Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

41 - 52 of 52 Posts

·
Registered
2002 chevy trailblazer_lt
Joined
·
281 Posts
One additional thing just to be aware of....your 2002 model year does have an external fuel pressure regulator and a fuel return line to the tank. Later models did away with this so If you find posts talking about pressure regulators be aware you have an external one. There is a small hose connection with an elbow on the front drivers side of the air intake plenum that leads to this regulator nearby. I would say this is NOT likely to be your problem here in this case, but it is something to be aware of.

IMG_20200630_102531.jpg
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
24 Posts
Discussion Starter #42
I agree with TJ here.... try the ether... but use it sparingly.... better still, use a carb cleaner since it is designed to burn decently under combustion pressure. Ether is for diesels... and they too can be damaged by overzealous use.

The idea of priming the fuel system by repeatedly turning the key on for a few seconds is a false flag.

All the priming this system needs is accomplished in one cycle.
Sorry for the delay in response. Death in family priorities.
Not getting a fuel pressure reading on gauge BUT I connected a clear fuel line to the OUT nipple of the fuel filter. Fuel flows steady but not fast during prime sequence when ignition switched to ON. If the fuel line pressure is supposed to be approx 40-50 psi shouldn't the fuel flow fast?
Are Delphi fuel pumps trash? This would make two in a row.
I also rented an Innova OBD2 Diagnostic tool, which I've no experience with. Is there something worth checking on in lieu of carb cleaner test?
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
24 Posts
Discussion Starter #43
One additional thing just to be aware of....your 2002 model year does have an external fuel pressure regulator and a fuel return line to the tank. Later models did away with this so If you find posts talking about pressure regulators be aware you have an external one. There is a small hose connection with an elbow on the front drivers side of the air intake plenum that leads to this regulator nearby. I would say this is NOT likely to be your problem here in this case, but it is something to be aware of.

View attachment 55311
TJ - Yes I am aware of the regulator, but is there a shade tree test that it's working/not working?
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
24 Posts
Discussion Starter #45
the fuel OUT connector has a test port, looks like a tire valve, I tighten test line to it just snug with pliers since it's plastic. Zero press at prime or crank.
I think I'll go with another make than Delphi; this is the second brand new part that failed.
You'd think for $300.00+ bucks you'd be buying with confidence.
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
281 Posts
I would check it out a little more first. Is this a rental fuel pressure test gauge? Can you confirm the gauge itself works by trying it on another vehicle? The reason I ask this is I once got a loaner test gauge the did not work!! Turns out the little valve depressor on this rental had no port machined through it so it just plugged off the test port and allowed no flow to the gauge.

When you tested this time did you jump the relay like shown in the video and can you hear the pump running?

I think even with a bad regulator you would show some pressure at the gauge.
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
24 Posts
Discussion Starter #47
I would check it out a little more first. Is this a rental fuel pressure test gauge? Can you confirm the gauge itself works by trying it on another vehicle? The reason I ask this is I once got a loaner test gauge the did not work!! Turns out the little valve depressor on this rental had no port machined through it so it just plugged off the test port and allowed no flow to the gauge.

When you tested this time did you jump the relay like shown in the video and can you hear the pump running?

I think even with a bad regulator you would show some pressure at the gauge.
Yes, the test gauge is a rental. Did all the relay tests from the video and all el is good. So, I got a clear hose and attached to the OUT port of the fuel filter and got flow during prime and crank. Fuel mostly filled the clear hose (4-5 ft) during prime, but the pressure sure didn't rush out like it was under 40-50 psi, as I would expect.
I 'curb' tested the new pump by attaching the included harness, running the wiring over the frame so I could hold the loose pump in my hand just below the drivers rear door jam while I turned ignition ON for prime. It hummed nicely (very quiet) for 1-2 sec and stopped, as expected. Repeated that a couple of times, fine. So I buttoned it all up.
If the fuel regulator fails would fuel still flow? I was getting slight fume odor in cabin upon startup way before this pump project began so it must have been leaking a bit to begin with.
I also rented a diagnostic tool. Guess I'll see if the brain's got anything interesting to say...
 

