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GMC Safari/Chevy Astro Starting/Stalling/Idling Problems



  • I'm surprised by the Autozone, I apologize for recommending them, I had ignition checked on an HEI distributor years ago, but it may have been another store, they have changed names of the stores around here. Discount is now Advanced and One-Stop is now Bumper to Bumper. I called the Autozone here in St Pete and they said they can only test the module, it has two screws, you take out the module and take it to them and they can test it. I would do that, and then test the magnet at the pickup coil. If the magnet gets weak, it can make the fire weak. You can lightly touch a small metal screwdriver blade to the poles pieces and feel for magnetisum. As far as testing the spark output voltage, the easiest way to do that is by "drawing an arc" like I desctibed before. The longer the arc, the higher the voltage, but be sure to have the battery charger on the battery when you are cranking the engine, because low battery volts will make low spark volts. I would think that if you can draw out an arc an inch or longer while cranking the engine, that should be good. A rough rule of thumb is the voltage is about 10,000 volts for every quarter inch. So a one inch arc should be about 40,000 volts.

    About your question: "The testing of the voltage of the ignition module has me confused No 4"Check volts at "+" and "C" and should I probe both together or probe one and apply the other lead to ground?"

    Your question is about Figure 12 steps 3 and 4. If you look in FIGURE 11, it gives you the answer. Those + and C wires go from the module to each side of the coil. The coil is fed "Hot" from the ignition switch and that same connection goes to one side of the coil and also to the "+" wire. Therefore the "Hot" wire from the switch feeds one side of the ignition coil and also the "+" wire, which feeds power into the module. This means the "+" wire should always show power when the ignition is on, I would assume it should be near battery voltage. The test says it should read above 10 volts, with the connector unpluged, measure from the "+" to ground with the key on for your reading.
    The "C" wire goes from the module to the other side of the coil from the power connection. This tells me that this is the wire that "Fires" the coil, by electronicly grounding at the instant the coil is suppose to fire. Everytime this wire grounds and then opens, it lets current flow through the primary of the coil, the coil builds up a magnetic field, then the instant the wire is opened (switched) by the module, the magnetic field around the coil collapses and creates the high voltage in the secondary coil. The module is an electronic switch that switches the "C" wire to ground On and Off. So to test the "C" wire, with the ignition on and the connector unpluged measure from the "C" wire to ground with the key on for your reading. The test says it should be over 10 volts. The voltage you are reading is what is coming through the primary winding of the coil. With no load on the circuit, the voltage you read should be the same or very close to the voltage you read on the "+" wire.

    What you are calling in fig 13, step 5 is step 4. Connect a 12 volt test light between the Tach Terminal and ground. The Tach terminal is exactly the same connection as the "C" wire, the "load" side of the coil. They call for the light to be steady when you crank the engine, to verify that there is no votlage drop across the primary coil as it is firing. If there IS blinking of the light, that means the primary has voltage drop everytime it has load placed on it, which means the coil is bad. An ordinary 12 volt test light will work for this, the most common electrical tool that there is.

    About the serpentine belt, the belt on my 97 used to make noise and would slip a little when it got wet, yet it looked ok. I put on a new belt, the the difference was like night and day, it's been perfect now for 4 years, no noise, no slip.

