Won't crank help please
#1
02-08-2019, 12:37 PM
Won't crank help please
ok so my 1999 4x4 blazer will randomly stall then it won't crank back up turn the key nothing. So I've replaced the ignition switch nope wasn't it. Starter, nope. Lock cylinder, starter relay, battery, nope. If i let it sit for awhile it will start back up it could take an hour or it could take 24 hours and it'll run fine and start fine for weeks. Here is where it gets interesting my 12v signal wire to the starter Isn't registering 12v in the start position after the stall happens so I bypassed the 12v signal wire to starter directly from a switch to the battery. Car cranks but won't start. So maybe fuel issues right? Well no if it was directly fuel related the car would crank normally and just not start. It's almost as if my PCM goes into limp mode turns off my fuel pump and starter signal wire. Idk the issue or why this is happening but I'd greatly appreciate it if someone has any input.
#2
02-08-2019, 12:48 PM
STARTER CIRCUIT OPERATION
When the ignition switch is turned to the START position voltage is either applied to the clutch pedal position switch (M/T) or the park/neutral position switch (A/T). When either the clutch is disengaged (M/T) or the transmission is in park or neutral (A/T), voltage is applied to the coil of the starter relay. Since the starter relay is permanently grounded the starter relay energizes.
Voltage is applied at all times to the starter relay contacts. When the starter relay energizes, the starter relay contacts close, and voltage is applied to the starter motor solenoid. Since the starter motor solenoid is permanently case grounded, the starter motor solenoid will energize two coils. The pull-in winding coil energizes in order to pull the starter motor solenoid contacts closed. When the contacts close, a plunger on the contacts causes the pull-in winding coil circuit to open. The hold-in winding coil then holds the starter motor solenoid contacts closed. Voltage is then applied to the starter motor from the battery through the closed contacts of the starter motor solenoid. Since the starter motor is also permanently case grounded, the starter motor will run until the ignition switch is moved out of the START position. When this happens, a spring in the starter motor solenoid moves the starter motor solenoid contacts and the plunger back to the rest position.
When the ignition switch is turned to the START position voltage is either applied to the clutch pedal position switch (M/T) or the park/neutral position switch (A/T). When either the clutch is disengaged (M/T) or the transmission is in park or neutral (A/T), voltage is applied to the coil of the starter relay. Since the starter relay is permanently grounded the starter relay energizes.
Voltage is applied at all times to the starter relay contacts. When the starter relay energizes, the starter relay contacts close, and voltage is applied to the starter motor solenoid. Since the starter motor solenoid is permanently case grounded, the starter motor solenoid will energize two coils. The pull-in winding coil energizes in order to pull the starter motor solenoid contacts closed. When the contacts close, a plunger on the contacts causes the pull-in winding coil circuit to open. The hold-in winding coil then holds the starter motor solenoid contacts closed. Voltage is then applied to the starter motor from the battery through the closed contacts of the starter motor solenoid. Since the starter motor is also permanently case grounded, the starter motor will run until the ignition switch is moved out of the START position. When this happens, a spring in the starter motor solenoid moves the starter motor solenoid contacts and the plunger back to the rest position.
Be aware, if you attempt to disconnect the wiring at the PNP switch on the side of the transmission, you will need to apply some heat to the switch body to soften whatever the goop is they put in there to seal it up. The stuff likes to set up like concrete making it almost impossible to remove at normal temperatures. It often is necessary to remove the switch from the side of the transmission to get the wiring free which also requires the removal of the shift cable and the shift arm so keep track of how/where everything goes back together. The PNP switch can also be adjusted, but that pretty much consists of ensuring that the engine only starts when the transmission shift lever is in Park or Neutral.
You can check the operation of the PNP switch by testing for power first at the CRANK fuse as well as at the starter relay with the ignition switch in the START position. You will have to properly identify the terminals that the starter relay plugs into. The relay can be flipped 180 degrees so just looking at the designations for pin # (if shown on the bottom of the relay) and using them off of the diagram above doesn't necessarily translate. Pins 85 & 86 are across corners from each other and can be interchanged. Same goes for pins 30 & 87. If you find the terminal with +12V all the time, that should correspond with pin 30 in the diagram and the terminal corresponding to pin 87 will be across corners from that terminal. The other two corners will be the terminals for pins 85 & 86 with the terminal corresponding with pin 86 on the diagram being connected to ground. This then leaves the last terminal which will be connected to the CRANK fuse through the PNP switch.
Long explanation, but hopefully it shows you the way to get things diagnosed as expedient and inexpensive as possible. Let us know what you find.
#3
02-08-2019, 01:01 PM
Thanks for the quick reply. Any way you could dumb it down for me and let me know which wires to check lol I can use a volt meter and all just don't really know what I'm looking for specifically NVM didn't see bottom of your post will check this out and let you know thankyou
#4
02-08-2019, 01:05 PM
I added a bit more information below the wiring diagram. You can test things at the underhood fuse box to determine if the PNP switch is properly providing the circuit for starter operation. I have described it as best I can without physically being there with you or having a vehicle to make a video for you. Hopefully it is enough...
#5
02-08-2019, 01:16 PM
Have 11.9 volts to crank fuse and terminal 85 of starter relay so this elimantes the PNP switch? Is there anything else?
#6
02-08-2019, 01:40 PM
Check battery ground? Nice clean connection?
Check cables for voltage drops.
Also engine ground on back of head
Clean battery connections real good with the wire reamer.
Check cables for voltage drops.
Also engine ground on back of head
Clean battery connections real good with the wire reamer.
