Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1994F 150 4WD PICKUP V8-351 5.8LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONPINPOINT TESTSX - CONSTANT CONTROL RELAY MODULE (CCRM)X166 - CHECK LFP RELAY
1994 Ford F 150 4WD Pickup V8-351 5.8L
X166 - Check LFP Relay
1994 Ford F 150 4WD Pickup V8-351 5.8LSECTION X166 - Check LFP Relay
- Key "OFF".
- Low Speed Fuel Pump (LFP) relay disconnected.
- Digital Volt/Ohm Meter (DVOM) on 200 ohm scale.
Fuel Pump Relay Connector:
- Measure LFP relay coil resistance between the LFP pin and VPWR pin at the fuel pump relay. Resistance should be between 40 and 85 ohms.
- DVOM on 10,000 ohm scale.
- Check LFP relay for internal shorts: Measure resistance between the LFP pin and both the power-to-pump and B(+) pins. Both resistances should be greater than 10,000 ohms.
- Are all resistance checks OK?
Yes -- Go to X167. X167 - Check LFP Circuit For Short to Power
No -- Replace LFP relay. Rerun quick test. Quick Test Appendix (Detailed Testing Instructions)
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.