    Good Luck,
    E.D. ISF
  • Well: I went through the guidelines in fig 13(fig 11 is for the 4cylinder) and approached from a "no spark" as oppossed to low spark because in box No.1 it says..."a few sparks and then nothing is considered no spark." Got a big spark from the ignition coil even with insulated tools. Reolaced rotor that was cracked. Got more than 10 volts from "c" and "+" but got 1-10 with tach lead to ground which indicates to replace module. Well I took your advice and had mine checked and it passed so I'm thinking maybe passing still does not mean able to do its job fully but I regreased mine...frustratted at this point and thinking of just getting a new distributor but I continued to put the parts back to gether and redo some of the tests. Specifically the crank test in step 4 fig 13 and the engine sounded like it wanted to turn over. I hooked all the wires back up and doggone if it didn't start. Purring like a kitten. God only knows cause I don't.
    Now mind you I had started pulling wires off to take off the intake plenum so it ran with the TPS and MAP sensors disconnected and I think it caused some codes; the Chk engine light is on now so I hooked them back up but the light is still on. I'll watch this. I did have a couple of plug wires crossed and after rearranging them the engine smoothed out. The saga continues but for now I see a bit of light....Thanks so much to you my friend. Oh; got a drive belt for the wifes' V8 Explorer.
  • Figure 11 is for the 4 cylinder engine, but the electrical drawing is the same, the pickup, module and coil and wiring is basicly the same for all of them.
    I know why the engine started, it's because of one of two things:
    1. either because you replaced the cracked rotor (it could have been leaking off the high voltage)
    2. or removing the module and replacing it could have cleaned and refreshed it's connections (it could have had resistance or corrosion in the connections to the module).
    Wow, So ends the Saga of the GMC Safari Van that wouldn't start! That was quite a lot to go through to find that problem, as we have been at this for over a week it seems? I'm glad the effort paid off, I was sure it would start, I was just hoping it would start before Christmas, So let this be a Christmas present to you! Stay in touch.
    Merry Christmas & Happy New Year,
    from Electric Designer In Sunny Florida
  • I would agree that refreshing the connections make sense because out of habit a cleaned them a little with a screwdriver before putting it back together. The cracked rotor also as well possible.
    Wow is right but I sure learned a lot and goes to show two heads are better than one. I need to do a top end clean of this van but I am glad you suggested I hold off on the fuel investigation. I am hoping that by having the intake and throttle body extension off while running the engine is what gave those TPS and MAP sensor codes and that once I get everything put back together they should reset. I'll check those circuits anywaay just to be sure.
    Hows your residential electrical? I get the idea you're an electrician. I need to install a couple of outlets in the new basement. Do they have a forum for that? I if not.
    Happy Holidays to you and yours!!
  • Your Welcome and Merry Christmas
  • i have a 95 safari that just quit. it will turn over but wont start. replaced the feul pump and steering column checked the fuses and pump relay. now for the funny part everything works execpt for the fuel pump head lights and interior lights. did a test on the wiring at the back of the fuse block and found that a fuseable link wire was testing as grounded. if i jump power to the fuel pump fuse it will start any ideas would be nice as it is my grandparents van and they are handicapped thanx
  • That fuseasble link is testing as grounded because it IS connected to GROUND THROUGH THE LOAD. The problem is you have lost your SOURCE of POWER to that FUSEABEL LINK. Go back to THAT point and toubleshoot from THAT point, UPSTREAM towards the BATTERY and you WILL find your problem. Being that all the lights are out and the fuel pump is out, the problem must be at a major connection towards the battery, and because this fuseable link carries so much load, it must be electrically near the battery, drawingwise. In other words, the fuseable link is usually connected very close to the battery, so you must be close to finding the problem.
    Good Luck,
    E.D. In Sunny and Warm Florida
  • i'm having the same problem, and i replaced the fuel pump and fuel relay and fuel filter, but when i replaced the fuel pump it ran for 1 day and now won't start any suggestions?
  • I have a 1990 astro with the exact same problem I have carbon cleaned,changed the fuel filter,fuel relay,temp.control valve,injector cleaner I can't figure it out have recieved any advice? :confuse:
  • Happy New Year! well the van came in handy moving and as such I am still in the mode of unpacking . The van broke again on the last mode. I thought it was "skipping" and my first thought was the distributor was somehow not aligned properly(I removed it to check it during the last diagnostic...wish I hadn't now. It was marked and seemed to align back up to the marks I had for guidance and it crank? ) but if so it would not have crank at I correct? Nevertheless the OBD1 showed TPC(throttle position sensor), MAP and IAC sensor codes. Both the MAP and IAC sensors have been manually cleaned and were chunk full of deposits and thus it still broke again. Does it appear as I should start changing out these sensors or does it appear that something in the timing may be the culprit..your thoughts as always appreciated.
  • Forgive me but I am a female and I may not know what some things are called but I do work on my cars. I had the same problem. First the altenator went and killed the battery. Replaced both. Simple enough. Then a few days later it completely stopped. The battery was low and I had to continuously charge the battery. Then finally no gas. Changed the fuel filter, the fuel relay, and finally the whole sending unit. Still no gas. Decided to look at the carburetor. I took some hoses and lines off to get to the carburetor. I could physically see that there was no gas going to the carburetor. I could feed it starting fluid it would start then die. So it sat in the driveway. Three months one of my other Chevy's lost the driveshaft. So I started working on the 11994 Chevy Astro. There is another module next to the fuel relay, upon inspecting it, there was very little power, replaced that. Also, on the cap of the fuel tank where the wires go to the sending unit, I had pulled one off, okay I pried it off with a screw driver. It was yellow, i had reattached it the wrong way. After all that, I finally heard the fuel pump humm. So now it is working, but I have some other issues. I had taken some lines off from the carburetor cover. Its a cirle piece and there is a line behind it CAN ANYONE TELL ME WHERE THIS LINE GOES?????
  • Also, what is it called?
  • Fuel punps range around 25.00 dollars for your vehicle?
  • What do you mean leaking gas down the exhaust?
    You might have a gas line that is leaking inside the top intake cover. It is comon on all safari's. Aroung 250 in labor.
  • Does any one knows how to get compression on all cylinders without taking it to the shop? Any special liquids?
  • my 1998 astro van was fine when i went to work then that night, i went to go home and poof! it hasnt worked since. we got it home the next day but then it was towed to a auto parts store in town. they replaced the fuel pump and filter for a small (HA!) price and it still didnt work. they then replaced the ignition control module saying they go bad in astros and today we found out that didnt work. we want to know if anyone has had this problem and what you did to get it corrected & how much. the van has over 150,000 miles on it.the parts shop said it is in the scurity system somewhere they think but they dont know for sure. they do not have the equipment to test it and see what is wrong and where. ANY HELP IS GREATLY APPRECIATED!!!
  • my idle on my astro van 1995 is so rough when i am stopped at the light it turns off sometimes and when it is parked it is also very rough, i do not know what to do but when it is moving it is very smooth. can some one please help thank you
  • First off get the van out of that shop ASAP and do not pay them a dime as they have not fixed anything. They are just throwing parts at it until it starts. This method will cost you big time.

