Astro fuel pump runs after shut down

[bnielsen]

Good Day,
My 97 Astro fuel pump runs from 30 seconds to 3 minutes after I shut down the engine. I understand that a small amount of time is ok, but this does not sound right. I replaced the pump about 1 year ago and the dealer replaced my plenum and in intake gaskets recently. The pump started running long shortly after the intake gasket was done.
Any thoughts are greatly appreciated.
B

[CD Smalley]

That's a long time for a pump to run. 5-10 seconds would seem normal.

I would guess a leaking injector(s). How's your mileage been of late? Is that van hard to start?

[bnielsen]

I am with you on the time.
Starts great and we are getting 21 mpg hwy (best ever).
Could it be a sticky pump solenoid?
B

[CD Smalley]

I would lean toward a soft fuel pressure regulator first.

Does it do this only when warmed up? Or does it do it cold also?

[bnielsen]

Only when warm.
How do I test fp regulator?
Looks like the part is $50, so that wouldn't bother me, If we weren't sure.

B

[CD Smalley]

Not sure on that. I guess you could get a FP gauge on it and see what kind of readings your getting when cold and start/shut off the engine. And what you get when it's warm and you shut off the engine. My guess is that when it's warm and you shut the van off, the pressure drops far enough that it takes some time for the pump to build up the pressure to where it will shut off....

[drew300]

Just curious. what year is this? The pump on mine ('97), shuts off with the key.
I'd be suspious of a sticking pump relay.
On '96 and newer, the A/C and fuel pump relays are the same, so to switch them is an easy test.

[drew300]

Sorry, I reread the post. (97) (@#$!)

[bnielsen]

The pump usually goes off with the key, then quickly starts back up and does runs for 30 secs to 2 minutes. It does it more when the rig is hot. I agree with you that it may be the regulator. I need to spend the $50 for regulator and see. If it is the relay, those are only $10.
Thanks for your help. I will let you know what happens when I replace the parts.

B

[CD Smalley]

Before you start replacing parts, get a fuel pressure gauge and check to see what your FP is when you shut it off when the van is hot. Then watch what happens on the FP gauge... I think you'll see it drop and then build up once the pump starts in....

[drew300]

Could some-one explain why the pump should turn on at all with the engine / ignition off?
From what i've been able to find, turn the key, the computer runs the pump for 2 seconds max. After that, the oil pressure closes a switch to keep the pump running. Kill the engine, the pump turns off.
How does it get a command to run longer / restart?
I've never heard my van or friends' run the pump with the key and engine off.

[CD Smalley]

Mine runs for anywhere from 5-10 seconds once the van is shut off. Remember we're talking about a VIN W engined van here. They run at a much higher pressure 55-60psi vs TBI at 9-13psi. It takes a while to maintain that pressure....

[drew300]

Curious.
I just replaced my fuel pump. Trouble-shooting was difficult as it was a maginal fault. (wouldn't start, but ran well after some starting spray).
A fellow on this site said the Haynes manual was wrong on their pressures, so i phoned GM. They said "minimum 60 psi". I had readings of 59 psi. (engine off). (and wouldn't start)
With the engine running, pressure was about 53 psi, and killing the ignition, no pump ran, and pressure dropped to about 45, draining down to about 42 after 7 minutes or so.
A new pump fixed it, but since i had to borrow and return a pressure gauge, I don't know the present pressure.
The GM center I talked with also said that they'd never had to replace a regulator.
Also, something i could measure is current draw. My old pump drew 4 amps, ramping up to 7 amp. (after about 15 seconds) The new pump draws 9- 9.5 amps. I measured this at the relay, in the engine bay fuse box. Pull out the relay, place the ampmeter across the top left pin and the lower right pin (socket). Meauring will work with the key off.
Hope this helps