Ever hear of an engine conking out while cranking?

need RX7 · 07-17-2012, 02:08 PM

Today, I went to start my car ('86 n/a) and when the engine began turning, I heard a metallic clattering sound. I didn't think much of it, chalking it up to a heat shield rattling around or something. But, as I cranked it more, the car wouldn't start. I pulled the EGI fuse and cranked it for a while, and noticed I could hear the compression pulses out of the exhaust. They sounded even, but more spaced out than usual.

Fearing the worst, I busted out the compression tester and discovered 0 psi on the rear rotor.

The last time I drove the car (day before yesterday), it ran perfectly. I gave it a bit of a romp before pulling into my neighborhood, but it ran fine in the neighborhood and idled fine in the driveway before I shut it off. It didn't make any odd sounds when I shut it off.

What happened?

bryant · 07-17-2012, 02:34 PM

sorry to hear this and doubt the damage was done cranking it more than likely was done the other day.
and you should hear three pulses, so more spaced out pulse would sound to me like one or more apex seals missing - chipped and or broken.

how many miles are on the motor?

need RX7 · 07-17-2012, 03:15 PM

Quote:

Originally Posted by bryant

how many miles are on the motor?

204,5xx, I guess it was about time.

The front rotor compression is starting to get pretty low too, looked to be about mid-80s.

At least I can cannibalize this car to finish my other one now.

bryant · 07-17-2012, 03:28 PM

i would say you diff got your moneys worth out of that one

WE3RX7 · 07-17-2012, 04:20 PM

Its a far stretch and very rare but low battery voltage and long dwells on aftermarket coils "can" crack a weak seal during cranking.

Most likely it was just your engines time to let go.

need RX7 · 07-17-2012, 06:41 PM

le sigh. I'll throw in some ATF or something and let it sit for a few days before I go tearing into things, just in case.

On the bright side, if this car is finished, I can swap over my 5-lug equipment to my nice car, and all the brake and clutch hydraulic stuff, reducing my list of stuff to buy. If I do that, the only thing I'll need to buy to get it on the ground and running is a set of bushings.

Tougemonster · 07-27-2012, 06:21 PM

I just had used motor seize on start up. It turned and fired normally, almost reached idle speed, then clunked pretty violent like. I'm tearing it down soon to see what happened. Thought it was carbon locked,still might be. I did break a 1/2 breaker bar trying to free it up though. Now i have swellbo, I thought N/A's weren't suppose to break this much

07-17-2012, 02:08 PM	#1
need RX7 Clean S4 Nutswinger Join Date: Mar 2008 Location: Sterling Heights, MI Posts: 485 Rep Power: 18	Ever hear of an engine conking out while cranking? Today, I went to start my car ('86 n/a) and when the engine began turning, I heard a metallic clattering sound. I didn't think much of it, chalking it up to a heat shield rattling around or something. But, as I cranked it more, the car wouldn't start. I pulled the EGI fuse and cranked it for a while, and noticed I could hear the compression pulses out of the exhaust. They sounded even, but more spaced out than usual. Fearing the worst, I busted out the compression tester and discovered 0 psi on the rear rotor. The last time I drove the car (day before yesterday), it ran perfectly. I gave it a bit of a romp before pulling into my neighborhood, but it ran fine in the neighborhood and idled fine in the driveway before I shut it off. It didn't make any odd sounds when I shut it off. What happened? __________________ -Ted -1986 Mazda RX7 Sport [DD/beater]: engine finally let go at 205k. parts car status. -1986 Mazda RX7 base [resto-mod project]: S5 n/a swap in progress.

07-17-2012, 02:34 PM	#2
bryant Rotary Fan in Training Join Date: Feb 2008 Location: Montgomery, Al Posts: 31 Rep Power: 0	sorry to hear this and doubt the damage was done cranking it more than likely was done the other day. and you should hear three pulses, so more spaced out pulse would sound to me like one or more apex seals missing - chipped and or broken. how many miles are on the motor? __________________ 94T-78 (Want 500WHP)

07-17-2012, 03:28 PM	#4
bryant Rotary Fan in Training Join Date: Feb 2008 Location: Montgomery, Al Posts: 31 Rep Power: 0	i would say you diff got your moneys worth out of that one __________________ 94T-78 (Want 500WHP)

07-17-2012, 06:41 PM	#6
need RX7 Clean S4 Nutswinger Join Date: Mar 2008 Location: Sterling Heights, MI Posts: 485 Rep Power: 18	le sigh. I'll throw in some ATF or something and let it sit for a few days before I go tearing into things, just in case. On the bright side, if this car is finished, I can swap over my 5-lug equipment to my nice car, and all the brake and clutch hydraulic stuff, reducing my list of stuff to buy. If I do that, the only thing I'll need to buy to get it on the ground and running is a set of bushings. __________________ -Ted -1986 Mazda RX7 Sport [DD/beater]: engine finally let go at 205k. parts car status. -1986 Mazda RX7 base [resto-mod project]: S5 n/a swap in progress.

07-17-2012, 04:20 PM	#5
WE3RX7 RCC Addict Join Date: Feb 2008 Location: VA Posts: 1,812 Rep Power: 19	Its a far stretch and very rare but low battery voltage and long dwells on aftermarket coils "can" crack a weak seal during cranking. Most likely it was just your engines time to let go.

07-27-2012, 06:21 PM	#7
Tougemonster Meat Popsicle Join Date: May 2010 Location: Missoula, MT Posts: 31 Rep Power: 0	I just had used motor seize on start up. It turned and fired normally, almost reached idle speed, then clunked pretty violent like. I'm tearing it down soon to see what happened. Thought it was carbon locked,still might be. I did break a 1/2 breaker bar trying to free it up though. Now i have swellbo, I thought N/A's weren't suppose to break this much