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jazzmaster
jazzmaster, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2357
Experience:  ASE .AUTO TECH FOR THIRTY-FIVE YRS,ELCTRICAL,FUEL INJECTION ETC.
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I have a 89 Chevy S10 Blazer with the 4.3 TBI that will not

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I have a 89 Chevy S10 Blazer with the 4.3 TBI that will not start. It has a new fule pump the TBI has been rebuilt the Distributer replaced new timing chain and gears new coil new cap new fuel pump relay, it has spark fuel and timed. teh battery has twelve volts until the starter kicks in then it drops to 9.5. The fuel pump also continues to run after the ignition is off and the key is removed. Any help?
Submitted: 4 years ago.
Category: Chevy
Expert:  jazzmaster replied 4 years ago.
hello, did you get the battery checked ,it should not drop that low , it sounds like the system is back feeding because of a low battery ...guy
Customer: replied 4 years ago.
I'll do that but let me ask this, with the fuel pump relay removed should the fuel pump run? even wiht the key off and removed? I removed the relay and i can still see fuel pump into the TBI and after you crank for about a minure you chn hear the fuel pup run for about two minutes it drop in pitch after one minute.
Expert:  jazzmaster replied 4 years ago.
wow thats weird let me check on a few things and I will be back in a 1/2 hr ...guy
Customer: replied 4 years ago.

OK, When you first turn the ignition on I don't hear the pump kick in wiht the relay removed but do with it istalled. It also continues to run wihte hte relay installed.

 

