blue_thunder91

Car has been running great and strong since about 2 months ago when code 43 was finally fixed. So yesterday it just wouldn't start, and I couldn't hear fuel pump priming anymore! Fuel pump is about 3 months old, and the fp relay was making a buzzing sound, so I replaced relay and no change. I supplied 12v to red wire on relay(fuel pump) and still no change. Sprayed some starting fluid and car starts and dies. Can my pump be bad? Since my pump isnt priming I havent put a pressure gauge on it! Also noticed that I was having no SES light during key on engine off! ECM is brand new but just to be on safe side went and got a brand new replacement from a buddy at parts store! Still no change, although i haven't checked bulb will tomorrow though! Any ideas?

ATX-Iroc

check the fuse by the battery. If its not blown test to see if you get 12 volts at the fuse if so unplug the ecm and test for power (not sure which wire it is youll have to look it up).

Carlos773

iTrader: (3)

Try wiring the pump directly to a power source? If you cant hear the pump, then its the pump. Don't judge it out just because its been recently replaced, anything can go bad.

blue_thunder91

so i supplied 12v to gray wire on relay which goes to fuel pump and it didnt seem to turn on. orange wire read about 1.24v shouldnt that be at 12v?

avilla20

wiring diagram?

John 89 Formula

There is a red wire off the pos battery cable, it has a 20 amp fuse on it, check the fuse it's probably blown.

ATX-Iroc

yeah i think it should but i think you just had it on the wrong range or something its kind of a coincidence that the decimal is just one off. Another thing you can try is putting 12v to the bottom left portal of the aldl plug, thats a for sure way to trigger the pump.

Murphy-Iroc-87

Hey man im having the excact same problem. but i replace the fuse and it just keeps blowing again? what do those wires go to? or ground to?

John 89 Formula

that wire is the main 12v supply for the ecm, fuel pump and maf sensor relays
there's probably more stuff there too, but you get the idea.

If you keep blowing the in line fuse, check the condition of the relay plugs for the fuel pump and maf sensor, over time the insulation slides down exposing the bare copper wire, if those wires come into contact with a ground source it will blow the fuse.

It happened on my 86, drove me crazy for a month before i discovered the bare wires, I insulated them with electric tape, problem solved.

Chevy86 IROC-Z

iTrader: (17)

Do what the other member said. Put a wire from the battery and insert it into ths ALDL (forgot which hole) and if the pump doesn't prime, then the pump is bad. This method Is the best way to confirm if the pimp is bad.

Chevy86 IROC-Z

iTrader: (17)

Your wiring may be bad too because once you turn the key to on, the ECM sends a 2 second signal to the FP relay to pressurize to fuel lines. Once you crank the engine, the dizzy sends a reference pulse to the ECM, which will trigger the FP to turn on again. But since there is no ses light turn on when the ignition is turned to the on posiition, then the ECM is not getting power, unless the bulb is burned.

Murphy-Iroc-87

yeah thx guys im not sure about the wirring being bad i think it just is touching somewhere kuz this has happened before and all of a suddon started working again. but im going to try those ideas out right now.

Chevy86 IROC-Z

iTrader: (17)

You mean a short? Possible.

Murphy-Iroc-87

yeah so no such luck. I taped up any wires by the maf power and fuel pump relay and when i put a fuse in it blows still and if connect it with a wire just for a sec the fuel pump relay starts buzzing. all i was doing was driving down the street started to turn and the car died, i tried starting it again and no luck. im pretty confused on what it could be. could the ecm be dead? but why would it blow the fuse? kuz it blows right away as soon as i turn that key you here a pop. the ses doesnt even get a chance to turn on.

Murphy-Iroc-87

i dont know what the aldl is? but i have replaced the fuel pump before. and the ses light still worked and the ecm still worked. this time its nothing. and the fuel pump relay never buzzed before when i replace the fuse with a wire just to see if it worked.

Chevy86 IROC-Z

iTrader: (17)

What fuse is burning? You have a short. ALDL = Assembly Line Diagnostic Link

Murphy-Iroc-87

Its the one right by the battery. almost tucked in the fender-well. it is a 20amp fuse. oh is that the lil clip you put a paper clip in the top 2 holes to get a engine code?

Chevy86 IROC-Z

iTrader: (17)

Thats it. The port where you pull the TC (with the paper clip) is the ALDL. Okay. The fuse that is burning up by the battery is the culprit. Now listen to this CAREFULLY......... That fuse that keeps burning up is the fuse that supplies power to 5 electrical components which are the following;
1. MAF Burn-off Relay
2. MAF Sensor Power Relay
3. Fuel Pump Relay
4. Fuel Pump Switch
5. ECM

One of the ones in red is shorting out (to ground or other wires). You said that the fuel pump doesnt turn on right? Well then there has got to be a short in either item 3, 4, or 5. When you turn the key to "ON", the circuit is "closed." So the fuel pump gets no power to prime and the SES light is not turning on because the ECM has no power because the fuse just burned out. Now get this that Im going to provide you and begin to open up the wire loom in the engine compartment to look for the short (bare exposed wire touching ground). I would begin to look for the short close to the battery because that is a hot spot for electrical shorts. Why? Because if terminals get corroded and dirty, the contact surface is reduced and the current that is passing through the dirty area has less area for current to travel. As more current travels through very thin or very poor contact areas, the wire or electrical path begins to heat up and melt it's insulation. The point of mass heat up is close to the source which happens to be the battery. Thats why when you hook up a very powerful sound system, you must use large gauge power cables so that the current can flow freely without burning itself up much like a fuse. The more current that passes though a fuse, the thicker the fuse has got to be. The less current that flows through a fuse, the thinner the fuse must be. So follow this color coded 1986 IROC-Z wiring diagram. it is very, if not, the same wiring that is in the 87 IROC-Z.

Here is a very helpful link to the electrical system to the IROC. It's featured here in the TGO homepage,,,, http://92b4crs.tripod.com/86wiring/86wiringindex.html

Murphy-Iroc-87

Wow hey man thanks i really appreciate everything you have done for me. tomorrow ill be getting up early and starting on it.

Chevy86 IROC-Z

iTrader: (17)

Hey man. It aint no thang bro. Were all here to help each other out, well some of us are here to help out, like me. Let me know what you find ok.

Murphy-Iroc-87

yeah hey it was a the maf power wire burned on to the header.

Chevy86 IROC-Z

iTrader: (17)

Hey. That's cool man that you killed that problem. Did the wiring help out any that I provided you?