4.3 won't fire after oil change

littleape

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I'm in the middle of winterizing my 2000 4.3, it started fine to warm up on the muffs, sucked the oil out through the dip stick, replaced filter, put new oil in and went to start it ..it just cranks and wont fire.

Oil pressure switch is connected, I see pressure climb when cranking. Fuel pump turns on and pumping throttle squirts into carb, I even tried putting some fuel into the carb. The big red breaker seems to be fine, I can't press it in. Throttle safety switch is not triggered.

No fire attempt at all, just cranks.

Not sure what I might have knocked in the engine bay while doing the oil change that could be causing this.

It seems like it's not getting spark, I'm not quite sure how to safely test for spark on these.
 

GA_Boater

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Have you checked for spark?

Flip the switch a few times.
 

littleape

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Have you checked for spark?

Flip the switch a few times.


Feel a little silly but whats the proper way to test for spark on these. I'm used to small engines where you just pull the plug out and ground it while cranking. I don't have a spark tester of any kind.
 

alldodge

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How about a serial number

Use a voltmeter and check for 12V at the coil + side purple wire
 

dlogvine

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You can check a spark on a plug by taking spark plug out and when your buddy is cranking the engine you hold plug with attached wire in about 3 to 4mm away from the block. The spark, if it is there will be visible if the coil produces the spark
 

littleape

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Early blast of cold is preventing me from trying anything until this weekend when temperatures go back up above freezing.

Motors drained of water so just need the weather to cooperate.


Someone asked for serial#: L662063
 

alldodge

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I'm seeing TBV ignition, so looking for power to the coil. I'm guessing, but think its lack of voltage
 

tank1949

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I AM ASSUMING THAT YOU HAVE A OIL SWITCH THAT SUPPLIES 12 VOLTS TO ELECTRIC FULE PUMP. They are a pain but will save your butt. Figure out how to by-pass an supply 12 vts directly to fuel pump. I believe that you can jump wires at switch. You may have dislodge a corroded connector at switch? Get your volt meter or test light out. You will need them!
 

GA_Boater

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It doesn't work that way. The pump power is from the key until the oil pressure builds after the motor starts, then the oil pressure switch powers the pump.

If it was the oil pressure switch, the motor would start and then die shortly after the key is released when the float bowl empties.


The OP has to verify spark or no spark since gas seems to be getting to the carb.
 

tank1949

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It doesn't work that way. The pump power is from the key until the oil pressure builds after the motor starts, then the oil pressure switch powers the pump.

If it was the oil pressure switch, the motor would start and then die shortly after the key is released when the float bowl empties.


The OP has to verify spark or no spark since gas seems to be getting to the carb.

It is supposed to.... It might be defective switch causing issues. Going to dead ground. But, if he is not getting spark at start up??? Back trace!
 

achris

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.... I believe that you can jump wires at switch. You may have dislodge a corroded connector at switch? Get your volt meter or test light out. You will need them!

This is correct.

The STARTER supplies 12 volts to the pump directly (not via the oil pressure switch) during cranking. Once oil pressure is achieved and the oil pressure switch closes, then power from the key is supplied via the switch to the pump. Before the oil pressure is up (and the switch closed) and without the engine being cranked, there is 12 volts on the key side of the switch, just waiting for the switch to close....

Having put fuel in the carb and still not got the engine to fire, I would suspect there to be no spark. This can be for 2 reasons. No 12volts to the coil positive, or the sensor pulses are grounded. I would check for 12 volts at coil +. If that's missing, check for a 'deadman' switch, or ignition cutout, usually on the throttle/shift control. If the 12 volts is there, check that the white/green wire isn't grounded.... (check the shift cutout switch).

Chris.......
 

littleape

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So we finally got some above freezing temperatures. Still no luck.

It was sitting for couple weeks and today the first thing I did was 3 pumps and start attempt; it had life for about a second before I shut it off. I didn't have muffs hooked up since I just wanted to check if it had life, it did. After I shut it down I went to turn on the water and then tried to start again, it had couple very short puffs where it tried to fire but did not. After couple crank attempts it was back to being totally dead with no signs of life just cranking.

I played with the electric choke; forced it totally closed or a little open but it did not help. Curious, is the choke supposed to adjust even when motor is not running? It's getting warm when I'm trying to start the engine. I thought the choke adjusted based on engine temperature.

Fuel is getting into the carb, fuel pump runs when cranking and after cranking until oil pressure drops or key is removed.

Could I have flooded it very early on in the day with the few initial start attempts?

Todays temperature is about 5C or 40F, had no issues starting in the summer months even after sitting for couple weeks.
 

Rick Stephens

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On an electric choke, when the key is on the choke coil gets warm and takes the choke off.

You might start back a step and do a compression check. You're getting fire and fuel. So now might be good idea just to make sure we don't have an underlying issue.
 

littleape

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Oct 2, 2017
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So I took spark plugs out, they were wet and covered in deposits, cleaned them up a bit (about to fog so don't want to put in new ones), reinstalled, two pumps and she fired right up.

I must have been doing something wrong where it was flooding the plugs.
 
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