Last post on Feb 09, 2013 at 7:23 PM
You are in the Chevrolet Metro/Geo Metro
What is this discussion about?
Chevrolet Metro, Geo Metro, Fuel System, Convertible
#252 of 410 Re: 93 metro 1.0 no start [heavyhook]
Jun 11, 2010 (8:35 pm)
Thanks for the feedback. I'll try to clarify some of the points you brought up here. It sounds like we may be miscommunicating about the coil wires used to test for spark. Of course the primary (12 volt) feed must be connected between the coil and the electronics in the distributor (which take the place of the good old points and condenser) in order for dwell current to charge and discharge the coil. But I wasn't asking you to make any changes in the primary circuit. What I suggested was for you to disconnect the distributor cap end of the 7mm diameter high voltage wire that goes from the coil tower to the socket in the center of the distributor cap, and hold the distributor end of THAT wire close to ground. This wire is totally independent of the little primary wires that feed 12 volts to the coil to charge it. So the coil will still produce sparks during this test; just like it does when you disconnect one of the 7mm plug wires from a plug and hold it close to ground. The high voltage current from the coil does not need to pass through the distributor cap or rotor in order for the coil to be recharged. It is only the primary circuit's little, 12 volt colored wires and the low voltage electronics in the distributor (that substitute for the points and condenser), which are needed to charge the coil. If the primary circuit works; the coil will produce sparks; regardless of whether they go through the distributor cap or not. (If that was not true; the new cars that have an individual coil on each spark plug and no distributor would not be able to work; as their plug wire goes directly from the coil to the spark plug). It is important to understand that once the coil is charged by the primary current; it will jump a spark anywhere it is strong enough to go; regardless of whether it is a large or small gap. The spark has already been generated inside the coil; it does not depend on the size or routing of the gap in order for it to fire or to recharge. Please trust me on this; I have made a living as an auto electrical specialist for over 40 years, I also taught courses in engine theory at MMI in Orlando, FL, and I have been developing and refining my own electronic ignition circuit since about 1970. I also have owned a 1990 Geo Metro 1.0 since 1992. And I have answered over 1,900 questions on the Edmunds Answers forum in the last 18 months (where I am now ranked # 3 in the last 30 days). Sorry if that sounds like boasting; but my students repeatedly told me that electronics was the most difficult part of the course for them to understand; and I often had to correct misconceptions they had about electronics before they could gain a clear sense of what was going on.
The reason I wanted you to check for spark at the coil wire instead of the plug wire is that the distributor cap and rotor can sometimes ground out from a high voltage arc breaking down their insulation. If you bypass the cap and rotor; there is that much less chance of a defective external part messing up the test. Also; the timing belt can sometimes slip and still turn slowly; or even stop turning after you put the distributor cap back on. There are several other spark tests which can be made with the cap off; which may prove valuable in sorting out what is going on here.
You are correct in concluding that it must have been a high current arc which blew the fuse; and that most components would have lost smaller individual fuses if they had failed. Incidentally; the starter is not fused; since it normally draws as much as 100-150 amps, so it could not have been the item which blew the fuse. This pretty much leaves the alternator as the prime suspect. FYI, over the years, I have gotten so many defective rebuilds from O'Reilly that I absolutely refuse to buy any more rebuilt components from them. They apparently have the work done in Mexico by people who are told to not replace anything they don't have to. It is criminal to not replace bearings in alternators; no matter how good they may look. So, in order to remove one more unknown factor from this process, I request that you please disconnect both the power cable and the smaller plug from the alternator, and wrap or tape them up while doing the rest of the testing. If there is a NAPA store in your area; that is a much more reliable place to get rebuilt parts.
Regarding the distinction between auto repairs being an art or scence; 35 years ago, I would have become a rich man if I had a dollar for every carburetor that someone wrongfully condemned because they weren't able to figure out the difference between a fuel system and an ignition problem. About 90% of the car problems people would bring in to my shop were ones they believed to be fuel system problems; but when I tested and repaired the car; 90% of the problems which the people had reported actually turned out to be ignition problems. And about 90% of the carburetors I adjusted were previously set too rich; because excess richness is a great band aid for covering up improper ignition adjustments. So science was just as important to know in those days as it is today. But I will agree that the old low compression, mildly cammed motors are far more forgiving about tuning errors than todays precisely calibrated, low emission, fuel efficient motors.
