Hi guys.

I have a 1992 RS Camaro with the 305 and a 5 speed. Car is in great condition (15,000 miles) but recently developed an issue when starting.

When you click the key halfway I don't hear the fuel pump prime like it used to. However if I crank it long enough the engine will start. Once its running it runs normally. Acceleration seems normal, idle seems normal. Throttle response is normal.

I was about to start taking the rear end apart to drop the tank and do a fuel pump replacement but I got to wondering if it could be a relay or something gone bad?

It seems odd to me that a failing pump would only have issues when starting but work fine the rest of the time.

I'm not the most knowledgeable when it comes to these engines. Will a TBI system run without a fuel pump? I didn't think it would.

I'd appreciate any advise you all might have, thanks!

 

The ECM should turn on the fuel pump for 2 seconds at key-on. If not there are several possibilities:

The fuel pump drive x-ister in the ECM may be bad, easy fix.

The fuel pump relay may be bad, easy fix.

The fuel pump wiring may be bad, usually around the relay socket. Another easy fix.

The reason it starts after some cranking is that the redundant oil pressure switch kicks on and runs the pump.

RBob.

 

Thanks for the info.

So if your last point is my situation then the fuel pump itself should be working? I.e. the car won’t run without one correct?

Thanks also for the things to check. I’ll start trouble shooting soon.

 

Correct about the fuel pump working.

The ECM provides +12 volts to operate the relay. Lasts for about 2 seconds at key-on. To re-enable that power, need to key-off for at least 10 seconds.

Or, tap the key to the crank position (for just a moment). When the ECM sees reference pulses from the distributor it will again activate the fuel pump relay drive voltage.

The power originates from pin A1 at the ECM. and is a DRK GRN/WHT wire. And retains that color at the fuel pump relay. That relay, under the hood, likely has a red pigtail hanging from the harness.

RBob.

 

Get a manual that can show you the location of the FP relay, ten lol around the engine bay, see if you have another one like it, use it, see if the pump primes. TPI cars use a few of the same relays, I didn’t have a TBI long enough to recall if they did as well. If there’s another “same relay” just a cheap way to eliminate/confirm the issue of it and not toss any $$ at it.