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GM-Frank
GM-Frank, ASE Master Certified
Category: Chevy
Satisfied Customers: 431
Experience:  37 Years Automotive Diagnosis and Repair. 25 Years of General Motors Dealer Experience
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95 chevy blazer: the fuel pump..started right..Drove..quit working

Customer Question

on my 95 chevy blazer 4.3, car will not start. Installed a new fuel pump thinking that it was the fuel pump because it started right up after about an hour. Drove it down the road and the car just quit working. Tried to get a reading on what the problem was, wasn't able to get a reading because the ecm was fried, replace the ecm and car started for about 20 mins, drove it down the road and quit working. checkd all the connections even did a fuel pressure test and it was sitting around 60psi.
Submitted: 5 years ago.
Category: Chevy
Expert:  GM-Frank replied 5 years ago.

 

HelloCustomer

 

OK I have read your compliant and I see you say the ECM fried?

 

Did you determine what caused an ECM failure?

 

If you feel the fuel pump is working, then after some basic checks, connect a quality scan tool, and check for any trouble codes that would lead you into the direction of a problem area.

 

Here's what I need to know.

 

Does the engine have Spark to the spark plugs.

Does the fuel pump run for about 2 seconds when you cycle the key to the on position.

And does the engine run and continue to run when you spray a starting fluid or carb spray down into the throttle body.

 

Now when you check the fuel pressure on this engine, you need to check to see that the fuel pressure regulator is not failing. If the fuel pressure gage does not hold the pressure at about 60 lbs after the 2 second fuel pump cycle, then you are going to need to get to fuel pressure regulator under the upper intake and replace it.

 

So basic checks first.

Fuel pressure gage holds at 60 lbs.

Engine has spark

Engine has compression.

 

And does engine continue to run while spraying starting fluid down the throttle body.

 

Sometimes just a bad fuel pressure regulator can flood an engine, and with wet spark plugs, the thing just will not start again.

 

Frank

Customer: replied 5 years ago.
on my 95 chevy blazer 4.3, car will not start. Installed a new fuel pump thinking that it was the fuel pump because it started right up after about an hour. Drove it down the road and the car just quit working. Tried to get a reading on what the problem was, wasn't able to get a reading because the ecm was fried, replace the ecm and car started for about 20 mins, drove it down the road and quit working. checkd all the connections even did a fuel pressure test and it was sitting around 60psi.
Expert:  GM-Frank replied 5 years ago.

 

I'm sorryCustomer

 

I must not have received your reply correctly. It appears that your original statement about your blazer came through to me instead of a reply.

 

Please try again

 

Frank

Customer: replied 5 years ago.
                   &nb sp;                                                                                                                                                                       do you think crankshaft maybe the problem?           & nbsp;                                                        
Expert:  GM-Frank replied 5 years ago.

 

Customer

 

You didn't explain why the ECM fried?

 

There is no question that a crankshaft position sensor could be causing your problem.

 

Frank

Customer: replied 5 years ago.
The emc fried because I took a paper clip to the OBD port and stick it in there and heard a pop noise
Expert:  GM-Frank replied 5 years ago.

 

OK,

 

I was just curious about what happened there.

 

Was trying to figure out if that may have had anything to do with the problems you are experiencing right now.

 

Frank

Customer: replied 5 years ago.
not that I know of. I tried to hook it up to a OBD II scanner and couldn't get any kind of code. So what is the two main reason why the car will not start? bad crankshaft sensor or a fuel pressure regulator?
Expert:  GM-Frank replied 5 years ago.

 

If the computer is incapable of doing its part, the engine will not start.

 

The signals or inputs from the sensors on the engine tell the ECM how to control fuel and spark. If you are unable to retrieve data from the ECM, then that needs to be addressed.

 

All power and ground circuits must be functional at the ECM. And the ECM must function.

 

Have you removed the spark plugs to see if they are wet with fuel? Have you checked for a Good strong blue spark at the plug wires while someone cranks the engine? Do you have a Fuel pressure gage on the engine to verify it is holding pressure after key is cycled on for 2 seconds. Have you sprayed starting fluid down the intake to see if the vehicle runs and continues to run while spraying?

 

Please try to understand that we are not compensated in any way, shape or form until you are happy with our answers and you click the "ACCEPT" button from your end.

