Generac Quietpact 40G (Gasoline) / 40LP (LP Vapor) Repair Guide

### Step 1: Preliminary Oil Check
The first step in diagnosing a unit that starts and then shuts down is to verify the engine oil level. Low oil levels will trigger safety sensors to ground the ignition circuit.
- **Action:** Check engine oil level and, if necessary, replenish to the "FULL" mark on the dipstick (Page 34).

### Step 2: TEST 39 - Check Low Oil Pressure Switch
The Low Oil Pressure Switch is normally-closed and is held open by oil pressure during operation. If it fails closed, the engine will shut down shortly after starting.
1. Set a VOM to the "Rx1" scale. With the engine shut down, check for **continuity** across the switch terminals (Page 59).
2. Crank the engine. The switch should open, and the meter should indicate **infinity** (Page 59).
3. **Branching Results:**
- **If the switch does not show continuity in Step 1:** Replace the switch (Page 59).
- **If the switch fails to open (shows continuity) during cranking:** Remove the switch and install a pressure gauge. Start the engine and measure pressure.
- **Technical Spec:** If engine oil pressure is below **10 psi**, refer to Engine Service manual No. 0C1103. If pressure is above **10 psi** but the switch stayed closed, replace the switch (Page 59).
- **If GOOD (Switch opens correctly):** Proceed to **TEST 30** (Page 59).

### Step 3: TEST 30 - Check Wire 18
Wire 18 sends the STOP signal to the Engine Controller. If this wire is grounded (via a short or a remote harness issue), it initiates an immediate shutdown.
1. Disconnect the remote harness connector from the generator. If the generator now runs, the short is in the remote harness (Page 52).
2. Remove connector J1 from the Controller. Measure resistance between Pin **J1-14** and frame ground, then between Pin **J1-15** and frame ground. Both must measure **infinity** (Page 52).
3. **Branching Results:**
- **BAD:** If continuity is measured at Pin J1-14, repair Wire 18 between the J1 connector and the Start-Stop switch. If continuity is measured at Pin J1-15, repair Wire 18 between the J1 connector and the remote panel connector (Page 52).
- **GOOD:** Proceed to **TEST 40** (Page 52).

### Step 4: TEST 40 - Check Oil Temperature Switch
Shutdown occurs if oil temperature exceeds approximately **305°F (151°C)**.
1. Remove Wire 85 from the switch. If the engine now runs but shuts down when reconnected, the switch is either sensing an actual overheat or has failed closed (Page 59).
2. To bench test: Remove the switch and place the sensing tip in oil with a thermometer.
3. Use a VOM to check terminals; it should initially read **infinity** (Page 59).
4. Heat the oil. When it reaches approximately **305°F (151°C)**, the switch must close and show **continuity** (Page 59).
5. **Branching Results:**
- **BAD:** If the switch fails either the infinity or continuity check, replace the Oil Temperature Switch (Page 59).
- **GOOD:** If the switch is functional, investigate cooling restrictions or improper installation. Ensure exhaust is not under the air intake (Page 59). Proceed to **TEST 24**.

### Step 5: TEST 24 - Check Start-Stop Switch
A defective switch may be internally shorted, sending a constant STOP signal via Wire 18.
1. Check Wire 0B (ground wire) between the switch and ground terminal. It must show **continuity** (Page 47).
2. Disconnect all wires (18, 0B, and 17) and the 7.5 amp fuse.
3. Measure resistance from the center terminal to each outer terminal. Both must measure **infinity** (Page 47).
4. Depress the switch; the meter should show **continuity** when the switch is toggled toward the respective terminal (Page 47).
5. **Branching Results:**
- **BAD:** If the switch fails resistance tests or if the engine only cranks when Wire 17 is manually grounded, replace the Start-Stop switch (Page 47).
- **GOOD:** If the switch and Wire 18 check out but the problem persists, go to Problem 8 in the manual (Page 34).

**Summary Recommendation:** Systematically isolate the shutdown circuit by verifying oil levels, then testing the Oil Pressure Switch, followed by checking Wire 18 and the Oil Temperature Switch for unintended grounding.