nascarfool.com

The car:
1989 Iroc Z-28
305 TPI/auto trans


Problem:
Cranks but won't start. No fuel.

Temporary cure:
Replace 20 amp fuse in the fuse holder located between the battery and radiator right under the radiator fan relay.

This fuse keeps blowing. I have replaced it several times. Sometimes it blows as soon as the car is cranked over and other times it blows shortly after the car starts. I can't find anything about this fuse in the Haynes manual. Does anyone know what this fuse is for ? All fuses in the fuse box are fine. The fuse is not an after market add-on.

* The fuse holder says "P.E.D. 7 FUSE" on one end. It mounts behind the right (passenger) headlight.

Stekman

If i am picturing it correctly, that is your fuel pump fuse. It protects the fuel pump relay.

Sounds like something is shorting out in the fuel pump circuitry. Go over the fuel pump wiring and make sure that there are no exposed wires that are causing the fuse to short out.

nascarfool.com

Thanks for the quick response. I should have done a search before posting. I see many posts about that fuse. I will double check the wiring and relay.

Trickster

Hey Stekman,

You are correct, it is a common occurrance for the insulation to peel back from the wires on the fuel pump relay connector and they will short out that fuse. Previous owner replaced four fuel pumps on mine because of this. I found out later from another source that the mechanic charged him for that and only changed out the fuse. The mechanic is no longer in business and has left town for parts unknown under questionable circumstances. BTW, welcome to the board nascarfool.com.

nascarfool.com

Ok, I repaired the wires by removing them one at a time and putting some heatshrink tubing on them. I replaced the fuse and it started. I pulled it off the street and into the driveway and the fuse blew. I replaced the fuel pump with an OEM about three years ago. Is it possible that the fuel pump is blowing the fuse ? If so, I think the tank is almost full. The pump relay was replaced a few days ago.

Thanks for the welcome.

Trickster

Here are a couple of other points that particular wire goes to and supplies power to each one. Pin "E" of MAF burn-off relay, pin "A" of MAF power relay, the oil sender/pressure switch, and the ECM.

nascarfool.com

Well, I have come to a conclusion that I will have to replace the pump. All relays are fine. The fuse gets very hot while the car is running and then it'll blow. I think the pump is drawing too many amps. As I recall, I am in for a not so fun job.

nascarfool.com

I am at the end of my rope. We installed an after market pump with a relay and wire harness. The car runs better but after a few minutes, you give it a little gas and it pops the fuse.

Parts replaced:
OEM fuel pump relay
ECM
fuel pump
several 20 amp fuses

Trickster

Hey nascarfool.com,

Here is a wiring diagram for the power connections coming off that 20 AMP fuse. You will notice on the diagram that there is s connector labeled C148 coming off fusible link "D" going to that in-line fuse. It is a single wire connector hanging at the base of the battery. There is also another connector there that is labeled C145, it sends power to both coolant fan relays. I am including a picture showing their location. Also, if that fuse blows after you give it the gas, you either have a wire shorting out somewhere in that circuit or the battery is putting out too much power.

Trickster

part 2

83ho86tpi

You might want to check your fuel pump ground wire, mine was questionable, I dont know if this might make a difference. Mine was under the drivers side rear seat ( under the carpet ) bolted to the body. I think this is where your pump ground wire would be also. Tracing and fixing wiring can be a pain. Hang in there because you are going through the same process a shop would, but you are not paying them the labor. Good luck!

nascarfool.com

I haven't looked yet but my son said it is the oil sender and wires. He told me they were melted. Electrical problems can be so much fun sometimes.

Trickster

Can't they though!!!!!!!!!!!

nascarfool.com

Yep, the oil sender plug is fried. I think the sender is bad too. The car runs fine with the sender unplugged. Now I need to search for a repair plug if such a thing exists.