Description

Impco 100 Technical Manual – What You Get on the Bench

If you’re working on an LPG-fueled engine with the Impco 100 mixer and its MSTS ignition system, you’ve already seen enough third-party diagrams that leave out the pinout or skip the pressure conversion chart. This 29-page Impco 100 Technical Manual is the factory document – the one that starts with the actual MSTS arrangement (Figure 1 on page 2) and walks through every sensor and module the way Impco intended. I’ve torqued enough head bolts to know that when the timing curve goes wrong on a propane engine, it’s because somebody used a generic gasoline EST table. This manual fixes that.

What the MSTS Module Really Controls

The Microprocessor Spark Timing System (MSTS) is the brain behind the distributor on Impco 100 setups. According to the manual’s DESCRIPTION section, the MSTS module takes signals from the Manifold Absolute Pressure (MAP) sensor and the Engine Coolant Temperature (ECT) sensor, then adjusts ignition timing for best fuel use and engine performance. Page 2 describes how the ignition module inside the distributor sends a square wave signal – if engine speed drops below 400 rpm, the EST function de-energizes and the ignition module handles start-up. You need to know that threshold. I’ve seen engines that wouldn’t start because the MAP sensor BARO reading was off by 0.5 psi. The factory manual gives you the full circuit description for every sensor under OPERATION.

7 Systems Covered in the TROUBLESHOOTING Section

The TROUBLESHOOTING chapter is where this 29-page manual earns its keep. It breaks down into seven distinct test areas: general checks, required tools and test equipment, MSTS module diagnostics, ignition system tests, Electronic Spark Timing (EST) circuit analysis, MAP sensor signal verification, and ECT sensor resistance checks. Each test description includes a circuit description first – so you understand what the signal should look like before you probe a wire. The TOOLS AND TEST EQUIPMENT list tells you exactly what meter settings and adapters you need. No guesswork about whether your multimeter can read duty cycle from a square wave.

Distributor Rebuild – Factory Torque and Clearance

Under REPAIRS, the manual covers distributor removal, disassembly, inspection, assembly, and installation in that order. It also includes the ignition module and sensing coil replacement procedures. Every step has the correct orientation for the timer core and the sensing coil gap. I can’t stress enough: if you install the ignition module without the proper thermal compound or misalign the pick-up coil, you’ll get misfires at idle. The manual also has an entire subsection for Ignition Timing adjustment after the distributor is back in. That’s where you set the base timing with the EST connector disconnected – procedure matches what every LPG fleet mechanic expects.

Why Factory Documentation Beats Aftermarket Reprints

This manual comes directly from Impco’s engineering files. The 29-page PDF is a scan of the original binder – no re-typeset errors, no missing pages, and the PRESSURE CONVERSION CHART at the end is legible. I’ve seen aftermarket versions that swap kPa for psi and get it wrong. If you need to cross-reference manifold pressure with timing advance, you want the factory numbers. For related OEM manuals, check the Drogobych Crane КТА-16, КТА-25, КТА-28 2004 Installation Manual or the Injectocean Diablo, Murciélago, Defender, Discovery, Freelander Technical Manual for other engine control systems. For older LPG conversions, the Minsk MMVZ-3.11212 Technical Manual – Factory Specs also follows factory formatting. When you’re dealing with mechanical systems like a Manual Transmission, the same principle applies – use the OEM data, not a summary. Same with Manual Transmission clutch adjustments: factory figures prevent slip.

Is This Manual Right for Your LPG Engine?

If you’re working on a forklift, generator, or stationary engine equipped with an Impco Model 100 mixer and the MSTS distributor system, this is the document. The manual assumes you have a basic understanding of ignition systems – it doesn’t re-teach Ohm’s law. Beginners should read the GENERAL section first, which explains how the MSTS begins operation when the ignition switch is turned ON. The FAQ below covers common questions.

Does this manual cover all Impco 100 mixer adjustments?

The manual focuses on the MSTS ignition and sensor system, not the carburetion side. For mixer diaphragm and idle adjustments, you need the separate Impco 100 service manual.

What torque specs are included for the distributor hold-down?

No. The manual does not list torque values for that fastener.

Can I use this manual on a gasoline engine with an Impco 100 conversion?

The MSTS system is designed specifically for LPG fuel. The MAP sensor compensates for the different density of propane. Using it on gasoline will produce incorrect timing curves – the manual warns against that in the OPERATION section.

Is the PRESSURE CONVERSION CHART in PSI or kPa?

Both. The chart on the last page gives kPa, psi, inches of mercury, and millibars. It’s a 4-column table that covers the normal operating range of the MAP sensor (20-105 kPa). This is the exact chart you need if you’re cross-referencing a digital gauge to an analog vacuum gauge.

Stop chasing internet forum advice that contradicts the factory calibration. Access the Factory Manual now and get the real MSTS test procedures, sensor resistances, and timing specs Impco wrote for this system.