Why won't my Acura Integra start when it's hot?

Short answer: On older Integras, a crank-no-start when the car is hot is the classic sign of a failing main relay (Honda calls it the PGM-FI main relay). It powers the fuel pump and injection. Its solder joints crack with age, and heat makes them lose contact, so the fuel pump doesn't run. Once it cools down, it starts again. Owners fix it by resoldering the relay or replacing it.

Symptom: On a hot day or after a short stop, the engine cranks normally but won't fire. Let it cool for a while and it starts fine.

What to check first

1. Listen for the fuel pump. Turn the key to ON (not start). You should hear a hum from the rear for about 2 seconds. No hum when hot points to the main relay.
2. Find the main relay under the dash on the driver's side, near the steering column.
3. Inspect its solder joints for rings or cracks around the pins.
4. Don't keep cranking. One owner cranked so long he flooded the engine.

Likely causes

1. Cracked solder joints in the main relay. The most common cause owners report.
2. Failed main relay. Replacing the relay is a plug-in swap.
3. Weak fuel pump. If the relay is good and the pump still doesn't run, test the pump.

What it usually costs

Resoldering costs little more than solder if you have an iron. The threads didn't give relay prices; replacements are sold new and used.

Is it safe to keep driving?

It won't hurt the engine, but it can leave you stranded or stall you when hot. Fix it before a long trip. Verify with a mechanic if it ever dies while driving.

DIY or shop?

DIY. Resoldering the relay with a small soldering iron and rosin-core solder is a common owner fix, or you can plug in a replacement.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists no recall for the fuel or main relay on the Acura Integra for these model years (checked 2026-10-23). Other recalls may exist for your car, so check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• NHTSA complaints: 14 keyword-matched complaints for Acura Integra 1994–2001 (of 240 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-23; keywords: relay, no start, won't start, stall, fuel pump, hot). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In How to fix the main relay if your car won't start on a hot day on Club Integra, members walked through resoldering the main relay with 60/40 rosin-core solder and a small iron. One owner said he cranked for an hour and flooded the engine before learning about the relay; others said a replacement relay fixed it.
• In Hot motor won't start on Honda-Tech, an owner had an Integra that wouldn't start when hot. Members pointed to the main relay and said to listen for the fuel pump's 2-second prime with the key on.

Quick tip

This is one of the cheapest fixes on an old Integra. Listen for the fuel pump on a hot no-start before you buy anything else.

Vehicle focus: 1990–2001 Acura Integra. Civics and Accords of the same era have the same kind of main relay.

Safety / mechanic note

A car that stalls when hot can leave you stranded in traffic. Verify with a mechanic.