always been that way.

Does the dizzy have a good ground?..When you find it you'll kick yourself in the head:)st

I had a bad rev limiter chip that made the motor backfire, pretty weird...
 

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Boat 502
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Discussion Starter #11
Old squirt-

Ya, the tech told me that you can check pwr going into the box but the only terminal on the box that will show pwr is the ignition terminal. Every other terminal will show dead, even while cranking. Would the ''single spark'' be caused by a bad cap or rotor ? The dizzy is spinning when cranking and I checked the resistance on the new pick up and its good. Keep the options coming ! I know its something simple.
 

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Have you diconnected the tachometer lead? The tach could have shorted...

It will be something dumb, but IMO not the rotor or cap...

GT
 

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Cantard
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I could, but I tested it w/ the jumper wire test that msd's web page recommends and it sparked like crazy, and its conected to the 7al box which is grounded to the block. It also really helps the boat start because it pulls 10* of timing when cranking (locked out timing). :)st
Only reason I ask is because I had a timing controler act up and it would do the same kind of thing. No start. Would short the white wire and kill the signal.
 

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Boat 502
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Discussion Starter #14
Have you diconnected the tachometer lead? The tach could have shorted...

It will be something dumb, but IMO not the rotor or cap...

GT
Your on it GT ! Thats what a buddy said too. I'm trying that first thing tomorrow (@work all night) . Any other thoughts ??
 

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Old squirt-

Would the ''single spark'' be caused by a bad cap or rotor ? The dizzy is spinning when cranking and I checked the resistance on the new pick up and its good. Keep the options coming ! I know its something simple.
Since you got the single spark with the coil wire out of the cap, that rules the cap and rotor out.

Is the harness from the distributor disconnectable at the box? If so, disconnect it leaving the distributor still plugged in to harness.. Hook up ohm meter to the harness terminals. Should measure essentially the same as the pickup coil by itself. If it is OK, switch meter to volts and crank the engine. You should see the voltage switching from high to low.

Regarding distributor ground--not needed on this type of distributor.
 

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Boat 502
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Discussion Starter #16
Only reason I ask is because I had a timing controler act up and it would do the same kind of thing. No start. Would short the white wire and kill the signal.
I hear ya, that was my thought also. So I tested it and its good. This is really pissing me off ! Trying to leave for the river Friday morning.
 

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Boat 502
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Discussion Starter #17
Since you got the single spark with the coil wire out of the cap, that rules the cap and rotor out.

Is the harness from the distributor disconnectable at the box? If so, disconnect it leaving the distributor still plugged in to harness.. Hook up ohm meter to the harness terminals. Should measure essentially the same as the pickup coil by itself. If it is OK, switch meter to volts and crank the engine. You should see the voltage switching from high to low.

Regarding distributor ground--not needed on this type of distributor.
Ya, its disconnectable. I will try that too.
 

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Regarding distributor ground--not needed on this type of distributor.
Not needed to run, but IMO recommended to elimiate static discharges and magnetism of the P/U coil...

I have had MSD ignition on my last three boats and have had them completely kick my ass, I actually got three bad MSD 6AL's in a row, one was mine and two went on customers boats, MSD took care of me huge.

Just grasping at straws.:)bulb
 

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mo balls than $cents$
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unplug the dist and use a paper clip between the terminals on the connector that goes to the box, kinda toggle the clip in between the terminals and see if the spark looks strong. if it does, pull the dist out, with it plugged in, hold it against the block to ground it, and spin the gear, see wtf happens compared to what it looked like when you did the paper clip toggle'n. kinda sounds like a shit pickup to me.
 

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mo balls than $cents$
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Ya, its disconnectable. I will try that too.
a weak pickup will go high/low as well, but may not toggle enough to be effective. most of the pickups i've tested that were good showed a 3-4volt ac high while cranking the motor.
 
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