Expert:  jazzmaster replied 4 years ago.
ok, I was looking at my data and wiring diagrams and was wondering if that the ignition source at the relay is not shutting off when you turn the key off ,which can be caused by a faulty ignition switch signal to the ecm which in turn goes sends a signal to the relay( to trigger the 2 second fuel pump prime)the prime signal should only be 2 seconds and then the relay should click off if it stays on and the fuel pump still runs it can be a faulty ecm to check this pull out the relay and on the relay socket check battery for power at terminal A ,then turn the key on and there should be 12 volts at terminal E , # XXXXX is a ground ,#D is a 2 second prime signal (ground) :graphicWhen the key is first turned ON, without the engine running, the ECM will turn the fuel pump relay ON for two seconds. This builds up the fuel pressure to normal operating pressure. If the engine is not started within two seconds, the ECM will shut the fuel pump OFF and wait until ignition reference pulses are present. As soon as the engine is cranked, the ECM turns the relay ON, which powers the fuel pump. The ECM continues to power the fuel pump during engine operation. If the fuel pump relay fails, it is backed up by the oil pressure switch, which continues to operate the fuel pump as long as oil pressure remains above 28.0 kPa (4 psi).
Customer: replied 4 years ago.
OK there is 12 volts to A and nothing on E. When the igntion is turned on there is still twelve volts to A and notheing to E. Switch or ECM?
Expert:  jazzmaster replied 4 years ago.
I was looking at the diagrams and a thought came to me about the oil pressure switch ,that when it senses 4 lbs oil pressure that it runs the fuel pump ,but it also looks like it has battery power (constant) to it on the orange wire ,the same wire circuit that the relay has on A ,so you say that the fuel pump runs when you turn the key on and stays running you are actually not getting a 2 second prime and when you shut it off the fuel pump stays running ...correct? and how long does it run after you shut the key off? can you hear the fuel pump running?..guy
Customer: replied 4 years ago.
With the relay hooked in I do get the 2 second prime. When I attempt to start it it will fire once or twice but does not start. If I crank it over for about 45 seconds and stop, I can hear the fuel pump running, it runs for about two minutes even wiht the ignition off and the key rmoved. You can hear a change in tone of the pump after about a minute. Wiht the relay removed you don't hear the 2 second prime but the rest stays teh same. I cna laos see fuel pumping into the theTBI under either condition (relay in or out.)
Expert:  jazzmaster replied 4 years ago.
ok,do you have a noid light or test light?....guy
Customer: replied 4 years ago.
Neither, I have a multimeter
Expert:  jazzmaster replied 4 years ago.
ok,do me one thing here before we procede any further ,can you disconnect the oil pressure switch and see if that changes anything,also a test light or noid light would be very helpful here,but you can use a multi-meter to check to see if there is voltage and ground at the fuel injectors,just hook up the meter to one of the fuel injectors ,one lead on each of the wires of just one injector and let me know what you are seeing,then with the key on see if there is voltage and ground feeding the injector ,key on engine off,...is the fuel spraying in on just dribbling in when you shut the key off?...you can also leave the multi-meter on when you crank the motor over and tell me what the meter is doing...guy
Customer: replied 4 years ago.
OK with the oil pressure switch disconnected the pump does not come on at all (relay still disconnected). With the fuel injectors when the key is turned on it goes to.03 volts then drops to .01 volts and stays there. When the engine is turned over it goes up to 1.68 volts. The fuel from the injectors sprays in a cone pulses alternating between the two. The battery checks out OK, wiht a full charge it only drops to 11.4 volts when the starter is engaged (still with relay and oil pressure switch disconnected). On the relay harnes I get 13.3 volts at A nothing at E. when thew switch is turned on there is still 13.3 volts on A and nothing on E.
Expert:  jazzmaster replied 4 years ago.
try leaving the oil pressure switch disconnected(fuel pump relay connected) and see if the 2 second prime is there ,then crank it over and let me know if the fuel pump still runs for 2 mins,also at the fuel injectors there should be 12 volts on each side of the injectors and then when you crank the motor there will be a ground pulse (no and off),did you check your plugs to see if they are wet from gas?it sounds like 2 problems.the injectors are leaking if they continue to run car into the throttle body when the key is off,did you have this problem from the beginning with the fuel injectors?..guy
Customer: replied 4 years ago.
The injectors are not leaking, there is not fuel going into the TBI except when you crank the enjine over. The problem started with leaky fuel injectors which is why I rebuilt the TBI. After the TBI was rebuilt the vehicle would not start, in tracking problems down the timing was off so I removed the timeing cover and noted that the chain had jumped a cog, put new gears and chain on. After putting the everything back together I noticed that the fuel pump continued to run after the ignition had been turned off, and the vehcile still will not start. I removed the starter tonight becuase i had noticed that the seal had moved now I need a new seal (bound in the flywheel). I will test the 2 second prime but cannot turn the engine over yet.
Customer: replied 4 years ago.
Ok with the relay in place I get the 2 second prime but the other test will have to wait until tomorrow evening as long as I get new seal.
Expert:  jazzmaster replied 4 years ago.
ok, also the fuel pump should only run for 2 seconds after the key is shut off,please check the plugs for gas fouling after all of this cranking and testing what eal are you talking about?.
Customer: replied 4 years ago.
Yes the plugs are very fouled I have cleaned them twice since the process has started and will clean them again. The seal I am refering to is the one between the starter and the bell housing, slides into the bell housing made of a foam rubber stuff and the nose cone of the starter fits into it, more to keeep dirt out I assume.
Expert:  jazzmaster replied 4 years ago.
alright, does the fuel pump run for 2 seconds when you turn the key off/
Customer: replied 4 years ago.
No
Expert:  jazzmaster replied 4 years ago.
well actually I meant after you crank it ,after you clean the plugs let me know what color the spark is and if it stays that color after you crank it for a little while and what kind of voltage the injector has,try with on lead on the injector hot side and one lead on the neg battery post ,I have to go to bed now 5:00 am comes pretty quick ,so I will talk to you tomorrow ..guy
Customer: replied 4 years ago.
Ok the spark color is blue yellow, as it cranks it gets more yellow and weaker then picks back up about the fourth rotation. As for the voltage from the hot side it is 13.05 at KO, when it cranks it drops to 10.40 (give or take a few tenths). Yes the pump runs for two seconds after cranking over a few times then stops - oil pressure switch still disconnected.
Expert:  jazzmaster replied 4 years ago.
ok .so now the pump is not running for 2 minutes like it was before?
Customer: replied 4 years ago.
Right it only runs for the two seconds and stops that is still with the eoil pressure switch disconnected
Expert:  jazzmaster replied 4 years ago.
I thought the pressure switch might be bad ,you need to replace that and see if it still has a problem starting,I was kind of figuring that there was 2 problems (1) pump running on ans (2) the plugs are getting fuel fouled ,so I would replace the oil pressure switch and with the plugs clean try and start the truck,...guy
Customer: replied 4 years ago.
In an earlier post you said "the prime signal should only be 2 seconds and then the relay should click off if it stays on and the fuel pump still runs it can be a faulty ecm to check this pull out the relay and on the relay socket check battery for power at terminal A ,then turn the key on and there should be 12 volts at terminal E , # XXXXX is a ground ,#D is a 2 second prime signal" I never did get 12 volts or any voltage at terminal E, is this going to be a problem?
Expert:  jazzmaster replied 4 years ago.
no ,i dont think so that terminal should have according the diagram 12 volts when cranking or 12 volts for 2 seconds now that I am looking at it more closely.that comes from the oil pressure switch and from the ecm,from the ecm it will only be hot when the engine is running or the oil pressure reaches 4 lbs pressure ...guy
Customer: replied 4 years ago.
Ok I'll try replacing the ol pressure switch and see what that doe for me, I'll let you know.
Expert:  jazzmaster replied 4 years ago.
ok.I will talk to you later ..guy
Customer: replied 4 years ago.
Ok sorry it has taken so long to get back to you, I had to install a new kitchen floor... so I put the new oil pressure switch in hooked everything back up, same problem as before vehicle will not start and the pump runs for about 45 seconds after cranking and the engine is off wih the key removed.
Expert:  jazzmaster replied 4 years ago.
hello again,can you get this truck running if you disconnect the fuel injectors?..guy
Customer: replied 4 years ago.
As in starter fluid?
Customer: replied 4 years ago.
The answer is no not with starter fluid not without it.
Expert:  jazzmaster replied 4 years ago.
what I meant is disconnect the wires to the injectors
Customer: replied 4 years ago.
Yes I under stand that and No it will not, I did get it to fire one cylander after replaceing theoil sensor but nothing since.
Expert:  jazzmaster replied 4 years ago.
sorry had to let the dog out ,I am going to get you a flow chart ,I will be back in a few...guy
Customer: replied 4 years ago.
Ok
Expert:  jazzmaster replied 4 years ago.
here are a few flow charts,I am including all that will relate to the fuel ,spark and injectors,dont mind the scan tool parts,you can do these without ,I want you to go through all of these and then tell me what you got, ,i KNOW IT MIGHT BE A PAIN BUT i AM NOT THERE AND YOU ARE MY EYES AND EARS ,so please be patient as you have been ,we will find the answer, I know that you have been through some of this but we have to start from the beginning(basics) ...guy;
Chart A-3 - Engine Cranks But Will Not Run
Chart A-4 - Injector Circuit Diagnosis
Wiring Diagram For Chart A-4 - Injector Circuit Diagnosis
  1. This test will determine if the ignition module is generating a reference pulse, if the wiring is at fault or if the ECM is at fault. By touching and removing a test light, connected to 12 volts, to CKT 430, a reference pulse should be generated. If injector test light blinks, the ECM and wiring are OK.
  2. This step tests for 12 volts to the injector. It will also determine if there is a short to voltage on the ECM side of the circuit.
  3. This test checks for continuity to the ECM .
    Chart A-5 - Fuel Pump Relay Circuit Diagnosis (One Fuel Tank)

