I decide to do a complete tune-up of my newly acquired 87 D-15 (381 carburetor engine) becuase it was very hesitant upon acceleration (pressumably the engine was re-built 30,000 miles ago. I also install a new pick-up coil and things improved considerably. However, the truck was hesitating and shaking when I stopped at intersections. So I decided to see if I could find a vacuum line or something else that might be causing this. I must have broken something when doing this because now I do not get spark or power at the ignition coil. The truck starts if I hot wire power directly to the coil. I traced the col positive wire (blue) to a relay on the left fender that has a connector with two blue and one blue/white wire and an orange/tello wire that goes to the PCM (I assume for control). There is no power to any of these wires with the ignition on or cranking. Does anybody know what this relay is an how I can test it? is it the ASD or an Ignition relay? Should the power be coming in from the blue/white wire? If I apply power to either of the blue wires in the connector the truck will start and run, I assume this is probably a dangerous thing to do? Thanks in advance for the help.

 

You say you replaced the pick-up coil. Did you replace both or just one and if just one which one? (there are 2, the start and run)

Sounds like the ASD relay. If it starts and runs by applying power to either blue wire, this tells me the ASD relay is good and the control wiring to the ASD is OK. The power to the ASD comes from the battery thru a torpedo shaped disconnect and passes thru a fusible link. If you have no power to the ASD but the engine turns over it is probably the fusible link that has burnt. If it won't turn over I would look at the positive battery terminal and the torpedo connector for corrosion.

 

Thank you, I will check that torpedo link when I get home.
There is only one pick-up coil inside the distributor. One thing I didn't do though is adjust the air gap on it, how critical is the gap? what's the easiest way to rotate the engine to adjust the gap?

 

Use a socket on the crankshaft bolt to rotate the engine. The gap must be set correctly with a NON METALLIC FEELER GAUGE to make it run correctly. I have no idea what your gap setting should be because I am surprised at only one pick-up. The single pick-up was used from 74-77 and the dual was from 78-87.

 

Traced the red power cable from the battery and it goes to a different relay, here is a picture: http://dl.dropbox.com/u/6607467/IMG_20110322_172136.jpg
I get 12v to the orange wire on the relay on the right, when I crank it I get 8-9v on the yellow and the dark brown wires on that relay. I don't get any power to the terminals of the relay on the left no matter what I do. I traced one of the blue wires in that relay to the ignition coil. when I apply 12v to that wire the truck starts and runs. I am assuming that that relay must be powered by the blue/white wire, but don't know where it comes from.
If my newly installed (but not gap adjusted) pic-up coil was not working, would the truck run when I hot wire the ignition coil?

 

If the pick-up coil was not working at all, the truck would not run no matter where you applied battery voltage. This doesn't mean it is working at peak efficiency if it isn't adjusted properly or if it is out of resistance specifications.

I see a fuse holder in the picture that is not original equipment is the fuse OK? If this fuse holder is there to replace the fusible link it will not provide the protection necessary. Fusible links are used instead of fuses for a reason.

Right relay is probably a start relay due to the fact that the voltage is effected during the starting period.

On the left relay why can't you trace the blue/white wire to it's source? It should trace back to the battery as I stated in my previous post and the power there should be constant (key on or off). You should also be getting power to one of the other wires on that relay only when the key is on. Does the fuel pump run when you first turn on the key? I would unplug that relay and do resistance checks on it.

 

I don't get any power to the relay on the left, the wires seem to come from the other side of the car, I traced one of them (through continuity check) with the + terminal in the ignition coil. I am wondering if the blue/white (which I am assuming should have constant power) comes from the voltage regulator (although the cable looks just blue at that end), Speaking of which, the other wire in the voltage regulator comes from the alternator, do you know what voltage I should see there?
Sorry for all the questions, I am trying to learn as I go. I have ordered a Haynes manual to see if I can go through a more systematic troubleshooting. The things is that it was working until I started poking around the engine trying to find the IAC (I didn't ind it) so I am thinking I disturbed some connection somewhere.

 

I have posted the proper routing of power for the blue/white wire and even repeated it. It does not come from the regulator but they are electrically connected and may give a continuity reading. You may have to unwrap the wiring harness to trace these wires to find the problem. Wire ties, electrical tape, and wire loom are cheap. Using continuity to check wiring is only good if the wire you are checking is disconnected so that it is isolated from the rest of the system.

The voltage at the regulator, at the wire that connects to the alternator, should be the same as the voltage at the large lug on the alternator. (14-15 volts) Another wire at the alternator should read the same as the voltage at the battery.(this voltage will depend on wether the battery is fully charged and what accessories are on) One wire is input and another is output at the regulator.

Does the fuel pump run momentarily when you first turn on the key?

 

Sorry, I traced the routing of power through the torpedo connector (red wire) to the relay on the right of the picture (through a non stock in-line fuse as shown in the picture) and that one has power. The blue/white wire (from the relay on the left which I still don't know what it is) definitely does not come from anywhere near the battery, I will trace it down as far as I have to to see if the problem is there. Since applying power to one of the output blue wires in that relay gets the car going I am thinking that I need to figure out why that relay is not getting power to begin with. There should be power there at least at some point and there isn't.
I still have to check if the pump runs momentarily when I turn the key. I definitely do not have spark unless I apply power to one of the blue wires or the ignition coil directly.
Thank you for all your help and patience.

 

this thing should have a mechanical fuel pump so you should not be able to hear it when you turn the key on.