95 Astro - Fuel problem

Can you guys please help me?

I have a 95 astro which I recently replaced the fuel pump.

Since replacing I have drove one 300 mile trip and about another 300 miles of city driving (with no problems).

Last week it got real cold like 4 degrees or so. And I started having problems. The truck kind of wanted to stall when I tried to give it more gas. This problem progressed over a couple days (60 miles of driving). I had not changed the fuel filter yet, so I replaced it last Saturday and it seemed to fix the problem. You could not blow through the old filter.

Then the problem started up again this week, after 50 miles of driving, only 10 miles of driving after filling up the gas (15 gallons).

The problem is getting worse.

Here are a couple more facts I have put together.

The original problem started after I filled up with gas (Thursday 16 gallons). After about 5-10 miles of driving.

The problem re-occurred after filling up with gas from the same gas station (Tuesday -15 gallons, After 10 miles); there were no fillups between this and the first.

When I noticed the original problem the first thing I did was add 2 (maybe 3 cans) of gas antifreeze. It did not help.

I only added 1 can immediately after filling up the second time (15 gal of gas). Then added another can later. It did not help.

The problem completely goes away if I shut the van off then turn it back on. Of course it slowly returns after a few minutes of driving.

The problem is progressive. It starts off mild and continually gets worse until the vehicle will stall. Right now it takes about 7 miles of city driving @30 miles/hour (stop and go) to get real bad.

Sorry for the long post. Do you guys have any idea on what I might check next?

I am thinking about changing the fuel filter again (and never going back to that gas station). I think that gas was 10% ethanol.

Any suggestions would be greatly appreciated.

Thanks,


Dave

Please keep in mind that any of the facts above could be coincidences. Maybe the gas from that gas station is just fine and has nothing to do with the problem. Maybe it was brought on by the cold weather.

What could cause stalling like this? Could it be a clogged EGR valve?

The fuel injection pressure regulator might be suffering a slow death, or you might have water in the gas tank from your (former) favorite gas station. If you don't have a manual on the van try www.autozone.com - fair amount of free repair info there.

Check your fuel pressure. If you aren't seeing 55-60psi when you first turn the key, and holding at least 40psi overnight, you need to replace the fuel injection spider. Start looking on ebay for a new AC-Delco unit. Expect to pay about $250USD.

Is the spider the same thing as the CPI unit?

I read up on the CPI unit and it seems like most ppl that had CPI units that were leaking internally, also had starting issues.

My van starts very easy. Does this rule out a bad CPI unit?

Mabye it is just the fuel filter again. I will take it off and see if i can blow through it this weekend. I would have done it already, but the damn cold, snow, and extra low running boards turn a 2 min task into an hour one :(

btw... the check engine light is NOT on.

Spider =CPI unit.

Mine started just fine too with the bad spider.

When you changed the fuel filter....did you have to bleed off the pressure from the system? I mean did you disconnect the fuel pump wires, then start the van and let it run until it stalled? If you didn't do this and just went and took the fuel filter off without getting soaked in 40psi of fuel pressure, then you have a bad spider.

I did not bleed off the pressure when i changed the fuel filter. I just opened the lines and let the gas squirt.

I'm not sure what 40psi of fuel pressure looks like, and really dont remember how much came out...

Because the old filter was clogged, I kindof think the fuel filter might be a good place to start. I will change it tomorrow and post the results. Please let me know if you have any more ideas.

I guess if that does not work, the next step will be to conduct the fuel pressure test you outlined earlier

I did not bleed off the pressure when i changed the fuel filter. I just opened the lines and let the gas squirt.

I'm not sure what 40psi of fuel pressure looks like, and really dont remember how much came out...

Because the old filter was clogged, I kindof think the fuel filter might be a good place to start. I will change it tomorrow and post the results. Please let me know if you have any more ideas.

I guess if that does not work, the next step will be to conduct the fuel pressure test you outlined earlier

Wow, I can't believe it. We are having the same problem with our Astro Van.

