4.3 will not stay running

[utexasrick]

I have a 4.3 2 barrel which I recently installed but I can not keep the engine running. It will start up the first time and will idle for maybe 40s then it dies. I can start it up again but it will do the same. I thought it was dying when the chock was opening so I held it slightly open but it still died. I took the boat out to the lake and it would shift fine and accelerate but it did the same thing after a few seconds it would die. At one point it was accelerating and it died midway.
Could this be an issue with bad gas. half was old gas that had been sitting for a few months, I had added fuel stabilizer when I got the boat and a couple gallons of 93 the last time I tried to take it out. I would think if it was bad gas it would be very hard to start.
I also replaced the fuel filter/separator and checked the fuel filer behind the fuel inlet in the carb, it was clean.
Anyone one have any ideas on what I could check next
How could I check to see if I'm losing spark when its dying?

 

[Don S]

Re: 4.3 will not stay running

Do you have a serial number, or even a year might help. Not all 4.3's are the same.

 

[utexasrick]

Re: 4.3 will not stay running

boat is a 97 sea ray, engine serial is 0K003732, block is rebuilt, electric fuel pump, 2 barrel carb

 

[Maclin]

Re: 4.3 will not stay running

Rick, the fuel pump is wired thru an oil pressure switch that will only let it get power when the engine is running. This switch is bypassed when the key is in Start while cranking the engine. If the wiring or the oil pressure switch is compromised then the fuel pump will only run when cranking and not have time to get much gas into the carb, this fits your symptoms. When it does die one thing you can do is check the carb for gas by looking down the carb bore and advancing the throttle a few times to see if there are 2 good squirts of gas each time, and that they do not fade after the first 1 or two times.

 

[utexasrick]

Re: 4.3 will not stay running

Maclin, thanks, the oil pressure switch connector was the problem. I jumpered the connector and the engine stayed running. While the engine was running i checked the continuity between the two terminals and it was good so I checked the connector and it seems like one of the contacts is loose inside.
Are there two oil pressure switches? I read in the manual that the black bulb with the blue wire is also a switch but is closed when the engine is not running and open with the engine is running but this is the opposite of the other switch.

 

[Maclin]

Re: 4.3 will not stay running

One is a switch, the other is a sending unit for the gauge. The switch is on/off based on 5psi or something close to that. The sending unit will produce a constant but varying voltage output to the gauge depending on psi.

 

[Maclin]

Re: 4.3 will not stay running

More accurately, the sending unit does not produce voltage, but the effect is as I just described. It varies the voltage drop across it with resistance, and the gauge shows the relative changing voltage in that circuit with the needle movement.