·
Registered
Joined
·
5 Posts
Yes, the test gauge is a rental. Did all the relay tests from the video and all el is good. So, I got a clear hose and attached to the OUT port of the fuel filter and got flow during prime and crank. Fuel mostly filled the clear hose (4-5 ft) during prime, but the pressure sure didn't rush out like it was under 40-50 psi, as I would expect.
I 'curb' tested the new pump by attaching the included harness, running the wiring over the frame so I could hold the loose pump in my hand just below the drivers rear door jam while I turned ignition ON for prime. It hummed nicely (very quiet) for 1-2 sec and stopped, as expected. Repeated that a couple of times, fine. So I buttoned it all up.
If the fuel regulator fails would fuel still flow? I was getting slight fume odor in cabin upon startup way before this pump project began so it must have been leaking a bit to begin with.
I also rented a diagnostic tool. Guess I'll see if the brain's got anything interesting to say...
Aye I've read your posts and I'd like to give a bit of outside perspective from someone who's not too familiar with these trucks.

From what I've read I can gather these few things:
The vehicle has a fuel pressure test port.
The fuel pump isn't making any noise, you have a new pump installed (delphi, OEM manufacturer for this vehicle, same as ACDelco).
You've tested fuel pressure, and are getting pressure out of the pump, before the filter when it's removed, and not afterwards installed and pressure tested in-line.
You've checked for flow and believe the flow rate is too low, which it likely is not as vehicle fuel pumps are very finely tuned to put the exact amount of flow out as is necessary under the most demanding conditions, and no more.

So from that information, I would do this: Can you get at the regulator's return line that leads back to the tank? Remove it and plug it. If the regulator has failed open and isn't providing enough pressure, you can plug it and run the vehicle for a VERY short time without causing damage to the lines/seals to see if it will run. I usually block off the regulator's return on vehicles by using a piece of fuel line that has a small hole in it to stop excess pressure from building up which prevents damage. Please be mindful, it only takes static electricity, sometimes so small that we can't feel it, to lose your life in a fire, be careful.

Now, if that works, you have a bad regulator. If not, have you checked pressure coming to the fuel rail? You should always check that at the source where it's needed, checking fuel pressure at the tank is useless unless you are testing a pump, and even then it's still kind of useless.

Now, here's what makes me think it is your regulator: You said before this happened, you were getting a fuel smell? When a regulator fails, it causes fuel to become circulated through the tank more than it should. This means more warmed fuel from the pump which is now running overtime to keep pressure up will now vaporize, and you will smell it. This can cause the fuel pump to burn out.
An explanation: Electric motors run best when at their maximum speed, they are most efficient in that state. When they are loaded (moving extra fuel), they produce an inverse voltage inside of them that causes them to draw more amperage through the windings, heating up the motor. If the fuel pump gets too hot, the lacquer coating on the windings will erode quickly and ruin the pump.

Now, back to the normal talk.

So, this vehicle has a vacuum controlled regulator, engine vacuum controls the fuel pressure. At higher vacuum, the fuel pressure is lower, and when the vacuum is lower, the fuel pressure will increase. These fuel pressure regulators of this style leak all the time on literally every car I have ever touched. I would check yours, see if it's leaking around it anywhere when priming the fuel system (ignition to on then off a bunch of times to prime the system). If it's leaking, replace it. If it isn't you still should replace it. It's a non-expensive, not too hard to install part #78616HZ. I'd do it if I were in your shoes.

One final thing: Are you sure you have a nipple to be testing fuel pressure from? Can't find it on any pictures of the filter or related lines for that year, and I'm beginning to think why it read 0 is because you possibly hooked it up to a EVAP line.
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
24 Posts
Discussion Starter #50
Firstly, Thank You TJ and jazz for the input.
Here's a pic of the furl test port (am i incorrect?).
Also, a new FPR runs $100.00+ so any shade tree suggestions are appreciated.
20200704_124356.jpg
20200704_124356.jpg
 

·
Registered
2002 chevy trailblazer_lt
Joined
·
281 Posts
I will have to say I'm still suspicious of the loaner test gauge, especially since I had a bad loaner once.

Not sure this would show anything but maybe carefully pull the vacuum hose from the regulator off the airbox and see if that's wet with fuel. It should be dry.

When you saw zero pressure on the test gauge,,,was the pump running while you looked at the gauge or had the pump shut off by the time you got to the see the test gauge?
 
41 - 52 of 52 Posts
Top