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Fuel system


Astroman's Avatar
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03-02-02, 12:32 AM   #1  
Astroman
Fuel system

My '94 Astro AWD 4.3 CPI has been idling erratically of late. I replaced the fuel pump in August of '01 when I was having cold start problems. It ran fine for a few weeks then it started to idle unevenly and will start when warm only after extended cranking with open throttle. A strong smell of fuel is present at start. When it's cold outside and the engine is cold it will usualy start right up like it is suppose to. If I shut it off it will usually start back up without throttle if it doesn't sit for more than fifteen minutes. When I replaced the fuel pump I did a pressure test, it was ok at 163 psi and seemed to be holding pressure. Does this sound like a stuck injector to you? What would you suggest I do?
I haven't done a pressure test since I replaced the pump mainly because I recently had back surgery. But things are getting better now and I should be able to start doing things again. Where would you suggest I go from here?

 
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03-02-02, 04:47 AM   #2  
Joe_F
163 psi would probably blow the lines to pieces . I think you mean 63psi.

Surging idle is usually dirt in the throttle body or a stuck idle air control valve. Your EGR valve could also have carbon hanging up the pintle....there are gaskets sold with a screen to "prevent" this.

The CPI injector is troublesome on these and yes, the pintle ends do get clogged up. If the injector is original, your problem is likely here (among other places) based on the trouble.

Check for any vacuum leaks as well. Do you get a check engine light?

 
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03-02-02, 11:14 AM   #3  
Astroman
Fuel system

Actualy, yes I do mean 163 psi maybe 161. When the original pump whent out it was only putting out about 145 psi which is low for this system.
I have had my check engine light go on not too long ago and its code refered to a EGR system problem. I removed the EGR valve and removed chunks of carbon from the pintle valve. After clearing the code it ran much better and the light hasn't come back. Would a fuel system problem trigger a trouble code? I havn't had one since the EGR incident.
What should I do to correct this condition?
If it turns out that it is a stuck or clogged poppet valve, can I fix this without disassembling the intake? Also, is it possible that I will be able to salvage the poppet valves or do they need to be replaced? My van has 148,350 miles on it but I have maintained it well. It otherwise runs good except for the hard start and erratic idle.

 
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03-02-02, 11:50 AM   #4  
Joe_F
I believe regulated fuel pressure is NO where near that, but if you say that, then sure.

A Ferrari doesn't have that kind of pressure and it's putting out over 500 HP .

A fuel systems issue will likely not trigger the check engine light, only a computer or sensor related problem will do that.

At this mileage, the poppets are likely clogged beyond cleaning. Pitch the injector for a new one (148k is great on one of these). Yes, you have take that whole schmere apart.

You can try runnng fuel injector cleaner through the rail/CPI assembly, but it's not likely to help much.

 
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03-02-02, 07:46 PM   #5  
Astroman
Fuel System

I feel rather ridiculous, you are absolutely correct about the fuel pressure. I decided I better look at my records again to refresh my memory, it was indeed 47 psi when I replaced the pump. 64 psi after I replaced it. Sorry for my brain cramp!
So you believe I would be improving the performance of the van by replacing the entire injection system, or just the poppets and tubbing? Is there a test I can perform on the fuel meter body before taking it out? As I understand, this system has no separate pressure regulator, the regulator is integrated with the meter body. All this, of course, assuming that another fuel pressure test detects a drop in static pressure correct?
I have heard that the injector assembly is about $350.00. I would like to have a pretty good feeling that it's bad before I invest in a new one. I have invested in a Fluke 88 resently, but I'm just starting to learn how to use it. Would that be of any help in troubleshooting this problem? Thank you for your help so far, you have already started my thought process in the right direction.

 
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03-03-02, 05:59 AM   #6  
Joe_F
This is a PITA type system .

Yes, the whole CPI assembly including the regulator comes as one piece. In later years, GM started servicing the regulator as another item.

What you buy is a thing that looks like an octopus. I think it's a bit cheaper than that through a parts store or an AC Delco outlet.

Usually the manifold fills up with fuel and the thing will puff black smoke. These early CPI injectors were troublesome.

Take it apart and see what you find. Check your fuel pressure again as well.

I suggest you pick up a repair manual for this to guide you through the diagnostic process. Try the links in my signature file for some ideas.

 
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05-03-02, 04:08 PM   #7  
Astroman
Just to update about this problem. I did replace the injector assembly as you suggested and the van has been running like new! Thank you for your help.

 
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05-03-02, 07:13 PM   #8  
Joe_F
Good to hear and good job!

 
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