oldgoat

Second that, a hairline crack in the old brittle tubing causes all kinds of trouble.

Take a look at the ID of the CA bushing dimension vs. the OD of the bolt, is there a steel sleeve inside the bushing? If the clearance is too great you will get a clunk as the control arms move.

I can promise that the tester at O'Reillys is not accurate. Over the years I have grown to not trust "testers". Real life is the best test.

Oh yeah, that was one of the first steps. At that point I could get it to start once in a while after prolonged cranking. That made me think CPS signal was weak. Installed new CPS, discovered existing was fairly new. Same story. With a used ICU/coil it lights up on the first crank.

I solved the riddle, drum roll please............... ICU, swapped from running Cherokee, lit right off first hit. I also discovered that the scanner I was promised would work, won't. Now on to the next.

Yesterday I removed the entire Renix wiring harness and laid it out on the bench. I stripped off all of the convo tubing and tape. I discovered that someone had previously done the same thing since all of the gang connections were wrapped in duct tape. I did validate each wire for continuity and cleaned all of the connectors and re taped and wrapped the whole thing then reinstalled. Still no fire. I went back and validated all of the fusible links at the starter relay. There is 12V getting to the ECU with the switch on and in the crank position. Tried to start again. Still cranks, no fire. It appears that it is either the ICU or the ECM. Interesting , the ECM has been replaced with a Cardone reman unit. I am checking with the guys I work with for a known good ICU. It is confusing that after the problem manifest I have been able to get it to start sometimes and not others.

Cruiser, I don't find the C101 that everyone refers to. Should I ?

Pretty much all applicable. I did remove the ECU and took it apart. I see one chip that has what might be a white burn bubble on it. I am going to see if I can test it tomorrow. I also found an abraded wire in the bundle from the ECU going out the bulkhead. Obviously lots more testing before I go any further.

We have a diagnostic code reader that will interface with the Renix. Are the readings reliable?

I forgot to mention that I have never seen a "Check Engine" light come on, ever. Also discovered that the FP relay has been bypassed in the harness for some reason. It is direct wired to an Ignition on terminal at the fuse panel. The 2 orange wires to the pump are ganged together with the 12v hot signal. right next to the resistor. Do you think this could have created a back feed to the ECU causing a problem? I have yet to determine why the FP relay was by passed. I wonder if the ground signal from the ECU to the relay is dead? More wiring to validate.

So it just keeps gettin better. Yesterday morning tried to start - dead. Came home last evening to pull the ICU to have it tested - Started right up. This morning - Started right up. Took the ICU to have it tested. Tests good. Brought it home hooked it up - dead. How can I test the ECU - I wonder if it is shorted internal on the ignition output side. The injectors don't fire which tells me that either I don't have a tach signal from the ICU or the CPS signal doesn't process in the ECU.

CPS is varying from .42 to almost .6 after I readjusted. I get absolutely nothing for coil output. The Yellow to coil + shows battery voltage. I did put a test light from the yellow to the green/white which I believe is coil signal from the ECU. I don't see a flash in the test light while cranking.

Is there a way to test the ICU? Truck started just fine this morning, I went about 1.5 miles and it shut off just like you turned off the switch. Won't restart, no fire at the coil. I have fuel. Pretty much the way things progressed last week. Any other ideas?

I probably have a 1/8 npt x 1/8 or 3/16 nipple in my brass collection. If time allows tomorrow I will perform the mod. Tomorrows big plan is really to work on finally re-doing the audio system in my GTO.

I will check that this weekend. Are the rubber blocks that the MAP tube plugs into at the TB available. The one I have is less than great.

I did discover a very small crack in the plastic tube going to the MAP sensor. Replaced the tubing, seems to run somewhat smoother and more consistent.

What is a good resource for the injectors?

Similar to the FP regulator signal being low. I will look at both. I did notice that 2 injectors seem to be weeping from the o-riing at the rail. I will say that the fuel economy is lousy and it always has a strong rich odor. Is the MAP responsive enough that if I hook my mighty vac to it I can make an influence? What range does it really operate within. I have a 2 BAR on my blown LS that is very sensitive.

I originally had no spark from the coil. I did replace plugs, wires, cap, rotor and the coolant tank and cap. Gave it a crank and got some popping, tried again sames result. One more time and it did fire, ran rough and smoked to beat the band. Settled out and ran smooth as glass. Now to answer the mystery. What was it that caused it not to start after it had been running for about 30 minutes without a hitch less than an hour previous. I really hate throwing parts and labor at an unknown root cause.

Cap rotor and wires were recently replaced. Obviously plugs were neglected. I have validated the cap and rotor. Wires are a question mark.

OK, here is what I have learned so far. This morning when I started I had nothing for spark at the coil. The plugs were dry, so I must assume the injectors were not firing. 1 - Repaired the burnt wires I mentioned in the beginning. 2 - Removed the coil and ICU, cleaned the contacts per Cruisers recommendation. 3 - Replaced the battery to engine ground with a "00" cable and added a 2 ga cable from the dipstick stud to the body ground point. 4 - Checked the new CPS and found .17 - .22 volts cranking. I did the mod and now I see .27 - .38 , not great but better. I buttoned everything up and tried to start. I got a series of pops like it wanted to start. I pulled all plugs (first time since acquiring the truck) 5 of 6 were loose to the point that the threads were wet with fuel as were 4 of 6 on the tip. Tomorrow I will replace the plugs and bring home a new surge tank and cap. What might I be missing?

I didn't have a helper today, so I couldn't verify some things. There is always tomorrow. I guess one additional question. From the research I see, the distributor doesn't actually create a signal to fire the coil. Is that signal generated by the CPS? Is it the same signal used to fire the injectors?

Pretty vague I know but here is the rest. 89 4.0 AT basically stock. Previous to today it sometimes takes several seconds, to minutes of cranking to get it to fire, other times fires right off. I replaced the CPS today after it would not start. The last couple of days I have experienced , "boil over" out of the surge tank. It has always started right up though. Today I replaced the thermostat and refilled the coolant. Started right up and ran great until the stat opened then I had the "boil over" issue again. Shut the engine off and let it cool, added more coolant. After about an hour I attempted to restart, it will crank but won't fire. Fuel is to the rail and under pressure. After about 10 seconds of cranking I get a very slight "pop" as if it wants to start. I can't prove that I have spark. Plugs are dry. I did try starting fluid with no success. Yes, coolant went everywhere and most of the connections and relays got wet. Digging further I found a heavy orange wire paired to a lighter orange/black stripe wire going to one of the relays that has the insulation melted off of it back into the harness about 4". It appears that this has been the case for a long time. Any ideas? Is there a way to hotwire the ignition system to validate that it works? I haven't been able to find a clear wiring diagram for the 4 relays adjacent to the coil or the distributor wiring code.