Car runs bad as voltage drops in car.

95 Formula
Has new.
Walbaro 255 pump
ICM, Wires
The car surges past 4700 rpms and it runs perfect when the volagte is at 14.5.

WHen the car is cold the gauge is at about 14.5 like its supposed to be. As the car warms the gauge acutlly will drop down to about 13.1.

I was going to replace my opti(still stock) but after watching this and the gauge Im not sure if it is the opti.

I do have a underdrive pulley. Im thinking of putting the OD alternator pulley on as well.

Can my alternator be taking a crap? Maybe I have a bad ground?(its wierd it does it the same everytime though) Or it is my opti causing a surge.

I would try the OD pulley first and see if that helps, if not then i would get the altenator tested.

What i think is happening is when my volts drop, my fuel pump doesn't have enough juice to run at high rpm. So that is why my fuel pressure was dropping orginally(reason i replaced pump in first place).

Im about ot order the overdrive pulley for my car and belt.

Anybody else ever run into this problem and was problem iam talking about here?

The voltage is higher at cold start because the idle speed is higher, and because the alternator needs to recharge the battery for the power used to start the engine. As the battery recovers, the voltage regulator pulls the voltage down. 13+V doesn't sound all that unusual at idle or under load... possibly down a little because of the U/D crank pulley.

It might be worth checking the voltage at the fuel pump. Did you install a wiring upgrade with the Walbro, or just tie in to the existing wiring?

I did not ugprade the harness. I have ordered teh pulley/new belt.

Am I just overthinking this and should just change my opti?

It would seem to me to be a lot easier to check the voltage at the pump, or check the fuel pressure under various operating conditions, than to start playing "parts replacement roulette" with the Opti.

Is there a way to test voltage at the pump without pulling my cover(its rtv up)?

If not, what color is the wire at the pump for power?

Shoebox has the wiring diagrams for the 95 LT1 on his website. Check the voltage at the connector near the rear axle. Better than that, check the fuel pressure and see what's happening to it when the engine "surges". Put a data logger on it, and have someone help you review it for problems.

I checked the fuel pressure before i changd the pump. Would drop down to 35 at wot and only when it was surging.

Changed the pump and it really didnt seem to be dropping when I had it on there, but maybe ill put the gauge back on today and test it agian.

Ill check out his ssite for the fuel pump info.

I can't find the fuel pump wiring info on his site. Am i just missing it?

PCM wiring diagram #3 shows the fuel pump relay, and the gray wire to the fuel pump through connector C405

No F-body content, but my wife's 97 9C3 Lumina (cop car) developed an intermittent idle quality problem at the same time as it showed evidence of low voltage (intermittent dim headlights). I replaced the alternator and the car ran perfectly.

HTH
kevin