    Wiring Diagram For Chart A-5 - Fuel Pump Relay Circuit Diagnosis (One Fuel Tank)


    CHART A-5 - FUEL PUMP RELAY CIRCUIT DIAGNOSIS (ONE FUEL TANK)

    Circuit Description :

    When the ignition switch is turned "ON", the Electronic Control Module (ECM) will turn "ON" the in-tank fuel pump. It will remain "ON" as long as the engine is cranking or running, and the ECM is receiving distributor reference pulses. If there are no reference pulses, the ECM will shut "OFF" the fuel pump within 2 seconds after ignition "ON" or engine stops except when a fuel module is used.

    The pump will deliver fuel to the TBI unit where the system pressure is controlled to about 62 to 90 kPa (9 to 13 psi). Excess fuel is then returned to the fuel tank.

    A fuel module is used on all 7.4L, G van with 5.7L, and all other 5.7L over 8500 GVW engines to correct a hot restart (vapor lock) during a high ambient condition. It is designed to over-ride the ECM two second pump operation and will run the fuel pump for twenty seconds at initial ignition "ON".

    Test Description : Numbers below refer to circled numbers on the diagnostic chart.
    1. This procedure applies direct voltage to run the fuel pump. If the pump runs, it may be a fuel pump relay circuit problem which the following step will locate.
    2. This step checks voltage from the battery and the ground circuit to the relay.
    3. This test determines if there is voltage from the ECM, terminal A1, to terminal "D" on the relay connector.
    4. This completes the fuel pump relay circuit but if this diagnosis was used because the engine would not run then oil pressure switch should also the diagnosed.
    Diagnostic Aids :
    • An inoperative fuel module may be the cause of a hot stall/no start condition. Check for power and ground circuit to the fuel module and a complete circuit to the pump from terminal "A". If OK, and the pump does not run for the specified 20 seconds at initial ignition "ON", replace the Fuel Module.

