86 w/ Z24, no spark, need troubleshooting help

$upra$rule · Feb 13th, 2006, 09:28 PM

I'm trying to get an 86 4x4 with the Z24 engine running. The engine cranks but won't start. The coils are brand new but neither seems to be sparking. I tested the transistors using instructions I found online and a DMM and both tested fine. I suspect the Crank Angle Sensor, but need to be sure. I've found instructions online for testing the crank sensor by checking 'terminal A' on a 4-pin connector that should be hot with the key on and grounded when off, but these instructions fail to explain what connector I am supposed to be checking. The connector to the distributor base is only a single blade. The trucks wiring is pretty hacked, so I really can't be sure that any of it is like it should be.

Also, I want to check the ECU codes, but can't find the ECU. I took the passenger seat completely out. It's definitely not down there and there is no sign it ever was. I must be looking in the wrong spot. I did notice what looks like a relay above the passenger side kick panel that is labeled coil on 2 of the blades, COM on the third, and I can't remember what the 4th was labeled. This 'relay?' is completely unplugged and there is a jumper wire on the plug from the center to one of the coil plugs. WTF? Anybody know what this is?

Anyway, I got the truck with the wiring all hacked like this, but it was running and they said the engine only has 9000 on a rebuild. It ran real strong then one day it just wouldn't start. Any help getting it going again would be greatly appreciated. Thanx in advance.

bkea · Feb 14th, 2006, 01:11 PM

If this is a D-21 and there is no ECM under the passenger seat, I think you've answered the question. Don't know much about 720s though.

Check the obvious things like the distributor cap and rotor button.

I think describing this wiring as hacked is not doing it justice.

brookwood61 · Feb 14th, 2006, 02:35 PM

Hi - Like said above check the obvious. Make sure the rotor has no burn through marks. Go thru the whole truck, clean all connections and grounds. There are two relays beside the battery on the inner fender, do not forget them. if it is a 720 the computer is under the drivers seat. Make sure it is grounded well and clean connectors too. I would not start any re-routing of wiring at this point if it ran good before.
Good Luck

dvdswanson · Feb 14th, 2006, 08:47 PM

try going here... http://home.sc.rr.com/creekrat/ go to diagnostics