Jakethewhite

Hey guys got a problem here. I had this car running but the knock sensor was not working so I decided to take that adventure and change it out. Afterward I put everything back together and now it won't start. The reason being us that there is power to the ignition coil but no spark out of it. Also the efi fuse keeps blowing as well. I have re check and sanded every ground that I can see 2x firewall, one on manifold . I'm not sure what else to check. Hopefully y'all can help

Co_94_PU

iTrader: (-1)

If your fuse keeps blowing it is likely shorted to ground somewhere, likely a pinched wire during reassembly, check your harness isn't in something it shouldn't be. Measure the resistance to ground from the down stream side of the fuse and follow that wire to measure again where it branches or is accessible. The closer you get to the short the lower the resistance will be.

Jakethewhite

Would that be the cause of no spark or what do I need to look at for that

RJR

Well, if the EFI fuse is blown you won't get any spark, because the ECU will be in a dormant mode. You'll still have power to the ignition coil, but the switch in the igniter needs a signal from the ECU to generate a spark.

Follow the advice of @Co_94_PU and track down your short circuit. Once you find and fix that, replace the EFI fuse and you'll likely be good to go.

I've attached a couple of wiring diagrams that might help you. Notice the EFI fuse in the upper right corner of the first wiring page in the eng3r.pdf file. That will show you what's downstream of the EFI fuse. The ign.pdf file shows the ignition coil and igniter connections.

Jakethewhite

I pulled the efi relay so that there is no power from the end the only thing is a wire b/g from the relay to the fuse and then the fuse leads to the batt on the ecm but I cannot see where the wire leads to the ecm. That must be the problem wire because I plug in a fuse and this is the only wire connected and the fuse instantly pops.

RJR

So are you saying that, with the CO relay unplugged, the short goes away? If that's the case I would check the fuel pump wiring. You can check the resistance from the FP terminal in the diag port to ground. It should be low (maybe 3-5 ohms - you're basically measuring the resistance of the fuel pump), but not a dead short. Could be a pinched wire going to the diag connector, or possibly a pinched wire going to the VAFM (air flow meter in the intake by the air cleaner).

It's unlikely that the circuit opening relay itself is the source of your short. Relays typically don't fail that way. They fail stuck open or stuck closed, but either way, that would only cause an operational failure, not a short to ground.

Jakethewhite

That is not what I'm saying I'm saying that there is one wire going from the fuse to the efi relay and I have the efi relay unplugged not the CO relay. They are two different relays. With the efi relay unplugged the efi 15amp fuse has a open circuit on that end and the only is one more wire connected to the fuse and that wire leads to the batt. Connection of the ecu. So that means that my short had to be somewhere along that strip of wire. If you look at the engr.pdf that was posted it's exactly what I'm saying. I just don't know how to determine if the location of the short along this wire. Because when I look at the ecu there is no black/green wire plugging into it but there it one leaving the fuse and headed through a white connector (possibly eb2 Connection on schematic) and then going into the passenger fender towards the cab and out somewhere under the cubby and into the ecu. I'm just not very good at tracking where this wire is going through the fender. Do I need to take the fender off to track this wire down?

RJR

Thanks for the clarification. It seems like you are definitely on the right track.

I've attached another diagram that might help. It shows the physical locations of all connectors. Notice EB2 is on page 30, and IH1 is on page 34. If you can get to both of those, you may be able to isolate it further.

With the EFI relay unplugged, and the EFI fuse out, the wire you are referring to should measure a fairly high resistance to ground. If it doesn't, continue by unplugging EB2 and then IH1, looking for any changes. It could be shorted where it goes through the firewall to the ECU. Looks like that's underneath the glove compartment. Last, pull the plug on the ECU itself. There's a small chance that the problem is on the ECU board itself.

Good luck!

Jakethewhite

Sorry it took long for response had to pick up the car and tow it to my house 300 miles away. That was a long journey haha. So I unplug the ecu and it looks as if the short on the line goes away. Does that mean the ECU is bad?

Jakethewhite

quick question on measuring the resistance. Can I do this with a normal tester? What do I need to do in order to measure that?

RJR

Yes, any multimeter set on ohms will work. By high resistance I mean greater than 10K at least, probably much higher. Anything down around 100 ohms or less is a problem.

Jakethewhite

ok so when I set my meter to the 200 ohm setting the lowest i can go it reads about .8 ohms pop and when I disconnect the 22 pin from the computer is measured nothing. The only wires that showing are the purple wire W at 35ohms and the greenwhite wire 4wd at 25ohms

RJR

Inexpensive multimeters won't measure accurately below 1 ohm, so assume that your .8 ohm reading indicates a short to ground somewhere while you have pin 22 connected. That short is what's blowing your fuse.

Now, when you say it measures "nothing" with pin 22 disconnected, I assume you mean the display is not showing a number, but rather is showing something like "-----" or "*****" or "INF" or "OL". This simply means the ohms reading is above your selected range, in this case 200 ohms. Your meter can't display the actual value, so it gives you an overload indication of some kind. The actual value could be 201 ohms, or a million ohms, or much greater even than that. For your purposes, it means that the short circuit has been removed when you disconnect pin 22, indicating that pin 22 is the problem.

Jakethewhite

I tried the higher settings 2000 20k and 200k and they all said OL as well. When I hook up my short finder to the fuse connection it shows that there is a short but when I unplug the 22pin connector from the ecu then the short goes away. Could this mean the ecu is just busted or is it one of the two wires above that have that high resistance is causing the short? Or does it sound like something else? I'm not sure why those two wires have that high of resistance or if they are suppose to might check my brothers truck and see if he has the same measurements on those

RJR

Those other wires are not the problem. It looks like the problem is indeed the ECU, specifically the pin that is connected to the fuse connection.

Jakethewhite

Hey man just got the new /used computer. Put it in and throw in the new fuse and wham starts immediately looks like that was the problem. But I do still have a knock towards the driver's side valve cover area . Any thoughts?

RJR

Congratulations on getting it running! That's a major first step.

As far as the knock goes, not enough info to begin to diagnose. I would suggest getting a 3 foot length of tubing and using it as a stethoscope to zero in on where it's coming from. Also, post a video/audio recording so we can hear what it sounds like.

Jakethewhite

Here's a video it sounds like it's coming from the back almost but towards the drivers side valve cover

youtube link to video for sound:
https://youtu.be/v40cCkooaqc

RJR

That sounds pretty intense, definitely something in the valve train. Could be just a valve with excessive clearance, or something else. I'd pull the valve cover and take a look. Fortunately you can pull the driver side cover without having to remove the plenum, so it's not too bad a job.

I seem to vaguely remember talk on this forum about over-tightened valve covers pulling down too much causing the valve train to strike the cover. Might be something to check out.

Jakethewhite

I pulled the cover off and it looks clean no burn Marks or anything but I'm not sure about the procedure for adjusting valve or checking them. Do I just use a feeler guage where those shims are? And is changing those out the only way to adjust the clearance or is there another way?