Question about 1994 Oldsmobile 88

1 Answer

No injector pulse width if system voltage over 12.5 volts

I work a a Gm dealer and pretty good at what I do, But this one has me stumped as well as others in the shop. The car is an 89 Pontiac Grand Am 2.5 with TBI. heres what it came in for and where we are now. It came in with a no start. when you crank it and keeped the key in start it would run. if you let go it would die. after running some diag. we did notice that there was no pulse wisth after starting it, there would be spark but the pulse wisth would go away. after a day of diag. i unplugged the alternator and it continued to run. pulse width was back, if you put a shop charger on it, the same thing, it would loss pulse width, seams anything over a system voltage of 12.5 would kill the injector pulse. the ecm and prom where replaced. its not the injector driver, we have even used another know good ecm and got the same results. the ignition module as well as the crank sensor have been replaced as well. all engine ground and grounds the pcm are good and solid. all power have been verified as well. any help would be appriciated. I was told just to give it back to the customer, but i dont like to give up.

Posted by on

  • 3 more comments 
  • support754 Dec 02, 2008

    with the alternator disconnected, if i apply a battery charger to the battery, once it goes past 12.5v i lose the pulse from the injector, the ground/driver sie, i still have power.

  • support754 Dec 02, 2008

    ignition switch is new, and im not lossing any powers anywhere in the system, as well as at the ecm.

  • support754 Dec 02, 2008

    i lose the ground/driver side, voltage is stable. with aternator disconnected and a charger on the vehicle, once system voltage hits 12.5 i lose the injector ground/driver circuit.

  • support754 Dec 02, 2008

    ignition switch is new, and i have all powers and grounds verified.

  • SM124 May 11, 2010

    Do you lose the injector feed or the ground side. Have you checked for a bad diode in the alternator putting out an a/c signal that could cause the pcm to misread the signal from the module.

×

1 Answer

  • Level 2:

    An expert who has achieved level 2 by getting 100 points

    MVP:

    An expert that gotĀ 5 achievements.

    Sergeant:

    An expert that hasĀ over 500 points.

    Champion:

    An expert who has answered 200 questions.

  • Expert
  • 255 Answers

Hi, it sounds to me that you are losing contact at the ignigtion switch..C1...

Posted on Dec 02, 2008

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

What is the voltage measurement fuel injector


The vast majority of fuel injectors are ground controlled. This means that of the two wires going to the injector one is held at steady 12 - 14 volts while the other lead is pulsed to ground by the ECM. This type of injector circuit is called negative trigger. There are, however, a few (European) manufacturers that have used positive or battery voltage trigger injector circuitry in the past. With positive injector trigger, the positive side is the one being triggered by the ECM.

May 24, 2016 | Cars & Trucks

2 Answers

NO INJECTOR PULSE SPARK IS GOOD HAVE BATTEY VOLTAGE AT INJECTORS NO GROUND PULSE WHY


Open circuit to PCM - the engine computer grounds the other side of the injector there by turning it on an off very rapidly . This is call PWM - pulse width modulation . There is a transistor in the computer that does this . Or the PCM is bad !

Aug 24, 2015 | 1997 Chevrolet K1500

1 Answer

I have a 2006 cobalt with a 2.2 i have no injector pulse what could cause this?


You should have 12 volts to every injector with the key on. The pcm controls the pulse. If you have 12 volts, then it is the wires to the pcm or the pcm is bad. You'll need a volt /ohm meter to check the wires

Apr 17, 2015 | 2006 Chevrolet Cobalt

1 Answer

My injectors arent pulsing on my 1989 k1500 suburban. I have 12 volt power to the injectors and have replaced the module in the distributior. Any one have an anwser for me


The injector ground circuit must not be working. What causes the pulse is when the computer internally grounds the injector circuit, power is passed across the injector solenoid terminals. All the injector grounds are spliced together on each bank of engine, and run into the computer. So, injector power, but no pulsing would seem a computer malfunction as long as the ground wires are good. Did you check all the injectors for pulse with the noid light, or at least both sides of engine?

