1991 5.0 LX Won't start
10-05-2017, 06:36 PM
#1
Thread Starter
Join Date: Apr 2007
Posts: 15
1991 5.0 LX Won't start
I'm having trouble getting my car to start. I've replaced just about everything to keep it from starting and I just can't figure it out. The parts I've replaced are:
Battery
Starter
Fuel filter
Plugs
Wires
Cap and rotor
Coil
TFI module
When I turn the car over it acts as if the battery is bad. The battery is new! I pulled the number one plug, rotated the motor to TDC and heard a whistle from the indicator I screwed in. The plug wires are all correct, what else is there!? So frustrated...
Battery
Starter
Fuel filter
Plugs
Wires
Cap and rotor
Coil
TFI module
When I turn the car over it acts as if the battery is bad. The battery is new! I pulled the number one plug, rotated the motor to TDC and heard a whistle from the indicator I screwed in. The plug wires are all correct, what else is there!? So frustrated...
10-22-2017, 04:08 PM
#3
Check your battery and starter cables from one end to the other.
My starter began dragging one time and after inspection,6" of insulation had been rubbed off the starter cable by the oil pan causing a short.The starter would drag everytime the engine got warmed up because of the excessive resistance added by the short.
One way to verify a short,which can drain the battery when the engine is off,is by using a test light.
1) Disconnect the neg battery cable.
2) Attach the test light clip to the neg battery cable terminal.
3) Attach the test light probe to the neg battery post.
4) The test light should be off.
If its on,that indicates a short is present.Post your results if you have a short.
BATTERY TESTS
Attach multimeter leads to the battery posts.
A fully charged battery should read 12.5+ volts,key on/engine off.
If your reading is lower than this,the battery needs to be recharged.
The battery should read 13.5-14.7 volts,
key on/engine running.
(Cranking Voltage Test)
1) Disable the ignition system.
2) Attach multimeter leads to the battery posts.
3) Remove the red/blue wire from the small post on the starter solenoid.
4) Jump a long screwdriver across the small solenoid post & the large solenoid post that the positive battery cable is attached to.
5) Take a meter reading while the starter is cranking or attempting to crank.
6) The meter should read 9.6+ volts during crank mode.If it doesnt,the battery doesnt have enough reserve capacity to power the starter.The battery needs to be recharged or replaced.
(Battery Ground Circuit Test)
1) Attach the positive meter lead to the negative battery ground at the engine block.
2) Attach the negative meter lead to the negative battery post,not the negative battery cable terminal.
3) Jump the solenoid again and crank the engine for a few seconds.
4) The meter should read 0.1-0.3 volts during crank mode.If the reading is higher than 0.3 volts,youve got a bad ground connection.
Your ground circuit consists of 3 grounds.
Primary,Secondary & EEC.
1) Primary- runs between the neg battery post and the engine block.
2) Secondary- runs between the driver cylinder head (rear) and the firewall.
3) EEC- runs between the neg battery post and the driver fender apron then it splits and leads to a black,tubular plug which connects to a mating plug thats part of the main eec wiring harness.
The ground loop should end where it started:
neg battery post to the block
block to the chassis (firewall)
chassis (fender apron) to the neg battery post.
If starting issues are present,the solenoid should be checked too.The back side of the starter solenoid and the fender apron should have clean metal to metal contact because the solenoid is case grounded.Make sure the solenoid mounting bolts are tight & corrosion free too.The nuts,holding the wires & cables to the solenoid,should also be tight.
My starter began dragging one time and after inspection,6" of insulation had been rubbed off the starter cable by the oil pan causing a short.The starter would drag everytime the engine got warmed up because of the excessive resistance added by the short.
One way to verify a short,which can drain the battery when the engine is off,is by using a test light.
1) Disconnect the neg battery cable.
2) Attach the test light clip to the neg battery cable terminal.
3) Attach the test light probe to the neg battery post.
4) The test light should be off.
If its on,that indicates a short is present.Post your results if you have a short.
BATTERY TESTS
Attach multimeter leads to the battery posts.
