Fuel System

Fuel System

Status

LPG confirmed. Factory vs. conversion unverified — pending Marti deluxe report. Blower fuel spec open.

Overview

The bus runs on LPG. Current hardware is stock naturally-aspirated: a single Impco CA425 mixer on a cast-style mount, single Model E vaporizer. Neither is adequate for the blower build.

Factory vs. conversion

Believed factory or ship-through — unverified.

Supporting evidence:

• Cast-style mixer mount, no obvious aftermarket adapter plate
• DSO special order tag (DSO 74 / SO 3152) — see Chassis Documentation
• Fleet options (traction sanders, tow hooks) consistent with a municipal/district order

Do not log as fact until the Marti invoice confirms. If it shows a ship-through or upfitter conversion, log as "factory-ordered LPG conversion" and cite the line.

Current hardware

Component	Current	Adequate for boost?
Mixer	Impco CA425 (single)	No — sized for NA
Vaporizer	Impco Model E (single)	No — will starve and ice
Lockoff	Unknown — inspect	Unknown — must be sized for combined flow
Tank	Unknown — inspect and record	Unknown
Plumbing	Unknown — inspect and record	Unknown

Blower fuel plan

• Dual Model E vaporizers, boost-referenced. One E cannot vaporize the airflow at target power; a starved vaporizer ices, pressure collapses, and the engine goes lean under load.
• Reference both E's to manifold pressure from a common source with equal-length lines — not two separate taps, or the units fight and deliver unevenly.
• Parallel liquid feed from a common supply with a shared lockoff rated for combined flow. A single-E lockoff becomes the bottleneck.
• Parallel coolant feed off the heater circuit, split so the rear unit is not downstream of the front unit's heat load. Marginal coolant flow ices a correctly-sized vaporizer.
• Dual mixers into a common plenum with a fabricated dual-plate adapter. A single CA425 chokes a blown big block — rich at idle, lean at load.
• Mixer sizing is driven by airflow at target boost. Specify with the shop, not by guesswork.

Open items

• Tank size, mounting, and liquid-vs-vapor withdrawal — inspect and record
• Lockoff model and line size — inspect and record
• Whether the current mixer mount is a bolt-on or fabrication pattern for the new adapter
• Factory vs. conversion — Marti deluxe
• Compression and cam — shop measures before boost selection; LPG engines run higher static compression than gasoline, do not assume gasoline figures

Safety and inspection notes

• Bag the mixer throat and vaporizer before any pressure washing.
• Photograph the mixer mount from multiple angles before disturbing it — it is evidence for the factory question.
• Record the existing single E and CA425 as spares or patterns; neither goes back on a blown engine.

Documentation

Photos filed: mixer and mount, vaporizer, lockoff (pending), tank and plumbing (pending).

See also

• Engine Identification
• Chassis Documentation
• The Original Specifications