Go Back  Offshoreonly.com > Technical > General Q & A
350 Magnum, no spark on new motor >

350 Magnum, no spark on new motor

Like Tree8Likes

350 Magnum, no spark on new motor

Reply

Old 09-04-2019, 09:58 AM
  #1
Registered
Thread Starter
 
Join Date: Sep 2019
Posts: 5
Question 350 Magnum, no spark on new motor

Hi,
I am a brand new member here and I need some help with a 350 magnum, Multi Point Injection engine that I just put together. Serial number OMO28646. My issue here is that I cannot get any ignition spark .

I used to work as a mercruiser mechanic 30 years ago but now I work on trains and haven't kept up with technology. In other words I don't see how I can trouble shoot this ignition system the old way with a test light like I did going back 50 years...lol.

It is my understanding that the pulse signal goes thru the ECM. I don't think I am getting a signal and I don't know how to check to see if I am. When I pull the primary wires off of the coil, the negative side feeding the coil is HOT with the ignition hot wired but the positive side is not. The positive side is hot when the wires are hooked back up because the voltage is going thru the coil of course. When I crank the engine over both primary sides of the coil remain hot. I do not see any signs of a signal being sent to the coil.

I picked up this engine disassembled and put it back together with new heads and therefore have never heard it run. I am trying to start this thing on the floor and when I hot wire the harness plug the fuel pump comes on for 2 seconds, so I am told the ignition should be hot as well.

Thanks in advance for helping an old man with his old Pachanga!
Metro man is offline  
Reply With Quote
Old 09-04-2019, 04:31 PM
  #2
Registered
iTrader: (1)
 
Join Date: Nov 2009
Location: KY
My Boat: 94 Formula 27PC 509, 95 232 Rinker 454
Posts: 2,277
Default

Thanks for the serial number
Gen 1 cool fuel, EST distributor and MEFI 1 ECM

When cranking the motor you should see the tach come up around 300 rpm
Here is how the EST system is tested




Do you hear any beeps when the key is turned ON, or hear the fuel pump prime for couple seconds?
Metro man likes this.
AllDodge is offline  
Reply With Quote
Old 09-04-2019, 06:07 PM
  #3
Registered
Thread Starter
 
Join Date: Sep 2019
Posts: 5
Default

Hi,
Thank You so much for the reply!! I will check or replace the pick-up sensor this weekend. I think I have one on the shelf.

I do not hear a buzzer as I am trying to start this thing on the floor. I do however hear the fuel pump run for a few seconds and then it shuts off. I am told that if I hear the fuel pump run then I have the right wire on the harness connector for the ignition also???

The coil I have looks like the old ,round conventional style coil, but I did try another used coil today to no avail.
Metro man is offline  
Reply With Quote
Old 09-04-2019, 06:19 PM
  #4
Registered
 
Join Date: Jan 2007
Location: Murrayville Georgia
My Boat: 1970 Wesco V-drive & 1974 CEE BEE Avenger jet boat
Posts: 1,206
Default

here is the ignition system you should have. if any of these parts are different then we can start to figure what is wrong.
https://www.mercruiserparts.com/bam/.../31745/2691/70
Metro man likes this.
compedgemarine is offline  
Reply With Quote
Old 09-04-2019, 06:21 PM
  #5
Registered
iTrader: (1)
 
Join Date: Nov 2009
Location: KY
My Boat: 94 Formula 27PC 509, 95 232 Rinker 454
Posts: 2,277
Default

Post a pic of your motor, because you should have the EST with your serial number, but if it has the round coil, then somethings have changed
SB and Metro man like this.
AllDodge is offline  
Reply With Quote
Old 09-04-2019, 06:23 PM
  #6
Platinum Member
Platinum Member
iTrader: (6)
 
F-2 Speedy's Avatar
 
Join Date: May 2012
Location: Midwest & T-Rock
My Boat: F2 Speed racer
Posts: 6,463
Default


I hooked an ignition switch to these leads and pug it in to run on my engine stand
Metro man likes this.
F-2 Speedy is offline  
Reply With Quote
Old 09-04-2019, 11:15 PM
  #7
BUP
Registered
iTrader: (8)
 
Join Date: Jul 2011
Location: Ft. Worth TX
Posts: 9,144
Default

He has a Thunderbolt V ignition system with MEFI 3 ---- totally different ignition set than a EST that the older small blocks used.. In my best guess you have a bad Ignition sensor under the rotor or YOU NEED TO HAVE A GOOD GROUND TO IT. If its a 3 wire then you can jumper the ground wire from the sensor to the battery ground to see if you get spark. If its the old 2 wire GET RID of that and buy the OEM 3 wire and DO NOT BUY THESE ONLINE junk crap. If you need help which sensor to buy you can hit me up.

I will post a diagram of what you have the sensor and do not buy Sierra - Those darn thing after some cycles of heat and and warm engine can have a misfire I know I have changed a zillion of them.

Also there is many past SB s about the ignition sensor and some changes that parts / engine side sensors added.
Metro man likes this.
BUP is offline  
Reply With Quote
Old 09-04-2019, 11:18 PM
  #8
BUP
Registered
iTrader: (8)
 
Join Date: Jul 2011
Location: Ft. Worth TX
Posts: 9,144
Default

Like I said T BOLT V -- OEM stock black side Mercruiser # 6 is the ign sensor I am talking about ---- the pic is the old sensor that is long gone. You want the 3 wire which has its own ground. ( black lead with big eyelet on it )

Distributor & Ignition Components for Mercruiser (350 Magnum Mpi Alpha / Bravo (Gen+) Engine) Engine
Metro man likes this.

Last edited by BUP; 09-04-2019 at 11:22 PM.
BUP is offline  
Reply With Quote
Old 09-04-2019, 11:25 PM
  #9
BUP
Registered
iTrader: (8)
 
Join Date: Jul 2011
Location: Ft. Worth TX
Posts: 9,144
Default

MEFI 3

Electrical Components for Mercruiser (350 Magnum Mpi Alpha / Bravo (Gen+) Engine) Engine
Metro man likes this.
BUP is offline  
Reply With Quote
Old 09-06-2019, 11:58 AM
  #10
Registered
Thread Starter
 
Join Date: Sep 2019
Posts: 5
Default

Thanks for all of the reply's everyone!! I will get back on this motor Sunday with the new info I have gathered here and see if I can make some fire in the hole.

I did try to post a photo but it looks like I am not allowed to do so until after I make 10 posts as a new member.

I will replace the pick-up with the 3 wire version before I do anything and go from there.

have a nice weekend!!
Metro man is offline  
Reply With Quote

OSO Sponsor
OSO Advertiser
OSO Advertiser
OSO Advertiser