First of all, I will admit that I am not the most knowledgeable about cars. I know enough to be dangerous - I can swap out alternaters, starters, etc., but that's about it.

1995 Astro minivan; 180,000 miles (I know, just get rid of the damned thing!)

When the gas tank is full, the car doesn't want to accelerate. Once it is down to 3/4 tank or so, it is fine. If I fill the tank up, it takes forever to get it moving from a standstill; if I'm moving and I hit the gas, the engine slows. I have to find that one place that is *just right* to get it to accelerate.

What could this be, and is it worth it for me to have it fixed (or could it be simple enough for me to fix?)

Thanks much.

Guess: This has (most everything does) an "evaporative emissions system" and when full of fuel it may be choking on raw gas somehow??

Try with the gas cap loose - it may behave. Then if that changes the problem we gotta find where system is screwing up. Canister to sort out fumes should be up front under hood and hoses back and forth - fumes are to be burned in intake is the idea. See what loose gas cap might do. Also be sure it's the correct gas cap as they are not all the same and very much a part of the evaporative emission system,

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

We've had the van for about 7 years, and this problem just came up in the last few weeks, so I doubt the gas cap is wrong (possible since we did buy it used). I did try loosening it, but the problem continues.

When I started having problems, I noticed that you gave it gas; the engine bogged down, but the problem came and went. Put in some Gummout to clean the injectors. No help. Thought it might be emissions - if the catalytic converter is clogged, it can do that. Needed a new muffler anyway, so I replaced CC on. No dice. Thought it might be fuel filter, but why then would it come and go? When I noticed it was only when the tank was full, that really told me it wasn't the fuel filter. Tried loosening the gas cap. Nope. Could it be water in the tank, but why wouldn't that be a bigger problem when the tank was empty? Just browsed the boards a little, and saw a post about the Fuel Pressure Regulator. Could that have gone bad? Logically, it sounds right to me. Like I said - I know enough to be dangerous, not enough to really know what I'm talking about.

What's interesting is this is sensitive to how full the tank is so I'm not thinking plugged converts or things like that. Fuel filter should just be up and replaced if not recently done. In line ones with flare nuts get real rusty and stuck so
you may want help to save a ton of headaches for what should be simple.

You're right about the fuel being low would be more of a problem if fuel was contaminated by something. I like Chevron's "Techron" as a fuel additive which may help better than what you already used and any can take a while to know if they helped at all if the do.

New fuel filter and old one drained into glass for inspection of what comes out would be helpful. Water is less likely but still possible or other junk that can stir up at the place you got fuel especialy if they were getting fuel while you were and perhaps something mixes up in tank when filled then settles down - hard to say so far.

When filter is known ok a fuel pressure test would be called for if problem persists and I don't know why that would care about the level of fuel in the tank??

This evaporative thing is a system to not allow the vapors on top of the fuel in tank to escape to the air. In that system probably lies the problem and I guessed that the cap was a maybe for a quick change at least. Even wrong caps not holding correct amounts of pressure and vacuum usually work well right after they've been loosened.

For now it's not a waste to put a new fuel filter in,

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/

First of all, I would like to thank you for your help and advise. Now, for the story of my odd-isy.

As I said before, I know just enough to be dangerous. I've got more and better tools than your average yuppie, but certainly nowhere near what a professional mechanic has. OK, fine. I'll change the fuel filter. The only time I have is Monday after a baseball practice (which, of course, runs late). Get the van up on blocks so I can get under it, start taking out the filter, which, of course, is pretty rusty. Get off the part by the tank easy enough. Other side ain't budging. Other side really isn't budging. Damn, now the bolt on the line is getting buggered up. Let's see if I can find my vice grips. After 20 minutes of looking, I finally figure out that my 8-year-old son "borrowed" them. Then it hits me - maybe it's not threaded backwards like I was assuming. Gee, it comes off much easier if I actually turn it the right way. D'oh! OK, get the new one on. Try to start it - it chugs away, but it's acting like it's getting no fuel. It's late; I'll take a day off work tuesday to look at it.

