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I am French and own a Chevrolet Blazer LS ZR from 1999. But it hasn't started for several months.
I use Google to translate ... Yes, my English is no longer very good!
I will tell you what happened so that you can help me solve this problem. Note that I am not a professional mechanic ...
One evening several months ago, I turned the key. the starter turns but it does not start. I sounded several minutes later and it started. A week later, while driving, the Blazer's engine suddenly stopped as if it had run out of gas. Vehicle on a tow truck ... Local mechanics don't want to get into trouble with this kind of vehicle, he drops it off at my house.
I search a little and I change the oil pressure regulator placed under the ignition distributor. The Blazer starts! Great.
2 weeks later (I have done about 400km) the engine stops like a gasoline breakdown and I come back again on the tow truck.
Fuel pressure tests (made from the sticky post on this site):
At the service port, ignition On = 58psi and does not hold after.
At the outlet of the fuel filter = pump pressure 70psi and does not maintain at 50 as it should.
Service port fuel pressure, pump on, ignition on, engine stopped and for good reason, it has not started for a long time
I had planned to do work on the Blazer, I took advantage of it and since then I have:
- Changed the complete fuel injector spider (pressure regulator included)
- the fuel pump
- The petrol tank
- The fuel tank filler neck
- The fuel filter
The pressure test results are the same before and after all changes.
I finally changed:
- The vapor canister purge valve and the vapor canister vent valve / Solenoid
The pressure test results are the same before.
I noticed that when the fuel filter is disconnected at the front, the fuel flows in a thin stream without ever stopping. I think air is entering the tank. But I can't find where!
I also noticed that the brake pedal remains depressed (they worked perfectly before stopping) and if the battery is connected, the stop lights stay on. Unable to move the pedal.
This is why I also think of the vacuum circuit ...
Can you help me find where this air comes from?
For example, what if the pressure does not hold at the outlet of the filter?
Last edited by FrenchZR2; 06-30-2020 at 06:15 AM.
Reason: Adding signature and change img
The vent solenoid is normally open so the tank is normally vented through the charcoal canister to the atmosphere. The vent solenoid is closed and the fuel tank system is sealed only during the routine test of the system by the ECM. The purge valve only opens briefly to purge the canister of fuel vapor fumes into the engine intake. The evap system should have nothing to do with improper fuel pressure.
Your fuel pressure does not hold at the output to the fuel filter so there is a fuel system pressure leak somewhere between the fuel pump and the output of the fuel filter.
Was there any change in the fuel filter pressure test results after you changed the fuel pump?
What brand of fuel pump did you use? Any pump brand besides AC Delco or Delphi may have quality problems.
Do you smell or see gasoline anywhere under the truck or near the tank indicating an external leak?
Your brake problem and any potential vacuum leak should be unrelated to the fuel pressure problem. How do the brakes work when the truck is running? Does the engine change speed when the brake pedal is depressed?
I am offering this as another possibility. However, it might be unlikely. Could there be a leak from the fuel injection lines inside the intake manifold plenum? If there was a leak there, fuel could drain into the intake ports directly. This would cause an over-rich mixture that could cause errors in the oxygen sensing and increased fuel consumption.
I am offering this as another possibility. However, it might be unlikely. Could there be a leak from the fuel injection lines inside the intake manifold plenum? If there was a leak there, fuel could drain into the intake ports directly. This would cause an over-rich mixture that could cause errors in the oxygen sensing and increased fuel consumption.
And welcome to the forum!
That could be an additional problem that is yet unprovable because he is not holding pressure at the fuel filter which means there is a leak somewhere before the filter. When he fixes that issue and holds pressure at the filter then he can retest at the fuel rail schrader and if he fails there then it’s either lines, injectors or regulator at that point. That’s the whole point of pressure testing in two places so you can identify which half of the system has failed (sort of). You may turn out to be right but the OP needs to find out why he can’t hold pressure at the filter first.
That could be an additional problem that is yet unprovable because he is not holding pressure at the fuel filter which means there is a leak somewhere before the filter. When he fixes that issue and holds pressure at the filter then he can retest at the fuel rail schrader and if he fails there then it’s either lines, injectors or regulator at that point. That’s the whole point of pressure testing in two places so you can identify which half of the system has failed (sort of). You may turn out to be right but the OP needs to find out why he can’t hold pressure at the filter first.