#253 of 410 Re: Timming problems [zenden]
Jun 18, 2010 (6:03 pm)
Tried moving plugwires. Could not turn dist. far enough to get stated.
Had to move timing belt off one notch on cam gear to get unit started and timing
set. Engine still runs rough.
Need to find out how to set tp sensor on 95 GEO with upgraded emissions.
Sensor only has 3 wires in the plug. MOtor manual says to use a Tech 1
scantool and I don't have one.
I may also have another problem upon inspection of the intake I found the locknut
on the throttle is loose. I don't know if it has been messed with.
#254 of 410 Re: Timming problems [trmechan]
Jun 18, 2010 (9:19 pm)
You need no TECH 1 to set the TPS
With Key On Use .14 inch or 3.5 mm feeler gage between throttle stop screw and throttle lever;
If the idle speed control motor plunger is making contact with throttle lever screw, then you must bring Eng. up to normal operating temp so that it will not touch it. Then back probe the TPS with the feeler gage in place. The TPS has 3 wires, using a DC volt meter on low scale puncture the middle wire with your probe; hold it there and probe the outer 2 one at a time until you get your reading. TPS should read between .98 and 1.02 DC volts, if not adjust or replace it. A good TPS will smoothly increase in volts as you increase the throttle. let me know how it goes
#255 of 410 Re: Timming problems [trmechan]
Jun 18, 2010 (9:20 pm)
I don't want to interfere with Zenden's good and helpful advice; but I think you need to consider the following: The compression pressure in this motor must not be less than the minimum manufacturer's specification (it must be greater than 165 psi, and optimally at 195 psi). The compression may be low either because it has a non-stock camshaft, or the camshaft timing has been altered by the use of an offset keyway, or because the head is cracked, warped or the valves are not seating properly. If that is the case, then there is no way that it can be made to run smoothly or properly. In that situation; trying to readjust the TPS or the idle air bypass, or the throttle stop will just throw you into a bottomless pit where it keeps running worse and worse despite everything you do. So please run a compression test BEFORE changing any of the engine adjustments. That will save you all kinds of grief.
#256 of 410 Re: Timming problems [zenden]
Jun 19, 2010 (6:27 am)
It sounds like you may need this info. There are two types of upper timming sprockets; the solid type and the 5 spoked type. This is how to alingning the common 5 spoked type.
The (Crankshaft) woodruff key will be at 12:00 ; this will make the lower marks line up.
The (Camshaft) has a alingment pin sticking out, it will be at 6:00 o'clock then put the cam sprocket on; ( it has two slots coming out from the center hole ) when alingment is correct the slots will be pointing toward 1:00 o'clock and 6:00 0'clock ( NOT at 6:00 and 11:00) . Now all timing mark will line up; both will point upwards. This info is correct for any GEO's with a 5 spoked type cam sprocket..
#257 of 410 Re: Timming problems [zaken1]
Jun 19, 2010 (11:37 am)
I can use any information I can get. I got the car from a friend, with a blown headgasket. He had tried to get the car running but couldn't find the problem.
I checked it for him and told him the headgasket was bad. He didn't want to mess with it any more. So I bought the car from him and changed the head gasket, had the valves ground, and head surfaced. Put it together and couldn't get it to start without removing the bolts from the distributor and turning the dist. beyond its limits. The only way to get is started within dist. limits was to move the timing belt off by one notch. The compression is about 180psi on all cyl.
The biggest problem I am running into now is trying to get things back to where they are suppost to be. From talking to previous owner I now know that he played with the idle screw, tp sensor, ign timming, cam timming, and idle control.
So I have my work cut out for me.
#258 of 410 Re: Timming problems [zenden]
Jun 19, 2010 (11:50 am)
I Researched cam timming, and did have the timming set correct until know. I don't know why I have to move the cam back one notch, unless their is a computer problem. Thanks for conferming the correct setting anything is in question right now.
