Just redid my fuel pump on my 95Z. The fuel bucket had come loose from the top and I replaced the sender unit.

Now the pump doesn't run. I can't hear it prime when the key is turned on and the car, apparently, isn't getting fuel as it turns over but won't start. The fuel system was working last weekend as the car would start and run so the wiring was ok at that point.

It was late but I did check the fuses (all good) and I know the pump is good. I'll be checking voltages and the relay. Is there anything in the PCM or other sensor that will cutoff power to the fuel pump that I might need to check out?

 

The PCM runs the pump for 2 seconds when the key is turned to “run”. Then it shuts it down, and will not restart it until 1) it gets the “fuel enable” signal from the theft deterrent module (part of PASS-Key II/VATS); and 2) PCM sees low resolution pulse from the Opti.

There are codes in the PCM for failure to receive the fuel enable system, and for lack of low resolution pulse from the Opti. The latter does not turn on the SES light, and may not set if the high resolution pulse is also missing, or if the engine is not cranked by the starter long enough to generate a certain number of high res pulses.

Sometimes, when there is no “fuel enable” signal, the engine will run for a few seconds using the fuel present in the rails after the 2-second pump prime.

Did you check fuel pressure?

When the engine is cranking does the tach needle move up ~200 RPM or so?

 

Thanks for the response and info Fred. I've got the 24x mod on my car with the LS1 PCM. Any similar pcm checks for that setup? I'm just getting back to the problem...maybe. It's going to be a very hot and humid week in Louisville. Hopefully I'll get on it early in the morning.

 

Don't know. You might want to highlight your use of a 24x system in the text of the post. I see you have it near the end of your signature, and I guess I should have looked more closely. My error.

I have little knowledge of the 24X system, and have no idea what specific PCM it uses. I took a quick look at a 1999 factory service manual covering an LS1, and the BCM incorporates the PASS-Key II system, and has a “fuel enable” signal it sends to the PCM. I have no way to know if the 24X PCM interfaces with your 95’s theft deterrent module (TDM) in the same way. P0230 indicates the PCM will not start the fuel pump if there are no ignition reference pulses.

Whether the PCM used in 24X has those features, and how the 24X system interfaces with the existing components in your car is an unknown to me.

If we actually had any traffic on this site any more I would encourage the site owners to add a “24X conversion” sub-forum in the “LT1 Based Engine Tech” forum. That would allow more productive conversation on the topic. But there’s no one here any more. You might want to try ls1tech.com or ltxtech.com. They seem to have more active members, and more people still hanging on by going to 24X conversions. I'm about to declare this site “deceased”.