Explain to me a fuel solenoid

[c5vettster]

The D1005 engine refused to start - no fuel on the injectors. Checked it by removing the solenoid - started right up. The solenoid has no reaction on when I turn the key despite having 12V across pig tail terminals. Also tested it with a battery - nothing deader than a door nail.

I ordered an aftermarket unit from amazon.

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Same thing - doesn't pull the rod when I turn the key, doesn't do it when I connect directly to the battery.
Now, I am on the third replacement unit from amazon and beginning to suspect that I may not be in the full possession of knowledge in this regard.

For the sake of the sanity, could people confirm that attaching 12V leads to the terminals should make the solenoid pull in its rod?

 

[GreensvilleJay]

hmm.. looks like a typical B&S 'anti dieselling' solenoid,which blocks gas from entering the carb....
if so...
then yes, applying 12VDC to the 2 pins should pull the plunger into the body of the solenoid,usually 1/8-1/4"

Before powering it ,I'd put an ohmeter on the two pins. I suspect it to read something in the 400-1000 ohm range ? If you read 'infinite' aka 'open', then the solenoid IS defective.
I've never read the resistance of a B&S one, simply put 12V to it, confirm the plunger moves. when installed I can just hear it 'click'.

You can check the 'tractor' side of the connector, to confirm there IS 12v getting to the solenoid. depending on the connector , you might need paperclips as test prod extenders.

 

[c5vettster]

hmm.. looks like a typical B&S 'anti dieselling' solenoid,which blocks gas from entering the carb....
if so...
then yes, applying 12VDC to the 2 pins should pull the plunger into the body of the solenoid,usually 1/8-1/4"

Before powering it ,I'd put an ohmeter on the two pins. I suspect it to read something in the 400-1000 ohm range ? If you read 'infinite' aka 'open', then the solenoid IS defective.
I've never read the resistance of a B&S one, simply put 12V to it, confirm the plunger moves. when installed I can just hear it 'click'.

You can check the 'tractor' side of the connector, to confirm there IS 12v getting to the solenoid. depending on the connector , you might need paperclips as test prod extenders.

Yes, that is the first thing I checked. It has 14V on the pig tale contacts once I turn the key. I am going to measure resistance of the solenoid right now!

 

[Henro]

This is a long shot, but some solenoids have two coils, a pull in coil that is strong to move the solenoid armature in the start mode, and a hold coil that is only strong enough to keep the armature in the run position when the key is released and the switch moves from the start position back to the on(or run) position.

It is possible that to test the solenoid, it may require that the solenoid case be connected to the engine, or to the negative battery terminal.

If you first measure resistance between the two wires, and then measure resistance between each wire to the solenoid case, you will know if this is likely or not. A single coil solenoid should not read resistance to the case, or if it doe, one wire should have resistance and the second should appear as a short.

A Work Shop Manual should explain how to test the solenoid for proper operation.

 

[c5vettster]

This is a long shot, but some solenoids have two coils, a pull in coil that is strong to move the solenoid armature in the start mode, and a hold coil that is only strong enough to keep the armature in the run position when the key is released and the switch moves from the start position back to the on(or run) position.

It is possible that to test the solenoid, it may require that the solenoid case be connected to the engine, or to the negative battery terminal.

If you first measure resistance between the two wires, and then measure resistance between each wire to the solenoid case, you will know if this is likely or not. A single coil solenoid should not read resistance to the case, or if it doe, one wire should have resistance and the second should appear as a short.

A Work Shop Manual should explain how to test the solenoid for proper operation.

I say! This could be the answer! Let me go and check right away

 

[GreensvilleJay]

The wiring diagram would really, really help ! Easily show how it's supposed to be connected....

 

[rbargeron]

Maybe the little ones don't shut the fuel off - I should remember I don't know anything about them.

 

[Henro]

The wiring diagram would really, really help ! Easily show how it's supposed to be connected....

For sure! At the moment we don't even know if that engine is part of a tractor or something else...unless I missed it...would not be the first time...LOL

 

[Henro]

Later in the '90s the fuel rack became permanently spring loaded toward "off" - with key-on required to enable fuel flow. That's where things are today I believe.

But the OP said the engine ran when the fuel solenoid was removed. And that is my experience with my BX2200 as well.

So it seems to me the fuel rack is spring loaded to enable fuel flow, and the solenoid pushes it to the fuel cut off position when the solenoid is de energized...

 

[c5vettster]

Thank you so much Henro! it was exactly as you said - I grounded the case and it started to work. I am up and running now. Live and learn!

 

[c5vettster]

But the OP said the engine ran when the fuel solenoid was removed. And that is my experience with my BX2200 as well.

So it seems to me the fuel rack is spring loaded to enable fuel flow, and the solenoid pushes it to the fuel cut off position when the solenoid is de energized...

Exactly. The injection pump has a spring-loaded slider and the solenoid pushes it all the way to the right when de-energized. When you put 12V across the terminals AND ground the case, the rod retracts and starts the fuel flow at the pump. The original solenoid became crusty and the needle wouldn't retract. My mistake was to test the new units w/o putting them on and thus grounding the case. It is very tight quoters in there and I didn't want to put a cheap solenoid w/o ensuring that it works. My mistake was not grounding the case when I plugged the pig tail in. Now it all works! Thank a million.