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86 SC no spark no fuel. I'm at a standstill.

7K views 149 replies 10 participants last post by  chromguy 
#1 ·
I'm throwing myself at the mercy of the forum. I've googled, i've printed pages, run through diagnostics, I've learned a lot and made progress, however I've hit a wall.

Back story this Shelby was found in a field and it hasn't been on the road in 25 years. Original owner died, and I assume this issue was present back then as well. I've repaired wires, cleaned connections, the engine turns over, I get codes at the cluster, mostly 33 and 55. This car has no AC. so I assume the LM is working, I hear some clicking noises from the PM when I turn the key on and I do hear a short whirring noise under the hood when I turn the key on. but that is as far as I've been able to get.

The HEP is new, the cap is new, rotor is new, wires and plugs all new. If I connect a test light to the + of the coil and ground, I get a one second flash when key on, and a steady light when cranking. On the other hand when I put that same test light on the - of the coil and ground I get nothing. according to an article I read, I changed the coil with a new Standard blue streak coil but nothing new.

I tried the ASD relay jumper from the under hood diagnostics connector to the ground on the battery but nothing happened except flashing a 42 & 43 code. and this is the part where I'm at a standstill. so If anyone can enlighten as to where I should go next I would greatly appreciate it.
 
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#2 ·
Here is clarification on how the coil works, so you may want to read the following about the coil.
https://www.turbododge.com/forums/f1/f25/1079097-confused-help-out-old-guy.html#post4126329

The one second light at the coil is fine as this is the fuel pump prime. It will do this for three "key on". During cranking it should be on all the time. So it sound like the ASD is working. Are you sure you are getting fuel pressure to the rail?
no pulse on the negative coil line point toward the coil - line voltage is not dropping. This is controlled by the PM/LM and yes it could be a faulty HEP.
Did you check NAJ's no start primer? https://www.turbododge.com/forums/f4/f14/358231-no-start-no-spark-84-90-a.html
 
#4 ·
early log style turbo motor will not start IF the woven ground strap running from the fuel injector rail bolt to the firewall is not intact or disconnected or excessively loose at the firewall

guaranteed no start without that strap

there's also a wire in top of the transmission with a bolt sized ring eye on the end

(below air filter area)

it simply bolts to the top of the trans case but it is also a ground that will prevent starting if not connected
 
#59 ·
did you ever go looking for the wire on the transmission ?????

I ask because back when I put the 86 log motor and it's turbo z harness into my 87 shelby z ... I forgot the wire with the big bolt ete on the trans...

...

..
yeah , two weeks of ... dot dot dot ...

before I noticed it then instant vroom

- yes you read that right log motor into the same shelby z the
TII stuff FOR T Z came out of .. the donner lived it was a dual swap transplant or an exchange of ..
 
#15 ·
not connected "enough"

also , a simple no spark cause is a broken or striped timing belt

if the belt is kaput then the intermediate shaft don't turn
the dist don't turn
the hep sends no signal to the controller
the controller shuts power off...

so , you have no spark

remove the cap

tap the key to bump the motor slightly

go back to see if rotor moved

if not you'll need to look up timing belt replacement
 
#9 ·
#14 ·
I'm Back!!!

From what i have read your ASD Relay (integral to the PM on 85-87) is functioning and the car is seeing a crank signal so the ASD Relay is being actuated, however...

Start at the top of these diagnostics and post back. I need to know exactly where we are.
https://www.turbododge.com/forums/f4/f14/358231-no-start-no-spark-84-90-a.html
(When checking fault codes since you have been testing systems...
Clear the codes, be sure the codes have cleared before cranking the engine and then crank the engine for 7-10 seconds, recheck for codes, did any codes return?)
 
#16 ·
He stated his test light was lit while on the + coil terminal and cranking the engine.
That indicates the controller is seeing a crank signal and he ASD is being actuated.

He then stated that he had no power at the - coil while cranking and that should have been the test lamp flashing on/off while cranking, he stated he replaced the ignition coil with no change.

This is why I posted the diagnostics and asked the OP to start at the beginning.
 
#17 ·
Thanks for all the replies, I had a miserable few days and was not able to get back to this. I am waiting for the service manuals that were recommended by John83. I tried going through the pages Chromguy linked here however I need more time to digest it all. The distributor is moving, the belt is still intact. I have replaced the grounding strap too. The car is outdoors and we are expecting rain for a few days so I'll wait patiently for my service manuals and read up on more info.
 
#19 ·
1)Verify no spark by removing the coil wire from the distributor cap and hold
1/4" from a good ground.
Crank the engine for 7-10 seconds, spark should be strong and consistent
Count 1-2 sparks as No Spark.
Is spark present?

NO

2)Verify...
Distributor is turning, if distributor is not turning repair timing belt issue.
Coil wire is not open, check resistance with an ohmmeter,3000-5000 ohms
per foot. Repair as necessary.
Are distributor and coil wire OK?

YES

3)Check ASD Relay circuit(84-90)(On 91-up do you hear the fuel pump cycle for 1 second with initial key on?)

NO fuel pump heard.

Locate the underhood diagnostic connector
With the key on/engine off ground the DB/YL(dark blue/yellow) wire.
This will actuate the ASD relay.(A Code 42 will be set in memory)
Power (battery voltage) should be present at the + coil, DG/BK
(dark green/black) wire at the injector(s) and at the fuel pump.
You should hear the fuel pump running.
Is power present?

