1997 Accord won't start when warm.?

Answer 1

This could be one of many things. Let's walk through them:

The Main Relay is, for most internet mechanics, the be all and end all of fuel injection problems. It's important, and we're starting with it first because it does create more than its share of trouble, but we're not going to end there. This controls power to two very important items: the fuel pump and the injector bank. It's in a horrific place--under the dash, bolted to the side of the car about level with your knee. It carries a huge amount of current, which means it gets very hot and it can't get cooling air...so it breaks. A lot. And sometimes it's intermittent--it works fine before it heats up, and then it stops working. You can test it by opening the driver's door and sitting on the ground with your ear about an inch from the dash, and having someone turn the key. Turn the key to "on" and you should hear one click...followed two seconds later by another one. When she turns the car to "crank" you should hear a third click. If you hear all three, the Main Relay is good. If you don't hear all three, unhook the battery, extract this thing from the car, resolder all the connections and reinstall it. That's usually all it takes, and hope that's the case because these are very expensive.

The next problem is the Thermowax Sensor. Honda uses computerized fuel injection. The system has two startup modes: cold start and hot start. During a cold start, the engine needs a richer fuel-air mixture than it does during a warm start. The Thermowax Sensor, which lives in the thermostat housing on top of the engine, decides which mode to use. If this sensor goes bad, it attempts to perform a cold start every time you start the engine, and the engine floods. The Thermowax Sensor (also known as a Coolant Temperature Sensor) is only active at startup, so once you're running the car stays running. Cure is to replace this sensor.

The third problem is vapor lock. Apparently older Hondas are susceptible to it. To "fix" this requires a bit of creative engineering. Go to RadioShack and buy a 30-amp switch, an inline fuse holder and some wire. You are going to make a switchable fuse. The inline fuse holder has a wire coming out each side of it. Crimp a male push-on (standard push-ons are female) to one wire, hook the other to the switch. Cut a piece of wire and put a male push-on on one end of it, and hook the other end to the switch. Take the fuel pump fuse out of the fuse block and put it in the inline holder, then plug the two push-ons (making sure they're the same width as the prongs on a fuse--you may have to trim them) where the fuse came from. Mount this switch somewhere on the dash. Now...when the car doesn't want to start with the switch on, turn the switch off and start pumping the hell out of the gas pedal. When the engine almost runs out of gas and dies, flip the switch back on and hold the gas pedal down. The car should stay running...if it doesn't, turn the switch off quick and keep pumping. What you're doing is working the vapor out of the line. When you get liquid gasoline coming into the engine, it will run fine.

Additional info:

Start with the basics first! When the no-start condition exists, immediately check for spark and fuel. Pull one plug wire, stick a screwdriver in the end, and set it on top of the valve cover within 1/8" of a bolt where it can ground to. Have a helper crank the engine and see if you have spark. If no spark exists, see ICM below. Cranking the engine for less than 10 seconds is more than enough time to check for spark. Don't risk damaging the ignition coil by cranking any longer than that with a plug wire disconnected.

If you have spark, check for fuel. Turn the key on for five seconds, then back off. Immediately and carefully loosen the bolt on the driver side end of the fuel rail. If there is fuel under pressure there, you'll know right away. Make sure this is tight when you're finished. It's 40+ PSI, and can very quickly start a fire if it's left leaking. If fuel pressure does not exist, check the fuel pump relay in the engine compartment fuse box, or the main relay as described in the previous answer.

ICM, Remove the ICM (ignition control module) from inside the distributor. Your local AutoZone can test it for you. Replacement part is approximately $50, but by all accounts the OEM Honda part is of better quality.

Note to earlier answer: Also remember the car has at least two temperature sending units, the other is located underneath the distributor.