It happened, my 86 acts like the fuel pump relay went bad.
1. I changed the fuel pump relay, and same thing happens.
2. I put a meter on the green wire, and the relay isn't given the power to prime the system.
3. Once I turn the key to start, the green wire gets voltage, and the relay energizes.
4. On the ALDL, the pin g wire runs the pump when it is given 12 volts, indicating the relay is in the relaxed position.
5. once started, the car runs fine.
6. I did not disconnect the oil pressure switch and try it because the fuel pump relay gets coil voltage to energize the relay.
7. according to the print, the fuse is good so I didn't go there.
8. I have to put a gage on the fuel rail,haven't done it yet.
9. once it starts, it acts like it is starved for fuel.
I have an 89 prom and computer, and that is next after I determine the fuel is/is not leaking back to the tank.

My question,
When you turn the key on, the fuel pump is supposed to run a short time. where does that signal come from? the prom or the computer?

 

On my 84',my manual states to run a wire from the POS terminal of the battery to the LOWER LEFT CORNER SLOT of the computor hookup terminal which is right below the steering wheel,and the pump should energize,which indicates that the pump is working,and the problem is somewhere else.I did that after I changed my pump relay and found that the problem was in the connector that plugs into the relay.Apparently someone tried to dis=connect the connector from the relay by pulling the wires,which did nothing but seperate one of the connectors from the contact inside of the relay. replaced both with new from local parts store for $21,and it seems to be working fine...Hope this helps.....

 

1. You are supposed to trouble shoot...THEN replace parts.
2. Do you have good connections for your meter leads? The voltage is only supposed to be present for about 2 seconds. Are you sure you didn't miss it?
3. Good.
4. It also indicates the fuse, the wiring, and the pump are good.
5. Good.
6. How is your coil wired into the fuel pump wiring?
7. You proved that in step 4.
8. ???
9. Check the fuel pressure. You could have a weak pump, a clogged fuel filter, a kink in a fuel line, etc. Since the pump runs when the engine is cranking, and when the engine is running, you know the fuel pump works. The year of the ECM and prom don't matter, here, because the pump is working. The fuel is not leaking backward into the tank via the pressurized fuel supply line.

"My question,
When you turn the key on, the fuel pump is supposed to run a short time. where does that signal come from? the prom or the computer?" The prom is plugged into the computer and has the programming for things such as ignition timing, fan temps, etc. The "signal" to do anything cones from the ECM. The prom only has the instructions of what the ECM is to do. The problem you express in #9, if it is a fuel problem, is not caused by either the ECM OR the prom. If you suspect fuel problems, you should have started with #8, to see if that were truly the case.

RACE ON!!!

 

I think the prressure is bleeding off fast which is why I stated that the
engine acts like it is starved for fuel.
I am thinking either the pressure regulator or fuel pump check valve may be at fault.
The fuel pump relay failed once before, and it acted the same way.
The car runs really good, has 130,000 miles, and I was going to change the pump anyway because of the mileage.
now all I need is a tank flange gasket to remove the pump.
I have a spare, and a spare fuel tank sender. If either is bad, I am prepared.
The car failed to start for the first time friday when I was leaving work. I haven't had time to troubleshoot, and I figured if I got a relay on the way home, if I indeed needed the relay, I would have one for the weekend. I plugged it in before leaving the dealership. The car started immediately. later when I backed it out of the garage after din din to wash it, it exhibited it's new malady again.
BTW
It's nice when you raise the hood, people come out of the woodwork to see what you are doing, and to check out what's under the hood......even the dealership mechanics who are supposed to know what's under there.
I finally got the windshield in my 57 chevy truck, and it ate up most of the day to remove it, get the seal and winshield reinstalled, and get it home to detail it to run out to the car show.
Tomorrow is a garage tour. Some rich folks invited a bunch of us at the car show to come over and see their car collections, and provide lunch afterwards. A once in a lifetime event!!!!!
Maybe I'll use the rest of the afternoon to play with the fuel problem. Why don't we get 3 days to every weekend?
umm then we would call it a weekback?

