No spark issue and needing help!

[87R10GMC]

Hey everyone. I bought an 87 r10 half ton 2wd awhile back and drove it home with a rod knocking. Now let's jump ahead a few months. I put the tbi unit on top of an older style block and dropped it in and days later I've yet to get it fired up. I have no spark and no injector spray. I suspected the ICM and it did test bad. I bought a new one and ran it through the test 8 times and it seemed to be a good one. After installation there was no change. I have 12 volts to the external coil. The pickup coil has 800 ohms. I have multiple grounds and they are clean and secure. Any idea on what I'm missing here? I used an online spark tester and NO fire out of the coil. I also put a new coil on it. I also put a new distributor in and ended up taking it back as there was no change. I really need to get this truck on the road soon.Thanks in advance for any and all help.

 

[1987 GMC Jimmy]

If you don't mind my asking, what brand of ICM are you using? I wouldn't touch MasterPro/Duralast with a ten foot pole. Eight false positives seems like a lot, but my money is on a second bad ICM. It's happened to me before, and that was with a Delco. Second one works great, and that's what I'd go with if I were you.

 

[87R10GMC]

Master Pro coil and Duralast ICM. I will try and exchange it tomorrow. I believe I will have to order the ac delco. I was thinking between the new distributor I installed and returned and this other ICM that is in it now that I would have fixed it. Thanks for the input

 

[1987 GMC Jimmy]

I would switch back to the Delco-Remy coil that you took off if you still have it. If not, I use Borg Warner Development from O'Reilly/Advance Auto with good results. Those MasterPro and Duralast ignition parts are good as glove box spares and nothing else. If you can hold off for a few days, I'd take back what you have and order everything Delco or Delphi (cheaper and still good) from RockAuto. There's a 5% discount code in the preferred vendor section, and you'll come out saving some money.

 

[HotRodPC]

I'm drawing a complete blank now. What came first? The chicken or the egg? Uhhh I mean, what gets spark first, the coil or the ICM? The coil, it's the coil that should have spark regardless of the ICM being operative or not. You say you're not getting any spark from the coil? How are you testing the coil to know this? And you're positive you have 12 volts going to the coil in BOTH the Run position AND the cranking position? If you have 12 volts in the RUN position that doesn't mean you have 12 volts in the cranking position and it's not going to start. Of course it might be a little under 12 while cranking due to starter draw, but not much lower.

So it ran fine other than a rod playing knock knock whose there? Then you did the engine swap and hasn't ran since right? So take a deep breath. Start back at the very basics and check all your wiring connections. You didn't break any plugs or sensors during the swap? How about power to the dash lights and gauges? If nothing is working on the dash, you might have damaged or arc'ed a wire and burnt the fusible link near the junction block on the firewall.

 

[chengny]

I have no spark and no injector spray.

With the ignition switch in RUN, do you get an SES warning on the dash?

Are the following fuses good: ECM I, ECM B, CRANK & GAUGE/IDLE?

 

[87R10GMC]

I'm drawing a complete blank now. What came first? The chicken or the egg? Uhhh I mean, what gets spark first, the coil or the ICM? The coil, it's the coil that should have spark regardless of the ICM being operative or not. You say you're not getting any spark from the coil? How are you testing the coil to know this? And you're positive you have 12 volts going to the coil in BOTH the Run position AND the cranking position? If you have 12 volts in the RUN position that doesn't mean you have 12 volts in the cranking position and it's not going to start. Of course it might be a little under 12 while cranking due to starter draw, but not much lower.

So it ran fine other than a rod playing knock knock whose there? Then you did the engine swap and hasn't ran since right? So take a deep breath. Start back at the very basics and check all your wiring connections. You didn't break any plugs or sensors during the swap? How about power to the dash lights and gauges? If nothing is working on the dash, you might have damaged or arc'ed a wire and burnt the fusible link near the junction block on the firewall.

I have 12 volts to the pink wire in the run position. I haven't checked while cranking. I assume check the pink wire going to the coil for 12 volts while cranking? I will do that today once I get some help. I put an inline spark tester on the coil and into the coil wire and cranked and it didnt light up. I have power in the cab to everything but the blower motor I believe. I have oil pressure as well. I'm no expert by any means and greatly appreciate the help on this

 

[87R10GMC]

With the ignition switch in RUN, do you get an SES warning on the dash?

Are the following fuses good: ECM I, ECM B, CRANK & GAUGE/IDLE?

Yea the check engine light comes on blinks once then stays on in run position. I checked the 2 ecm fuses and the crank fuse. I missed the gauge/idle one. I will check on that asap.

 

[chengny]

Assuming that last fuse is good, it's looking like an ECM issue - or a wiring problem between the distributor and the ECM. BTW - have you checked whether it's throwing any codes?

No injection and no spark is generally due to the lack of a reference signal from the distributor to the ECM. But from what I read above, you have replaced or checked all the related components in the distributor. On top of that, you installed a complete new distributor. So, provided it was good, that essentially eliminated everything except:

1. An internal problem with the ECM,

2. A problem with the wiring between the distributor and ECM or,

3. Low voltage supplied from the ignition switch to the B+ terminal.

Heed HRPC's advice - be sure to take the time and check voltage to the B+ terminal while the starter is cranking the engine. It doesn't happen often, but if there is a problem with the starter/solenoid assembly, it can cause a major drop in overall system voltage. It might be the case that - while cranking - the 12 volts you see at the B+ terminal in the static condition, drops. If the voltage to the primary windings falls below 7, the coil will be unable to produce the 40,000 volts in the secondary required for a proper spark.

Below is the ignition system diagnostic chart for your truck - but as noted above, by installing a new distributor you have essentially eliminated every possible problem described in the procedure:

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[87R10GMC]

Where exactly is the B+ terminal at? Is that the pink wire feeding the coil? That last fuse was good and I'm not getting any codes. Only the flash of 12. What am I looking at on the wiring from distributor to the ecm? I know there is a 4 prong terminal on back of the distributor. Should i have power there or? I thought that was the exit and wasn't sure what I was looking for or at. Thanks again for the help. It's greatly appreciated!

 

[chengny]

Yes, the B+ terminal is the one where the pink lead connects. That is the one you want to check for 12 VDC while cranking. You can pull it off the distributor cap to test.

Code 12 flash is good.

Yes, that 4 pin plug is where the wiring from the ECM connects to the distributor (specifically the ignition control module).

Which of those leads has voltage, how much voltage and when they have voltage gets pretty involved. If I were you, at first I would just do a visual inspection of the wiring from the plug at the distributor to the firewall. Next would be to check all 4 leads for continuity from the distributor end to where they terminate at the ECM connector:

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[87R10GMC]

I have a volt meter. How do I check from the distributor to the ecm for continuity? This is just to make sure a wire isn't broken correct? I am going to follow the info on the flow chart and the other things you mentioned and I will post back with my findings

 

[HotRodPC]

Yes, Please do post back what you find out and what the fix was if you were able to get it figured out.

 

[87R10GMC]

I sure will. I haven't had time the past couple days. Hoping tomorrow or the weekend at the latest I will have an update.

 

[87R10GMC]

I finally got a chance to check things out. I have 8 plus volts on b+ while cranking. 12 in run position. This wire is the pink one feeding the external coil I do believe. I started going through the flow chart and am currently on step 5. How do I check for continuity on wires? Any more i put is appreciated. I should be able to spend some time on the truck now. The last week was hectic