Fuel System: Difference between revisions
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=== Documentation === | === Documentation === | ||
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Photos filed: mixer and mount, vaporizer, lockoff (pending), tank and plumbing (pending). | Photos filed: mixer and mount, vaporizer, lockoff (pending), tank and plumbing (pending). | ||
Latest revision as of 04:58, 1 November 2026
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.
Tank Specifications
| Field | Value | Notes |
|---|---|---|
| Manufacturer | BRUNNER ENG. & MFG. CO. |
Bedford, Indiana |
| Capacity | 80.8 GAL |
Water capacity (W.C.) |
| Serial Number | AF5255 |
|
| Manufacture Year | 1982 |
|
| Max Working Pressure | 312 psi |
|
| Service Temperature | 450°F |
|
| Tare Weight | 324.32 lbs |
|
| Outer Diameter | 18.0 in |
|
| Length | 77 in |
|
| Head Thickness | .187 in |
|
| Application | FOR LP GAS ONLY |
Tank Certification and Marking
| Status | ASME vessel, 1982. Certified to Section VIII, Div. 1. No DOT special permit visible. |
ASME and DOT marking
| Field | Value | Status |
|---|---|---|
| ASME stamp (Section VIII, Div. 1) | U |
Confirmed |
| U stamp | U |
Confirmed |
| National Board number | RT3 |
Confirmed |
| DOT special permit / exemption no. | None visible | Confirm with supplier for highway service |
| NFPA 58 clearance — fill connection | Not on plate | Ensure 5 ft from ignition sources |
| NFPA 58 clearance — fixed level gauge | Not on plate | Ensure 5 ft from ignition sources |
| Black diamond PROPANE decal | Not visible | Replace if missing |
Why these matter
- ASME tanks carry no requalification cycle like DOT cylinders — the plate is the pedigree. If the plate is unreadable, traceability is gone and a filler may refuse it.
- "Above Ground Only" is a stationary rating. Confirm the ASME stamp and any special permit cover mobile service before the shop plumbs high flow.
- Any welding on the pressure boundary needs a commissioned inspector and an R-stamp plate. Budget for it if the blower plumbing needs a new bung — no driveway drilling and welding.
Plate protection
- 44 years old. Protect the plate from corrosion and abrasion or the traceability is lost.
- Photograph and transcribe before any cleaning. Do not scrub the stamping.
- If pitted, log as a problem — an unreadable plate is a tank a filler can refuse.
Documentation
Photos filed: tank data plate (confirmed), stamp block close-up (confirmed), decal location (pending).
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).