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JohnF2015, Small Engine Technician
Category: Small Engine
Satisfied Customers: 1132
Experience:  Owner/Service Technician at S & J Small Engines
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I am replacing a briggs engine on a craftsman Ltd 1000. The

Customer Question

I am replacing a briggs engine on a craftsman Ltd 1000. The old engine is an 31h7770202e1. The new engine is a 17.5 hp 31r7770021g1. The swap was easy but the new engine wiring harness does not match the old one so I am stuck. Can you help to connect this correctly?
Submitted: 1 year ago.
Category: Small Engine
Expert:  JohnF2015 replied 1 year ago.

Hi, my name is***** will be assisting you.

You can still use this with just a little bit of rewiring.

What color wires do you have on the engine connector?

What color wires are on the tractor connector?

Customer: replied 1 year ago.
On the new engine there is a 2 wire grey an black coming from the side by the carb with a connector on that side. The black goes into the engine and out the other side to the 2 prong connector I am looking at which is also grey and black. From under the engine is a single yellow wire connector hard wired connected to briggs part 593510 which us hard wired with a red single connector coming out. The old connector is a six wire connector with Orange, black, blue wires from the back of the tractor using three terminals. There is a jumper from the blue one to a second terminal which is red. My cell is(###) ###-####
Customer: replied 1 year ago.
By the way the tractor is a LT 1000 which is about 15 years old. Model###-##-####
Expert:  JohnF2015 replied 1 year ago.

Here's what I want you to do.

Do you have any wire butt connectors? If so we are going to need three in order to splice wires together.

I want you to cut the connector from the old engine leaving as much wire attached to the connector as you can.

Then we are going to cut and splice the old connector onto your new engine wiring and then you will be able to just plug it together with the tractor wiring and you will be ready to go mowing.

Expert:  JohnF2015 replied 1 year ago.

The old engine connector has what color wires on it?

Customer: replied 1 year ago.
I am attaching pictures for you. One red and black connector under the engine by the starter and then the main harness with the red and Orange connector and the grey and black running to the connector harness.
Expert:  JohnF2015 replied 1 year ago.

Okay, Thank you for those pictures.

You will cut the black, gray, and red wires leaving a couple inches of wire on the connector.

You will cut the orange wire as close to the connector as you possibly can as it will not be used with the new set up.

You will then cut the connectors from the wires on the new engine as close to the back of the connectors as you can.

You will then connect the black to black, gray to gray and red to red on the new engine and the old connector.

Then you should be able to just plug the connector into the wiring on the tractor and you are ready to go mowing again.

Thank you it has been a pleasure to assist you.

Please take a moment to rate your experience.

Customer: replied 1 year ago.
What was then Orange one used for before?
Expert:  JohnF2015 replied 1 year ago.

It was for an extra AC charging wire but you don't have that on the new engine.

Customer: replied 1 year ago.
Thank you, I will let you know how it goes and rate you too!
Expert:  JohnF2015 replied 1 year ago.

If you follow the instructions that I have provided you should have no issues.

Thank you.

Have a great week!!!

Customer: replied 1 year ago.
Oh, are the black and grey just ground wires?
Expert:  JohnF2015 replied 1 year ago.

No, the black wire is a ground going back to the ignition coil from the connector. The gray wire is actually a power wire which supplies voltage to the fuel solenoid on the bottom of the carburetor in order to make it operate.

Customer: replied 1 year ago.
I see. I was curious because when I turned over the old engine I see black to the chassis and also the black to the bottom of the carb. Then they went on to the connector so I wanted to make sure polarity was right. I am sure you are correct on it since on the new one the grey is on the bottom of the carb and is solid under the engine. Looks right now on the harness too now . Black to black in second position with the jumper to the blue wire which must be the power from the back. When you said the ac charging wire was the Orange before does that mean that the battery will not recharge from the running engine now? That seems silly.
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  JohnF2015 replied 1 year ago.

No the red wire is for your battery charging circuit which should pair up with the blue on the tractor harness connector. The only thing the orange may have been there for is headlights but since the wires are jumped in the tractor harness you should still have lights as well.

Customer: replied 1 year ago.
The problem is that is started. I ran it for a minute. I started it a second time a few minutes later and it was OK so I put the hood back on ready to go mow a absolutely nothing. It did try to crank but then it smelled flooded. I had to go to the doc yesterday so I couldn't reply. Just tried to start again an same thing. Nothing and then a gassy smell. Gas at the spark plug. This one is a bummer. What could be wrong?
Expert:  JohnF2015 replied 1 year ago.

Was this a new engine that you installed or a used engine from another machine?

My first thought is that the carburetor is leaking fuel which would cause it to be flooded. Check your oil level in the crankcase as if this were the case you could get fuel into the oil or crankcase.

Customer: replied 1 year ago.
No. This is a brand new engine. Could you please check into the engine number and the wiring diagrams on the engine number I gave you? The old fuel system was gravity for the gas and the new one has a pump on the top of the shroud.
Expert:  JohnF2015 replied 1 year ago.

There is nothing in the wiring that would cause you to get a fuel smell when trying to start the engine.

Is the engine actually turning over or does it try to but never turn? Does it just come up on compression and stop?

What happens if you remove the spark plug and then try to crank the engine? Will it turn over then?

Customer: replied 1 year ago.
No. It won't start at all. Did you look up the diagrams for both? With the difference in the fuel pump system I am wondering if there should have been a different configuration. I think we blew out a component.
Expert:  JohnF2015 replied 1 year ago.

So the engine is not even turning over or cranking?

The fuel pump system doesn't matter, the fuel pump is vacuum operated not electric so there are no wires going to it that would make any difference.

The only reason that you would smell fuel is if the carburetor is overflowing and passing fuel through the float valve when the engine is not running therefore flooding the engine and when you try to start it you would smell the fuel.

Expert:  JohnF2015 replied 1 year ago.

I have been in the small engine/lawn equipment repair industry for 28 years and done many engine changes where I had to rewire in order to make engines work due to various different reasons. I assure you that we have the wires attached correctly, there has to be some other issue that is causing the fuel smell.