engine stalled and wont start Please help!!!

[sebas54]

Hi I have a 1987 Gm 4.3l v6 alpha 1. It has a electric fuel pump and the oil pressure cut off switch.

Today I went out and as soon as I gave it gas it stalled. I started it up and drove for a little with no problems. I wanted to moved to a new location and it stalled again as soon as I gave it a little gas. I started it again and I give it gas and I hear it sucking air and it sounds like it was going to stall so I put it back in neutral and the rpms bounced around untill it stalled again. One more try, I start it and give it gas bring the rpms up to get on a plane and it stalls on me at high rpms. After that I was unable to start it up again. I checked the carb while priming it and no gas was coming out. I relieved the pressure from a fuel line and try to start it up again but the fuel pump did turn on.


Okay, I followed the fuel line ground wire and it was connected by 1 stran of wire to the ground.

Is the fuel pump bad?

Could it be the oil pressure cut off sending unit?

Or could it be the carb?

Thanks again

 

[180shabah]

Re: engine stalled and wont start

Re: engine stalled and wont start

Okay, I followed the fuel line ground wire and it was connected by 1 stran of wire to the ground

Fix this first.

 

[sebas54]

Re: engine stalled and wont start

Re: engine stalled and wont start

Sorry, I guess I must have forgotten to mention that I did re-attach the ground wire.

 

[maxxman04]

Re: engine stalled and wont start

Re: engine stalled and wont start

check to see if you have power to the fuel pump. no power, check at relay (download manual in the "Adults Only" sticky for your motor, should be able to find wiring schematic) check fuses, come back then, report.

 

[cooter2506]

Re: engine stalled and wont start

Re: engine stalled and wont start

No relay to check. Power comes from starter when cranking and then when it starts comes from the oil pressure switch when oil pressure comes up. Jumper the oil pressure switch and see if pump runs. If not check power at fuel pump. If you have power then pump is bad. If jumping switch works replace switch.

 

[sebas54]

Re: engine stalled and wont start

Re: engine stalled and wont start

Thanks for the advise. I just checked the pump by bridging the connection from the oil pressure switch and it worked. I left it bridged and started the engine and it stalled like it did yesterday. I connect the wires back to the switch and started the engine it ran but stalled again. I felt the pump pumping while it stalled. the fuse is fine.

I am going to check the screen on the carb but I just cleaned it a month ago. Also do you think I should change the fuel filter and water separator as well. I just changed them a month ago also. I am also going to check the fuel line for blockage by blowing on them.


If the filters aren't the reason for it stalling what else could it be?

The carb. needs to be rebuilt?


Thanks

 

[bruceb58]

Re: engine stalled and wont start Please help!!!

I would be checking your fuel pressure. It will at least point you toward the carb or backwards to the fuel pump and the tank.

 

[scipper77]

Re: engine stalled and wont start Please help!!!

What do your plugs look like?? How is your compression? The compression probably isn't worth checking right away but the spark plugs should tell you something.

 

[cooter2506]

Re: engine stalled and wont start Please help!!!

Sounds like you have blockage somewhere. Check all filters. Pickup tube in tank, bottom o fuel pump has one I think, screen at carb and water seperator. Also check your fuel tank vent for blockage.

 

[sebas54]

Re: engine stalled and wont start Please help!!!

Just got back from the boat. I checked the screen on the carb and it was clean. When I took the carb off it was full of gas. I also check the fuel filter and it was not clogged. I blew air through the fuel line and it was not clogged and also sucked a little. I forgot the oil wrench so I didn't take the water separator off but I blew air through it and it was not clogged.


I am thinking that the carb needs to be rebuilt?

I got the engine running and it ran fine at idle. Once I push the throttle it sounds like it is sucking air and it stalls. I tried this over and over and the same thing happened.

i just replaced the fuel filter, fuel pump, and water water separator at the beginning of the season and did all of the fuel blockage diagnostics as I did today.

I have a similar problem for a long time. If I gave it gas too fast it would stall.


Please help and thank you to everyone.

 

[Bondo]

Re: engine stalled and wont start Please help!!!

I am thinking that the carb needs to be rebuilt?

Ayuh,... I guess that would be the most logical thing to do...

 

[sebas54]

Re: engine stalled and wont start Please help!!!

Thank you all for your help.

After rebuilding the carb. I had the same symptoms, so I did all the trouble shooting steps again. This time I had an oil wrench to remove the waster separator and when I removed it the gasket was broken and not seated right.

I replaced the water separator and it runs good.

The only thing is that when i give it gas really fast it will suck air and stall again but if i give it gas at a steady pace or slow it runs fine. I replace the accelerator pump in the carb. when i installed the gasket kit.

Thanks

 

[maxxman04]

Re: engine stalled and wont start Please help!!!

might still check for vacuum leaks. one small leak could cause this. check all vacuum lines, also with motor running at idle, using a squirt bottle, spray water in a stream along where intake manifold meets the heads. if there is a leak, you should be able to hear motor stumble a little. the little bit of water that MIGHT get into motor is not enough to do damage.

 

[sebas54]

Re: engine stalled and wont start Please help!!!

Thanks for the reply. I checked for a vacuum leak with a can of carb cleaner and a can of starting fluid. I didn't notice the engine change at all. I sprayed along the manifolds and carb. where it meets the b lock and heads.

 

[maxxman04]

Re: engine stalled and wont start Please help!!!

i assume you mean that you "didn't" notice the engine change. if that is the case, it does sound like a carb issue. possibly stuck, bent, or incorrect floats, clogged jets. a good carb overhaul sounds in order.

 

[sebas54]

Re: engine stalled and wont start Please help!!!

Thanks again. I edited did to didn't.

When I took the carb apart it was very clean with no gunk build up. i also set the float to specs.

Do you think that I need to buy a new carb?

Also the power piston assembly didn't come in the carb kit so i used the old one. Could this have anything to with it. When i brouth that part to the store they didn't know what it was.

 

[maxxman04]

Re: engine stalled and wont start Please help!!!

when going thru carb, did you clean out/blow out EVERY little passage and hole? pull the jets and clean them? it's also quite possible the oil sender/switch is bad. maybe replace that.

 

[sebas54]

Re: engine stalled and wont start Please help!!!

I did clean it all out. like I said it wasn't dirty at all with nothing clogged.


I think I figured out the reason why it stalls if I give gas too fast. The choke doesn't work so it is always opened. Could this be the reason??

 

[Maclin]

Re: engine stalled and wont start Please help!!!

That description sounds like the carb's accelerator pump is needing some work. The accelerator pump is inside the carb and pumps fuel into the carb throat thru squirters when the throttle is opened. It is purely mechanical, there is a linkage from the throtle arm that controls this. If the plunger or diaphragm for the accelerator pump is old then not much fuel will be squirted. This squirt of fuel is needed anytime the throttle is opened.

It is easy to check this, especially with the choke all the way open. With engine off look down the carb throat then open the throttel briskly to half or more. You should see and hear two healthy stream of fuel going into the throat from two squirters at the top of the carb. If these streams are weak or non-existent or not equalt between themselves then the accel pump needs new parts and passages inside the carb may also need to be cleaned.

If no fuel is squirted at all then the linkage from the throttle arm to the accelerator pump lever or plunger may not have been reconnected and/or adjusted properly.