Shawn537

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.

Tuned Performance

iTrader: (92)

What 12v reference pin did you supply 12v to ?
1227165 or 1227730 ecm ?
Do you have spark ?

Shawn537

122765 . Touched reference wire on plug which leads to ecm to positive side of battery

Tuned Performance

iTrader: (92)

B5 purple/white ?
Sounds like a good way to blow the ecm.

Shawn537

Just tapped it through meter. Any suggestions what the problem could be?

Tuned Performance

iTrader: (92)

You didn’t state do you have spark ?
could be a bad ignition control module.

Shawn537

Yes I do have spark and oil pressure switch is made for fuel pump relay

Tuned Performance

iTrader: (92)

If you have 42 psi and prime doesn’t 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 ?

Shawn537

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?

Tuned Performance

iTrader: (92)

You can have spark but no drp with a bad icm.

Shawn537

That’s 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 .

Tuned Performance

iTrader: (92)

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.

Shawn537

I agree that it is not seeing a reference pulse. The only thing that has got me stumped is I have 2 ecm’s and when I was able to start truck I swapped ecm’s and 2nd one ran truck. Now neither one will. Maybe I’ll pick up another icm and see if that works. You can see where my frustration comes from.

Tuned Performance

iTrader: (92)

If you applied 12v to the reference on both ecms that might fry them. Reference voltage is only 1.5v running.

Shawn537

No I only tested after truck wouldn’t run on one ecm . I’ll keep trying thanks

Shawn537

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

Tuned Performance

iTrader: (92)

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.

Shawn537

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

Shawn537

success!! thanks to scott at tuned performance where i had my chip programmed. he pointed me in the right direction that i was loosing power to my computer on startup. traced back and found broke wire , repaired and starts right up. thanks again

Tuned Performance

iTrader: (92)

Glad you got it going