We have replaced the following parts:
egr valve
fuel pump
fuel filter
throddle body
cleaned injectors and fuel line
catalytic convertor and exhaust system
tune up
numerous relay switches
transmission filter and strainer
replaced several vacuum lines and hoses
Also filled up with premium gas and added a few gas cleaning additives.

and it's still doing the exact same thing.

I've read a few trouble shooting guides that said it could be a knock sensor or possibly something called a lifter in the engine.

I am just clueless. We were hoping to get it running good enough to trade it in. This has been going on for a month now. Replacing part after part leaving seasoned mechanics clueless.

I don't know what to do next.

Tiger,

Have you checked your fuel pressure? Which year and engine do you have?

My van is
1995 CHEVROLET TRUCK ASTRO VAN 2WD
6 Cylinders 262 W 4.3L CPI

The problem is getting worse... now i cant drive over a mile or so. I have not yet determined if the problem starts after it warms up or just a period of time.

I really suspect the fuel filter, but dont want to change it right now because there is a damn blizzard outside. I will wait until morning i guess.

I will post the results.

Okay... I just took off the fuel filter. The filter is fine. I can easily blow through it.

The bad thing is there was no pressure when i took the line loose. There was plenty of fuel in the filter, but the gas did not squirt.

Is this the problem? Does this mean my fuel system as a leak somewhere? Is the most likely location the spider as suggested earlier? Is the spider the first place i should start, or is there an easier/cheaper place to start?

Thanks for the advice guys... I really appreciate it!

If you did NOT burn off the pressure before you changed the filter, and only had a small amount of gas that dripped out vs. sprayed. Then yes I think the spider has failed. Start checking on ebay for a replacement. Make sure you get a new GM part. Get the whole spider. Don't mess with just the fuel pressure regulator. It might be one of the poppets has failed as well. Expect to pay roughly $275 including shipping. Here's the seller's address that I bought mine from fastburn1@yahoo.com. He shipped promptly and the part was new GM part in the box as advertised. $255 to my door.

Man... I can't get the plenum to come off. I took out all 10 bolts/nuts.

I have tried pulling on it. Prying on it. I can't get it to budge. Is there something I am missing, or a certain technique to use?

How stuck are the usually?

Never mind... i missed the front center bolt. It was much easier to find in the day :)

Even in the daylight I had a hard time finding everything.

Did you get a spider already?

Yeah, I ordered the CPI, nut kit, new gasket, still looking for an ERG gasket :( No one has one in stock.

Also I need to find a new throttle cable because I got a little rough with mine and kinda broke the plastic ball joint on the end. I might stop by napa to see if they have an adaptor or something.

I can't find the cable anywhere on the new hardly. I guess I will have to go to a dealer.

Should have it all done by Sunday. I will let you guys know. Thanks for the help!!!

Okay... a quick update.

The mailman never delivered my CPI until Monday, so I am back to my 1 hour/day of daylight before work to work on it.

I got the nut kit in, cip in. One concern is I do not think the fuel pressure is high enough.

It is like 60psi when the pump is on, then drops to 23psi when it is off over a period of 15 seconds or so.

Is this a problem?

It did drop much lower before (to like 6 or 8 psi). Also, I did not see any leaks while the pump was on. I would think if it was leaking i would see gas squirt with 60psi behind it.

Is this sequence of events happening just when you turn the key on? I seem to recall this happening on mine as well. Start the van and see what you get for FP. Let it run a little while and then turn it off and see what the FP does. It should hold around 40psi once the van has been rand and shut down.

No, that is not what I did. I just turned the key on and let the pump run a few times. It fully pressurized the system at 60+ psi

Then dropped it to 22 or so. It does hold pressure above 20 for extended periods of time.

I have the van back together and I am ready to test my work :-)

I just have a dead battery so I will give it a jump start tonight and hope it goes well.

Keeping my fingers crossed....

Bad news.

It still runs like crap. Same as before pretty much. Ran real bad at first (rough). Then after running 10 min or so it really smoothed out.

So I took it for a test drive. Accelerated pretty good at first. Drove for 5 minutes then put on the express way. Tried flooring a couple times and it slowly but surly stared running real bad. Stalled on me once. Turned it off and back on and it ran good enough to get me home (a mile or so).

