Build Just had to treat myself for Halloween... 65 SWB

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The saga continues…

6 new injectors and no change. Still not getting combustion in #5.

No change in idle when I pull the #5 plug wire but spark tester shows it’s getting spark.

Tomorrow I’m going to pull the valve cover and look at the valves.

Only other thing I can think of is bad wiring that passes the noid light test but isn’t enough to fire the injector?

I think I’m going to plug in an uninstalled injector on #5 harness plug to see if it’s activating. Can I do that?
 
Yes you can, it should make an audible clicking. Im sure you have ruled out a vacuum leak at #5 intake area. Hate to say this but it could be a headgasket. Pull #5 plug and see if its super clean. Other thing is tight valves will cause a misfire.
 
Thanks Brian…

Plugs all look good. Compression test was good in all cylinders.

I did a robust leak test several times without any indication of issues.

I’m really stumped on this. It happened all at once on an uphill climb about 1/2 throttle.

I’ll put a few injectors on the harness to see what I’m getting. I know 1-3 are on one bank and 4-6 are on another. Pulling any of 1-3 has a bigger effect on the idle than 4 or 6. 5 no change.
 
Weird that is passes the NOID test. Do the noid lights have the same resistance as the injectors? Maybe its like you said, there is an issue with the incoming power to injector 5, or the ground splice/junction in the loom that runs to the no.10 /no.20 terminal on the ECU (cant remember which is for which batch)?
But check the valves first since that is the easiest. :)
 
Pulled the valve cover and all looks great. Valves all opening/closing.

Old injectors firing on #5 wiring plug which matches the intensity of clicking on the other bank.

Tested spark on #5 again and it’s good.

Test drive resulted in continued frustration and intensified grumpiness.

I’m walking away for awhile and when I don’t have the urge to douse the truck in gasoline and light it on fire I will start from scratch.
 
The other you can check is see if wire that attaches terminal. It may be hard to see but check if has broken strands at connectors. If the terminal has one or two strands attached to terminal lug itwill pass a continuity test but under a load may not function like should. And check all grounds.
 
I have even gone as far as removing the negative battery terminal. And start cleaning the terminals with a fine wire brush on the circuit in question. These circuits sit out in the elements for years. So a little cleaning won't hurt if you are gentle. Also resitting a connector(s) may do the trick.
 
My opinion on the noid test it's great test if all the wiring is good shape. And it's a go to test to run. But when it passes and system still doesn't function it says to me that you don't have short. It kinda reminds when you have a dim lighting on instrument panel...still works but when you clean the both battery cables on both ends and all of sudden your lighting is brighter in instrument panel. Or installing another ground wire to the starter from the frame to help with grounding issues. Anyhow, because there is a voltage drop at the injector (solenoid) it may not have the required threshold to toggle it. That is assuming everything is working. Oxidation on the connection and broken strands on the wire may cause these type of issue. Do visual checks and clean and re-seat connections my help. Anyhow, like I said that is my opinion.
 
So the good news is this is solved.

The bad news is I wasted a lot of time and heartburn (ie:stress) going down a few rabbit holes that I never should have gone down. The other good news is I learned a lot and appreciate everyone’s assistance in trying to troubleshoot.

So….

I decided last night that when I got back to sorting this out I would 100% rule out the easy stuff before I dug into the harness anymore. It took everything I had not to come out to the garage at 1am to test my theory. But I did wait until this morning.

Weeks ago an initial test of spark with a timing light confirmed spark on all the wires. Once I found that the #5 injector harness made no difference in how it ran I knew #5 was an issue. I subsequently put a spark plug test light on #5 and had strong spark. Today I decided to double back and ohm test the plug. Unfortunately it passed the ohm test with flying colors. Same 6k as plug #1. Ugh. My 1am theory and hope for a simple solution crushed.

As a last resort I decided to swap plug 5 into cylinder 1 and put plug 1 into cylinder 5. Low and behold now pulling #1 plug wire and injector wire made no difference. Pulling #5 now caused significant rough idle.

Turns out it was spark plug #5 all along. Embarrassing.

I thought I did my due diligence on the plugs but obviously not. Not sure how a plug can look good and ohm test fine but not work? I’ve owned cruisers for more than 30 years and never had a plug failure. I should’ve swapped plugs right at the beginning.

Thanks to all who used their brain power to help me try to resolve this silly issue. Especially @cruiserbrett. I’m glad it wasn’t the harness, the ECU, head gasket, etc!

And now I have a few more spare parts on the shelf to keep in stock for my next troubleshooting adventure.
 
DomSmith said:
So the good news is this is solved.

The bad news is I wasted a lot of time and heartburn (ie:stress) going down a few rabbit holes that I never should have gone down. The other good news is I learned a lot and appreciate everyone’s assistance in trying to troubleshoot.

So….

I decided last night that when I got back to sorting this out I would 100% rule out the easy stuff before I dug into the harness anymore. It took everything I had not to come out to the garage at 1am to test my theory. But I did wait until this morning.

Weeks ago an initial test of spark with a timing light confirmed spark on all the wires. Once I found that the #5 injector harness made no difference in how it ran I knew #5 was an issue. I subsequently put a spark plug test light on #5 and had strong spark. Today I decided to double back and ohm test the plug. Unfortunately it passed the ohm test with flying colors. Same 6k as plug #1. Ugh. My 1am theory and hope for a simple solution crushed.

As a last resort I decided to swap plug 5 into cylinder 1 and put plug 1 into cylinder 5. Low and behold now pulling #1 plug wire and injector wire made no difference. Pulling #5 now caused significant rough idle.

Turns out it was spark plug #5 all along. Embarrassing.

I thought I did my due diligence on the plugs but obviously not. Not sure how a plug can look good and ohm test fine but not work? I’ve owned cruisers for more than 30 years and never had a plug failure. I should’ve swapped plugs right at the beginning.

Thanks to all who used their brain power to help me try to resolve this silly issue. Especially @cruiserbrett. I’m glad it wasn’t the harness, the ECU, head gasket, etc!

And now I have a few more spare parts on the shelf to keep in stock for my next troubleshooting adventure.
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Alright!! Happy to hear you solved the issue! Nice work.
 
whitey45 said:
Sometimes it is the simplest thing, but now you know everything is in good order! The only test for a spark plug for me is to lay it on the engine and physically see it spark!
Click to expand...
I know. Every time I thought of it I made an excuse why I didn’t want to potentially get zapped and that all these other tests ruled that out. This is a case in point to watch the spark on the plug to be 100% sure.

I should’ve just swapped the plugs like I did… a few weeks ago!
 
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