Hello,

Hopefully this is a simple question that all you PROM burners will be able to answer in merely half a second. I have recently had some difficulties starting my vehicle and now I'm trying to rule out an faulty custom PROM. I will explain.

I have a 383 that isn't terribly radical. Its in an offroad vehicle, the ECM is a 730 and the PROM was burnt by a custom programmer that has never seen the vehicle. I gave him the specs and he burnt a chip, that for the most part, works just fine. My problem surfaces when I try and start the vehicle. During cranking the left side (driver's side) of injectors do not pulse, while the right side is okay. I did a test with a noid light.

This has created issues when I try and start the vehicle, but has never prevented me from getting it started. On a typical morning I'll crank the engine, it will ignite, and asoon as that happens I kick the throttle and then the engine turns over. As soon as that happens both injector banks pulse like crazy and the engine purrs like a kitten. So far I can't figure out why once bank of injectors pulses during cranking, but the other is dormant.

My question is this: is it possible that my problem might lie in the PROM? When the PROM code is written does the programmer have to do something, write code or do what ever programmers do, that instructs each bank of injectors to pulse at start up?

Thanks for your help

 

The 730 only has one injector driver.
Both banks fire at the same time, you must have a wiring issue there.
Maybe the power to each back is coming from different fuses.
One may be off while cranking.
BTW, ECM is the grounding side of the injector circuit. There are separate ground paths for the left/right sides. I don't think that is the issue though.

 

thanks for the reply,

A few nights ago I completely rewired the driver's side bank and then tested with an ohm meter. All circuits are good. Also, each bank does have an independant fuse but the fuses are good. What is wierd is that the left bank pulses once the engine ignites, but does nothing when cranking. I can't figure it out.

If there is only one injector driver, then I'm assuming that its working. I'll double check all the wiring tonight.

 

trace the positive power supply to each bank. I bet you will find that one is miswired - specifically, one bank is tied to a +12v line that is hot in both start and run, and the other bank is tied to a +12v line that is hot in run ONLY - not start.

hook a probe light to the right bank fuse, turn the key to run. Light is on, right? now crank the engine. light is still on, right? all is well here. now hook the probe light to the LEFT bank fuse, turn the key to run. Light should be on. Now crank the engine again, and I bet the light goes out. That's the source of your problem if so.

you need/want the injectors to be hot in both start and run.

your problem is not with the ecm/prom/ground side of the injectors.