Now i really dont know what to do.

I guess Saturday I will check the flow rate. Then I will check the fuel presure when it is acting up (I will drive it with pressure guage on it).

Other than that I really dont know what to do.

I am open to any suggetions.

I really appreciate your help!

Dave

I just looked it up. The fuel pressure should drop 3-10psi with the key off.

That is a minimum of 50psi. Mine is more like 22psi. So that must be my problem.

I guess the question is where could the pressure be bleeding off to?

Could one of my new parts be faulty? I installed a CPI (spider), fuel lines (nut kit), and a new fuel pump, strainer, filter.

Wouldn't I see/smell 30lbs of pressure bleed off? If it bleeds down to 22psi, why doesn’t it go all the way to 0psi?

Please state the obvious because I could have easily missed it.

I suppose there is always the remote chance that my problem is not related to fuel pressure even though it drops below spec when the pump is not running.

I just looked it up. The fuel pressure should drop 3-10psi with the key off.

That is a minimum of 50psi. Mine is more like 22psi. So that must be my problem.

I guess the question is where could the pressure be bleeding off to?

Could one of my new parts be faulty? I installed a CPI (spider), fuel lines (nut kit), and a new fuel pump, strainer, filter.

Wouldn't I see/smell 30lbs of pressure bleed off? If it bleeds down to 22psi, why doesn’t it go all the way to 0psi?

Please state the obvious because I could have easily missed it.

I suppose there is always the remote chance that my problem is not related to fuel pressure even though it drops below spec when the pump is not running.

The pressure should drop 3 - 10 psi when the engine starts not when you turn the key off. With the key on and the engine off you should have a minimum of 55psi (it takes 54psi to open the poppet) Once the engine cranks it applies vacuum to the fuel pressure regulator, the regulator then reduces the pressure. The higher the vacuum the lower the pressure.

Is your check engine light on?

I would try replacing the gas cap, sounds like it isn't ventilating like it should.

Actually my book (HAYNES MANUAL) said it should drop 3-10psi with the key off. It did not list a spec for running, though you guys did, thanks.

I was planning on removing the gas cap when I get home tonight and taking if for a test drive.

I don't see how it could drop to 20psi and hold 20psi. I should see fuel somewhere and I don't. If the cpi or nut kit were leaking I should have seen it squirt.

So I guess it must be leaking back into the tank. I guess a negative vacuum could cause this if the return lines were clogged or pinched.

Check your manual again. Let me know where it says that. Give me a page number.

Forgot to answer. The check engine light is not on. I will post the page number tonight. I am referencing the first page of chapter 4, and I definitely admit that I could be mistaken.

Thanks for the help.

You were right. The spec states that it should drop 3-10psi when running. Any idea on how much it should drop when the pump is not running? Is this test irrelevant?

As long as all of the pressure is not bleeding off when you turn off the key I think you're OK. I was seeing all of the pressure go away, down to 0psi....

As long as all the pressures are up to spec with the key on or the engine running losing pressure with the key off should not cause the drivabilty issues that you speak of.

You you very much guys! That is exacally the responces that I needed. Now I can move on past the fuel issure. Everything now points to the catalytic converter. I will post back and let you know if that fixes it.

I just replaced my exaust/convert from the O2 sensor back and it did not help.

I think i will try pumping out the old gas and re-change the fuel filter.

This is getting expensive :(

I just test drove the van with the fuel gauge hooked up and the needle
swept between 50psi and 70psi when I accelerated. The pressure never
dropped below 50psi even while the van was running poorly.


I also drained the gas and re-changed the fuel filter and it did not
help.


I will try and better explain how it is acting.


The van always starts and runs fine.
It drives fine for a short distance then starts to run very bad,
sometimes backfires, stalls, and completely dies.


It takes as much as 10 to 15 minutes of regular city driving to cause
these symptoms or 2-3 minutes of driving under a load (when I hot rod
it).


If the van completely dies, I can turn it off for 10 seconds then right
back on and I can usually baby it home (1-2 miles). If I leave it off
for 15 minutes it usually runs quite a bit better.