I did not actually know how to test this, Im very mechanically inclined but electrically dumb


4)Check HEP (hall effect pickup) circuit.
Remove the ground wire from the diagnostic connector.
Using a 12 volt test lamp connected to + coil and ground crank the engine.
The test lamp should illuminate.
Did the test lamp illuminate?

YES

5)Check coil control circuit
Using a 12 volt test lamp connected to - coil and ground crank the engine.
The test lamp should flash on/off repeatedly.
If the lamp flashed on/off but no spark...replace the ignition coil.
If the lamp did not light...replace the ignition coil
If the test lamp illuminated but did not flash...repair the coil control circuit.

This is where I am. As you know I have replaced the coil but still no spark. I do hear something activating while I am in the car when I turn the key on. The sound is either coming from
the injectors or somewhere else around the top of the engine.
 
#22 ·
You need to test the ignition coil, new does not always = good.

1)Disconnect and isolate the wire from the - coil terminal.
2)Disconnect the coil secondary wire from the distributor cap and place 1/4" from a good ground.
3)Manually actuate the ASD Relay.
a)Locate the underhood diagnostic connector.
b)Using a jumper wire ground the DB/YL (Dark Blue/Yellow) wire in the diagnostic connector.
c)Turn the key "on".
d)Verify you have power (12 volts) at the + coil terminal.
4)Using another jumper wire connected to the coil - terminal momentarily touch and remove the other end of the jumper to a good ground.
a)Each time you touch and remove the jumper to ground you should have spark from the coil secondary wire.

If you do not have spark and you are sure your jumper is being touched to a good ground, replace the ignition coil.

MANUALLY ACTUATING THE ASD RELAY
Text Font Document


Wire Technology Electronic device Auto part Cable


TESTING THE IGNITION COIL
Torch
 
#23 ·
ok I removed the - coil wire, manually actuated the ASD relay, I had power at the + side of the coil.
I applied a jumper to the - side of the coil with the secondary coil wire about 1/4" away from the strut tower bolt and I could hear it spark when I touched the jumper.
I could barely se a spark but I heard the spark. sometimes I didn't hear anything but if I moved the jumper I did.

I put the - wire back on the coil tried the test light again on the - side of the coil and didn't get anything on the light.
 
#24 · (Edited by Moderator)
#25 ·
I have limited time this weekend but I will get back to my shop and check codes. I appreciate the help.
I swapped out the PM with one I got in a huge lot of parts I acquired and it made no difference. I am concerned with the - coil wire to the coil, at the coil. The original Owner had a blue connector snapped onto it. I assumed he had done that searching for the same issue. it was one of those connectors that you snap over a wire, it cuts the casing and you can add a second wire in the connector. the connector had made a cut in the original wire a little deeper than I was comfortable with so I used a heat shrink butt connector, cut the wire and put it back together. I'm comfortable with that connection, my concern might be where the wire connects to the metal eye connector when it connects to the coil. There is a black rubber like bulge right before the metal. the wire looks a little bent inside the casing right before that. At some point I may want to redo that metal end. Can I assume that black bulge is not important and I can use just another metal eye connector?
 
#26 ·
Did you check with your meter if the wire from the PM to the -coil is good?
The coil signal is created at the LM and transmitted to the PM.
Are the grounds good at the LM?
Some folks have reported bad connections at the LM.
Are you certain the HEP is good with rotating dizzy?
Do you have a good digital meter? I am asking cause we may need to backprobe a few low power signals.

Does any reader here have an 86 or 87 diagnostic manual?? I have the 88 but it is SMEC based and uses a DRB II.
 
#28 · (Edited)
I assume your dizzy is a turbo. Please check the four flags, one should have a cutout for turbo use. I assume the dizzy turns when cranked, correct?
Do you feel comfortable with checking the LM/PM signals?
Since you don't have code 11 and 54, I will assume the HEP circuits are OK. But beware that at times codes can mislead you. I had a bad O2 sensor that cause a few other codes but did not report a O2 error code. This was on an 87 LM.
HEP stuff
backprobe pin 2-12 on the 12 way The 1985 - 1987 Turbo Power Module - MiniMopar Resources
This is an 7.5-8V power for the logic module(LM) and also powers the HEPs. I have seen both 7.5 and 8V mentioned in documents. I have measured SBEC and they are 8V and SBEC2 are 9V. Please left me know what you measure.
We should have 12V on 1-2, 1-3 and 1-4 and 2-6 with IGN ON.
Check the 1-9 and 1-10 and 2-2 are good grounds. Check with ohmmeter for now. If you can load test these LMK as this is the best way to test electrical connections. A ohmmeter can mislead you.


The next is we need to look at the HEP signals. With the IGN on, and we are backprobing 1-10 and 2-17 on the LM 1986 Turbo I Logic Module - MiniMopar Resources
We should see a steady 7.5V,
Now crank the car and now the voltage should not be steady and should bounce up and down. Depending on your DVM, it may appear as a lower steady value as it depends of the update rate of the DVM. On my Fluke 87, I can see the bouncing.

Coil drive signal from LM to PM
Also 2-10 on PM anti dwell, should also bounce with cranking which is connected to 1-6 on the LM red connector.
If you are comfortable reading a schematic LMK anf I can PM one.
 
#29 ·
Chromguy, You are speaking above my pay grade. if you're comfortable helping someone who is very mechanically inclined, but electrically illiterate, I would be comfortable testing anything. I have a basic Harbor freight digital meter. that is all.

I put a brand new hep in, standard brand, the distributor does spin. and I don't have a code 11 & 54.
 
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