Tuesday morning, bright and early. Solid line from the filter towards the engine runs into a rubber line, and that was all kinds of bound up. After playing a bit, turning a lot, etc., finally got the filter on without the line being twisted. Tried to start - nothing. Maybe it needs to be running a bit to get fuel into the system. Chug. Chug. *GRIND*. Oh @%!#. *GRIND* whirrrrr. Starter goes. OK, that's something I can fix.

Starter changed easily enough. Try to start the car. Nothing. Call up my friendly professional (his kid plays on my T-ball team). "There's a valve for testing the fuel preasure under the doghouse; make sure you have something coming out." Do you know what it takes to get the !%!#ing doghouse off of this van? Two screws and two bolts to take off the front counsol; two more screws to take off a couple of braces; then two bolts that are about 15" back. Luckily, I do have enough extentions for my sockets to get those #$&ing things off. Finally, I can finally take the cover off. Damn. It's been a long time since the last tune up. Yeah, gas is coming out of the check valve, but I have no idea if it's enough. Call my mechanic. "Well, I go home for lunch. Let me bring my tester and we'll see." Puts the gage on. Long crank, only gets up to about 40. Preasure drops quickly. "I'm not sure what it needs to be, but you really need to do a tuneup anyway. Why don't you replace those plugs and the distributer cap / roter while I check what that preasure should be.

I hate cars. When I started driving, you had these land yachts that you could practically climb into the engine compartment to work on them. Now, they're trying to cram so much new and improved functionality into the engine compartment, while shrinking the size of the vehicles to conserve gas. I really hate minivans. Changing the plugs on the passenger's side wasn't too bad. There was almost 4" of clearance. I was able to get my large fat hands in there, around the plug wires, fight to pull them out with only minor nicks to my hands. By the way, is there a logical reason for them putting sharp edges on the holders for the wires? Or those shields right by the plugs? Anyway, on to the driver's side. Hmmm. Driver needs more room because of the gas pedal. So much for the 4" of clearance. I can get the front plug if I take off the wheel. OK, that one wasn't that bad. Now, let's get the other two.

I sit on my butt for a living. I work in an office. My exercise is coaching youth sports and mowing the lawn (and my oldest son is doing that for me now!). I can barely get my fingers in by the wires, much less get the leverage to pull them off. 40 minutes and a pint of blood later, I've finally got the last two changed out. Every direction I tried pulling, there was something behind my hand, or there was one of those wire brackets or or or or or.... My right hand looks like hamburger. Or, it would if it wasn't covered in grease. Changed distributer cap / roter. Not a big deal. I know enough to swap the wires one at a time so as not to mess up the firing order.

OK, now, after all of this, it had better start. Turn - CATCH - crank-crank-crank. Hey, it thought about catching. Crank-crank-crank-crank. Nothing. Give it a few minutes. Turn - CATCH - crank-crank-crank.Talk to my mechanic - "Oh, the preasure should be about 60. Let's get it towed in here and I'll run some tests." Well, he couldn't actually get to it until this morning. Yeah, it's the fuel pump - and the pulsator. Gonna cost me $500 - $600, depending on what else in the tank has tanked. The way the fuel preasure dropped quickly, the return valve is probably bad. The way it was acting (remember the original post?), I have a feeling there's going to be more bad in that tank.

Thank you for letting me rant about the engine compartment, and thank you again for your help and advise.

Site is really sponsored by Band -Aid! Sorry things are such a hassle - it goes with the territory. They do make a neat tool for plug wire boots and of course by design anything near them is sharpened to cause the most blood loss! And to think folks are sqeemish about donating blood - huh!

I worry about twisting up a rubber fuel line especially AFTER the fuel filter. From there it's on to injectors and we don't want any junk going that way!

I don't have the spec but GM fuel pressures should run higher than the 40 you read. Some are very fussy about that.

Good luck with the fix. Sounds like a lot of maintenance items are getting done in the course of this too,

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/