I have replaced:
Leaky CPI (spider)
Inlet outlet fuel lines (nut kit)
Fuel Filter
Fuel Pump and strainer
Exhaust from O2 sensor back (waste of $$$... my dumb fault)
Drained the gas


Is it time to take it to a mechanic? I am out of ideas and do not know
what else to check. Is there a certain test that a shop could perform
that would tell me what is wrong such as a general diagnostic or run it
on a computer?


Does this still sound like a fuel delivery problem?

I can't believe that the check engine light doesn't come on....does it come on during the lamp test when you first turn on the key?

Forgive me if this has already been answered, but have you tried cleaning the EGR valve?

Have you noticed if it happens when the engine reaches a certain temperature? The computer stays in open loop (default setting) until the engine is warmed up. When the engine is warm it then goes into closed loop, when it goes into closed loop it starts adjusting performance depending on info it gets from the sensors.

You could replace the PCV valve ($2) ...there is no way it would cause all your problems, but it is was clogged or stuck it could slightly worsen them. (no need to make a special trip to the parts store for this one.)

Engine light does work and does not come on.

I took off the EGR valve and it did not look clogged. One guy suggested that I use plate to test plug the hole while i test drive. He said it might be sticking open.

The problem does not have much to do with engine temperature. I can let it warm up at idle and it will run fine. It only starts acting up after I put it under a load.

I did replace the PCV valve.

I've been rehabilitating a poorly maintained '89 astro I inherited. I'm closing in on replacing every engine control and emissions sensor on the engine.

Here's a few thoughts.
If it's dogging under load it may be a timing issue. the first suspect is the knock sensor. The second is the crankshaft postion sensor. The third(worse) is the timing chain.

In spite of the eratic symptoms in relation to engine temperature, it may still be temperature related or air intake related.

My van idled good when cold got worse as it warmed. A new EGR valve helped some but didn't solve the problem. Even though the temperature gauge seemed to be working OK, I replaced the coolant temperature sensor. Things improved a bit more. Last night I pulled out the Idle air valve - totally gooped. Put in the new part. Idle improved 100%, but the by product was that the engine ran better all the way around - during idle and acceleration. I suspect because the valve was basically stuck it was running rich and as the engine accelerated it was still trying to flush the excess fuel out. On the '95 you have another temperature switch as well. The temperature sensors in general are cheap, 10 bucks or less. If they aren't working correctly the ECM either thinks the engine is cold when hot or vice versa and your fuel / air mix is screwed up.
There's one other possibility - the fuel injection pressure regulator. I read a thread on another astro site where the symptoms were similar to what you are experiencing. The pressure regulator turned out to be the culprit.

You've spent a lot of money chasing this problem. I hope the final solution turns out to be somewhat less expensive. Try not to leave a palm print on your forehead when you find it.

P.S. Every sensor on my van was performing under spec. The check engine light never came on. ( and yes, the bulb is working)

I took off EGR valve made sure it was closed then reinstalled without the plug. It did not help.

One more thing I just noticed. When the van is not acting up and I turn it on then back off it will hold 25lbs of fuel pressure.

When it is acting up and I turn it off it will not hold any fuel pressure. Even if I leave it off for a couple minutes it still will not hold fuel pressure.

After an extended period of time (hours or overnight) it will again hold 25lbs of fuel pressure when the key is off.

Also, I misspoke earlier. It is not backfiring it is popping back at the engine. I am not sure what you call that. Sorry for the confusion.

btw, I just rented (deposit/free) an Actron Super AutoScanner. I will read the manual today and post whatever data I can get out of it tonight.

Thanks for the suggestions,

Summarizing

Fuel/Ignition/Other? Please help

I have been trying to figure this out with no success. Can you guys take a look and offer any suggestions you might have?


Vehicle:
1995 CHEVROLET TRUCK ASTRO VAN
2WD Automatic Transmission
6 Cylinders 4.3L CPI
105,000 miles

Symptoms:
The van always starts and runs fine for at least a minute or two.
However after a short distance it will not accelerate properly and it will try to stall. As it progresses I might get some popping at the engine and eventually it will die. When I press the accelerator it acts like it wants to die.

