Yesterday I was attempting to set my idle speed. I think I may have adjusted it too low because I am sure my tach is off by about 500 rpm. Anyways, after unhooking the IAC, and restarting the car and adjusting idle speed to what read 1000rpm on the tach, the car starts losing idle and starts stumbling. The tach jumps between 500rpm and 1000rpm. Then it just dies and throws a code 33, which haynes says is MAP sensor voltage. Well I let it sit and tried to restart it, but noticed when in the "ON" position, I didn't hear the fuel pump prime like usual (it was rather loud). Tried to crank it but wouldn't start. So I unhooked the battery all night to clear the codes, and tried to restart it again. Same scenario, no priming sound and no starting. I'm kinda stumped as to what happened? I have a 91Z28 with L98. could a fuel pump relay have gone bad? If so, how would I check that? could someone shed some light on this please? Thanks

 

OK, I found the fuel pump relay on the firewall. Now, how exactly do I go about checking to see if it is working properly? I did a search, and from what I gather, even with a bad relay, people could still hear their pumps priming. Does this mean, since my doesn't prime at all, that I may just have to go ahead and replace the pump?

 

Turn your key on and listen for the relay to click.That's one way.Or just buy a new one for 13 bucks.The fuel pump is also run from the oil pressure switch in the block.

 

The oil pressure switch is that switch right above the oil filter correct? Well after my header install, my oil guage seemed to go crazy so I sprayed some electronic cleaning spray in the connector as well as the sensor, think that was the oil sending unit Well my oil pressure reads 30psi, steady, as of now. But could that sensor keep the pump from priming?

And yes, I do believe I hear a "click" when the ignition is in the ON position....just no priming.

 

What it does is if your relay goes out the oil pressure switch will give the fuel pump the power to prime as soon as the oil press. builds.I'm not too sure if it would keep it from priming.Maybe if it wasn't reading enough pressure.

 

hmm...maybe that could be the cause of it? the relay sounds good though so maybe??? Erg, frustrating.

anyone else have any suggestions?