Fuel Gage and Fuel Pump

[SolidState]

So, I've got these odd problems that developed on the 91 over the last couple weeks.

First, the fuel gage. On cold morning, I had about 3/8ths of a tank, and suddenly the needle climbed sharply to about 3/4" PAST the F. Now, it is inaccurate at best. I pulled the sender and replaced it with a different sender to no avail. The manual says that the gage uses 143 ohms when full, so it going that far past suggests a resistance much higher than that. I am thinking of bypassing the ASM tomorrow, but then this happened...

Tonight, the car stutter three times. First was abrupt, second happened a couple minutes later and felt like the fuel cut-off, and the third happened about 10 minutes later when I downshifted to 3rd and punched it. This time, the engine just stopped running, but had power and no indicators on the dash. No idiot lights, nothing. The car just seemed to retard. Almost like it was fuel related.

With the two combined, I am wondering if the harness leading to the fuel pump/sender is damaged.

An suggestions on where to start?

 

[Storm-Chaser]

After you've done a basic KOEO/KOER tests to pull codes and validate operation of the CCRM fuel pump relay, start by checking the fuel pressure.

If it's electrically related, you should see distinct drops in fuel pressure as power to the pump is shorted. Basically, the pressure will begin a steady drop toward/to zero, depending on how long the circuit is shorted. As soon as the circuit-short has cleared, pressure should immediately return to what it was before the temporary short.

If it's mechanical, one of the several possible symptoms will be the engine acting like it's running-up against the rev-limiter well before 7300 rpm, especially during hard runs. In such cases you're likely to see a progressive drop in fuel pressure as the pump continues to operate but fails to meet demand, at a time when the fuel pressure should be increasing as a result of how the fuel pressure regulator operates.


Going back to the Fuel Gauge reading - it could be due to a failure of the fuel sender, the fuel gauge, or the anti-slosh/low fuel warning module on the back of the instrument cluster.

You make mention of the Service Manual and one of the tests - applying a 145 ohm resistance load to the fuel sender circuit should make the gauge read full; 22.4 ohms should read empty. There is an expanded troubleshooting section in the Service Manual - walk through the steps and it should at least help you eliminate some of the possible sources of the gauge error. It will require you pull the instrument cluster and the connector at the fuel pump, if I remember correctly.

 

[SolidState]

Thanks.

I was looking into that with a resistor, but before I could troubleshoot it, things went all to ****.

See my post in emergency issues.