    ECM Connector Terminal Identification & Voltage Specifications.

    try these specs on the ecm too

Customer: replied 4 years ago.
Ok this could take me a couple of days so I will et back to you with the results.
Expert:  jazzmaster replied 4 years ago.
ok, it is better to take some time with these flow charts ,this should show what the problem is ,well time to hit the hay so to speak ,have a good night and talk to you soon ..guy
Customer: replied 4 years ago.
I don't know what the problem is but I cannot see the flow charts, I'm not sure if you have to be on line for me to see them or what? I attempted to save them last night but that did not happen either. Is there some way you can send them to me so i can look at them when I have the vehicle in front of me?
Expert:  jazzmaster replied 4 years ago.
graphicgraphicI loaded these a different way you should be able to see them now,this site does not allow e-mails or outside contact ,sorry I didnt make the rules..guyI am going to give you all the information ,so if you went through some of these things ,I am just trying to get you a solution
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 220 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 injectors disconnected. Replace an injector if it sprays fuel or drips like a leaking water faucet.
  4. Use an injector test light like BT8320, or equivalent, to test each injector circuit. A blinking light indicates the ECM is controlling the injectors.
  5. This test will determine if there is fuel pressure at the injectors and that the injectors are 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 grounded CKT 423 (EST) may cause a "No Start" or a "Start then Stall" condition.
  • Basic engine problem. graphicgraphic
    1. This test will determine if the ignition module is generating a reference pulse, if the wiring is at fault or if the ECM is at fault. By touching and removing a test light, connected to 12 volts, to CKT 430, a reference pulse should be generated. If injector test light blinks, the ECM and wiring are OK.
    2. This step tests for 12 volts to the injector. It will also determine if there is a short to voltage on the ECM side of the circuit.
    3. This test checks for continuity to the ECM.

    When the ignition switch is turned "ON", the Electronic Control Module (ECM) will turn "ON" the in-tank fuel pump. It will remain "ON" as long as the engine is cranking or running, and the ECM is receiving distributor reference pulses. If there are no reference pulses, the ECM will shut "OFF" the fuel pump within 2 seconds after ignition "ON" or engine stops except when a fuel module is used.

    The pump will deliver fuel to the TBI unit where the system pressure is controlled to about 62 to 90 kPa (9 to 13 psi). Excess fuel is then returned to the fuel tank.

    A fuel module is used on all 7.4L, G van with 5.7L, and all other 5.7L over 8500 GVW engines to correct a hot restart (vapor lock) during a high ambient condition. It is designed to over-ride the ECM two second pump operation and will run the fuel pump for twenty seconds at initial ignition "ON".

    Test Description : Numbers below refer to circled numbers on the diagnostic chart.
    1. This procedure applies direct voltage to run the fuel pump. If the pump runs, it may be a fuel pump relay circuit problem which the following step will locate.
    2. This step checks voltage from the battery and the ground circuit to the relay.
    3. This test determines if there is voltage from the ECM, terminal A1, to terminal "D" on the relay connector.
    4. This completes the fuel pump relay circuit but if this diagnosis was used because the engine would not run then oil pressure switch should also the diagnosed.
    Diagnostic Aids :
    • An inoperative fuel module may be the cause of a hot stall/no start condition. Check for power and ground circuit to the fuel module and a complete circuit to the pump from terminal "A". If OK, and the pump does not run for the specified 20 seconds at initial ignition "ON", replace the Fuel Module.

     

    graphicgraphic
    1. Two wires are checked, to ensure that an open is not present in a spark plug wire.
    1A.If spark occurs with EST 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 distributor 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 ignition 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. Checks for an open module, or circuit to it. 12 volts applied to the module "P" terminal should turn the module "ON" and the voltage should drop to about 7-9 volts.
    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 could determine which, is at fault.
    Diagnostic Aids :
    graphic graphic graphic
jazzmaster, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2357
Experience: ASE .AUTO TECH FOR THIRTY-FIVE YRS,ELCTRICAL,FUEL INJECTION ETC.
jazzmaster and 9 other Chevy Specialists are ready to help you
Customer: replied 4 years ago.
The fuel pressure goes to 13 PSI when the pump turns on and then drops slowly after the pump shuts off. As long is the pump is engaged it statys between 10 and 15 is that normal? Possibly have a leak in my gauge i will check that and get back with you.
Expert:  jazzmaster replied 4 years ago.
the fuel pressure looks fine ,it will drop down a little after the key is turned off ..guy
Customer: replied 4 years ago.
It drops to 0, injectors are still disconnected.
Customer: replied 4 years ago.
No leaks on hte gauge it still drops to zero after the pump stops.
Customer: replied 4 years ago.
It has started and is running, I found two shorts one leading to the left side injector and one to the ESC. Thank you very much for all of your efforts. Thanks again for all you did.
Expert:  jazzmaster replied 4 years ago.
you are very much welcome and thank you ...guy

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