New 3.4 motronic build won't idle
 

Hello

I bought a nice rebuilt motor from the late Fred Apgar which is a 3.2 to 3.4 build. It has the Sal Carcellers ECU and throttle body etc....programed to the upgraded specs. of the engine. It also has a lightened patrick racing flywheel, power clutch and clewett crank pulley.

Upon first start up I can't get it to idle. Checked for vacuum leaks everywhere and no issues. Fuel pressure is good. I also had an issue with the coil but got that replaced to get it to fire. It revs strong

Any ideas?

Bob

Check to make sure all your grounds are attached properly.
Trans to chassis and harness to left side intake stack.

Thanks Henry, I am going to double check the ground wires as you recommended. Also someone else suggested the ECU was not picking up the Patrick racing flywheel signal but I have no idea if that is possible.

"Compression, fuel, spark."

You probably know this, but sometimes we all get fixated on what we "think" is the problem, instead of making sure. What testing have you done to determine whether you are lacking fuel or spark?

A quick check is to squirt starting spray in the intake to help get it started, and to continue short bursts of spray after it starts to keep it running. If the starting spray does not help it start or run, then you are back to spark. If it helps, then focus your troubleshooting on fuel.

Fred was a great guy and I’m sure you have a special engine. Good luck with the tuning.

No direct experience, but I've heard that the Motronic can get confused by a light flywheel, and can corrected by a tune. Might be worth checking with Sal Carcellar to see if your configuration is compatible.

If it runs good but won’t idle, it’s all in the tuning resulting from the light FW. Sal, I bet can fix that up in the tune.

Just in case it's a revvy motorsport engine, if there's overlap in the cams you won't have compression at low revs, in which case it will never idle smoothly. You will need to up the idle speed.

What's the redline?

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