Last edited by motorbreth77; 02-08-2019 at 01:43 PM.
#7
02-08-2019, 01:40 PM
If the starter isn't spinning over the engine and you have verified that +12V is getting from the starter relay to the starter (continuity from pin 87 to starter solenoid connection), then no, that is the entire circuit you have tested for the starter solenoid... You have removed any jumper wires, correct? And correctly identified the terminals in the fuse/relay center?
Have you tested that the main positive power cable to the starter is good? There is a fusible link in this wire that can sometimes cause intermittent power flow to the starter. It can test ok under no load, but open up under the high amperage draw that occurs when the starter engages. I test this by connecting a test lead to the main positive post on the starter and the other test lead to a ground point on the engine itself and place the multimeter somewhere that I can see it while inside the vehicle turning the key. This tests a two things at once really. If the power level remains near that of stable battery power, then there is no problem with both the power & ground circuits to the starter & engine respectively. If the power dips dangerously low (<9V), then there is a problem somewhere. If that is the case, repeat the test with the negative lead from the meter on the battery negative. If the same voltage is noted during cranking, then the main positive power lead is bad. If it does not reoccur, then there is a problem with the engine ground circuit that may be solved in the easiest & most expedient way by installing another ground to the engine block.
I didn't mention checking cables at first because you said it will turn over when you put a jumper wire to the starter solenoid from the battery which would appear to confirm that the cables are good, unless...in the process of installing the jumper wire, you moved the positive cable to a position that it made a somewhat proper circuit allowing the starter to turn.? I'm grasping here, but if the tests from my previous post returned +12V power at the appropriate terminals only with the key in the START position AND that there is proper continuity between the starter solenoid pin and terminal 87 of the starter relay, then the starter should operate.
You could also try jumping the connections between pins 30 & pin 87 at the starter relay which should put +12V power to the starter solenoid directly similar to how you did with your jumper wire.
As a further observation, you did have the key in the RUN position while attempting to jump start the starter with your jumper wire, correct? Just trying to cover all bases here.
Have you tested that the main positive power cable to the starter is good? There is a fusible link in this wire that can sometimes cause intermittent power flow to the starter. It can test ok under no load, but open up under the high amperage draw that occurs when the starter engages. I test this by connecting a test lead to the main positive post on the starter and the other test lead to a ground point on the engine itself and place the multimeter somewhere that I can see it while inside the vehicle turning the key. This tests a two things at once really. If the power level remains near that of stable battery power, then there is no problem with both the power & ground circuits to the starter & engine respectively. If the power dips dangerously low (<9V), then there is a problem somewhere. If that is the case, repeat the test with the negative lead from the meter on the battery negative. If the same voltage is noted during cranking, then the main positive power lead is bad. If it does not reoccur, then there is a problem with the engine ground circuit that may be solved in the easiest & most expedient way by installing another ground to the engine block.
I didn't mention checking cables at first because you said it will turn over when you put a jumper wire to the starter solenoid from the battery which would appear to confirm that the cables are good, unless...in the process of installing the jumper wire, you moved the positive cable to a position that it made a somewhat proper circuit allowing the starter to turn.? I'm grasping here, but if the tests from my previous post returned +12V power at the appropriate terminals only with the key in the START position AND that there is proper continuity between the starter solenoid pin and terminal 87 of the starter relay, then the starter should operate.
You could also try jumping the connections between pins 30 & pin 87 at the starter relay which should put +12V power to the starter solenoid directly similar to how you did with your jumper wire.
As a further observation, you did have the key in the RUN position while attempting to jump start the starter with your jumper wire, correct? Just trying to cover all bases here.
#8
02-08-2019, 01:48 PM
I'll check the other things you mentioned thanks alot for the help so far. Yes the terminals on the relay were identified correctly ground is good as well. I have 12v leaving the starter relay but nothing at the solenoid. So would this mean I break in the wire to the solenoid somewhere? Also if I just bypass the relay why wouldn't it start but just crank? The signal is intermittent in this starter wire some reason I'll keep diagnosing thanks again will update soon yes key has been in start position for tests and when I jumped it it was in the run position I also had someone hold it in the start position while jumping the solenoid
Last edited by Matthewrcarrier; 02-08-2019 at 01:52 PM.
#9
02-08-2019, 02:09 PM
Ok finally think I'm getting somewhere thanks again. I have power for sure in the relay 30 spot but not the 87 spot. I also put a jumper like you said from 30 to 87 and nothing to the starter checked 30 and 87 with the key at start position. Now 87 won't show volts unless it has a relay to pass threw correct? Also when I jumped the starter i cut the purple signal wire rubber casing off in a spot ran a wire from the cut directly to the positive battery cable and the starting turns the motor
Last edited by Matthewrcarrier; 02-08-2019 at 02:11 PM.
#10
02-08-2019, 02:15 PM
That is why I mentioned that the key was in the RUN position when you jumped the starter solenoid straight to +12V at the battery in my last reply. That is the only reason that I can think of that the engine would turn over, but not start other than some other issue compounding matters; e.g. lack of spark or fuel pressure. If the CRANK wire between the starter and the relay was chaffed, that could have been the intermittent no crank, but there could be something else affecting matters...
Can you hear the fuel pump prime when you turn the key to the RUN position? If so, have you checked that you have at least 58psi at the fuel pressure test port on the back side of the intake manifold?
Can you hear the fuel pump prime when you turn the key to the RUN position? If so, have you checked that you have at least 58psi at the fuel pressure test port on the back side of the intake manifold?