Thank you for your response GeorgeLG and christine_208.
christine_208, the injectors are new and indeed I think GeorgeLG is right. I must first resolve the problem of pressure not maintained at the outlet of the fuel filter.
GeorgeLG, I'll answer your questions first.
Was there any change in the fuel filter pressure test results after you changed the fuel pump?
No, precisely, the pressure at the schrader valve is always the same after replacing the pump and even after all repairs. I had not taken the pressure at the filter outlet because the fuel pump made an abnormal and irregular noise. Upon disassembly, there was some black powder in the bottom of its case. Coals.
What brand of fuel pump did you use?
The pump that was installed was a DELPHI FG0072 installed in 2015. Returned to Rockauto under warranty. I ordered and installed an ACDelco MU1755 in the new fuel tank with also the new fuel tank filler neck. I always order a part in advance of those I change to lower the delivery costs and especially to have the parts immediately available because I am in France. So I have a DELPHI FG0072 in stock returned by rockauto in exchange for warranty.
Do you smell or see gasoline anywhere under the truck or near the tank indicating an external leak?
Before the breakdown and for a year or two, I could sometime smell the fuel when I was driving. This is why I planned to change the injectors. Today, precisely, I did all the visual research on the fuel line to detect a leak. I see nothing and feel nothing abnormal.
I think air is entering the fuel line and the tank. But I don't know of a method to find this air intake.
Maybe you know a specific place that usually breaks on the fuel line, or a method to detect it.
For the brakes, they worked perfectly because they were redone last year. When the car starts, I will see if it comes back. the car has been running and has not started since January.
As I said before, the fuel tank is always open to the atmosphere through the evap vent solenoid except during the routine ECM testing so there is always an “air leak”.
If you get the exact same pressure leakdown after all of those parts replacements and you cannot find any external leaks then you should verify those pressure leakdown readings with another pressure gauge if you can.
As I said before, the fuel tank is always open to the atmosphere through the evap vent solenoid except during the routine ECM testing so there is always an “air leak”.
If you get the exact same pressure leakdown after all of those parts replacements and you cannot find any external leaks then you should verify those pressure leakdown readings with another pressure gauge if you can.
George
Hello,
I understand however, the pressure gauge being new, I hesitate to buy another because this Blazer is starting to cost me as much as a new one ... But yes, it is possible that it is defective.
Especially since I detected a problem with the charge of the car battery yesterday . Not very surprising since immobilized for several months. I'll have to settle this before ... I believe this may have consequences for the operation of the pump.
Is 70 psi a good working pressure for the ACDELCO pump?
So, with regard to the petrol net which naturally flows out of the petrol filter when it is disconnected, that would be normal?
I didn't have this when I changed the fuel filter for the first time. It sank a bit and then it stopped. Hence my question. So I'm going to drop this track.
As I said before, the fuel tank is always open to the atmosphere through the evap vent solenoid except during the routine ECM testing so there is always an “air leak”.
If you get the exact same pressure leakdown after all of those parts replacements and you cannot find any external leaks then you should verify those pressure leakdown readings with another pressure gauge if you can.
George
Hello,
I understand however, the pressure gauge being new, I hesitate to buy another because this Blazer is starting to cost me as much as a new one ... But yes, it is possible that it is defective.
Especially since I detected a problem with the charge of the car battery yesterday . Not very surprising since immobilized for several months. I'll have to settle this before ... I believe this may have consequences for the operation of the pump.
Is 70 psi a good working pressure for the ACDELCO pump?
So, with regard to the petrol net which naturally flows out of the petrol filter when it is disconnected, that would be normal?
I didn't have this when I changed the fuel filter for the first time. It sank a bit and then it stopped. Hence my question. So I'm going to drop this track.
Is the only reason for the pressure not maintained at the outlet of the fuel filter a leak between the pump and the filter?
06-29-2020, 03:18 AM
Chevy Blazer ZR 1999 doesn't start / fuel or vaccum leak?
. Not very surprising since immobilized for several months. I'll have to settle this before ... I believe this may have consequences for the operation of the pump.