No Start, No injector pulse when cranking, runs on starter fluid until shut down - JeepForum.com
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Unread 04-14-2015, 04:06 PM   #1
psu
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1997 TJ Wrangler 
 
Join Date: Mar 2015
Location: state college, Pennsylvania
Posts: 5
No Start, No injector pulse when cranking, runs on starter fluid until shut down

I have an annoying no start condition going on with my 97 wrangler.
Summary at bottom of post.

Backstory:

It all started after I changed my water pump. The gasket was installed incorrectly causing it to lose most of the coolant while driving( Thankfully only had to go 3 miles and I could take breaks every mile or so to let it cool off.)

I then correctly installed a new gasket and had no issues with it leaking etc.

After installing the waterpump I took it for a short drive to make sure everything was working correctly, I noticed the alternator was charging at 18 volts(verified with multimeter)

I then replaced all major power and ground wires along with grinding down to bare metal for a solid connection on grounds. This did not help the overcharging issue.

Since the regulator for the alternator is located inside the pcm on the jeep I added an external regulator that works exactly as it should. After installing the external alternator I was unable to start the jeep, it would just crank.

Getting desperate I decided to try using starter fluid to start it. The starter fluid worked and it ran perfectly until I shut it off. After shutting off it would not start without using starter fluid to do so.

I used starter fluid to get it started and then drove it 120 miles home with no issues at all, drove exactly how it normally did before the issue.

I purchased a fuel pressure gauge and have 48 psi which is right at spec.

I have spark since it will start on starter fluid.

I used a noid light when cranking and it showed no pulse. I check the positive to the injector and they are all 12v as they should be. This means that the pcm is not sending the signal to ground the injector during cranking.

What could cause the pcm to not send the signal to pulse the injectors when cranking but after its started to send the signal?

Summary:
  1. Replaced water pump, gasket fail, reinstall correctly
  2. Alternator charging at 18v verified by multimeter, replaced and cleaned all grounds and main positive wires
  3. Put in new alternator, did nothing to help the 18v charging, learned that the pcm controls the alternator voltage
  4. Installed an external alterator regulator, works perfectly
  5. Jeep would crank but not start
  6. Uninstalled external regulator but had same issue, reinstalled regulator
  7. Managed to get started using start fluid, ran perfectly until I turned it off
  8. Currently runs perfectly after using starter fluid to get started(made the 120mile trip home with no issue)
  9. I have good spark and 48 psi fuel pressure
  10. Used noid light to test if injectors were firing while cranking, they were not. Found the problem, no idea what is causing it.
  11. Tested positive to the injectors and they all have 12v
  12. The pcm is not switching the ground to the injectors to make them fire while cranking. They fire perfectly after starting with starting fluid.

Any insight is appreciated.

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Unread 04-14-2015, 04:16 PM   #2
Jeepsr4me
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Join Date: Dec 2004
Posts: 7,485
you have a copy of the fsm? it will walk you thru a lot of the injector issues.
http://www.jeep.on-line.no/documentation/TJ/Jeep_TJ.htm
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Unread 04-14-2015, 04:40 PM   #3
Rubi4MyMrs
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2005 LJ Wrangler 
 
Join Date: Mar 2011
Location: Trails of, Nevada
Posts: 2,932
Will it start if you put gas in the TB instead of starting fluid?
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Unread 04-14-2015, 05:25 PM   #4
Jeepsr4me
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Quote:
Originally Posted by Rubi4MyMrs View Post
Will it start if you put gas in the TB instead of starting fluid?
I find any combustible vapor works... so not sure where your going with that.
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Unread 04-27-2015, 07:38 PM   #5
psu
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1997 TJ Wrangler 
 
Join Date: Mar 2015
Location: state college, Pennsylvania
Posts: 5
Well on the opinion of the jeep dealership I ordered a reman pcm, poor decision. Even with the new pcm I have exactly the same issue of no injector pulse while cranking but it will start no issue with starter fluid and continue running afterwards with the injectors firing as they should.

Guess thats what I get for listening to a dealer. With the new info of the pcm not being the cause of the problem, what would your best guess be?
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Unread 04-28-2015, 06:17 AM   #6
Jeepsr4me
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Did you get the FSM and start reading the trouble shooting section on injectors?

Cause thats where I would start,,,,,, And it would have saved ya the trip to dealer and cost to FIX that did not work..
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Unread 04-29-2015, 02:23 PM   #7
psu
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1997 TJ Wrangler 
 
Join Date: Mar 2015
Location: state college, Pennsylvania
Posts: 5
Quote:
Originally Posted by Jeepsr4me View Post
Did you get the FSM and start reading the trouble shooting section on injectors?

Cause thats where I would start,,,,,, And it would have saved ya the trip to dealer and cost to FIX that did not work..
I read through all I could find relating to injectors and didnt see anything that I havnt already tried.
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Unread 04-29-2015, 03:27 PM   #8
Jeepsr4me
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You may not have power to the PCM during cranking or a ground to the injectors during the cranking cycle.... There is a couple ways it can happen..
page 793
The ASD relay is used to connect
the oxygen sensor heater elements, ignition coil,
and fuel injectors to the 12 volt + power supply. Jeep
models of previous years had used the ASD relay to
apply the 12 volt + power supply to the generator
field source (+) circuit . This generator circuit is now
supplied 12 volts + directly from the PCM.
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