Help GMC AWD Safari dome light/mileage problem

I just bought a used 94 Safari van. The problem I am having is with the dome light. The lights will not turn on with both of the front doors. The rear and side doors turn the light
on with no problem. The switch on the dash also turns them on. The slider switch on the top center dash also works fine when in the off position the lights do not come on with the rear doors. When I leave the key in the ignition the key buzzer works telling me that the door switches are fine. I suspect that the front doors used to activate a interior light timer ( don't know because I bought it used) Does anyone know where the timer is and what it looks like.
Also I can only get about ten miles to the gallon in the city and fifteen on the hiway. The exhaust smells like an old sixties car. (very strong no pollutin control) I have changed spark plugs, dist cap, rotor, air filter, advanced timing 2 degrees, repaired leaking vacuum hoses etc. There are no stored codes. I removed the six wire EGR and it seems fine moves free and not clogged. I can hear it click open and close when I play with the throttle with the engine cover off. It has very good starting a smooth idle and lots of power. Before doing all the above repairs the mileage was about 30 percent worse. With no code what would be a good guess of parts to replace to get it to smell less rich. There is no rotten egg smell and good power so I don't suspect the catalytic converter as I was told. Could the o2 or other sensor's be out of range just enough to give no code but make it burn ritch? It has 205 km on it. I doubt that any sensors have ever been replaced based on the paper work from the previous owner. Would the o2 sensor at $100.00 be a good guess? The EGR control valve is $450.00 so I would block it before I guesed on that part. Where can I find info to check these sensors with a VOM. Ok to email direct thanks in advance.
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The door jamb switches contain multiple contacts for the dome light/key buzzer. The key buzzer contacts can be working fine while the dome light contacts are not. Bad assumption.


If yours is a Vortec engine, the first thing to suspect is a faulty CPI unit, including a failed fuel pressure regulator and/or the plastic fuel lines that are internal to the manifold. Checking the fuel trim numbers on a scan tool is a very effective method for determining whether there is a problem with the CPI. You can remove the tuning valve from the top of the upper plenum and take a look at the inside of the manifold, anything looking like it's been washed clean is sufficient proof that there is an internal fuel leak in the manifold.
Just did a CPI and nut kit on a 92 S-10 Blazer this morning, there was a puddle of gasoline about 3 inches deep in the bottom of the intake manifold...
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Update :I took off the kik panels today. On the drivers side the light wire was broken off easy fix. On the passenger side the wire was melted easy fix. The lights are now working. Yes I have the Vortec W in serial # but what does CPI stand for? Is it the round black thing in the middle of the intake? What does it invole to fix this fuel leak?
Neil Nelson wrote:

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I tryed to remove the tuning valve to take a look but it wont come out. Is the tuning valve that black plastic round thing with wires in the top rear of the intake?
Neil Nelson wrote:

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Yup, that's it.
Remove the two Torx head screws and give it a gentle twist, back and forth. It's just a gooed up O-ring holding it back.
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Hey thanks for your help I got the tuning valve out. I then discovered that it was seized. You can tell that it has not moved in years by the marks on the flapper. I was able to free it up with wd40 and few got smack with a wrench while holding the flapper. I put it back in and took a test drive. I can tell that it flips over under hard execration. How mush difference would this have on my mileage if any? I don't expect much difference it seems to be needed only when I am flooring it. I cant see an obvious fuel leaks inside because of it being a van. From what I can see there are a few slight clean spots so if there are any leaks they are minor. I got a quote today for a new CPI assembly for $517 CDN. plus gst. I sure hopes this helps the mileage and the smelly exhaust. How many kms can one expect from these vans on average any ways? I get about 400 kms per tank and about 300 kms when towing 2000 lbs of trailer. Neil Nelson wrote:

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How many kms can one expect from these vans on average any

Hey guys I gotta comment on this one . I'm a previous and present chevy astro owner/ safari is the same Van . My older 1992 astro with 379,000 Km's still running strong still get 750 km per tank/ summer/ plus or minus 100km winter driving . No load or trailer with a 102 litre fuel tank. Here's the real kicker that has got me into a battle with GM. My 2003 astro with 35,000kms. gets 535km average per (same size) fuel tank no load or trailer. Where did 215 km of fuel go to!! I'd appreciate hearing from other safari/astro owners as to their gas milage. My mechanic laughs as says its because its not loose yet??!! Ok but do I have to wait that long ???
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UPDATE: 5 hours a six pack and $708.00 CDN. in parts. I put in a new CPI unit that came with two O rings for the fuel lines ( orig AC Delco). When I first fired it up it still smelled very rich untill I took it for a 20 minute blast. I can now stand beside the exhaust pipe without chocking. I still think it could be better though. I will just have to burn a tank or two to see what the killomage is and I will let you all know. Darn thing is sure running sweet not a ripple at idle and much smother at lite exceleration and no differant when I am flooring it ( allways was good when I floored it). Just one big question what does the fuel tuning valve do to fuel/performance. I am asking because that was siezed for some time. Now how will I never know what made the most improvement? 1234 wrote:

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Damn, I wish I'd have seen your post from Monday -before- you spent money on parts, I could have steered you to a company that sells completely remanufactured CPI units for way less than you paid, assuming you could afford to wait for it to be shipped.
The stuck tuning valve shouldn't/wouldn't cause a problem with fuel mileage, it's there to change the ram length of the intake manifold, so it's only effects are in the amount of torque the engine is able to produce under various load conditions.
Believe me, the improvements came from the new CPI, they're -that- trouble prone.
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Thanks any way on the offer for rebuilt parts. I did a little research and because of the labor involved I choose OEM. I did find a jobber that was selling a new one for three hundred less but I still choose OEM. I just got back from a 200km towing trip. just by looking at the gauge it looked like I got very good mileage on the way there but terrible on the way back. But still better than before. I am still not happy with the smell of the tail pipe it is better but still a little strong. What bugs me is that I might as well go with a full sized truck with a V8.
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