Description

Infiniti M30 1991 Service Manual

If you’re wrenching on a 1991 Infiniti M30 Convertible, the factory supplement is the only document that covers the convertible-specific systems. The coupe manual won’t tell you the top timing sequence or the power pull-down actuator specs. This supplement, 274 pages, written for technicians who treat torque specs like law, gives you the raw data straight from Infiniti. Aftermarket reprints get the wiring colors wrong—this one doesn’t. Infiniti M30 1991 Service Manual is the original OEM print, not a scan of a scan.

Every shop that touches one of these convertibles knows the top hydraulics are a pain. The manual dedicates a full chapter to the hydraulic system—pump, motor, cylinders—starting on Section 22. You get the procedure for bleeding the system in the correct order, not the generic method that leaves air trapped in the rear cylinders. Use the wrong fluid and the seals swell. The spec calls for genuine Nissan PSF or equivalent. That’s in the General Information section, page C-2.

Hydraulic System: Pump, Motor, and Cylinders

Section 22 lays out the entire hydraulic circuit: pump flow rate, motor stall current, cylinder stroke lengths. The top stack timing sequence on page C-2 tells you exactly when each cylinder fires during the top-down cycle. Aftermarket manuals skip the timing data—they say “use your judgment.” That’s how you bend a No. 3 bow. The OEM sequence is 1) deck lid open, 2) top back, 3) top fold, 4) deck lid close. Follow it exactly or you’ll snap the stay pads. Torque values for the pump mounting bolts are listed in Section 22, but you need the base manual for engine bay fastener specs.

Does This Manual Cover the Coupe Systems?

Short answer: no. This is a supplement. It only covers convertible-specific components: windshield header trim, power pull-down actuators, quarter glass, weatherstrips, top cover assembly, backlite assembly, bows 1 through 4, deck lid and hinges, hydraulic system, and convertible-top electrical controls. The engine, transmission, brakes, and suspension are in the regular Infiniti M30 1990 Service Manual (that’s the base manual). If you’re doing a valve adjustment, buy that one. If you’re fixing a leaky top actuator, this supplement is all you need.

3 Critical Sections You Cannot Skip

• Section 23 – Electrical Controls: Covers the convertible top control unit (CTU) logic. The wiring diagram on page 23-4 shows the position sensor inputs and relay outputs. One common failure: the top halfway down and stops. The manual gives you the diagnostic flowchart to check the deck lid position sensor circuit—three steps, no guesswork.
• Section 24 – Electrical Troubleshooting: Lists voltage at each connector. You need a DVOM and a test light. The manual says to check for 12V at pins 1-3 of the CTU connector with the ignition on. Aftermarket diagrams often show the ground path reversed—this one doesn’t.
• Section 26 – Body Structural: Required reading if you’re replacing the windshield header or quarter panels. The spot-weld locations and reinforcement plate drawings are critical for restoring structural integrity. Section 26 includes a diagram of the side guard molding attachment—use the specified clips or the molding pops off at 70 mph.

Each section references the base manual where needed. For example, the electrical schematic for the top uses the same power distribution as the coupe, so Section 23 tells you to cross-reference the base manual’s wiring diagram for the fuse box. That’s why you need both manuals on the shelf.

Safety Warnings for Convertible Top Operation

The foreword in this manual contains a safety notice that’s worth reading twice. It says: “If you choose to use service procedures, tools or parts not specifically recommended by INFINITI, you must first completely satisfy yourself that neither your safety nor the vehicle’s safety will be jeopardized.” That’s not lawyer fluff. I’ve seen a tech try to bypass the hydraulic relief valve with a 50-psi shop line—blew the top bow through the backlite. Follow the manual’s procedures for power-pull-down adjustment: Section 3 tells you the exact linkage clearance (0.020 to 0.040 in) and the sequence for loosening the actuators. Do it out of order and the header won’t seal.

Get the Right Torque Specs for the Deck Lid

Look up Section 21 for deck lid hinge bolts. The torque spec is 35–48 ft-lbs. Over-tighten and you strip the captive nuts in the unibody. Under-tighten and the lid rattles loose. The manual also covers the high-mount stop light removal (Section 20)—two screws, 10 mm socket, no RTV needed. And the backlite replacement (Section 14) requires urethane adhesive with a 30-minute open time. The manual gives you the curing time before the car can be moved (2 hours).

For other Infiniti models, check the Infiniti FX35, FX50 2009 Service Manual – OEM Factory Specs if you’re working on a later SUV, or the 2003 Infiniti G35 Coupe Service Manual – Wiper & Washer Systems for electrical diagnostics on a G35. The same OEM quality is in each of those—no aftermarket shortcuts.

When it comes to wiring diagrams, the automotive industry standard for color-coding and connector pinouts is consistent across OEMs. You can read more about that in the Automotive Industry Overview. For safety information on convertible structural integrity, the Automotive Industry Overview provides context on why OEM documentation matters—because the manufacturer tested the failure points, not the aftermarket.

Common Mistakes DIYers Make with This Supplement

Beginners ignore the “Normal Top-Down/Top-Up Operation” section (page C-2). They think they can manually force the top. Don’t. The manual shows you the hand-crank procedure for the pump motor if power fails—turn the hex shaft clockwise only. Counterclockwise releases hydraulic pressure and the top drops on your head. The safety catch must be engaged first. Page C-5 lists the safety information: never work under a partially raised top without a prop rod. The manual specifies a minimum 1-inch diameter prop rod, not a 2×4 scrap.

Another mistake is using aftermarket weatherstrip adhesive instead of the OEM-specified 3M 08001 or equivalent. Section 11 tells you the correct adhesive for the windshield moldings and the curing temperature range (65–95°F). Below 65°F, the bond fails within a month.

FAQ

What years does this manual cover?

1991 model year only.

Does it include wiring diagrams?

Yes, Section 25 covers electrical wiring diagrams for the convertible top circuit, including the CTU connections.

Can I use this for the coupe?

No, this supplement is only for convertible-specific components. The coupe systems are in the base service manual. You need both manuals to cover the full vehicle. The supplement assumes you have the base manual for common systems like engine, transmission, brakes, etc. If you’re working on a convertible top issue, this is the document you need. If you’re doing an engine rebuild, look elsewhere.

What tools are required for top adjustments?

The General Information section lists required tools, including special pull-down actuator tools (Part No. KV99903100) and a hex wrench set for the hydraulic manual override.

If you’re restoring a 1991 Infiniti M30 Convertible or just keeping it on the road, this supplement is the difference between a clean repair and a headache. The manual has 274 pages of convertible-specific data—no fluff, just factory procedures. Access the Factory Manual from AutoRepairManuals and put it on the bench next to your cat’s paw.