I have an 88 automatic 4runner that had a 3.4 from a 99 auto 4runner swapped into it. I did not do the sway and the wiring is a little sloppy for my taste, but it usually runs great. On my way to work I have my efi fuse blow a couple times and once returning home. I have had this blow once before and I thought my fuel pump might be shorting our, but all was well. that was months ago. I spent all day trying to trace the wiring gremlin to see what might be shorting the circuit, but found nothing except a couple melted and unused harness for what look to be solenoids under the vehicle. I am just looking for some helpful pointers as to what may be causing this. I fear it may be my harness and I think I will try to buy a new one due to mine being an ugly mess. Let me know your thoughts..Thanks.

 

Seeing as someone else did the wiring its really hard to say. Any sign of melted anything is not good and would either bring it back to them and have them fix it or re-do the wiring yourself. As to a cause it could be many different things sorry as to not be able to help.

 

Wiring issues suck, especially when you are talking about a whole harness. Finding the short in one exposed wire can be hard enough.

 

The melted wires were under the vehicle and came into contact with the exhaust pipe. If the original fuel pump is used, and not a new one could that stress the efi circuit out enough to blow? Before the fuse would blow it would chug a little and the rpms would drop then come back.

 

That harness that I found that was melted might be my rear o2 which if I am right can cause the the efi to short out if it is grounded. I might play with it a little more.

 

Well 45 minutes of driving around 70 mph was a success. It must be the harness. What color are the wires going to the second o2 sensor so I can confirm this? My wiring diagram does not show this.

 

Well glad to hear that it is working now. To answer some of your questions. No the 3.0 fuel pump will not blow the the EFI fuse. I'm running 3.0 EFI fuse and fuel pump. Now was the wires melted from the exhaust? If so did you re-route the wires so this does not happen in the future? As for the wiring diagrams the ones I have are for different years.

 

PM sent, so you can get the EWD's for the 99 runner.

 

The actual harness came into contact with the exhaust pipe. It has since been sealed up and ziptied far away from the exhaust. It ran fine to and from work today so I think that was it. On a similar note, would using the 3.0 fuel pump make the response be somewhat sluggish due to lower pressure?

 

I don't know the exacts on what the actual pressure is but it could be to a blocked filter or debree in the line. Something to look for. Especially if the vehicle has been sitting around.

 

The only time it is sluggish is when it is started after the ecu has been reset by hte battery being disconnected for a few minutes. After it throws the 2 o2 code then it is just fine. It is not significant but I was just wondering. The fuel filter was replaced about 6 months ago so i think it is ok.

 

hamish_18 was nice enough to send me the ewd and as long as my ability to read the diagram is correct, that was the o2 sensor. This is good that I found that because I need to either make a sim or put in a high flow cat and a second sensor. Due to finances I will probably go for the sim. We will see..