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L98 no start

Old 04-14-2019, 10:17 AM
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L98 no start

Hi all installing l98 into my 61 c10. Installed using painless harness. Fired up several times and then one day no start.
ohmed all injectors (16). Provided 12 volts to reference signal to ecm and noid light fired. 42lbs fuel pressure. Stumped any help would be appreciated.
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Old 04-14-2019, 12:03 PM
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Car: 1967 Camaro, 91 z28
Engine: Lb9
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Re: L98 no start

What 12v reference pin did you supply 12v to ?
1227165 or 1227730 ecm ?
Do you have spark ?
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Old 04-14-2019, 12:10 PM
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Re: L98 no start

122765 . Touched reference wire on plug which leads to ecm to positive side of battery
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Old 04-14-2019, 12:16 PM
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Re: L98 no start

B5 purple/white ?
Sounds like a good way to blow the ecm.
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Old 04-14-2019, 01:38 PM
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Re: L98 no start

Just tapped it through meter. Any suggestions what the problem could be?
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Old 04-14-2019, 01:41 PM
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Re: L98 no start

Originally Posted by Shawn537 View Post
Just tapped it through meter. Any suggestions what the problem could be?
You didnít state do you have spark ?
could be a bad ignition control module.
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Old 04-14-2019, 01:42 PM
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Re: L98 no start

Yes I do have spark and oil pressure switch is made for fuel pump relay
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Old 04-14-2019, 01:46 PM
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Re: L98 no start

Originally Posted by Shawn537 View Post
Yes I do have spark and oil pressure switch is made for fuel pump relay
If you have 42 psi and prime doesnít sound like a fuel pump problem.
You do have injector pulse with a noid light ?
could spark be weak ?
no trouble codes ?
The check engine light comes on key on ?
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Old 04-14-2019, 01:59 PM
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Re: L98 no start

No spark on noid light when 4 pin connector is plugged in . Spark looks pretty solid . What could be holding out reference signal on startup?
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Old 04-14-2019, 02:05 PM
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Re: L98 no start

You can have spark but no drp with a bad icm.
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Old 04-14-2019, 02:09 PM
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Re: L98 no start

Thatís what I thought but changed out icm and ohmed out harness. Do any of the map relays come into play on startup. Sprayed starting fluid and unit fired up and would stay running .
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Old 04-14-2019, 03:38 PM
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Re: L98 no start

Can you view ecm data with tuner pro rt or hand held scanner.
It seems like the ecm is not seeing drp on startup. The reference pulse voltage must be low or the ecm is bad not seeing atleast 400 rpm.
The maf power relay has no connection with having injector pulse or not.
I wonder if you have two issues a bad icm now replaces and a bad ecm.
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Old 04-14-2019, 04:17 PM
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Re: L98 no start

I agree that it is not seeing a reference pulse. The only thing that has got me stumped is I have 2 ecmís and when I was able to start truck I swapped ecmís and 2nd one ran truck. Now neither one will. Maybe Iíll pick up another icm and see if that works. You can see where my frustration comes from.
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Old 04-14-2019, 04:21 PM
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Re: L98 no start

If you applied 12v to the reference on both ecms that might fry them. Reference voltage is only 1.5v running.
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Old 04-14-2019, 04:46 PM
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Re: L98 no start

No I only tested after truck wouldnít run on one ecm . Iíll keep trying thanks
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Old 04-22-2019, 02:42 PM
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Re: L98 no start

digging a little deeper into no start, no injector pulse. i am getting a 3vdc reading on EST bypass terminal at D5 and should be reading 0vdc. does anyone think this would hold out injectors on startup. this is a intermittent problem where sometimes truck will start right up and sometimes will not rum at all unless i use start fluid and will remain running
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Old 04-22-2019, 02:51 PM
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Re: L98 no start

Have you checked to see if the ecm is powered up during the no start.
running d5 is 4.75v .
http://chevythunder.com/fuel%20injec...ecm%20#1227165)
I don’t think the bypass has anything to do with the no injector pulse.
maybe b5 if anything.
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Old 04-22-2019, 03:54 PM
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Re: L98 no start

i believe the ecm is out of the picture until engine reaches 400 rpm. B5 only has 1.5 volts after startup
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