 

You realize that the ECM only brings on the FP relay for the first 2sec after you turn on the key, until after you start the engine.

Indeed you need a gauge on the fuel rail to see what is happening to the prime and to see if pressure is being maintained during Run.

 

The check valve is in the fuel pump. It doesn't come into play when the pump is pumping. There is no back flow when the pump is pumping out. The regulator can fail in two ways. The first is if it is leaking fuel into the vacuum hose, and the other is if bypasses fuel back to the tank without causing the pressure to build. If the vacuum hose is dry and you have the correct pressure, the regulator is OK.

RACE ON!!!

 

The ECM energizes the fuel pump relay any time it receives pulses from the distributor. That means that in addition to the 2 second priming period, when the key is first turned to the "On" position, the ECM runs the fuel pump any time the engine is turning and the distributor is generating pulses. This happens during both cranking AND running.

RACE ON!!!

 

If you're not sure about the ECM, then wire a test light from ALDL pin G to ground. Any time the light comes on during cranking or running, the pump is behind powered by the oil pressure, and not by the relay/ecm.

 

ok, don't beat me up on this.
I guess I meant to say I think the prime is not working, and that is why I thought it was the fuel pump relay.
The car does start, and it sounds and feels like the pump is "catching up" the pressure, and when it does, the engine is fully normal.
That scenario leads me to believe that the fuel rail is somehow losing the static pressure. It could be the pump check valve, or the regulator. The engine is not flooded, or running rich. The fuel totalizer gives me 32 instant on the highway when on straight and flat road @ 75mph, and there is no smoke or indication of anything amiss when I start it except the pump seems to be filling an empty fuel line.
When the engine is in the crank or run cycle, there is 12 volts at the green wire which is the relay coil. That leads me to believe the computer is sending the energize voltage to ask for the fuel pump.
by the way, thanks to everyone who responded.

 

Buy a fuel pressure guage.

 

Ok, car is fixed.
Took Central coaster's suggestion and bought a gauge.
buying a gauge didn't fix it.......................
ok, seriously,
the fuel pressure bleeds off almost immediately to 10 psi. That I was guestimating and was correct. but! the gauge was fluctuating like the injectors were opening and closing.
when the fans came on, the gauge got steady. like the volume of the pump was barely adequate for the injectors. pressure went from 38 to 35, then when I stepped on the brake, the pressure went from 35 to 33..then when I turned on the headlights, the engine wouldn't idle. The pressure went to 30 psi. then the engine died and the pressure went to 10 psi.
I figured the voltage had something to do with it, and checked the volt meter. 13.1 volts, rev the car, and with the lights on, the a/c on, the brake lights on, and the radio on, and the volts are still 13.1 @800 rpm. The car idles @600 rpm normally.
I removed the pump/gauge bracket, and there was some rust on the flange, and the pump had been changed once before I got it because there were worm drive clamps on the hoses and splices on the pump wires.
I went to a wrecking yard and bought a pump/gauge, and to Chevy for a new sock and gasket, and back again.
the used unit was out of a 90, mine's an 86. GM changed the grounding circuit for more reliability, and I used those wires repinned into my connector. the wrecking yard pump was toast, and I re-used my old pump.
changed the pulsator, and assembled the whole thing. manifold pressure is now 40 psi shut off, and holds 30 psi for over an hour,the engine revs faster, and the car starts easy.
I had 3 things I know was bad.
1. the pump ground was questionable.
2. the sock was plugged up
3. the pulsator was leaking.
what a brain gymnastic..........now I have to see if my gas gauge is affected with the new tank unit.
the 90 gauge unit had two bars spot welded to the tubes instead of one, and the ground system was better, and the connector had 4 pin connector instead of the 3 pin that came on mine.

 

Congats on your successful R&R...