reggiestewart

My '97 Astro 2wd cargo has been hard starting lately. I've read through many posts on here, and it appears to point in the direction of the fuel pump.

It starts on starting fluid and runs fine. It will even restart once warmed up.

cold fuel pressure with key in on position: ~50psi
while cranking: ~50psi
pinched off return line: ~50psi
running: ~50psi
accelerating in town: ~53psi
accelerating up to highway speed: ~59psi
cruising at highway speed: ~52psi
Shutoff: Instant drop to between 40-47psi

cleaned fuel pump ground
no visible leaks

If I am not mistaken, this should rule out anything but the fuel pump. Correct?

I have not checked voltage at the pump, but can't think of anything aside from the ground that would cause low voltage.

Ironically, this all started 2-3 weeks after changing my fuel filter....and yes the arrows point forward. The pump does sound weak, so I'm assuming that is the culprit. This one only lasted about 50-60K.

One other odd question. I've noticed for a couple of years now (I think it started after the first pump was replaced), that when I am driving the van before it has warmed up, like when I first pull out of my driveway, I hear a "tick-tock..tick-tock". That's it, just one little cycle. It seems to be coming from the passenger side of the engine. Any ideas what this is?

Thanks in advance!

old_master

Low voltage at the fuel pump can cause low fuel pressure readings. The electrical connector at the fuel pump is a known problem. High resistance in the fuel pump circuit, positive or negative, will shorten pump life. If you are replacing the fuel pump, replace the connector if it appears burnt, corroded, or melted. Most auto parts stores have the connector and it comes with a pigtail attached. Solder the wires using 60/40 lead/tin rosin core solder and use heat shrink tubing, don't rely on crimp connectors. From your readings, fuel pressure is low. Make sure the connector is ok and the pump is getting battery voltage and ground at the pump connector. If that's ok, the pump needs replacement. Here is the procedure for testing fuel pressure:

Fuel pressure is not monitored by the On Board Diagnostic (OBD) system and therefore cannot set a Diagnostic Trouble Code (DTC), or illuminate the Service Engine Soon (SES) light.

Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump through a relay continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the PCM/VCM will shut off the fuel pump approximately 2 to 3 seconds.

Fuel pressure test:
Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates excessive leak down. Likely cause would be a leaking fuel pressure regulator, leaking fuel lines under the upper intake manifold, a leaky fuel injector, a leaking fuel line, or the check valve in the fuel pump is not sealing properly.

reggiestewart

I know this is a horribly old post, but I am just now getting around to getting my van right.

I bought a Delphi pump, and was getting ready to install it. I forgot that I had never checked the voltage at the pump. I pulled the plug and found that the center pin was pretty badly coroded. I cleaned both the male and female sides of the connector and plugged it back in. After the cleaning I decided to crank the van "just for the heck of it". I cranked it, it almost started, then nothing. Now, when I turn the ignition to the "on" position, there is no more hum from the pump. I checked the voltage at the connector, and am getting no voltage most of the pins, and only 5 volts at two of the corner pins. I swapped the relays and checked the ECM-2 fuse, and still nothing.

Before all of this, I had fire the van up on carb cleaner and pulled it in the shop with no issues. I've been driving it this way almost every week since the first post.

Any suggestions???

Thanks in advance!

old_master

The fuel pump wire, (grey) in the connector at the fuel pump will only have battery voltage for 2 to 3 seconds after the key is turned to the RUN position, then it will show zero volts. You'll probably need an assistant for that test.

Fuel pressure that drops to anything less than 55psi is a problem. I realize you're only building 50psi, and that could be either a weak pump or a fuel leak, either internal or external. If there are no external fuel leaks, it may be the fuel pump check valve, fuel pressure regulator, fuel lines in the plenum, or an injector leaking. The pressure drop needs to be diagnosed before replacing the pump.

reggiestewart

Ahhh! This is why I have 3' of jumper wire!

I got an 11.75 volt read for the 2-3 seconds, which I would guess to be acceptable with my rigged up jumper cables.

The pump still doesn't hum, but maybe that connector is bad?

I guess my main question is whether or not it is even possible for the failure to be at the connector versus the pump? Or, is it more likeley that the coroded connector has just cause the pump to deteriorate over time?

old_master

11.75 is a good reading.

Pump not running: make sure you have ground to the connector too, less than 5 ohms resistance from the connector to ground.

Poor connections cause high resistance, high resistance shortens motor life.

50psi fuel pressure with the return line restricted is too low. You cannot determine what the problem is from this test, only that there is a problem present. The fuel pressure line must be shut off somewhere between the pump and the pressure test port, and a gauge installed between the shut off and the pump, to determine if the pump is capable of building sufficient pressure and holding it.

drew300

For what it's worth, when I phoned GM, the service rep said "minimum 60" in reguards to fuel pressure. The borrowed guage I had read 59 psi, and I had very hard starting, but when started ran fine.
My new pump draws about 10 amps of power. Good connections are very important as it doesn't take much to start them corroding.