A fully charged battery should read 12.5+ volts,key on/engine off.
If your reading is lower than this,the battery needs to be recharged.
The battery should read 13.5-14.7 volts,
key on/engine running.
(Cranking Voltage Test)
1) Disable the ignition system.
2) Attach multimeter leads to the battery posts.
3) Remove the red/blue wire from the small post on the starter solenoid.
4) Jump a long screwdriver across the small solenoid post & the large solenoid post that the positive battery cable is attached to.
5) Take a meter reading while the starter is cranking or attempting to crank.
6) The meter should read 9.6+ volts during crank mode.If it doesnt,the battery doesnt have enough reserve capacity to power the starter.The battery needs to be recharged or replaced.
(Battery Ground Circuit Test)
1) Attach the positive meter lead to the negative battery ground at the engine block.
2) Attach the negative meter lead to the negative battery post,not the negative battery cable terminal.
3) Jump the solenoid again and crank the engine for a few seconds.
4) The meter should read 0.1-0.3 volts during crank mode.If the reading is higher than 0.3 volts,youve got a bad ground connection.
Your ground circuit consists of 3 grounds.
Primary,Secondary & EEC.
1) Primary- runs between the neg battery post and the engine block.
2) Secondary- runs between the driver cylinder head (rear) and the firewall.
3) EEC- runs between the neg battery post and the driver fender apron then it splits and leads to a black,tubular plug which connects to a mating plug thats part of the main eec wiring harness.
The ground loop should end where it started:
neg battery post to the block
block to the chassis (firewall)
chassis (fender apron) to the neg battery post.
If starting issues are present,the solenoid should be checked too.The back side of the starter solenoid and the fender apron should have clean metal to metal contact because the solenoid is case grounded.Make sure the solenoid mounting bolts are tight & corrosion free too.The nuts,holding the wires & cables to the solenoid,should also be tight.
10-22-2017, 10:28 PM
#4
3rd Gear Member
Join Date: Jul 2017
Location: AZ
Posts: 849
...One way to verify a short,which can drain the battery when the engine is off,is by using a test light.
1) Disconnect the neg battery cable.
2) Attach the test light clip to the neg battery cable terminal.
3) Attach the test light probe to the neg battery post.
4) The test light should be off.
If its on,that indicates a short is present.Post your results if you have a short.
1) Disconnect the neg battery cable.
2) Attach the test light clip to the neg battery cable terminal.
3) Attach the test light probe to the neg battery post.
4) The test light should be off.
If its on,that indicates a short is present.Post your results if you have a short.
What type of test light? Incandescent? A '91 model will always have a battery current draw of 0.005 to 0.010 ampere, 5 to 10 Milliamperes, Keep-Alive current for the PCM. That test light would be placed in series with the PCM Memory.
Would the test light indicate current flow by illuminating, giving a false result? imp
10-23-2017, 01:24 PM
#5
I had a dome light causing a short one time.With a test light connected,between the cable & battery post,the light was on.Once I disconnected the harness from the dome light,the test light went out.The ecu didnt cause the test light to come on in this case.However,if somebody is worried that the drain from the ecu's kam might trigger the test light to come on,that issue can be resolved easily by using one of the following two methods:
1) Remove the wire from the starter solenoid that feeds pin 1 of the ecu.
2) Disconnect the harness from the ecu,remove the red/plastic/ wire lock with a pick,push pin 1 out of the harness plug,reinsert the lock then reconnect the harness.
Either one of these methods will remove the possibility of electrical drain from the ecu.
With the neg battery cable disconnected and a test light inserted between the neg battery cable & the neg battery post,the only way current can return to the neg battery post is by passing through the test light,which will turn the test light on.Since current should not be flowing with the key off,unless its from the ecu or radio clock,the test light should be off.
1) Remove the wire from the starter solenoid that feeds pin 1 of the ecu.
2) Disconnect the harness from the ecu,remove the red/plastic/ wire lock with a pick,push pin 1 out of the harness plug,reinsert the lock then reconnect the harness.