    Step one is it not getting fuel ? Or is it no Spark ? An easy way to test is will the van run on ether (staring fluid). If it runs then the problem is no Fuel. If it doesn't then it is spark.
  • I have the same problems. Whenever it's damp outside, the van will not start. I have brought it to the mechanics several times and still have not figured out the problem. As I can see, this is a problem with the safaris and the astro vans. Has anyone been able to diagnose the problem?
    If so, please respond because I have 4 kids and I need my van!
  • jateegeejateegee Posts: 1
    Okay, I'll try to keep this short, but i dont want to leave anything out.
    93 Safari Engine Code Z. Bought for four hundred bucks 2 years ago, never laid down on me till last wednesday. best vehicle i have ever had.

    Stalling at idle and low revs

    It just quit on the way too work. Pulled over, looked for obvious under the hood. Nothing. Magically it restarted. I drove to work. That day on the way home, it quit. Did not restart. Got a ride home. The next day i went back to where I left it. this was 12 hours later. it started. I drove it back to work and left it in the heated garage. i will mention that temps have been just around the freezing mark, but this seems to have no bearing on it. At work I park in a heated garage where temps are around 60f. At home I park outside. I removed the doghouse, spent the afternoon poking around. Never started. Not once. This was after I drove it back to work that morning. The next day, I brought my mechanic friend in. He figured it was the fuel pump. It only seemed to prime intermittently, and the the mallet on the gas tank trick didn't really work. I had it towed home. Luckily i have a large shop where i live. Assuming it was the pump. I proceeded to remove and replace the pump, sending unit, tank (I had a brand new one laying around) and the filter. Yippee!! All done!! Its starts!! yahoo!! STALL!!
    Next. Now it wont start again. I then proceeded to flight test some of my tools. Hmmmmm. Having a closer look, we noticed no fuel spray at all from the injectors when the starter is engaged. OK. Check the voltage. I have 12V at the injectors, but no pulse. I do not have a noid light but i dont think i need one. We unplugged the idle air controller. BAM!! it starts, runs, does not stall. Let the engine get good and hot, plug the IAC back in, idles down real smooth and nice. now it will restart when i Shut it off with the IAC plugged in (I should mention I had a recent oil change, new plugs, cap and rotor. And the van has been exhibiting these symptoms of stalling for a few weeks before any of that, or the fuel system work was done.)
    So i had a used IAC. Tried that, seemed to work for a bit but in the end it still is stalling. My buddy works at a GM dealer, so he orderd me a new one. I drove to his place of employment this morning onmy way to work to pick up the new IAC. By then, the engine is good and hot. I put the part in right there. Idles down nice and low drove the LONG way to work. About a half hour. Never stalled once. I went out to the garage several times today and it started every time. Five oclock i got to leave. Start, reverse, STALL.
    Tom the security gaurd, was watching. He found it rather amusing. I didnt, I lost it. I unplugged the IAC started it, left a strip of rubber about forty feet long in our newly surfaced indoor parking garage, said a bunch of things to Tom that even going to church would never excuse. Boy, am I ever gonna have to apoligize to him tommorow. Yikes. I dont think I have a vaccum leak either, not totally sure, but I left the van over night on the weekend, and first thing I did in the morning before trying to start i was to unplug one of the hoses (small one) from the cruise control servo. It was holding there any way.
    I was starting to think this was a hot/cold engine problem but it doesnt seem to matter wether the engine is hot or cold.
    Someone help.
    I just had a brainstorm. Do i need to unplug the ecm fuses inorder to clear any fault codes before the ecm will recognize the new IAC? I do not have a scanner, just the little metal key. Is there any web pages that give you what the engine ligh flashing sequences are?
    :confuse: :mad: :sick: :lemon:
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