Car dies randomly; mechanic stumped

2002 Hyundai Santa Fe, 68K miles. No other problems. Car made a chunk noise and died. Started up again in a few minutes. Drove 60 miles and it happened again. Diagnostics show nothing. Mechanic says it could be the fuel pump but lacks confidence in this.

When the engine dies, what exactly happens?

Quits suddenly as if the key was turned off, or stutters/stumbles to a stop?

I 'spose could be pump or could be ignition module. Went it dies, you really need to either test for fuel pressure with a tester or for spark. Then you can narrow it down and focus on either the fuel or spark system.

This might sounds silly, but can you describe the “chunk” sound a little more accurately?

Broadly speaking, some electric, or electronic part, suddenly cut off. Instead of trying to find the one failure; rather, ensure that all ignition and fuel supply wiring, and components, are working as they should. For example: check the power to the ignition module; from the ignition module, through to the next component, etc. Check the power to the fuel pump, through the fuel pump; power to the fuel injectors, through the fuel injectors. Check power to the ignition coil, through the ignition coil, etc. By ensuring that all of the parts are working as they should, the working of the whole should be assured.

If it sputters and stumbles before dying then my guess would be that it’s fuel pump related. So when was the fuel filter changed, if ever? Filters can seriously shorten a fuel pump’s lifespan.

If it quits instantly then I would suspect it’s ignition or electrical related; ign. module, ignition switch, fusible link connection, etc.
Fusible links and ign. switches can have their lives shortened by add-ons such as amplfiers, high amp driving lamps, etc having their power leads incorrectly routed.

I am having a somewhat similar problem with a 1987 Subaru, but it bucks and kicks and doesn’t always die. If I pull over and sit it idles OK, or starts up again no problem. This is after new fuel pump and new fuel filter and running OK for 2 months. Gradually the bucking and kicking – apparent fuel starvation – gets worse and worse. Mechanic is stumped. A few days ago I siphoned a quart of fuel from the bottom of the tank (ask your mechanic how to get in from the top) and prepare to buy the siphon, bring a large clear glass liquor bottle or similar. After letting the liquor bottle gasoline settle for a day there was a thin layer of fine off-white sediment. My mechanic says he’s seen it, and it has something to do with a gasoline additive. There was one drop of water in the fuel. If I can get the car to run to the repair shop I’m going to have the fuel filter replaced and held for me in a baggie for inspection. If that solves the problem, then I’ll have the fuel tank removed and all sediment cleaned out. I believe the sediment is clogging the filter due to the cumulative worsening. I don’t blame the mechanic because this isn’t seen very often – and after all, the car is 20 years old.