89 Camaro 350 TPI setup, starts and runs fine when engine is cold. When it warms up even a little, it will not start. I have replaced the Ignition Module, (which was already new), with a known good one and another new one, no help. I have replaced the harness at the distributor, as when I tested the no start, I could get the injectors to pulse manually and the module has been eliminated as the fault, no help.

When it is cold all the injectors have good pulse and the engine starts and runs great, with no trouble codes present. I checked the timing and set a trouble code. I tested the TPS and disconnected the MAF when it would not start. I installed a known good ECM and Prom. I am still at square one. Nothing seems to be a problem, yet it still has no injector pulse and will not start until the engine cools to cold.

I also checked all the engine and ECM grounds, and verified all the battery voltages at the ECM. I am confident the problem is something well outside of the norm. I have seen and repaired some pretty tough problems in the past, this one is biting me. Any help is appreciated!

 

Hi Shane,

So, you have no injector pulse when the engine warms. Maybe the injectors are shorting out when they warm up. Have you ohm checked the injectors warm and cold? Because they are batch-fired (4 at a time), if one on each bank is shorted, the pulse may short through the defective injector coil instead of powering the other injectors.

Hope this helps.

 

Is this behavior consistent (i.e. you have been able to start cold many times when it wouldn't start hot many times?)

I second the injector short. Disconnect all the injectors from the harness the next time it happens, and see if it pulses.

You may also want to verify that the ignition module is good. I know a bad module prevents the fuel pump from running, but Im not sure how it affects the injectors. To test it, connect a test light to the negative terminal on the ignition coil (+ to battery). Test light should pulse when engine is turned over.

 

The stock multecs are extremely prone to coil failure. This is probably your problem. Once the injectors get hot the coils fail/short out. When customers insist on having theirs flowtested, the injectors sometimes flow extremely well on static. Once we start putting them through the various duty cylces they shut down, stop flowing, then depending on which cycle the machine is running at they begin to flow again.The internal coils on these injectors are exposed to the constant flow of fuel, so over time they just wear down.