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jazzmaster
jazzmaster, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2535
Experience:  ASE .AUTO TECH FOR THIRTY-FIVE YRS,ELCTRICAL,FUEL INJECTION ETC.
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87 s10 blazer: intermittent..fuel injector..pulse..cranking, if you

Customer Question

87 s10 blazer has intermittent no start caused by lack of fuel. fuel injector noid light doesnt pulse while cranking. but while cranking, if you shoot brake kleen in the t.b., the truck will start and run, and the noid light will start blinking.

i get power to the injector at all times with key on.

i tried putting key in the ON position, and jumping the starter solenoid, still no start. so that eliminated the start circuit on the ignition cylinder correct?

replaced the
ignition controll module
tried new computer

ALSO: it seems to start more consistently when the batt charger is on 40amp charge.
when no batt charger is on the vehicle, no start condition is more common.
Submitted: 4 years ago.
Category: Chevy
Expert:  jazzmaster replied 4 years ago.
hi,try unplugging the throttle position sensor and starting it,it sounds like the tps is in the flood clear mode ,in this mode it wont let the injectors pulse the ground from the ecm but will start and run if carb cleaner or brake kleen is sprayed into the tb...guy...
Customer: replied 4 years ago.
already tried unplugging tps to eliminate clear flood mode, no help. this thing is goofy. i just noticed theres no engine to frame ground that i can see. so im going to make one. doubt it will help, but it cant hurt.
Expert:  jazzmaster replied 4 years ago.
it may help,let me know...guy
Customer: replied 4 years ago.
well, that did nothing.

went from exhaust manifold to fenderwell. cranked for 10 sec and nothing. turned key off, cranked for 5sec, nothing. keyed it one more time and it started.
Expert:  jazzmaster replied 4 years ago.
ok, give me a few mins so I can check into my data base ...guy..did you check for spark and for fuel pressure?

Edited by GUY V.I. on 10/20/2010 at 11:26 PM EST
Expert:  jazzmaster replied 4 years ago.
do you have spark and fuel pressure?
Expert:  jazzmaster replied 4 years ago.

ok. I am giving you these flow charts and diagrams ,this will help you find the problem ....guy...

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CHART A-3 - ENGINE CRANKS BUT WILL NOT RUN

Circuit Description :

This chart assumes that battery condition and engine cranking speed are OK, and there is adequate fuel in the tank. This chart should be used on engines using the Model 700 throttle body.

Test Description : Numbers below refer to circled numbers on the diagnostic chart.

  1. A "Service Engine Soon" light "ON" is a basic test to determine if there is a 12 volt supply and ignition 12 volts to ECM. No ALDL may be due to an ECM problem and CHART A-2 will diagnose the ECM. If TPS is over 2.5 volts the engine may be in the clear flood mode which will cause starting problems. If coolant sensor is below -30~C, the ECM will provide fuel for this extremely cold temperature which will severely flood the engine.
  2. Voltage at the spark plug is checked using spark tester tool ST 125 (J26792) or equivalent. No spark indicates a basic ignition problem.
  3. While cranking engine there should be no fuel spray with injector disconnected. Replace an injector if it sprays fuel or drips like a leaking water faucet.
  4. Use an injector test light like J34730, BT8329A or equivalent, to test injector circuit. A blinking light indicates the ECM is controlling the injector.
  5. This test will determine if there is fuel pressure at the injector and that the injector is operating.

Diagnostic Aids :

If no trouble is found in the fuel pump circuit or ignition system and the cause of a "Engine Cranks But Will Not Run" has not been found, check for:

  • Fouled spark plugs
  • EGR valve stuck open
  • Low fuel pressure. See CHART A-6.
  • Water or foreign material in the fuel system.
  • A ground CKT 423 (EST) may cause a "No Start" or a "Start then Stall" condition
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  • CHART C-4B - IGNITION SYSTEM CHECK

    Test Description : Numbers below refer to circled numbers on the diagnostic chart.
    1. Two wires are checked, to ensure that an open is not present in a spark plug wire.
    1A.If spark occurs with 4 terminal distributor connector disconnected, pick-up coil output is too low for EST operation.
    1. A spark indicates the problem must be the distributor cap or rotor.
    2. Normally, there should be battery voltage at the C" and -"+" terminals. Low voltage would indicate an open or a high resistance circuit from the distributor to the coil or ignition switch. If "C" term. voltage was low, but "+" term. voltage is 10 volts or more, circuit from "C" term. to ignition. coil or ignition coil primary winding is open.
    3. Checks for a shorted module or grounded circuit from the ignition coil to the module. The dist. module should be turned "OFF", so normal voltage should be about 12 volts. If the module is turned "ON", the voltage would be low, but above 1 volt. This could cause the ign. coil to fail from excessive heat. With an open ignition coil primary winding, a small amount of voltage will leak through the module from the "Bat." to the tach terminal.
    4. Applying a voltage (1.5 to 8 volts) to module terminal "P" should turn the module "ON" and the tach. term. voltage should drop to about 7-9 volts. This test will determine whether the module or coil is faulty or if the pick-up coil is not generating the proper signal to turn the module "ON". This test can be performed by using a DC battery with a rating of 1.5 to 8 volts. The use of the test light is mainly to allow the "P" terminal to be probed more easily. Some digital multi-meters can also be used to trigger the module by selecting ohms, usually the diode position. In this position, the meter may have a voltage across its terminals which can be used to trigger the module. The voltage in the ohm's position can be checked by using a second meter or by checking the manufacture's specification of the tool being used.
    5. This should turn "OFF" the module and cause a spark. If no spark occurs, the fault is most likely in the ignition coil because most module problems would have been found before this point in the procedure. A module tester (J24642) could determine which is at fault.
    Diagnostic Aids :

    The "Scan" tool does not have any ability to help diagnose a ignition system check.

