1991 S-15 Jimmy; No Start

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Old 09-01-18, 05:04 PM
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1991 S-15 Jimmy; No Start

1991 S-15 Jimmy has never acted up before. It sits at camp most of the time and only gets several hundred miles per year. Started right up, ran for a few seconds then ran rough and died. I checked the distributor cap for moisture and cracks, saw none, sprayed ether in the air filter and no attempt to start, attached spark tester and get an orange colored spark in the tester. Checked tester on lawn mower and lawn mower gives less glow than the the Jimmy. Checked ECM fuse and it appears good. What do I check next?

Thanks,
Mark
 
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Old 09-01-18, 09:13 PM
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sounds like probably not getting fuel would probably try the starting fluid again and remove the air cleaner and spray a little down the throttle body see if it will start, if it does run for a few seconds you can check for fuel pressure if you have pressure then check for injector pulse.
 
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Old 09-01-18, 10:23 PM
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When you turn the key to ignition on...... you should hear the electric fuel pump run for 3-10 seconds. The pump should be in the tank so it would be easier to test with two people. My guess is the pump froze from lack of use and age.
 
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Old 09-02-18, 07:14 AM
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Fuel pump is in the tank IIRC, can I crack a line up at the valve body to verify a problem? And where is the filter located (in case I can find it).
 
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Old 09-02-18, 07:43 AM
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OK, pump runs and gas comes out of the line at the valve body. How strong should that spark show in the tester? Is it possible to have a weak spark with this thing?
 
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Old 09-02-18, 07:57 AM
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Whatever produces your spark high voltage is not working right.
Also, after that many attempts to start, plugs are fouled with gas and you do not have good spark anyway.
Take plugs to butane torch and burn tips white hot.
If you have good spark+fuel+air, it's timing. If it started, ran well then bogged and died, I'd go for timing check.
 
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Old 09-02-18, 08:33 AM
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Any hints on what socket fits the spark plugs? I'm have to work in the blind on them and can't seem to get one seated.
 
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Old 09-02-18, 08:50 AM
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should be 5/8 in size, have you looked down the throttle body to see if the injectors are spraying fuel?
 
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Old 09-02-18, 08:58 AM
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Did you put some fresh gas in recently?
 
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Old 09-02-18, 09:17 AM
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Have not looked down the throttle body, don't know anything about this system but I will check on that. I have sprayed ether and get no kick out of it. Yes, put fresh gas in it a couple of weeks ago when I moved it out of the garage, also left it run and warm up and all worked well. And added more fresh before I started it. The gas that comes out of the cracked open line does not smell like turpentine.
 
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Old 09-02-18, 09:29 AM
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the spark should be plenty capable of jumping a 1/4 inch gap at a plug wire if it doesn't it could be weak due to a bad coil or coil wire but the coils did not fail very often, since you did put gas in recently may want to take a sample place in a jar and see if you have any separation witch would indicate water in the fuel.
 
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Old 09-03-18, 07:56 AM
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Old 09-24-18, 04:47 PM
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OK, here's where it stands today. I had a rough time getting one of the spark plugs out and some other projects kept me busy. One spark plug I needed to use an easy out on but I got it. I replaced cap, rotor, wires and plugs and added five gallons of fresh gas to the couple that were in there to dilute bad gas if that is an issue. It does start but runs erratically, smooth sometimes, rough others and cuts off after about three minutes. The service engine soon light illuminates intermittently and seems to light up when the engine is running the best then stops when it runs rough. It will start back up after it cools off for a couple of hours. I did order an OBD I tester for it but it's not here yet.

Thanks for any help.
 
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Old 09-25-18, 02:59 AM
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really only need a paperclip or jumper wire to get codes out of older gm vehicles jumper a and b terminals on the diagnostic connector.
https://www.obd-codes.com/faq/read-g...codes-free.php
 
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Old 09-25-18, 10:32 AM
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OK, I've got some more data. It starts right up when cold and runs like a champ for about three minutes then cuts out. I checked the exh manifolds with the IR thermometer and the right bank reads around 240 but the left bank reads in the 70's (I did try restarting it before shooting the manifolds). I don't believe that it has the capability of cutting spark on one bank so I'm suspecting the fuel injection system somehow.
 
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Old 09-25-18, 12:40 PM
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And another update: I have the throttle body exposed and started it up. The two things up top, I guess they're injectors spray what looks like an equal amount of fuel and it's consistent. Open the throttle and it revs. The, suddenly it makes a bigger sucking sound like a choke is activated or something and it stalls and won't restart. All cylinders yield similar temps with the IR thermometer.
 
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Old 09-27-18, 09:32 AM
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OK, jumped the OBD connector and got a water temp sensor error. Replaced the sensor that feeds the ECM and all is back to normal.

Thanks for the help.
 
 

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