 

If we are asked to get into detailed long distance diagnosis that can take us hours and hours to help you with, it is customary that you follow closely the procedures we recommend, and use the tools and test procedures we offer along with being prepared to offer a little extra in the way of compensation for our work.

 

There are many situations where we don't just have a quick fix for a vehicle where the description is that ...."my car won't start"

 

It sounds as if you may have a very complicated and extensive bit of work to accomplish on your Blazer. This may be something that is way beyond trying to do via text with the vehicle there and me here.

 

Frank

Customer: replied 5 years ago.
when you say key cycle, do you mean having someone bump or just have it turned on?
Expert:  GM-Frank replied 5 years ago.

 

When I say cycle the key to the on position, that is simply to on and not all the way to start.

 

If I ask to have the key bumped, I will say cycle the key to the start position.

 

The on position is just when the dash lights up but the engine is not cranking.

 

 

Customer: replied 5 years ago.
when you test a sensor where do you test it? and does it have to be on the car and the car being on?
Expert:  GM-Frank replied 5 years ago.

 

In the case of your Blazer, most of the sensors will provide a voltage value that is viewed via a quality scan tool. For instance, you would look at the parameters of a Throttle Position Sensor with a scan tool, and you would be able to see the voltage vary from about .54 volts at throttle closed to about 4.90 volts at wide open throttle.

 

Important inputs and outputs for fuel control and are IAC, Coolant Temperature and Crank and Cam position.

 

Yes, you can toss a crank sensor at this thing, but you need to know the ECM is working. One of the first steps in determining if the ECM functions is to view the Check Engine Light on the Dash. If that doesn't work, that needs to be the first step in your repair.

 

All of the inputs to the ECM are interpolated, and then the ECM decides the spark timing, the amount of Fuel to be delivered, and it looks at the RPM and Load all in an effort to make any necessary adjustments to the systems so that the drivabiility is best for the conditions.

Customer: replied 5 years ago.
the emc has already been replaced. If you test the sensor would you test it on the connector or the connector on the sensor itself?
Expert:  GM-Frank replied 5 years ago.

I've been trying to tell you we use a scan tool. oOr Just install a new sensor and see what happens.

Diagnostic Trouble Code (DTC) PO337 and DTC P0338 will set if there is a crank sensor malfunction. Refer to Diagnostic Trouble Code Charts .

graphic

 

 

 

graphic

 

 

CIRCUIT DESCRIPTION
The Crankshaft Position (CKP) sensor sends a reference (0 volt/5 volt, "OFF," "ON") signal to the Vehicle Control Module-A (VCM-A) to indicate crankshaft position and RPM so that the VCM-A can determine when to pulse the ignition coil and control ignition timing. DTC P0337 is a type "B" DTC.

DTC PO337 WILL SET WHEN

  • Engine speed is less than 2000 RPM.
  • Crank sensor duty cycle is greater than 50% (or the ratio High Ref/Low Ref is less than 0.176).

ACTION TAKEN (VCM-A WILL DEFAULT TO)
The VCM-A will turn "ON" the Malfunction Indicator Lamp (MIL) (Service Engine Soon) after two consecutive driving cycles with the fault active.

DTC P0337 WILL CLEAR WHEN
The VCM-A will turn the MIL "OFF" after three consecutive trips without a fault condition present. A history DTC will be cleared if no fault conditions have been detected for forty warm-up cycles [coolant temperature has risen 22°C (40°F) from start-up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle] or the Tech 1 clearing feature has been used.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

  1. This step determines if DTC P0337 is the result of a hard failure or an intermittent condition.
  2. Checks for crankshaft sensor low duty cycle.
  3. Determines if voltage is available to the CKP through the VCM-A.
  4. If the feed circuit is shorted to ground, the test light will be "ON." This step determines if the circuit is open or shorted to ground. If the circuit is OK, then the VCM-A connections or VCM-A is faulty.
  5. This test checks the crank sensor, crank sensor signal circuit and VCM-A.

DIAGNOSTIC AIDS
An "Intermittent" problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.

Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.

 

 

Expert:  GM-Frank replied 5 years ago.

You may be able to check the crank sensor by putting your low AC volt meter on the wires with the sensor out of the car. Move the magnetic pickup near a large piece of steel an watch the meter to see if it fluctuates as you move the sensor close to and away from the steel.

 

I've heard of people checking them in that way.

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GM-Frank
GM-Frank
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37 Years Automotive Diagnosis and Repair. 25 Years of General Motors Dealer Experience