LT42 EFI starter won't engage . . recurring wiring issue?

rider89

Forum Newbie
Joined
Dec 10, 2014
Threads
2
Messages
6
  • / LT42 EFI starter won't engage . . recurring wiring issue?
Model 13B9A1CS010 ser#1D108H40176 115hours Won't turn over. When starter button is pressed, LCD shows voltage for ≈2 seconds, then a barely audible relay click in the keyswitch and hum (fuel pump?) and showing hour meter, then nothing changes until timeout. No (louder) click from starter solenoid. If I don't push the brake pedal, LCD shows "br". if I engage the PTO, the LCD show "pto". If I'm not on the seat, the LCD shows voltage and nothing else happens, so the panel is recognizing those switches. Last year, I pulled the dashboard off and cleaned a molex type connector that was near the keyswitch panel, and got it to start. This season, I pulled & cleaned 2 connectors on the right side of the engine, and got it to start. Today, cleaned those again and 2 more on the left side of the engine, and nothing. The mower mechanically works fine, so I hate to scrap it over bad wiring components. Is there any info available on how to make the wiring harness more "old-school" ?
 

StarTech

Lawn Royalty
Joined
Feb 19, 2020
Threads
116
Messages
12,587
  • / LT42 EFI starter won't engage . . recurring wiring issue?
This is the problem. Cub/MTD has not released any info on the wiring to us non dealers. I called my tech support at RBI and Mike is having to reach out to his sources to see if any info is available. But as of right now most of us are in dark just as you are.

Keeping things so secret is hard on all of us that are independent shops that are sometimes have better techs than the dealers.
 

StarTech

Lawn Royalty
Joined
Feb 19, 2020
Threads
116
Messages
12,587
  • / LT42 EFI starter won't engage . . recurring wiring issue?
Well at least I got a X90 engine manual out of this. Now trying to find the diagram for mower side.
 

StarTech

Lawn Royalty
Joined
Feb 19, 2020
Threads
116
Messages
12,587
  • / LT42 EFI starter won't engage . . recurring wiring issue?
Okay, looking the engine wiring schematic the starter not engaging is on the mower side. If not a bad connection it is probably the module that you use to start the start up sequence. So basically it not an engine problem.
 

rider89

Forum Newbie
Joined
Dec 10, 2014
Threads
2
Messages
6
  • / LT42 EFI starter won't engage . . recurring wiring issue?
Looking at it again this morning, I was going to remove the solenoid to bench test it and thought the ground terminal pulled off a little too easy. I squeezed/deformed the female harness connector a little so it would push on the solenoid tab a little tighter, and the mower started. I didn't think about the solenoid too much because of the time delay listening to the keyswitch, but now I realize that delay is probably to give the fuel pump some time to pressure up. I wish they would have put the solenoid under the gas tank right behind the engine, so terminals could be probed in place under power. I'm sending schematics that I got during one of the other times I was working on it. I think the pdf is the appropriate one that has the fuel pump for EFI. The jpg I'm not sure about. I think I still might rewire from scratch as a winter project. Thx for your help, much appreciated.
 

Attachments

  • Schem1.pdf
    681.5 KB · Views: 1
  • schematic1.jpg
    schematic1.jpg
    90.5 KB · Views: 4

StarTech

Lawn Royalty
Joined
Feb 19, 2020
Threads
116
Messages
12,587
  • / LT42 EFI starter won't engage . . recurring wiring issue?
Okay the schematic can't be for your mower. As there is a little more involved connecting to engine. On top that it is a keyswitch version.

Here is the X90 engine wiring diagram. As you can see there is two interconnects from the engine to mower. But it should be possible to convert to keyswitch but it will take some experimentation.
1727441480785.png
 
Last edited:

rider89

Forum Newbie
Joined
Dec 10, 2014
Threads
2
Messages
6
Okay the schematic can't be for your mower. As there is a little more involved connecting to engine. On top that it is a keyswitch version.

Here is the X90 engine wiring diagram. As you can see there is two interconnects from the engine to mower. But it should be possible to convert to keyswitch but it will take some experimentation.
View attachment 69741
The mower refused to start for the 6th time, and the formerly successful cleaning of fittings didn't help. The mower is mechanically in good shape so I didn't want to scrap it over a shoddy wiring harness, so I installed an external start button. Tapped into a fused red wire near the main +battery eyelet, then to a pushbutton switch n-o terminal, then to the solenoid tab where it replaced the hot lead from the wiring harness. When the keypad button is pressed, the efi fuel pump runs for ≈4 seconds. During that time, pressing the external pushbutton starts the mower. Killing the engine with the keyswitch or the seat switch works as before.
 

Auto Doc's

Lawn Addict
Top Poster Of Month
Joined
Sep 7, 2024
Threads
18
Messages
1,646
Hello R.,

Shop around for a product called DeoxIt D5. It is an effective contact cleaner that leaves a protective, yet conductive film on the pin contacts.

Go through and clean every connection on the machine the apply this stuff.

The old method of applying silicone compound has caused more problems than it has fixed over the years. It keeps moisture out, but it also insulates pin contacts which affects proper conductivity.
 
Top