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1993 chevy 350 tbi issues

10K views 64 replies 9 participants last post by  Hogg 
#1 ·
I'm sorry if this is double posted. I tried posting earlier but idk if it stuck or not cause I had bad service so I wanna try again.

I have a 1993 chevy k 1500 4 wd with the 350 (or so I was told). When I first bought it the truck wouldn't even crank. It was/possibly still is having/had flooding issues. So I replaced

IAC(and connector. Spliced wires)
Throttle Position Sensor
Fuel pressure regulator
MAP Sensor (the small hose is easy to undo)
Plugs (fouled need to replace...again)
Coolant Temp Sensor (and connectors. Spliced the wires)

Once I replaced the coolant temp sensor I was able to get it to fire a couple times but I still feel as if it's flooding. But once It got warm wouldn't crank again until it cooled and then it got to where it would crank anymore.

So I went back replace the Pickup coil and distributor cap and rotor button even had the ignition module tested.

I'm stumped as to why it won't crank and it's got to the point where I just wanna, sell it cause I'm putting too much into it. So any help would be appreciated and thanks in advance.
 
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#2 ·
As you're finding out, it gets very costly & frustrating to keep guessing & throwing parts at a problem like this.Save yourself alotta time, frustration, & money by finding someone with the knowledge & tools to diagnose your truck's system & pinpoint the problem.
 
#5 ·
these TBI systems can be a headache without a proper throttle body fuel injection manual that matches.. an obd1 scan tool will save you days of work.



you will have at least 2 ground wires attached to the back of the passenger side head.. there is probably one more on the thermostat housing stud.. these are really important.. you cannot have bare wire twisted around the stud.. it just won't work..

the oxygen sensor should be hooked up or it will run dead rich.. as the system is blind .... there should be no exhaust leaks.. no diverter valve /air injection system leaks. any uncommanded air injection flow into the exhaust manifolds will dilute the exhaust stream and the computer will freak out..

can you verify the actual year.. perhaps a few underhood pictures..

do you know how to pull codes from the check engine light..

do you have a decent hand held digital volt meter.. more than 10 bucks.. and perhaps some of the T shaped upholstery needles so you can backprobe some of the connectors..
 

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#6 ·
Ive been told about jumping 2 connectors on the OBD connector to get the dash light to flash but I've replaced my check engine light and it still won't come on so I'm blindly going into this.

As far as the ground wires I will have to check into that. And for the 02 sensors I haven't looked into them yet but from the outside they look pretty bad. But I've been told the 02 sensors wouldn't be causing my problem and there's a donut gasket missing I've got one just have replaced it yet.

I don't have a volt ohm meter and I don't know how to check how much fuel pressure I'm getting so idk where to turn next that's why I'm here
 
#7 ·
Without an accurate scan & code check,there's not a lot anybody here can do either,except continue to guess at your problems.
@ things offhand I can tell you to do is to fix your exhaust leak.You don't want any leaks in front the O2 sensors.
My next thing I would have you do is to check all the plugs/wiring going into the ECM & make sure they are all connected,clean,& fitting snuggly.Your ECM could possibly be bad,or,not getting adequate voltage/ground.The ECM doesn't take over engine control until the engine is up to operating temps.This may explain the engine starting up at cold temps,but,not,after warming up.Your SES light not working could also indicate a bad ECM,or,faulty wiring/connections.You really need to invest in a scanner & cheap volt meter,or,take to someone who has these things.If you can get it there,several of the autoparts stores such Autozone,O'Rielly's will scan it for free.
 
