Im the proud new owner of an 87 IROC. The car has 4 wheel disc brakes, T-tops, TPI 350, and a 700r4 trans. When you turn the key on, the electric fans come on and the Service Engine Soon light illuminates. The fuel pump does not run. This is the reason the car was parked 2.5 years ago. It has some minor rat damage to some of the wiring harness, but i don't see anything chewed up that goes to anything important (mostly the wires that used to go to the AC). My fuel pump relay is not clicking on. (no current on the fuel pump trigger wire, but has 12v on the constant hot wire) If i jump 12v+ to the trigger wire on the relay, the fuel pump relay and MAF relay click on. The pump still does not run. I slid under the rear of the car, and am only getting 6 volts to the fuel pump. (same if you jump power directly to the fuel pump wire on the relay) The car also does not flash any codes (nothing at all, light just stays on) if you jump terminal a&b in the data link connector. Anyone had any issues of the sort? Even if the pump was stuck, i should still be getting 12v+ to the pump wire correct? I have done extensive work on TBI and Vortec injected pickup trucks, but this is my first rodeo with a TPI setup and i am lost as a goose on this and have to trace things down the hard way because i really don't know anything about how this injection works, or what it takes to make it run. Any help would be greatly appreciated.

 

If the pump was stuck , It would load down the circuit greatly . Figuring that with the engine not running , your likely at or a little below 12V , and the length of wire from front to back and the fact that these aren't exactly known for being "overwired" (wires just large enough gauge to get the job done) , yea , it's possible . Of course , a high resistance connection in the circuit is also a very real possibility as well . The fact that it doesn't attempt to prime bears looking into but as you said even with the relay jumped you still only saw 6V at the pump , did you check the ground connection of the pump for corrosion where it connects to the body under the rear seats ?

 

PS , I'd fix any rat chewed wires before I went replacing the ECM due to it not flashing the proper code 12 when A&B of the ALDL are jumped . If the little bastards chewed the right wires ( well , the WRONG ones , actually ) all kinds of odd results could be expected .

Start with the harness verified 100% and take the troubleshooting from there

 

Have not made it this far yet, this is the kind of advice i am looking for. I don't even have any idea how to get the back seats out of the car. This is the first car i have ever owned. Been all trucks until now. I ohm-ed out the ground wire, and it showed no resistance to the bottom of the floorboard. I tried to bump on the tank when the relay was jumped out, but with the shield on the tank, not sure how much good i did I realize the wiring harness needs a solid once over, but nothing is standing out. Everything on top of the motor and all looks ok other than the vacuum lines and 1 injector wire being chewed off, gonna have to get a pigtail for it and splice it in. Im just trying to get the fuel pump to run for the moment. Trying to fix 1 thing at a time. Does anyone know exactly how the wire runs from the fuel pump relay to the pump?

 

And does anyone know specifically how the energize wire on the relay gets its power, thats the next problem i am going to run into. Im assuming it has some sort of timer (maybe in the ECM) and power comes from the ignition switch to it?

 

I have found the majority of the problem. Rats have chewed almost the whole wiring harness in two (the one that runs inside the passenger fender). I got the inner fender pulled out of the car, and can get to the damaged wires, but its gonna take alot of solder and heat shrink to fix it all.

 

I'm happy to hear you found that !

The harness that runs on the passenger's side is the ECM harness that , among many other things , does signal the fuel pump relay to run . This chewed harness is also a great reason for why the ECM would not report the proper code 12 when you attempted to enter the diagnostic mode .

I'm NOT so sure that this chewed harness would have caused your fuel pump wires to only read 6V when you had jumpered the relay , this is still a likely separate problem , but getting your harnesses in order , down to every last compromised wire fixed , will put you well on track for further diagnosis of this .

Good Luck with it and keep me posted of your results .

 

I got on the alldata at work today and printed off every wiring diagram they have for it. I did a temporary splice on all the wires i could find chewed up last night. After a quick system check, it is showing code 12 now and the fuel pump relay does click when you turn the key on. The pump still does not run, but as mentioned above, I assume that is another issue all together.

