1990 Mitsubishi Mighty Max (6G72) V6 NO START!

Ok, I need some assistance. I picked up this little truck right about a year ago with some cooling system issues, No problems there, but it took me so long to figure them out that the truck ended up blowing a head about 6 months ago and i have slowly been piecing the top and front back together with number matching parts and OEM parts. Now that everything is back together I have a no starting issue that i have simply narrowed down to a No fuel, No spark, or 180 degree out of time problem. I have changed the fuel pressure regulator, fuel injector seats and o-rings but not the injectors them selves, fuel lines, fuel pump and filters including the in-line filter and the one on the electric fuel pump, relays and fuses are good, I cannot seem to find the exact fuel pressure amount that is supposed to be running through the fuel rail itself, i just bought a fuel pressure testing kit and need to know what i SHOULD be getting. ALSO another part of this is, the truck will crank its heart out without starting i have tried old tips and WD-40 tricks and starting fluid, while cranking i have tried to open the throttle body all the way and the engine sounds healthier the minute i let off and let it close OR spray starting fluid in the trucks sounds like it is detonating very hard. I have the resistance checked the fuel injectors and only #1 is a wee bit out of spec but not too bad. I am an experienced mechanic and myself as well as four others are stumped on this truck. Any tips, tricks, or ideas would be very helpful at this point seeing as i do need the little guy to run very soon and have been working at this no start issue alone for about 3 weeks now.

Little hard reading that long paragraph. I have the exact same truck though. 90 is a one off year and different from the rest. To clarify does the truck fire and run normal for several seconds when you spray with starting fluid? If not you have an electrical issue. I’m willing to bets it’s a bad ECU then as several of the capacities have a shelf life and leak out over time, shorting components. It’s a difficult ECU to find but there might be several other ECU’s we could help you out with.

No spark, no fire - getting any error codes off the ECU? Could easily be a bad ICM in the distributor as well (it triggers both spark and injector pulses) but as Charger has mentioned it may be a bad ECU (very common failure in all ECU managed trucks but not hard to fix). The '90 model engine management is a PITA to work on.

The truck does NOT start just cranks over, i have tried grounding the ECU to reset the values in it but i have 2 plugs and not sure which one is REALLY the ECU grounding plug. The tone of the engine cranking gets rough as i spray starting fluid in it then it detonates hard. But does not start what so ever. I am getting spark, we are thinking its fuel related at this point but i can not find fuel rail exact psi specs.

The ECU has been reset since i disconnected the battery and i need the truck to actually crank over and run to get any feed back to trigger the check engine light back on.

If you are spraying starting fluid in your intake while turning over the motor and it doesn’t start and run for a second...you are not getting spark.

I would check the ignition solenoid or the fuses on the positive battery termal. Maybe even the ignition switch. My dumb truck fried the ignition switch that plugs into the column check engine light would come on and nothing. Look for burns or if there is bare wires showing. Most common thing stick a screw driver in one of the spark plugs and wires and test the distributer. Then go from there!! Good luck

Its ignition or ecu related. The ecu & ecm/feul relay tells ur fuel system to come on,
My ecm/fuel relay just crapped out myself, least that's my hope.
The kick plate on the passenger side in front of the door under the dash hides your ECU and the aforementioned
relay. You shud hear the relay click & ur feel pump come on wen ur turn the key on to prime the system.
If I'm not mistaken it also controls ignition so that mite be a place to check too.
My truck cranks & cranks but won't start. I haven't tryed starting fluid, my relay sounds like a door buzzer,
I'm sure its not supposed to....

I'm gonna say bad capacitors in the ECM.

If you go to my thread about error codes it will show you a pick of ECM that leaked the capacitors and lifted some of the traces from the board.

You can get it fixed, or, you can go digging for a used remanned ECM from a wrecking yard like I did. I live in Canada and found mine in Pennsylvania.

New reman ECM can be around $300, I got a used reman from a wreckers for $150.

If you pull the ECM out and the caps look good ( no leaking on the bottom or buldging on the top of the caps) I would still suggest recapping it. It quite simple to do if you have a soldering iron and patience.

Quote:

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Originally Posted by Can1991Ram

I'm gonna say bad capacitors in the ECM.

If you go to my thread about error codes it will show you a pick of ECM that leaked the capacitors and lifted some of the traces from the board.

You can get it fixed, or, you can go digging for a used remanned ECM from a wrecking yard like I did. I live in Canada and found mine in Pennsylvania.

New reman ECM can be around $300, I got a used reman from a wreckers for $150.

If you pull the ECM out and the caps look good ( no leaking on the bottom or buldging on the top of the caps) I would still suggest recapping it. It quite simple to do if you have a soldering iron and patience.

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Im almost certain its this is he isnt getting any ignition.

Chargerx3,
Educate Me... 6G72 distributor equipped production years?
THX!

Ill give it a shot, but im a little rusty.

For Max's/Ram 50's
*1990-1995 had dizzy. 90 is its own special year as electronics are a bit different.

Montero
*1989-93? 89-90 is like the above Max's

Dodge Stealth
*1991-1993 these ECU's work in our trucks except the early ones with trashcan MAF. These engines also have a little more HP. Not sure if the timing and fuel maps are the same, but one might notice a small power increase. They built that motor until 1999 for 3000gt's when they ceased production.

A lot of Chrysler cars and vans used this engine as well with small changes during the 90's.