The Mitsubishi 4G32 and you. A comprehensive guide to surviving poor financial decisions and overhauling a terrible engine.

[brdgbldr]

Purchased a 850dollar 642b that was told it had a bad head gasket. Turned out it had a cracked block. Finally got it rebuilt and put the engine back in my 642b and not getting any spark. Looking for some help here. Can someone assist with the wiring? The starter side I believe is good. Looking for assistance with the wiring on the coil and distributor. I have two blue wires in a loom on the right side going to each side of the white block mounted on the side of the coil. The wire that comes from the distributor is on the bottom bolt of the coil and the top wire goes to one of the lugs on the white block. Is that correct? The only other wire I am unsure where it goes is a white 16ga wire that is bolted on the same spot the negative battery cable is mounted to the frame of the skid. Also still has points so most likely going to go with the Petronius but uncpsure what to remove when doing so. Any help is greatly appreciated.

Attached is the wiring diagram for the 742B with 4G32 engine. Should be the same or very similar.

 

[Justintime_3]

Appreciate the diagram. It's different than the 642,742 one I currently have as it has the resistor but doesn't have any of the other safety shutoffs that this has. I will see if I can make sense of what is there when I go over there in a little bit.

 

[oldwoodak]

Hello,
I have a 1991 642B and I'm trying to figure out the function of engine temperature (coolant ?) switch; it is wired through the engine oil pressure sensor
to the warning light. Will the light go on if the coolant temp is too high? Could this switch be replace with a sender for a temp gauge? Thanks

 

[mike.lippmann]

I have a 1986 642B that suddenly wouldn't start. I checked spark which is good and put new plugs in it and after troubleshooting the fuel system which all checked out I pulled the carb and found about 1/4" of fluid which did smell like fuel in the intake manifold. I pulled it all apart, drained the fluid out, replaced the intake manifold gasket, put everything back together and still couldn't get it to even sound like it wanted to start so I took this video to find out it's dumping fuel like crazy when trying to start. Before I pull everything apart I figured I would see if anyone has any suggestions.

 

[ZekeSkyree]

Carb rebuild time. My guess is crap in the needle/seat and that gas going into the carb is being dumped directly into the engine ...

 

[mike.lippmann]

Carb rebuild time. My guess is crap in the needle/seat and that gas going into the carb is being dumped directly into the engine ...

Here's my questing with that - If that were the case I would guess that I wouldn't hold any pressure in the fuel line running to the carb and wouldn't see any fuel in the site window as all that run through the carb? Although now that I type that out I should test what happens when I just turn the key on to open the electronic fuel shut off? If the remaining fuel runs through, until it runs out of pressure, this should prove this correct.....

 

[ZekeSkyree]

Those carbs are so simple, pulling it and a quick visual should be enough to figure out the problem ...

 

[mike.lippmann]

Those carbs are so simple, pulling it and a quick visual should be enough to figure out the problem ...

Sounds good, I'll have to order a carb kit for gaskets and dig into it.

 

[ZekeSkyree]

By the way. Which motor do you have?

 

[Dave1234]

I recently ran into a similar problem with my 1994 742B--I left it idling for a short while, noticed it running increasingly rough, smoke getting black. Eventually died and I couldn't get it to start. Left it for a few days, then managed to start it, but running rough. Turned off the fuel line needle valve from the tank, and it slowly began running better and better, and the exhaust got to smelling more and more normal (not rich as it always had). Eventually died for lack of fuel in the carb, but took a long time. Pulled the carb (no sight glass on mine--real bummer) found possibly one piece of crap in the needle valve area, but couldn't tell for sure if it was the immediate problem. Then moved on to trying to investigate long-term too rich problem before reinstall of carb. Eyeballed center of where the sight glass should have been, hand pumped gas into carb with float in place, opened it up--fuel to high, bent float tab, did it again over and over. Very touchy. Don't feel confident I have it right. Looking at Chinese carb instead and/or finding carb body with sight glass. Anyway, if you think you are too rich to start or run right, might try shutting off the fuel needle valve and see what happens.

 

[mike.lippmann]

By the way. Which motor do you have?

Mitsubishi 4G32

 

[mike.lippmann]

So I rebuilt the carb and even did a float test, putting the top section of the carb with the float in water and blowing in the fuel inlet. I couldn't get any air through there blowing as hard as I could but yet I'm still getting to much fuel. Is there any sort of adjustment on the mechanical pump? Driving me crazy that this just started happening out of nowhere and nothing seems to make sense. Have talked to quite a few guys on this issue and we all come up with the same answer for this....C4 lol

 

[Dave1234]

Any progress? One observation--gasoline weighs ~ 6.2#/gal, while water weighs ~ 8.3#/gal. If you filled your carb so that the water level was in the circle on the sight glass, it might raise the float high enough to close the needle valve, while with gas it might not if the float height was set too low. Did you verify the fuel level with gasoline in it and normal fuel pressure? If yes, maybe a loose main jet or hole/crack from the fuel bowl to the inside of the carb? Not many choices it seems. In your vid fuel is pouring out the instant you begin to crank. Really looks like fuel in the carb too deep, and the full volume of the fuel pump is passing right through. Seems like it has to be the needle or seat leaking.

 

[dfb]

Good needle and seats is a problem. They do not stand up to alcohol in the fuel. You may need to use actual fuel pressure from your pump or another source to accurately test the needle and seat sealing properly.
The info is on this site somewhere, I remember buying 2 kits to do the carb on my 4G32, 1 of the kits had the needle/seat that fit. If this turns out to be the problem, there are carburetor rebuilders that can make needle/seats that will hold up to alcohol.