502 mag mpi dies for unknown reason
 

I have a 99 502 mag mpi that will just shuts off after running. it has done this on multiple occasions. its happened at idle as well as when cruising. It will start right back up and go. It has done this on several occasions. Then after a few times it stops,. I have checked connections and don't see any loose or corroded.

Anyone else have this issue?

Eric

Electrical issues are very hard to find, and you have your work cut out.
It happens because of bad connections or failing part.

The MPI motor has a relays (main power and fuel pump) which if either one looses power will kill the motor. You have a kill switch which can also kill the motor. Connections to/from all components can get weak/loose/bad and if it breaks flow, the motor dies. The ignition switch can also do this

Start with connectors, remove, inspect and clean contacts. Move on to switches and relays and their contacts

In 1st bold, how long does it run continuously until it first shuts off ?

And second bold,How long until it ill restart ?

prob pick up coil and its rusty as hell causing it to get hot.

cap and rotor and ign coil how old is that. U prob need a FULL COMPLETE tune up along with a pick coil

other tests - what is your voltage showing when running and when the engine shuts off on its own ?

the cannon plug does that have great solid connection and very clean and tight with a hose clamp on it ?

battery connections good and clean and tight ?

Connections at the starter good clean and tight > Back side engines grounds the same ?

Alldodge/Camalot - I installed a new ignition switch this year, Kill switch I need to check and I have recently put new relays in for the ECU/Fuel pump.

SB- I don't even have to cycle the key when it dies. It will instantly restart and run. It happened to me three times yesterday. The fourth restart it ran for over an hour with no issues.

BUP - I recently installed a MSD blaster coil, Cap and rotor were new the beginning of this season, Voltage doesn't fluctuate at all (13 - 14V depending on load), cannon plug I recently checked. The batteries I rewired the beginning of the year with new marine grade 2 gauge wire, Blue sea systems ACR. I recently had a issue with my fuel pump circuit. Turned out to be a bad fuse block. I have rewired all the fuse blocks with new blue seas systems blocks.
all connections are secure.

Thanks for the inputs. I will probably try my backup coil to see if that could be the issue, check the kill switch for shorts and possibly replace the ignition switch. I will check all connections again as well.

When you fist turn the key to on position do you get a constant horn or no horn?

Chris

Yep we unplug the cannon plug and use a hand pick straight thru the middle to spread the male connectors open for better contact with the female side. Man that almost sounds X RATED.

blueabyss - yes when I first turn the key the horn is momentary then turns off.

30ftpanther/BUP - I did spread the male pins out before. I'll go back in there and clean it up really good then try it again.

Any chance it might be the distributor module?