 

Oh , and I almost forgot , Two things to mention ;

In order to check your fuel pump ground connection for corrosion , the way to take out the back seat bottoms is to use a 13mm socket on a 4 or 6 inch extension and right under the front of the seat in abouts the middle , there will be a single 13mm bolt on each seat . I'm just about positive the ground connection will be under the carpet , under the rear seat on the driver's side .

and , I hope you got lucky and incurred no ECM damage when you put battery power to the car with the ECM wires shredded . In the event some of those wires were shorted and power applied , the possibility exists for ECM damage . The best you can do now is to make darned sure every wire is repaired and then do the ECM diagnostics again . The real proof of no damage will , of course , be a good running engine when you get to that point .

I ran into the situation where my passenger's side exhaust manifold fried the harness , and after many "western union splice" and solder/electrical tape connections were done , I was treated to a good running engine . Here's to hoping you have the same result !

 

The code 12 is a real promising indication , that's for sure !!!

 

Nothing seemed to be shorted. Did not blow any fuses, and all the wires are chewed off flat, Im pretty sure it didn short anything out. Thanks for the seat advice. I saw the bolts under them, just have not taken the time to pull them out and see if thats all that holds the seats in it. My learning curve has been pretty steep on this car, like i said, my expertise is 4x4 pickups.

 

Hey , I'm happy to help if I can . My only formal training is in aircraft maintenance and so each different car is a learning experience for me as well . It's great to have dedicated forums where the particulars of each vehicle can be learned , it sure saves time and patience when trying to figure things out !

 

No kidding. Im usually sharp as a tack on automotive stuff, but it saves so much time to be able to ask a simple question and get a positive answer before you dive into a project you have never fooled with before.

 

I got the car running nicely. I got all the wiring patched up and re-loomed. I had 12v to the fuel pump wire under the car, but the pump still would not run. Ohm-ed out the ground wire and it checked good. No corrosion or anything. Debated on cutting a hole in the trunk floor, but decided to drop the tank. It was pretty nasty in there. Flushed it out to the best of my ability, installed a new fuel pump and put the tank back in the car. I tried to clean up the fuel sending unit but the gauge still does not work. Im sure it needs a sending unit, but thats a project for another day. I got the car to crank, but it loped sporadically. CEL brought up a code 33 and 36. Found a broken wire at the MAF sensor connector. Soldered it back together and reset the computer. Idle is now smooth, Took her for a spin and the power is decent. No CEL at this point. Now i just got to get the interior electrical stuff working and she will be ready to drive. Cooling fans do not run, but i think i am going to do away with the computer controlled fans and wire them both on a 75A relay on a temp sensor. I'd rather see them come on at 180-190ish than the factory 220/240 setup, thats a little warm for me, especially in the summer.

 

Very happy to hear you got it running . So , indeed , a stuck pump can load down the circuit enough to show only 6 volts , that's good to know .

Now , about this messing around with the fans business ;

This is where you will run into trouble . The ECM is programmed to see 220 or so temp to consider the engine properly warmed up . All of the warm engine operating parameters are set to see that temp and when they don't see it cause you've altered the fans (or thermostat) the computer will keep operating under the assumption that the engine has yet to fully warm up . This will result in a constant too rich condition ! Now , if your willing to do the ECM tuning that must accompany altering the engine's operating temp range then yes , such a change is possible . Always remember , when you change one condition in an established system , other conditions must be modified to accomodate that change . Were it mine , I'd concentrate on getting it back to 100% factory condition before I considered any modifications , and then I would weigh each modification carefully as to the side work it will create .

 

I plan on running the stock thermostat, and may use the stock fan control wire (granted that it works) and just wire both fans on a 75A relay instead of controlling them separately. The fan wires are currently a hack job (looks like someone else was attempting to do what i am going to do but had no idea what they were doing). I could live with both fans on at 220-ish. Thanks for all the help. This forum has been a priceless resource to someone who has never touched one of these cars.