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| Help getting SC3800 swap troubleshooting (Page 1/3) |
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KissMySSFiero
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FEB 21, 06:20 PM
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I’m trying to figure out why my new to me l67 sc3800 swap isn’t running.
It’s an 88 GT getrag combo.
It runs on starter fluid. And runs well.
But it won’t start without starter fluid.
All testing was done on the rear bank only(cyl 2-4-6)
There’s no injector pulse on any cylinder until it gets the ether.
Then the noid light flashes and the car fires and continues running
It won’t restart on its own.
I have 12v to the injector. Normal. Tested the pink wire to ground.
Measuring across the inj connector I see 7 volts. I thought this was odd.
If I remove the ECM fuse, the voltage goes to 12v across the connector.
Edit: this needed to have a load to check. With the inj plugged in, I see 12V on each pin. This is normal.
PCM was tuned by Darth fiero.
Harness by someone on here that builds reputable stuff.(Dan Mc)
I have not contacted either of them at this point.
Thanks.
I’ll add more as I go.
Edit to add. Fuel pressure is normal. The pump runs momentarily with key on and constant while cranking.
Edit, Car Runs and drives once started(needs a clutch)
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SSFiero@Aol.com[This message has been edited by KissMySSFiero (edited 03-02-2022).]
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MichiganReefer
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FEB 21, 07:34 PM
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Where/how are you measuring fuel pressure?
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KissMySSFiero
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FEB 21, 07:50 PM
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| quote | Originally posted by MichiganReefer:
Where/how are you measuring fuel pressure? |
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The adjustable fuel pressure regulator has a gauge.
I also have a test gauge on the rail. Both match.
I’ve adjusted the pressure up and down from 40-55psi with no change.
I still dont have injector pulse when cranking. Until I spray starter fluid. ------------------
SSFiero@Aol.com
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MichiganReefer
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FEB 21, 09:27 PM
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I'm just spitballing, but have you checked the individual resistances of the injectors? Google is telling me they should be reading 12 ohms +-.6.
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olejoedad
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FEB 22, 09:09 AM
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I would suggest a call to Ryan.
I don't think you have an injector issue, or injector driver issue, as the engine will run after supplying some starting fluid.
It could be a wiring issue regarding ICM to PCM communication, or a faulty ICM.
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Frenchrafe
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FEB 23, 09:14 PM
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Dennis LaGrua
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FEB 24, 10:11 PM
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PCM's do go bad but before we arrive at that conclusion its time to hook up a quality scan tool to see what that says. If I were to guess it sounds like the PCM is not going into the cold start mode. ------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "
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olejoedad
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FEB 28, 08:07 AM
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KissMySSFiero
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FEB 28, 10:13 AM
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| quote | Originally posted by olejoedad:
Any updates? |
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Sort of.
I fixed a coolant leak so I could drive the car. I've gone around the block and to the gas station. Just enough to hit each gear and use the brakes.
One thing is that it runs and drives once started. For some reason people(not here) seem to glance over that. But it does start with starting fluid. It will run and drive at that point.
I put an old school O-scope on it since I don't have a scan tool. All of the sensors give a reading that looks good. HOWEVER...
According to this video, the 3x and 18x Crank signals operate on a 10V input giving a 7V square wave output. I'm only seeing about 5v output but have 10V+ input.
https://www.youtube.com/watch?v=jACyNHl_L1g
It's very difficult to see the voltage on my old scope(I'll edit to add some pics) but I used a multimeter to check the average voltage.
The average voltage is described here in the video
https://youtu.be/jACyNHl_L1g?t=621
I'm seeing 4.5-5v average on the 3x signal and less than 3v avg on the 18x. Where it should be appox 5.5v and 4.5v respectively.
This makes me suspect of the Crank sensor so I have one on order. The resistance of the harness was good(<1Ω), so I don't think it's the harness.
I really want to fix the starting issue prior to pulling the engine to replace the clutch. The crank sensor looks like a lot of fun while in the car.  ------------------
SSFiero@Aol.com
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olejoedad
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FEB 28, 11:14 AM
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The ICM controls fuel delivery at initial cranking, and sends a voltage signal to the PCM to initiate the PCM fuel injector drivers.
Have you tried replacing the ICM?
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