#9 ·
http://www.askatech.com/askatechlive/aatfileshare/references/fasttrack/g005.pdf

the above file describes on the last page how to test the sensor ground.


your truck would be the A201 or A204 file.. and that is not linked.. might still work.. i used to have those files in a PC code .. i am a mac user.. but that USB scan tool set up might work if you have a PC laptop.. i did see a guy tuning with a full tower computer and 19 inch monitor strapped into the front seat of his 69 camaro one day.. i guess he did not realize he could jack up the rear wheels.. but that is off subject..

you might want to breeze thru this post offsite..

which used scan tools for 82 to 94 corvettes with OBD1 connectors.. Page1 - Corvette Forums at Super Chevy Magazine

since you don't have a volt meter.. buy one of these.. its the same one i use daily.. Digital Multimeter - Save on this AC/DC Digital Multimeter


you will want the fuel and emissions manual.. either printed or DVD..

Search

if you have a 1993.


you will also want to use this to gain some knowledge of the TBI system

http://www.gmceast.com/technical/Swartzendruber_Generic_TBI_SlidesNotes.pdf

i have some more stuff.. but without you owning a digital volt meter... you won't have any luck even if you used a baseball bad..

are you in the los angeles area.. where i could just come over and plug in a scan tool.
 
#11 ·
It'll Turn Over But Won't start. And the reason For Having To splice them was Because where the connector Goes into THE coolant temp sensor Was burned. And the reason for splicing the one on the idle air control valve was because the plastic that went around the metal wires on the connector were broke of into the old IAC so I cut the wires and retied them and wrapped them in electrical tape.
 
#15 ·
code 15 is the coolant temp sensor..... disconnecting it will set the code..

code 43 is the electronic spark control circuit.. could be the EST module is unplugged or the knock sensor is unplugged..

code 54 is low fuel pump voltage monitored.. there is a circuit that comes off the fuel pump wiring that tells the computer how much voltage the fuel pump circuit has..


code 66 could be transmission code.. 3/2 shift solenoid circuit..

code 67 could be a torque converter clutch circuit problem..

code 82 QDM Solenoid "A" monitored voltage differs from commanded

now that you have written these down... disconnect the battery to clear the codes and try again.. see if any codes reset..

i am taking your truck is an automatic..
 
#16 ·
Wayne has you going in the right direction, but two things to check when it won't start - 12 volts at the battery trigger wire (small wire) and are you getting a priming pulse of fuel when you cycle the key?

Here's my low budget voltmeter of preference : Actron Auto Troubleshooter - Digital Multimeter and Engine Analyzer CP7677: Advance Auto Parts

I've had my home unit for 3 years and works like a champ - even measures dwell on a points style ignition. Once you have one you'll wonder how you ever got by without one!!!!
 
#18 ·
You need to dianose the mechanical no start issue before proceeding to read codes, this is basic.

For an engine to run it needs, proper timing, fuel, compression and spark.

To find out if you have all of the above you need basic automotive service equipment, compression gauge and a timing light to even begin.

Fuel should be obvious, the fuel pump should run, you have fuel pressure at the rail and its making it into the cylinders which you should be able to smell on a spark plug.

Spark can be seen by pulling a plug and grounding the shell and have someone observe the plug firing while cranking over.

Timing is checked by observing the light pointed at the balancer while its connected to the #1 plug wire.

Compression is done with a proper tester, instructions on how to use it will come with it.

If all these things are present and in the proper quantities the engine should run, it needs to run before checking codes or else all your doing is wasting your and our time.

If any of this is completely foreign to you, look up each item on the web and figure it out, this is a hotrod forum not auto mechanics 101. We will assist you but first you need to be equipped to do the basics of automotive repair, this is the bare minimum of knowledge required.

Start with the basics, computer codes are useful but a no-start situtation needs to be rectified first.
 
#25 ·
Truck sounds like it is idling a bit slow. What rpm are you playing with at idle? Where is the timing at? and has the balancer moved if it is a 2 piece?

Is it hard to start still?

Despite sounding like the timing may be off a few degrees and that truck sounds like around 650rpm it does not sound that bad.
As a good merit yank those pos plastic vacume lines one at a time. Shoot the gunk out with a air hose(or just blow through them), plug one end with your finger and blow on the other. This is a quick way to find cracks.