Customer: replied 4 years ago.
im going to go through the flow chart today.

there is spark, because it starts with brake kleen squirted into the t.b.
Expert:  jazzmaster replied 4 years ago.
I gave you the whole flow chart series for engine cranks but will not run ,...guy
Customer: replied 4 years ago.
Ignition system checks out fine. fuel pressure is ok.

as far as pulsing the injector, is that done by the hall effect and the icm? so since i replaced the icm that would leave the hall effect switch being the coulprate?

i have power to injector at all times when not pulsing, so that would mean the ecm isnt getting the signal to ground the injector correct?
Expert:  jazzmaster replied 4 years ago.
I have seen the pick up coil do this a few times ,there is really no way to test this,outside of using an ohm meter to see if it has continuality,this does send a signal to the module and then to the ecm to pulse the injectors,perhaps it is exciting the module when you spray fluid into the throttle body,enough where as it wont under just a cranking situation with no fluid ,also you need to check if there is a loss of spark or dim spark until it gets that signal ,....guy
Customer: replied 4 years ago.
well, i tried a different distributor, still no fuel injector pulse!

so far i have tried

distributor
i.c.m.
e.c.m.

performed fuel pressure test, 8lbs fuel pressure, a little low, but the injector isnt pulsing so it doesnt really matter at this point.

seems to start more consistantly when battery charger is hooked up. but still doesnt start every time.

I AM GETTING SPARK WHEN CRANKING, THE IGNITION SYSTEM IS FUNCTIONING.
The truck will start with starting fluid. the fuel injector is not pulsing, that is the problem at this time.
Expert:  jazzmaster replied 4 years ago.
as soon as my system is back up and running ,I will send you the application and id for the ecm this is a chart of what the powers and grounds and values are at the ecm with the key on and off ,,we will have to check that out before going further,the only thing that controls the ground pulse of the injectors is the ecm,so we have to see if something is not geting to the ecm to regulate the ground pulse ...guy..
Customer: replied 4 years ago.
ok thanks for the help.

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Expert:  jazzmaster replied 4 years ago.
my data system should be back online around 6:00 pm ...guy..
Customer: replied 4 years ago.
ok thats fine
Expert:  jazzmaster replied 4 years ago.

whats weird is you have spark ,fuel and when you prime it ,it runs ,you have bat voltage on one side of the injector but no ground source ,which comes from the pcm/ecm,I have a flow chart for the injector ,follow that ,also check the wire from the ground side of the injector to the ecm (blue wire)also check the voltages and grounds going into the ecm as well as D16 injector ground side to the injector to see if you have a ground pulse while it is running or cranking,,did you change over the prom in the ecm to the new ecm?...guy,does the truck run good ?

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Customer: replied 4 years ago.
i think that is the info i need. ill try it tomorrow. thanks!
Expert:  jazzmaster replied 4 years ago.
yep ,let me know ....thanks guy
Customer: replied 4 years ago.
i got to it today
Customer: replied 4 years ago.
i got to it today and i have a question.

do i test the fuel injector plug wiring with it connected or disconnected to the injector.

if i test it with the plug connected to the injector, the test light lights up on both wires.

with the plug disconnected, the test light only lights up with the red wire.

i have power to the d16 connection at the ECM, and tried wiggle testing it to see if it had a bad connection. but still no start.
Expert:  jazzmaster replied 4 years ago.
you test it with it unplugged ,plugged in it will light on both wires until it is cranked over then the wire that did not show bat voltage should pulse a ground signal,it usually best to have a noid light ,or even a bulb with 2 wires to plug into the connector to the injector ,it should pulse off and on when the motor is cranked over,and it is always best to check all the powers and grounds to the pcm ,with the connectors disconnected,....guy...
Customer: replied 4 years ago.
well i guess with 1 light on at injector, it says faulty connection at d16 or bad ecm, but i had a parts store send a ecm out, and it didnt help.
Expert:  jazzmaster replied 4 years ago.
did you use an ohm meter to check the wire from D16 at the ecm to the injector ,this should show little resistance ,also if possible insert a paper clip end into the d16 at the ecm with the connectors connected and crank it over to see if you get a pulsating ground right at the ecm ,if you do then the wire from the ecm to the injector is bad or corroded or pinched,,...guy...
Customer: replied 4 years ago.
checked the wire at ecm, resistance tested good. the light was on at the ecm. no blinking. im kind of running out of ideas.
Expert:  jazzmaster replied 4 years ago.
did you check all the grounds and hots at the ecm?also did you check to see ,while the ecm is plugged in if there was a ground(pulsating) signal from the ecm the ecm ?does this oil pressure read right?,Was this ever put on a good scanner to read the data and values of the sensors(live) as well as other data ? ...guy...if not it may be a good idea to check that ,as you may be missing something

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jazzmaster
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ASE .AUTO TECH FOR THIRTY-FIVE YRS,ELCTRICAL,FUEL INJECTION ETC.