Jan 23, 2013 | 1989 Chevrolet K1500

1 Answer

2000 Dodge Grand Caravan only have two injectors pulsing?


I would check the wiring harness for the injectors

Should have 12 volts with key on-- to all injectors,same
as the ignition coils

Ignition or Injectors are turned on by PCM Drivers

Do not put any voltage to injectors they are pulsed

Dec 20, 2012 | Cars & Trucks

1 Answer

Crank sensor


Print


Location

Specific to:
Ford Taurus 2008-2009
Mercury Sable 2008-2009


0996b43f80e43304.jpg enlarge_icon.gifenlarge_tooltip.gif

Fig. Crankshaft Position (CKP) sensor (7)


Operation

Specific to:
Ford Taurus 2008-2009
Mercury Sable 2008-2009
The Crankshaft Position (CKP) Sensor is a permanent magnet output coil device that monitors the speed and position of the crankshaft. A reluctor is attached directly to the crankshaft, and is used to generate a constant signal as it passes the CKP sensor magnetic coil. The CKP Sensor utilizes system voltage (12 volts DC), or reference voltage (5 volts DC) to generate a digital output signal to the PCM that is based upon a 0.5 volt AC reference. The alternating magnetic field is used by the sensor output electronics to produce a digital pulse. The CKP sensor returns a digital ON/OFF signal pulse during each revolution of the crankshaft, with a momentary signal interrupt for the top dead center (TDC) position of the #1 cylinder. The Pulse Width Modulation pattern is used by the Powertrain Control Module (PCM) to calculate ignition timing, fuel injector timing, misfire diagnostics, and the tachometer display

Jun 20, 2012 | 2008 Ford Taurus X

1 Answer

Wont start no fuel injector pulse


of so you have spark and fuel pressure, next check for a constant 12 volts to injectors, pulse is controlled by ground, if you have voltage check wiring to ecm

Nov 19, 2010 | 1989 Oldsmobile Cutlass Supreme

2 Answers

I have a 1995 gmc jimmy 4x4 i check fuel pressure an the voltage


a simple 12vdc will not due, it needs a pulse signal from the computer. a full 12vdc could fry the injectors, but the spider assemblys in them v6's are always a @$!$@ up design. i have encountered alot of them with bad pcm, or the spider.

Sep 15, 2009 | 1995 GMC Jimmy

1 Answer

My 1990 Chevy Celebrity wagon 3.1 multiport fuel injection is getting fuel to the rack at 45psi, but is not going through the injectors. Any idea the probable cause?


DO YOU HAVE 12 VOLTS ON INJECTOR WIRE ON ONE SIDE WITH KEY ON? IF SO ARE YOU GETTING SPARK? IF YOU HAVE NEITHER YOU MAY NEED A NEW CRANK SENSOR. VERY COMMON ON THIS ENGINE WHEN THERE IS A LOSS OF SPARK AND INJECTOR PULSE. INJECTOR PULSE(GROUND SIDE)IS CONTROLLED BY THE COMPUTER. IF YOU HAVE SPARK BUT NO INJECTOR PULSE AND 12 VOLTS ON INJECTOR FEED WIRE YOU MAY HAVE A FAUTY ECM(ENGINE COMPUTER)

Aug 31, 2009 | 1990 Chevrolet Celebrity

2 Answers

Fuel injectors don't work on 1994 Saturn sc2


There is a (#1 Ignition Fuse) located in the under hood fuse box. Remove the fuse to make sure it is not blown. If the fuse is good we will have to check for injector pulse. Let me know if you have a 12 volt test light and you will need a "noid" light to figure out if the ECM is driving the injectors.
Let me know.
Regards,

Apr 25, 2009 | 1993 Saturn SL2

Not finding what you are looking for?
Cars & Trucks Logo

312 people viewed this question

Ask a Question

Usually answered in minutes!

Top Oldsmobile Experts

yadayada
yadayada

Level 3 Expert

61037 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

21949 Answers

Jeff Turcotte
Jeff Turcotte

Level 3 Expert

6812 Answers

Are you an Oldsmobile Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...