No injector pulse

michael evans

Active Member
Feb 27, 2008
808
77
28
Louisville, Kentucky
Having one huge problem. No injector pulse.

I have trouble shot this thing using vortec.com trouble tree several times.
Before I switched over to FAST tried a couple factory computers.
new crank sensor.
new cam sensor
new engine harness
injectors are getting good power

So far I am in $3300.00 and several hours trouble shooting.

The new FAST computer and harness ran another car.

The new cam sensor from Carpers has a LED light built in the blinks even after you let go of the key (engine run).

Any idees on what else I can check ?

Ready to drop a match into it and walk away.
 

michael evans

Active Member
Feb 27, 2008
808
77
28
Louisville, Kentucky
Tried two other stock computers before I switched to FAST.

I have a new engine wiring harness in place.

The two other things have it could be I guess could be is the knock sensor and the spark control sensor.

No injectors shorted. Even with all unplugged there still is no pulse.
 
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Tom87GNX

Active Member
Nov 29, 2012
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Southeast PA
I don't really know anything about the FAST system so I don't want to mislead you in any way, with that said I can say that the cam sensor controls injector pulse timing with the stock ECM. If it's know the cam sensor and cap are both good I would look at the chip in the ECM (check for damaged pins, improper seating of chip etc.) also check injector harness connections back by the bracket for ign module.


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No disintegrations

Active Member
Dec 27, 2015
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Make sure the fast is getting full battery voltage. If it gets say 9 volts during crank this can cause no start I think. Possible ignition switch problem.
 

bison

Moderator
Staff member
Dec 19, 2005
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Have you followed the cranks but doesn't start flow chart?


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TurboBob

Resident mad scientist
Staff member
May 24, 2001
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Commerce Township, Michigan
Shotgunning parts at the car is not the best way to fix it.

in any case, what ecm is in the car now....? get data while cranking, while crankiing look at the fast crank LED and see if its getting pulses, and/or the injector LEDs and see if the ecu is trying to pulse the injectors.

if no crank sensor pulse, then we need to swim upstream in the signal chain. the crank sensor signal for the ECU/ECM comes from the ignition module, and no pulses are sent until the module is synchronized, i.e. both cam and crank signals received. the later modules will not sync unless the sensors are properly timed (the early ones didn't care)

if you are getting crank pulses, then make sure the TPS is not stuck high and in clear-flood mode.

Let us know.

Bob
 

Chuck Leeper

8/10's of a century!
Staff member
May 28, 2001
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Bob, I have the Holley Dom system, and have the ability to do a "system log", to see these kinds of problems.
Does FAST have the "sys log" capability?
 

michael evans

Active Member
Feb 27, 2008
808
77
28
Louisville, Kentucky
The FAST unit is in the car (floor) and can see that the crank and cam sensor. Power light is on and blinking are the injestors LEDs on the red box.

No pulse is coming out of the box as I set up a light next to it and checked along the way.

One of the parts just changed was the ignition switch for a different reason that led me to change the engine wiring harness.

The car does not have theft deterrent

On the dash board you can see the engine cranking and is at 8% TPS.
 

michael evans

Active Member
Feb 27, 2008
808
77
28
Louisville, Kentucky
Kind of.

Not knowing the inner workings. If the LEDs flash does that mean it is trying to pulse the injectors ?

I guess what I am asking is are the drivers burn even if they are flashing ?
 

Mike T

Well-Known Member
May 3, 2013
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This may help. My car was parked in running condition due to HG's. A few years later after a full rebuild the car had no spark when trying to fire it up for the fist time. Tried a few simple things and finally decided to put a spare spark module and coil pack on. This at least gave a little backfire through the TB so now it's trying to fire but won't run. It had a fairly new crank trigger and cam sensor the had just been adjusted with a caspers led tool so I really didn't suspect the cam sensor at the time.

At this point I've got 2 frustrating days of trying to figure whats going on. Car would seem as if it was hydro locking when it did try to start so I pulled the fuel pump power and the "hydro lock" would go away. Finally decided to do it the "right way" and go down the no start tree from A to Z.

Everything was checking out until I got to the ground side of the injector pulse (no injector pulse). Start tree points to ECM if cam sensor is known to be good and I was 100 percent certain that it was good and perfectly timed......how wrong I was about that. For whatever reason I decided to try a different cap on the cam sensor and it helped, the darn car actually was close to starting but was still kicking against itself. Still frustrated but encouraged I decided to take a wag at the cam sensor adjustment and retard it a few degrees. To my amazement after two days of fighting it started and ran perfect!


Now in a nut shell I think the cam sensor cap had a problem but still illuminated the cam tool causing me to adjusted it wrong and in turn an out of sync signal that cause a no spark/injector pulse situation. My guess would be that the original spark control module and the coil was ok and it was just a coincidence or happen to sync enough to regained spark.
 
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michael evans

Active Member
Feb 27, 2008
808
77
28
Louisville, Kentucky
Yes the pink pin at the plug and all six black wires (injector plugs) have 12 volts and continuity all the way to the computer.

Boost crew has the computer and corrected an issue with it what ever it was.
 

Mike T

Well-Known Member
May 3, 2013
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So something was wrong with one of the original parts that you replaced causing no pulse and to top it off the FAST had a problem too? That would be frustrating.
 
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