Either one of these methods will remove the possibility of electrical drain from the ecu.
With the neg battery cable disconnected and a test light inserted between the neg battery cable & the neg battery post,the only way current can return to the neg battery post is by passing through the test light,which will turn the test light on.Since current should not be flowing with the key off,unless its from the ecu or radio clock,the test light should be off.
10-23-2017, 08:52 PM
#7
3rd Gear Member
Join Date: Jul 2017
Location: AZ
Posts: 849
With the neg battery cable disconnected and a test light inserted between the neg battery cable & the neg battery post,the only way current can return to the neg battery post is by passing through the test light,which will turn the test light on.Since current should not be flowing with the key off,unless its from the ecu or radio clock,the test light should be off.
Air bag power supply is active at all times, also, causes small battery current drain. imp
10-24-2017, 11:26 PM
#10
Yes a defective tfi will cause a no start issue,but the poster has replaced it already.His symptoms of slow cranking might have the engine turning over too slow,for startup.If the engine is cranking at normal speed,but wont start,things like the tfi module,pip sensor,etc can be looked at as possible causes.
I would connect jumper cables to the car,to get the engine cranking at normal speed,and see if it starts.If it doesnt start,leave the jumper cables attached,remove the small black breather tube from the throttle body elbow,spray starting fluid or carb cleaner into the port then push the breather tube back onto the throttle body elbow.Now turn the key to start.
If it starts and runs for a few seconds then dies,youve got a No Fuel issue present.
If it doesnt start at all,youve got a No Spark issue present.
If the pip sensor is bad,it can cause a no spark and no injector pulse issue.
If you wanna make sure the timing hasnt jumped (which is doubtful) do this:
Mark the 0° & 10° btdc balancer marks with Witeout.Install your whistle indicater in the #1 plug hole.Rotate the crank CW til the whistle starts to blow then slowly continue rotating until the 0° timing mark is aligned with the timing pointer.Pull the distributer cap off and view the rotor.It should be pointed between the two front upper intake bolts,like shown in the picture below.This also means its pointed towards the #1 spark plug position on the cap.If your rotor isnt pointed in this direction,the distributor is off by 1 tooth or more.If the distributer is indexed correctly,like the picture shows,reinstall everything.If you can ever manage to get the car running,check the timing by removing the spout plug and aiming the timing light at the balancer, to make sure timings at 10° btdc.Over-advanced timing will cause the starter to drag during crank mode too,but I doubt this is the problem,since the no start just popped up out of the blue.
Make sure you see the rotor spinning during crank mode,to rule out a broken timing chain (very unlikely)
I would connect jumper cables to the car,to get the engine cranking at normal speed,and see if it starts.If it doesnt start,leave the jumper cables attached,remove the small black breather tube from the throttle body elbow,spray starting fluid or carb cleaner into the port then push the breather tube back onto the throttle body elbow.Now turn the key to start.
If it starts and runs for a few seconds then dies,youve got a No Fuel issue present.
If it doesnt start at all,youve got a No Spark issue present.
If the pip sensor is bad,it can cause a no spark and no injector pulse issue.
If you wanna make sure the timing hasnt jumped (which is doubtful) do this:
Mark the 0° & 10° btdc balancer marks with Witeout.Install your whistle indicater in the #1 plug hole.Rotate the crank CW til the whistle starts to blow then slowly continue rotating until the 0° timing mark is aligned with the timing pointer.Pull the distributer cap off and view the rotor.It should be pointed between the two front upper intake bolts,like shown in the picture below.This also means its pointed towards the #1 spark plug position on the cap.If your rotor isnt pointed in this direction,the distributor is off by 1 tooth or more.If the distributer is indexed correctly,like the picture shows,reinstall everything.If you can ever manage to get the car running,check the timing by removing the spout plug and aiming the timing light at the balancer, to make sure timings at 10° btdc.Over-advanced timing will cause the starter to drag during crank mode too,but I doubt this is the problem,since the no start just popped up out of the blue.
Make sure you see the rotor spinning during crank mode,to rule out a broken timing chain (very unlikely)