#259 of 410 Re: Timming problems [trmechan]
Jun 19, 2010 (2:02 pm)
There are two different types of distributors which were used on the 1.0 motor. The 1989-1991 motors used a distributor with a dual diaphragm vacuum advance unit that had 2 vacuum hoses; the auxiliary advance diaphragm (outer hose on the distributor) was connected to a spigot on the cyl # 1 intake manifold runner, and the main advance diaphragm (inner hose on the distributor) was connected to the center spigot of the three spigots on the lower front edge of the throttle body. Later model throttle bodies (on engines that did not have vacuum advance distributors) only had 2 vacuum spigots; the one closer to the passenger side is used for the EGR system; while the one closer to the driver's side is used for the vapor purge cannister.
The 1992 and later models used a distributor which does not have vacuum advance, and instead has an electronic advance circuit. With this distributor; the vacuum spigot on the # 1 cylinder intake runner should be capped off, and if there are three vacuum spigots on the throttle body; the center one should be capped.
In this situation, I would first make sure the timing notch on your crankshaft pulley is really at TDC. That can be done by lining up the pulley notch with TDC on the degree scale on the timing cover. Then pull the spark plug in # 1 cylinder, insert a 1/4" rod into the plug opening, and rock the crank pulley in both directions while holding the rod; to see if the piston comes up any further than where it was when the timing marks were lined up. If the timing marks are true; you can trust them for use in further tests. But if the marks are not correct; the pulley may be the wrong model; or the Woodruff key may be missing or broken. If the key is not in place; the mark may be able to move around, which would make it impossible to set the timing accurately enough to tune the rest of the settings. So you'd need to fix that issue before going further.
I'm going to give you a little more information here, but please do not apply it until you've gotten the timing marks to be trustworthy.
Have you tried connecting a timing light to # 1 cylinder, and seeing where the timing is when the engine is idling as slow as possible (with any vacuum hoses disconnected from the distributor and plugged). If your motor has the electronic advance distributor, the check connector terminals next to the firewall on the driver's side should be shorted together with a jumper wire or a paper clip to disable the electronic advance circuit, before checking the timing. The stock ignition timing on the 1.0 motor is 6 degrees BTDC 750 RPM or less.
The normal plug wire positions are; the # 1 cylinder (closest to the fan belt) plug wire is at 12 o'clock on the distributor cap. The # 3 cylinder (closest to the distributor) plug wire is at 8 o'clock on the cap. And the # 2 cylinder (center cylinder) plug wire is at 4 o'clock on the cap. The distributor rotor rotates counter-clockwise.
If you've checked and applied all the above information; and the motor still does not run with the distributor set in the normal range; see where the ignition timing now runs best when checked with a strobe timing light. If it is advanced a lot (notch on the pulley is further to the left than the stock setting on the degree scale) from the stock setting; then move the timing belt back to the stock setting, and try moving all the plug wires one position clockwise in the cap, and then turn the distributor back to the stock range. See if it now runs well like that.
But with the timing belt still set one tooth off; if the motor now runs best when the ignition timing is very retarded from the stock setting (mark on the pulley is located to the right on the degree scale from the stock mark); set the timing belt back to the stock position, and move the plug wires one position counterclockwise on the distributor cap, and then turn the distributor back to the stock range. See if it now runs well like that.
Let me know how it all turns out.
#260 of 410 Re: Timming problems [zenden]
Jun 21, 2010 (12:53 pm)
For Zenden and Zaken1 I think I found the problem. Will checking cam timming once again, and checking timming marks on crankshaft I found that the key for the crank gear was broken. Both the gear and the crank are badly worn from the key working around. Know I will have to decide what to do with the vehical.
Fix or Junk.
Thanks to both of you for your very good and experienced help.
#261 of 410 engine decreasses rpm and stop
Jul 20, 2010 (10:15 pm)
I have a Chevrolet Geo Metro sedane, 1,3 ltr, 1997 and I have this problem :
Sometime when outside is very hot, durring the summer time, and I drive slowly(trafic) the rpm decreases and the engine stop. When I start again the engine, that run perfect another 30 seconds and after this the problem start again. My mechanic scan the engine and find evrything perfect. No Error code. I already chek the EGR valve, the catalizator and the IDLE control solenoid, and all this is perfect.
Can somebody help me, please?