Cranking issues is one of 4 things. The timing, some kind of safety feature like with a clutch or interlock, the wiring to the starter, or the starter.

Either the thing has to much timing, the wiring to the starter, or starter itself is bad. Think it was said this is an automatic and I doubt you have a interlock. But who knows what the people before you did with the thing.

2 bolts and you can test the starter. You can test the wiring with a test light/meter.


Use that computer and paperclip. It is your friend and will eliminate a massive amount of headaches.
The obd1 is limited. Obd2 is a massive improvement. But, it is not until you run something like Renix that you realize just how good it is to have a obd system to point you in the right direction.
 
#26 ·
Idk what rpms it was runni MG at luckily I had this video and I also have a couple more. But the last time I had this, truck cranking like that was, about a month ago and aftee a week of changing my temp sensor it stop cranking again but it was still a pain in the *** when it was cranking.

I Know THE Starter Is Good Because It's Brand new
 
#28 ·
It's an old video. Even when I was able to get to start then it was pain. I had to keep trying and the only thing that helps is pressing the gas pedal. And last time I check it was getting spark at the plugs it might also help to add that the other day after putting in the Pickup coil that I could get it to want to start up but the moment I let out of the key it would turn back off
 
#37 ·
I did. I meant to message you back but I'm at work and I got busy and forgot. I'm on my phone and its not letting me open them. I'll have to try my computer when I get him


I appreciate the help guys. I really do. It's giving me hope that this truck can live again lol
 
#43 ·

Ok... lets have a look... i grabbed your images thank you and added some test to them..

see the attachments below.. i see lots of things i don't think are going to be good for this..

i see a lot of tiny wire used for spliced.. i would want to remove the tape and examine the way the wires are connected.. TWISTED Will not work.. must be mechanically crimped...

i see bare wires on the MAP sensor pigtail.. there is a way to determinate that connector using a 10 buck tool and slide shrink tubing over the bare wire.. then lifting the latch finger back up on the crimp end and reinstalling it in the proper position..

i am wondering where the sensor ground connection is that is usually by or on the thermostat housing stud..

if you don't have a good wire crimper.. my favorite is the dorman version for smaller wires.. they are NOT Cheap.. like 20 bucks at most autozones. some other stores have them also.



if budget is a concern 9-1/2" Wire Crimping Tool

120 Piece Heat-Shrink Tubing Set

this is even less money.. 9 Piece Heat Shrink Wire Wrap Assortment


if you need wiring to make splices.. you might find it in a GM wiring harness from the junk yards on cars and trucks prior to about 2003..

http://www.autozone.com/electrical-and-lighting/terminal-strip/oem-terminal-strip/191676_0_0/

Lisle 56500 - Wire Terminal Tool | O'Reilly Auto Parts
much cheaper at oreilly..
 

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#41 ·
The one that doesnt go to the the distributor is the one that should be hot with the key on and cranking
This is the terminal that you could supply power to to see if the ignition switch is the issue. I recently repaired a no start on one of these that a critter had chewed the wire off at the fuse box.
 
#44 ·
i just looked it up. looks like both connectors have a pink and a white wire, gotta love GM. So the feed for the coil is the pink wire that does not go to the distributor. This is where you want to feed the voltage or at least check for it. The white wire on that same connector is the tach wire
 
#47 ·
that is totally corroded... chop off an inch of wire.. strip the insulation.. make sure you get past the green oxidation.. new 3/8 ring terminal.. you can do both wires into a yellow if you cannot get them in a blue.. i like to go to the yellow as the rings are bigger thicker..

look on the back side of the drivers side cylinder head for more ground connections.. they will be coming out of the harness about 3 feet from where it goes thru the firewall.. almost impossible to see.. use your fingers.

were you able to download at least the emission version.. must be done from a computer usually.. that is like 110MB file size..
 
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