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Hep is essential to run.
It's like a Cam or crank sensor on a modern car. No start period.

I have seen a shorted speed sensor shut down the spark so try that

but most likely the Hep is bad.
Also make sure the distributor is spinning...
 

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Thanks everyone!
NAJ, I agree. I had tried most of the troubleshooting before I stumbled upon your post. It gave me the framework to record my observations, and yes - it was very quick. Thank you again. I have some more information.....

First, I am getting 12.7V at the battery. That's measured at the battery with the kill switch off. When cranking, I am only getting the 9.3V at the coil. I also went ahead and checked continuity back to the large connector near the battery to ensure there wasn't a broken wire on the rotor pickup; it appears to be good.

Now, to reply to the troubleshooting steps above.

1. Yes, I am still getting 54 at the computer.
2. No spark, with new HEP installed
3. Confirmed
4. When grounded, I can hear the fuel pump come on and I get near battery voltage at the coil (11.7)
5. As stated above, low voltage at the coil. Test light comes on plenty bright and stays on during cranking
6. Test light flashes very bright at beginning of cranking, and then becomes very dim after. Less than 2V on the multimeter.

-Tim
U can unplug the smec and test the wires to the hep. Look for breaks or shorts in the harness. Also unplug the speed sensor. I've seen that short out the smec. Is the shutter wheel turning when cranking? Code 54 means no signal from pickup so there won't be any spark.
 

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Continuity all they way to the computer.
I am guessing by speed sensor you mean the distance sensor on the transmission? I just disconnected it, no start
I am sorry, but I am not sure what you mean by shutter wheel?

-Tim
Under the hep is a metal wheel held on with plastic blobs. Make sure it's spinning when cranking. It's what triggers the hep
 

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Thank you for the confirmation. The battery is brand new and when I am not working on the car, kept on a tender.


Thank you again. I have the third HEP in there, same results. To be honest, the only reason I tried a third one is because I already had it on order. So, it was just sitting there and it only took a second.


It was very bright for a split second, and then became very dim. This tracks correctly, as when you first crank the mutimeter shows 12.7 but then drops to 1 - 2. Step 6 was on the “-“ terminal. It does not flash.
Battery is brand new.


Primary is 1.6 ohms
Secondary is 9510 ohms


Confirmed.


Confirmed (?), 11V


No spark. When I move the temporary ground wire, IT sparks on the grounded surface (my A/C bracket). But, no spark from the coil lead (also using the A/C bracket).
The coil is brand new, but since I had the set up – I went ahead and tested the old one and got the same results.


-Tim
Test the wires going from the HEP to the SMEC or swap in another SMEC.




U can use any SMEC 88-89 t1,t2,2.5 t1 (supposedly Tbi smec will run on 2 cylinders) just to see it run.
Also in reverse you can take the SMEC out of your car and try it another one just to test it.

Final option is to get DRB2 scanner and look at the hall effect pick up output. or whatever checks u can do with it (I've never used one)

If you are in New England I have a couple lying around or you could bring yours over and plug it into my car and see if it starts..
 

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You all have no idea how much I appreciate y'all sticking with me through this. Thank you! I am sure we'll figure this thing out.

I have traced the HEP wires all the way back to the SMEC harness and they have continuity. Also, I have another SMEC and I have tried it out only to get the same results. Now, I have NO IDEA if the second SMEC works, I bought it second hand and never put it in an otherwise running car.

Aireskcar - That is an awesome gesture, thank you!!! However, I am all the way down in Houston.

-Tim
If you want to ship it to me I can plug it in the car and test it like I did with this SBEC.

Or cover shipping I can send you one of my spares to test. I think I have 2 2.5 T1 SMEC'S and my 88 town a country 2.2 T1 SMEC that had a weak voltage regulator so the alternator would charge between 12.8 and 13v.
 

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2. I am not 100% sure how to check. I checked the voltage across the three terminals with the key on. The voltage across VT/WT & OR/DB was <1V, across VT/WT & BK/LB was ~4.9V, and across OR/DB & BK/LB was also ~4.9V.
View attachment 282203
3. Results:
Pin 1 - 5, 0.3 Ohms
Pin 1 - 15, 0.4 Ohms
Pin 1 - 16, 0.4 Ohms
Pin 2 - 2, 0.3 Ohms
Pin 2 - 6, 0.3 Ohms
Pin 2 - 7, 0.3 Ohms
View attachment 282204 View attachment 282205

I have already given my results to test NS-1 yesterday. So, I'll pick up with the results from NS-7:
Since I don't have a diagnostic tool, I assumed the tool was somehow tricking the computer into closing the ASD relay so the sensors would all think the car was running. After I jumped the ASD I went to work.
The first test was to check voltage at the "-" terminal of the coil with the wire disconnected then check it again at the wire itself that would normally be on the coil. Both tests gave 11.7V. The flowchart recommends replacing the coil. This is already a brand-new coil, but perhaps it is bad? (I popped an old one in I had laying around and still no spark on the coil secondary wire, so I doubt that's it. Nonetheless, I am going to order another one.)
I removed the ASD jumper and moved to the second page of NS-7. Note that pin 1 - 19 on this diagnostic corresponds to 2 - 12 on my '88. The resistance of the wire connecting the "-" post on the coil to pin 2 - 12 was <1 Ohm. (The "-" wire was disconnected from the coil during the test.) The flowchart says to replace the controller. (n)
Next, NS-13:
Again, I had to use some assumptions to check the resistance in figure 2 but I checked the BK/LB wire back to the SMEC pin 1 - 4 and got 0.3 Ohms.
Next, was to test the voltage across the gray distributor connector. I got 9.5V between the BK/LB & OR terminals and <1V between the TN/YL & OR terminals.
Finally, I checked the resistance of the TN/YL wire back to the SMEC pin 1 - 26. This was <1 Ohm. The flowchart says to replace the controller. (n)(n)

View attachment 282210 View attachment 282208 View attachment 282211
View attachment 282207 View attachment 282206 View attachment 282209

So, here I am. I have another SMEC, but I bought it used and I have never put it in a running car, so I have no idea if it works either. Hopefully, I just got a bad coil - but that's unlikely. I may be taking some of you up on testing this SMEC out.

One thing of note, the old engine that came out of the car had the distributor go out on it in our last race. If I recall, the rotor popped off somehow. We replaced the distributor and got the car running, but we lost compression #4 cyl (unrelated); so I disconnected that injector and we raced on 3 cyl with the boost turned down. Yeah, the car ran terribly but was making laps. That shortcut got us within 15 min of a checkered flag when another unrelated wheel issue ended our day (racing is hard). Anyway, I only bring that up for two reasons; 1) The car was 'running' before using this SMEC and 2) None of that should have fried the SMEC, right?

-Tim
Actually if you pull the spark plug wire off while it's running there's a warning that you can destroy the computer. I think NAJ has the warning in one of his diagnostic pictures
Rectangle Font Circle Monochrome Metal



 

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We did disconnect the spark plug wire and the injector connector, but not while it was running.
So the spark plug wire was always on whenever it was running?

If it was taken off before starting it and then running after it would still cause damage because that energy would have nowhere to go and it would back feed into the coil or jump all over causing damage to the electronics...
 
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