It takes as much as 10 to 15 minutes of regular city driving to cause these symptoms or 2-3 minutes of driving under a load (when I hot-rod it). It does not seem to be directly related to engine temperature.

If the van completely dies, I can turn it off for 10 seconds then right back on and it definitely drives better (not completely normal). If I leave it off for 15 minutes it usually runs quite a bit better. Overnight and it runs normal when I first start it.

Parts Replaced:
Leaky CPI (spider)
Inlet outlet fuel lines (nut kit)
Fuel Filter
Fuel Pump and strainer
Exhaust from O2 sensor back
Drained the gas
Ignition coil
PCV Valve
Tune up (plugs,wires,cap,rotor)(6 months ago)
Oxygen sensor (6 months ago)


Current Diagnostic (I am a complete amateur so some/all items could be irrelevant)

EGR (sticking)
Tapping/ticking started after I removed/checked this. I am pretty sure I just need to take it off again and clean or replace. I do not believe this is my main problem because I took it off, closed the valve, and reinstalled without hooking it up. This test did not change any of the symptoms listed above.

Distributor
I just examined the distributor and one of the plug wires and probes on the distributor was severely corroded; the rest were fine. I will get a new cap and wire tonight and check the plug.

Fuel Pressure
Test with a fuel pressure gauge. After sitting overnight, turn key on and I get 62psi pressure (in spec). Turn key off and it holds 25psi pressure (there is no spec that I know of for this).
While running it never drops below 50psi (in spec) even when it is acting up. While it is acting up and I accelerate the needle will sweep between 50psi to 70psi very fast.
What concerns me is that after it is acting up and I turn the key off the fuel pressure instantly DROPS to 0psi. It this an issue?
If I let the van sit for two minutes and turn the key on (pump on) then back off again it will still drop to 0psi. If I let it sit overnight it will again hold 25psi of pressure with the key off.

Codes
The check engine light (service engine soon) does work, but does NOT turn on. I do not get any codes. To verify I rented an “Actron Super AutoScanner” and checked the codes. I do not get any.

I know I can monitor real time data with this device (scanner) but I do not know what to look for (suggestions?).



Do you guys have any suggestions on what to try next? I am about out of ideas and I am thinking about taking it to the shop. If/when I take it in, do you have and advice on what type of shop or diagnostic test I should ask them to run (or not to run)?

You replaced the fuel pump and strainer. Can you check the voltage going to the pump when it's acting up? Since you're seeing the FP flucuate during the bad periods, I wonder if the wires running to the fuel pump are overheating somehow and causing a voltage flucuation which then causes the FP to swing. Might start at the fuel pump relay to start with. Check your voltages there when the van is acting up...

Update.

I double checked my work on the CPI install and found a problem. One of the fuel lines was not all the way in and it was slowly leaking. I oiled (really helped) the lines up real good and made sure it was all the way in this time.

I gas fouled all the plugs so I have to change the plugs before I can let you guys know if that fixed it. Also, it is still bleeding off pressure with the key off. It has been going all the way down to 10psi.

My current guess is it is the pulsator since it was never replaced. From what I understand this might not cause problems after the van has been started.

I will try and change the plugs before work tomorrow and let you guys know . I might not get finished because it is not the easiest job on that van.

Pulsator? What and where is that?

I am not entirely sure what it does.

GM released a bulletin that says you are suppose to change it when you change your pump. It prevents pressure loss and quiets the pump.

As far as I can tell only AutoZone carries it.

Hmm.. So it must be in the tank then? Interesting.

www.autozone.com has a description of the pulsator in their repair link, in the "products and how to information". Look under "F" for fuel pump pulsator.

I finally got it fixed. I suspect it was the pulsator.
I ended up dropping the tank and replacing the pump, threw out the pulsator and replaced with fuel line, replaced the main gasket and a missing o-ring on one of the fuel lines to the tank. I am not sure if the o-ring was lost when I dropped the tank or some other time.

It runs great now. Thank you guys so much for all you help and suggestions!!!!!

Good to hear you got it fixed. I've never heard of the pulsator before.

Man, Dave gets the gold star for shear determination.