GF1800 Fuel Shutoff problem

T

TimAT

Member

Equipment
GF1800E
Oct 5, 2023
31
8
8
Kansas City. MO
I've checked the wires, replaced the fuel pump, WSM states 20ohms resistance, had 3ohms. And a new shutoff solenoid. Starts and runs just fine, then the solenoid starts rapid cycling causing a miss and power loss. Sometimes at idle, it will shut the engine off. Then it will be fine for a while, then back to this. From what I see on the wiring diagram, the solenoid is directly controlled from the combination box. Brand new one of those too. Shuts down with the key normally. I have a short video, see google drive link below This one is making me even more crazy that I already am. Link to google drive video:
https://drive.google.com/file/d/1a-c1osLK24mESsgBKF6Ohy13SbgqmqEH/view?usp=sharing
 
Last edited:
R

Russell King

Well-known member
Lifetime Member

Equipment
L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
Jun 17, 2012
5,365
1,415
113
Austin, Texas
Video can’t be directly on this forum.

post it to somewhere like YouTube then post link to it here
 
J

jaxs

Well-known member

Equipment
B1750HST
Jun 22, 2023
734
522
93
Texas
TimAT said:
I've checked the wires, replaced the fuel pump, WSM states 20ohms resistance, had 3ohms. And a new shutoff solenoid. Starts and runs just fine, then the solenoid starts rapid cycling causing a miss and power loss. Sometimes at idle, it will shut the engine off. Then it will be fine for a while, then back to this. From what I see on the wiring diagram, the solenoid is directly controlled from the combination box. Brand new one of those too. Shuts down with the key normally. I have a short video, see google drive link below This one is making me even more crazy that I already am. Link to google drive video:
https://drive.google.com/file/d/1a-c1osLK24mESsgBKF6Ohy13SbgqmqEH/view?usp=sharing
Click to expand...
You can throw more parts at it or hook a multimeter to shut off valve to see if 12v power is modulating or if valve isn't responding to signals. Report results.
 
L

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
5,207
1,893
113
Mid, South, USA
two things come to mind.

Combination box
and
bad connections and/or grounds

both are pretty common. Before I forked out the money for a new combination box, I'd go through each and every connection, drop test every circuit. Fix the problems. IF that solves it great, you're out some time. If not, put a box on it. Or fix the original, but I'd just as soon replace it with the newest version.

Connections are the most common failure point on these antiques. Great mowers, but the wiring SUCKS.

Try wiggling the keyswitch too and see if that makes any difference.
 
T

TimAT

Member

Equipment
GF1800E
Oct 5, 2023
31
8
8
Kansas City. MO
lugbolt said:
two things come to mind.

Combination box
and
bad connections and/or grounds

both are pretty common. Before I forked out the money for a new combination box, I'd go through each and every connection, drop test every circuit. Fix the problems. IF that solves it great, you're out some time. If not, put a box on it. Or fix the original, but I'd just as soon replace it with the newest version.

Connections are the most common failure point on these antiques. Great mowers, but the wiring SUCKS.

Try wiggling the keyswitch too and see if that makes any difference.
Click to expand...
Thanks, I'll go back through the wiring again and double check the grounds. The combi box is brand new, the original had zero output to the shutdown solenoid. The original shutdown is locked solid, won't move at all. I'm guessing it shorted and smoked the stop circuit in the box. If I could figure out how to get into the potting I would see if I could fix it. I like challenges.
 
L

lugbolt

Well-known member

Equipment
ZG127S-54
Oct 15, 2015
5,207
1,893
113
Mid, South, USA
TimAT said:
Thanks, I'll go back through the wiring again and double check the grounds. The combi box is brand new, the original had zero output to the shutdown solenoid. The original shutdown is locked solid, won't move at all. I'm guessing it shorted and smoked the stop circuit in the box. If I could figure out how to get into the potting I would see if I could fix it. I like challenges.
Click to expand...

There was a writeup about repairing them. I don't remember where I saw it, but it was pretty good. Might "google" it.
 
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T

TimAT

Member

Equipment
GF1800E
Oct 5, 2023
31
8
8
Kansas City. MO
I spent a few hours digging into the wiring. Visual inspection of insulation, checking resistance in each wire end to end, checking for opens and shorts to ground. No defects. Took all of the switches out of the circuits with jumpers, including the key switch. Ran for 20 minutes, no problem, then right back to the shutdown solenoid going crazy. Back into my paper copy of the service manual, and found another wiring diagram that has a slightly different display of the circuits. Followed the power feed to the combi box. 12v+ from the battery, to the key switch, to the fuse box, to the conbi box. Pulled the fuses to test the out of the circuit. All good but the fuse holders were really nasty dirty. Cleaned the holders and the fuses. got it all back together, fired right off and ran for a solid 2 hours, changing throttle settings from low to high and back. Runs perfectly.
Thanks to everyone that contributed ideas and guidance!!
 
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