hello, my 91 4.3 is not starting. it hasnt been starting with a key since i bought it. we were told that it was the starter, so we replaced it and it still does not start. when you turn the key the lights on the gauges come on, the radio will turn on, and stuff like that, but it does nothing else at all. my friend thinks it is the ignition switch itself, but i am not sure if it is since it it letting the radio turn on and it is turning on the lights on the gauges. went to pep boys tonight and they sold me a piece for the ignition. its the piece that has the relays built in to it. where would this go? right now the only way to start it is by putting a wire from the batt to the solenoid. for some reason it wouldnt just let us jump the solenoid, but that might have been just an error on out part. if we cant fix this we will just install a toggle switch to start the truck. how many amps does that take? the largest toggle i know of is like a 30amp toggle. would that work? or does it take more? i actually think it would be pretty sweet to install a push button start, but i dont know how many amps those would hold. maybe i will just have to install a push button and a relay......

 

So. let me see if I get this right. You can actually get the car to run, but you have to run hot 12 volts to the solenoid, to make it turn over?

Path used to be from key to solenoid. Always hot supply at key connects to purple wire leaving key. A ckt in clutch (switch under dash on clutch pedal)) to make sure you push clutch in when starting, or ckt through contacts in auto shift selector to make sure you cant start car while in a drive gear.

A bad switch at clutch pedal is possible in stik shift model. Everything I apply at P/N sw below is also aplicable at this simple switch.

Best real start would be to check ignition switch wiring, but this may mean taking the steering wheel off. Thats the last thing I want to do.

I would start at a different point. Perhaps the Park/nuetral position switch and check the purple wire going to the solenoid pull in winding. Of course the wire itself may be bad at the starter also. If I wanted to check the starter connections, I would very carefully find them well before they reach the starter and check for 12 volts at a point where I could stay away from everything IF THE STARTER WERE TO ACTUALLY START WORKING???? See; the only way to check it is to set the ignition to start position with sojmeone holding it there and go to P?N sw. and wire going to solenoid.

If none of this gives you 12 volts, going to the ignition switch itself might be next. I would make an attempt to locate the correct wire at the location under the steering column where the wires enter the column. I remember there ought to be a purple wire, maybe yellow in later models, perhaps in yours. The right wire situation would be to find a hot at all times red one and a purple or yellow that becomes hot when key is moved to start position (not regular "RUN" position) I would be looking for same color wire that was at the P/N switch location. If this is the case, good for you. If not proceed anyway to P/N sw.

P/N sw. ought o have just two wires, one in and one out. If one is hot, odds are its the "IN" and the switch is malfuctioning. If one of these wires were yellow, it ought to be the hot one. If the other was purple, then the solenoid ought to have THE SAME PURPLE WIRE ON IT. If this wire were disconnected at either end it would not work either. Note. If one is hot, it (12 volt) has made it from the key in start position.

In my own case, being fairly sure about what I was looking at, or for, I might try to pass 12 volts past the P/N switch. This means I would BYPASS the switch. - I do this with an inline fuse of about 15 or 20 amp so that less will go wrong should I be completely wrong. To BYPASS this park nuetral switch is DANGEROUS. If you leave the car in gear and do this the car will proceed to run something over. I do not recommend this to anyone, I just do it myself. I do it with the full knowledge that the car is IN PARK or NUETRAL and the PARKING PRAKE is set. Of course, once again the ignition has to be placed to the START position. If you were working all by yourself, then you wouldnt run yourself over if you got in the car and did everything else wrong. When working with others, make sure they dont kill you.


All small print accounted for?

The right way is to use an ohm meter and check the switch itself for closing when going to the park or neutral position. Take off the plug and set meter to ohm scale. Insert leads of meter into plug, one wire to one terminal and other to second terminal. In park or neutral you should read continuity or NO resistance. The meter should go full scale to 00. I only use digital meters on modern cars. Damage can happen to computer or sensors with analog meters.

Man I hate all this small print.

Yes the igniton may be bad. It is the hardest item to replace. The Park/Neutral sw can be bad or out of adjustment. The wiring can be open anywhere along the way. I would do all else to pro

 

Have to add something. In the older chevy cars and trucks the "ALWAYS ON" power to supply the key had a distinctly treacherous path. I always thought so cause it was from a fusible link that was also located at the starter. If the starter wires were connected wrong, you could actually crank the car non stop as soon as the battery was hooked up. The solenoid would pull in and cranking would be nonstop as soon as the battery was connected.

BTW this path was needed "once upon an olden day' cause there were TWO terminals on the solenoid. One for (S) start and the other for a resistor supply to the run mode of the key. You dont have a need for the second wire any more. Make darn sure your purple? is hooked to "S" lead?

I have no idea if this ckt is still getting its basic power from the wire at the starter through a fusible link. But I would think that yours is hot because you seem to say that only the starting cycle is bad, not the running cycle. I believe this problem was corrected somewhere along in the 80's with better power distribution.

The ckt still has a possible one or even two fusible link situations in it. While you may not have seen it melt down, it easily could have. Check at starter. Check at back of Alternator.

Now I am really running out if ideas. I would have to plagerize after all this.

 

yeah, the truck starts right up when you jump the solenoid. but when you turn the key absolutely nothing happens. we replaced that part i talked about up there, it goes on the colum, and the same thing happens, absolutely nothing. i will look into the P/N switch, but i will not be replacing the ignition switch if its that much of a PITA. this is gunna be a 100% mud truck so it doesnt have to be pretty . but i do realise the danger behind running a toggle to start it. thanks for the posts as they are very informative. when im not so tired i will re read them over, that and when i am near the truck so i can remember all this, lol.

 

Muddin truck.
Install a push to start switch. Make sure the switch is not a flip to on, and flip to off type. You want the switch to work only when you are pushing it. You will still have to turn the key to on, then the push button switch to start. You could replace the ignistion switch completely, and install a swicth to on/off tpye switch to turn power on, then push the start button.

Personally, it sounds like the wrie running from teh ignistion switch to the starter has break in it. test it.

 

my buddy worked on it today while i was at work. he said that something had to be adjusted, that the key "didnt know" so to speak that it was in the START position. it starts with a key now . thanks guys

 

I was going to add this yesterday, but thought better of it, too much is too much. Would like to add this now though. Through the years, there have been models built of our cars, by GM that used the P/N switch and it position to indicate to the COMPUTER that the car was parked. This controlled certain ckts and having the P/N working in those models is a VERY important functin. The very way the car runs is affected.

I guess there is no need to get real explicit about the particular models and the wiring. Suffice it to say that on many//many cars out there the Park Nuetral Switch has some additional functions and should NEVER be jumped. Of course I have not looked to see if yours was in this class of vehicle or not. No need to now.

Just had to add this for the rest of the world and those tempted to overide that ckt without full information.