Date: 202112
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Powerplant Fuel System
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Workload; Troubleshooting; Time Pressure; Situational Awareness; Communication Breakdown
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Maintenance; Flight Deck / Cabin / Aircraft Event Illness / Injury; Ground Event / Encounter Fuel Issue
Detector: Person Maintenance
When detected: Aircraft In Service At Gate
Result: General Maintenance Action
Contributing factors: Human Factors; Aircraft; Procedure
Primary problem: Human Factors

Narrative: Certified Technicians Name and Name1 were tasked with replacing an E2 fuel low pressure switch on Aircraft X at the DS XX remote pad. They arrived at the aircraft which was currently having a Service Check and Star Flight Inspection complied with; and the APU was running. At approximately XA35 MT on Date; they were working on gaining access to the switch. They opened the E2 engine cowling; noticed some fuel dripping from the low pressure switch; and when they backed it off by a quarter turn; the switch shot off and fuel began spilling out of the line. Both Name and Name1 had fuel spray in their eyes. They immediately ran up to the cockpit and directed the other Mechanics on board to shut down the APU and the fuel pumps. They then notified me in order to inform me what happened and to have ZZZ Fire Department and EMS called to their location. Fire department and EMS arrived within minutes to assess the situation and provide first aid in the form of eye washes to both Mechanics. Name and Name1 were encouraged by EMS to seek medical attention from a hospital to err on the side of safety. Both Mechanics were then transported to the closest hospital emergency room by Crew Lead Name2. There; they were instructed to continue eye flushes as necessary; were discharged; and returned to work. I learned after the fact that this same fuel low pressure switch was removed by morning shift Mechanic Name3 earlier that morning. When Name3 learned that we did not have the appropriate o-ring packing in stock for to complete the removal/installation; he then temporarily installed the switch again. This maintenance went undocumented; and was not mentioned in any turn over from the morning shift Supervisor. No circuit breakers were pulled/collared; and no entries were made in the logbook. Of course; this does not dismiss the fact that Name and Name1 should have double-checked whether these circuit breakers were pulled and the aircraft was safe to perform this maintenance either.


Second narrative: During the replacement of the #2 engine fuel low pressure switch;  it was discovered after removing the original part that the o-ring required for the new part was not available for the installation. I was told to temporarily install the old component without the old o-ring to prevent FOD ingress; but failed to document this. In addition; I forgot to pull all the relevant circuit breakers to fully lock out the affected systems. After returning to the office from the aircraft; I was assigned another task before I was able to complete the documentation.Reinforce that all circuit breakers associated with the system under maintenance must be pulled to lock out the system when working; and documented accordingly. Additionally; reinforce that when a part is ordered for a component replacement; that all the relevant components should be ordered. It should not be assumed that a component will arrive with the required seals.


Synopsis: Maintenance technicians reported fuel sprayed into technicians' eyes from a partially installed fuel quantity switch. Investigation revealed a third technician previously reinstalled the switch without replacing a faulty O ring that was not in stock and did not record the maintenance action correctly.