Fuel Pump???

My 1991 Astro has been "weak" for several months. Today when I tried to pass, it had no guts and refused to downshift so I really stood on it. This seemed to compound the problem as it started missing and idling very rough and became difficult to start. I suspected a fuel problem so tried the easy one first and replaced the fuel filter. This may have caused a slight improvement but so little it's hard to tell. Now I suspect the fuel pump. I do not have any pressure testing devices but am willing to spend a few $$ to get something to do the job. Any recommendations? But first, let me ask this: Should I have detected pressure in the system when I opened the line in removing the fuel filter? I removed the filter within about 20 minutes of shutting it off and there was no pressure there. Zip, nada, zilch.

Does anyone think this is a fuel pump problem or does my passing/downshift problem described above indicate something else?

Thanks.

P.S. I read all the posts out of the last 150 referring to similar type problems and saw a lot of possibilities but didn't get enough insight to solve this.

No one seems too interested in this so I'll add some info I've discovered.

I discovered by accident that removing the gas fill cap causes the vehicle to run better. Not perfect by any means but it stalls a lot less when accelerating. Furthermore, removing the gas cap causes it to be harder to start.

I hope this info piques someones interest. I'm not making too much progress on this. Thanks.

TWD

Okay, let me drop another possible clue. I drove this beast today over 25 miles at highway speeds. It was missing so badly I thought I might have a wheel coming off with all the shaking going on. About 1/2 hour later, I drove it back home the same distance at highway speeds once again and it ran fine. Never missed, never hesitated.

I'm even more stumped now. I changed the fuel filter, checked a plug for fouling, cleaned the throttle body and observed the injectors which looked good (according to what the guy in the auto parts store told me, nice consistent conical shaped spray). I also checked as many vacuum hoses as I could find. Can anyone help?

I'm tied up all weekend so won't be able to look at it again until Monday. Maybe it will miraculously heal itself. Nah.

Thanks.

TWD

i'm willing to bet a beer(maybe even a canadian one) that you have a plugged cat convertor. put a vacuum gage on the engine and see what it does if it goes way down it's plugged exhaust. or try unhooking the exhaust in front of the cat and going for a quick burn. there are checkvalves in the fuel pump that stop it from spraying fuel everywhere when you remove the filter usually it gives a little spray then drips if you don't relieve pressure. you whould get all the sensors checked too a bad tps, O2 sensor, maf or tps can cause problems like this. also check the tranny kick down cable(tv) it might be broken or misadjusted. check the egr too the 4.3L has been know to get deposits in the egr passages causing it to stick. good luck

Thanks for your advice earlier. I do think the cat converter is the problem. You would not believe the difference in how my van acts now. I'm working on the idle problem, but now at least I have power whenever I'm driving. I was totally amazed. I don't feel like I'm a sitting duck in traffic anymore. We've suspected a vaccum leak, but so far haven't been able to find one. Have you ever heard about a recall concerning alternators? I've put 2 on my van already in two years. Heard through the grapevine that recall was cause alternators from store weren't stout enough. Friend of mine rewired his van and put an alternator from a 350 on it. Thought he remembered a recall, but I haven't been able to find anything. I think we're gonna have to put another o2s on mine after running it with a stopped cat converter for a year or less. Good luck and keep us updated

i'm not aware of an alternator recall but there might be one. are you usung gm alternators? theres a few cheap jobber alternators that are junk!!!http://www.alldata.com/recalls/index.html

the link above has information about recalls and service bulletins might be some help. good luck

Thanks amac209. I'll add cat convertor to my list of things to check. I won't get back to working on the beast before late tomorrow or Tuesday. When I get this fixed, I'll post the solution here. And I'll take you up on the beer bet. In the meantime, I'm still interested in any other replies people might want to make.

I don't know how my thread ended up being a discussion on alternators. I've had 5-6 on this vehicle including two within a month last summer. I've also heard that they are weak and not up to heavy loads and heat. BUT, please confine this thread to the rough running problems I'm having on my 91 AWD with 236,700 miles.

Thanks to all.

TWD

After swapping everything except the kitchen sink, I'm going back to my original hypothesis that this is a fuel pump problem. I've checked just about everything else it could be. Today, I finally measured the fuel pressure and came up with a lousy 5 psi, which is about 1/3 of what it should be.

Unfortunately, I won't be able to drop the tank and replace the pump for another two weeks so won't know for absolutely positively sure until then. I'll post the results here at that time. (And I'll admit to being wrong if I am but I doubt that will be necessary.)

TWD

Boy did I chase my tail on this one. YES, IT WAS THE FUEL PUMP. My initial thought was fuel pump but I ended up trying just about everything else first. I finally got back to the fuel pump and now it runs like a new one. Which isn't saying much. I've got several tips on doing this replacement if anyone else is interested. These tips apply to an old rusty vehicle as well as a new one.

Here are a few.

If you suspect a fuel pump problem, invest in a pressure guage and check fuel pressure first before trying a zillion other things.

When you remove the straps holding the fuel tank, be careful about breaking or stripping or breaking weld nuts loose. Back them out a little and then hit them with WD40 (or equivilent) and then tighten them back up. Do this several times until they turn more freely.

After you drop the tank, dump at least a half can of liquid wrench on the cam locking ring and let it sit over night. It will come off much more easily if it soaks in this stuff for a while.

Good luck.

TWD