frequent HEP failure at 14psi = cracked piston?

[acannell]

I recently cracked a new piston in a rebuilt 2.5 turbo engine.

I was running 14 psi.

AFR was =< 11.4.

I had a BIG intercooler.

My HEP fails frequently and intermittently, causing the engine to instantly die out and then re-start. Sometimes it restarts immediately, othertimes its takes long enough to where I have to pull over and wiggle the wiring around.

This happened SEVERAL times (10+) while at 14 psi at WOT.

Could this somehow have hurt the engine? I thought it cut fuel COMPLETELY, so its not really leaning out, its just NO fuel.

[ol"blue]

Unless I'm mistaken, when it shuts off the pump there's still pressure in the lines, so it does go lean briefly before it dies. You could have a wiring issue in the harness leading to the HEP. That could explain the intermittent problem and the "jiggling the wires" issue. Those old wires do become brittle. If you can, check the continuity of those wires.

[acannell]

hmm. i would think it would turn off the injectors instead in addition to turning off the fuel pump.

i know where the wiring problem is im just lazy :P

[ol"blue]

Seems we all suffer from that at times. Good luck.

[tryingbe]

I hope you spent the money and bought a new hep...

[rx2mazda]

See where laziness got you? A cracked piston! Sorry about your troubles.

[acannell]

no prob. piston is already replaced and its running okay. it was good practice to do that since im sure i will crack another one some day. it was surprisingly easy and cheap to do too, maybe 12 hours of labor and $100 in parts and shipping.

anyways i just put in a new hep, and i cut off all the connectors and soldered everything together and heat shrinked it. END OF HEP PROBLEMS.

[bfarroo]

The problem is the wires break where they come out of the distributor not at the connector. Also if you didn't buy the HEP from the dealership plan on replacing it in 6 months. I've replaced the HEP on every TD I've ever owned, I've been down the parts store HEP road. I recommend anyone with a TD to carry a spare HEP in the glove box. Would be hard to change for you since the plugs are gone now.