Hard Starting
Thread Starter
Pro
Joined: Jan 2005
Posts: 579
Likes: 0
From: Denton Texas
Hard Starting
95 LT1, 72,000 Miles
The car seems to want to turn over for a while before it fires. I replaced the plugs & wires. Still the same condition. Ran 2 bottles of fuel injector cleaner through. Same condition.
What else should I check?
Fuel Filter?
Fuel Pump?
Fule Injectors?
The car seems to want to turn over for a while before it fires. I replaced the plugs & wires. Still the same condition. Ran 2 bottles of fuel injector cleaner through. Same condition.
What else should I check?
Fuel Filter?
Fuel Pump?
Fule Injectors?
Race Director
Joined: Jan 2002
Posts: 12,264
Likes: 88
From: O'Fallon Missouri
Do a fuel pressure leakdown test. That will either eliminate/diagnose a bad fuel pump or fuel pressure regulator.
If you are still running a stock fuel pressure regulator, I am guessing it is the fuel pump.
-Mike
If you are still running a stock fuel pressure regulator, I am guessing it is the fuel pump.
-Mike
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Engines need spark and at the right time, fuel, air, and in the correct ratio in order to start and run. First use your timing light while someone cranks to see if you have spark and the timing is correct. Next, go to a car parts store and buy a fuel pressure gauge (about $12) and measure the fuel pressure at the shraeder valve on the end of the fuel rail. Turn the ignition off and see how long it takes for the pressure to drop. If it drops rapidly, you may have leaky fuel injectors. Next, unplug an injector and place a noid light (also at the parts store), or a 12v low power lamp like a 194 side marker lamp across the injector plug and crank the engine. The light should pulse during cranking showing that the ECM is excercising the injectors. Remove the hose from the MAF to ensure that the engine is getting air, you could have a clogged air filter. Report your findings.
Thread Starter
Pro
Joined: Jan 2005
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From: Denton Texas
Went to the parts store. Picked up an air filter, PCV Valve, & fuel filter. Also picked up a fuel pressure gauge. Replaced the air filter & PCV valve & hooked up the pressure gauge. When I turn the ignition on the pressure goes to 40, then I crank the car & it immediately fires up. When the car is turned off the pressure goes down to about 37 with no rapid decrease.
I assume my injectors & pump are fine. Correct?
Tonight I will replace the fuel filter just to help it flow a little better.
I assume my injectors & pump are fine. Correct?
Tonight I will replace the fuel filter just to help it flow a little better.
Thread Starter
Pro
Joined: Jan 2005
Posts: 579
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From: Denton Texas
Well after replacing the fuel filter this morning & doing some driving, the problem still seems to be there.
What should I look at next?
I still have not checked the timing or placed a noid light across the injectors. The fuel pressure seems to be right where it needs to be.
What should I look at next?
I still have not checked the timing or placed a noid light across the injectors. The fuel pressure seems to be right where it needs to be.
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Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
If the engine runs, I doubt the injectors are involved.
If hard starting occurs only when the engine is cold during cold weather, the cold injector may not be turned on. measure the voltage across the cold start injector, if it is on, there will 12v across it. Measure the voltage across the TPS (throttle position sensor) with the ign on. It must be less than 0.7 volts. If you have a scan tool, see what the coolant temp shows. A high resistance from the coolant sensor located at the front of the engine under the MAF tells the ECM that the engine is cold. See if you have an error code 14 or code 15 stored. Code 14 sets if engine temp exceeds 266 F and code 15 sets if engine temp is below -47 F. The sensor voltage is normally between 1 to 2 volts. If you measure 5 volts across the sensor, it is open circuit (defective) or there is a poor connection in the wiring harness plug that plugs into the sensor. The plug is a two pin connector.
If hard starting occurs only when the engine is cold during cold weather, the cold injector may not be turned on. measure the voltage across the cold start injector, if it is on, there will 12v across it. Measure the voltage across the TPS (throttle position sensor) with the ign on. It must be less than 0.7 volts. If you have a scan tool, see what the coolant temp shows. A high resistance from the coolant sensor located at the front of the engine under the MAF tells the ECM that the engine is cold. See if you have an error code 14 or code 15 stored. Code 14 sets if engine temp exceeds 266 F and code 15 sets if engine temp is below -47 F. The sensor voltage is normally between 1 to 2 volts. If you measure 5 volts across the sensor, it is open circuit (defective) or there is a poor connection in the wiring harness plug that plugs into the sensor. The plug is a two pin connector.
Last edited by jfb; Nov 26, 2005 at 02:46 PM.
Thread Starter
Pro
Joined: Jan 2005
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From: Denton Texas
[QUOTE=jfb]If the engine runs, I doubt the injectors are involved.
If hard starting occurs only when the engine is cold during cold weather, the cold injector may not be turned on.QUOTE]
Which injector is the cold start injector? 95 LT1
If hard starting occurs only when the engine is cold during cold weather, the cold injector may not be turned on.QUOTE]
Which injector is the cold start injector? 95 LT1
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
[QUOTE=DG'sVette]
there is no cold start injector on a -95, he just got his years mixed...
BTW, did you check to see if you have any error codes? On your '95, just short pinA and PinB if OBD1 style ALDL, or Pin4 and Pin12 if OBDII style.
Originally Posted by jfb
If the engine runs, I doubt the injectors are involved.
If hard starting occurs only when the engine is cold during cold weather, the cold injector may not be turned on.QUOTE]
Which injector is the cold start injector? 95 LT1
If hard starting occurs only when the engine is cold during cold weather, the cold injector may not be turned on.QUOTE]
Which injector is the cold start injector? 95 LT1
BTW, did you check to see if you have any error codes? On your '95, just short pinA and PinB if OBD1 style ALDL, or Pin4 and Pin12 if OBDII style.
Last edited by MikeC4; Nov 26, 2005 at 04:19 PM.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Originally Posted by DG'sVette
Now I'm going to show my ignorance. Where do I read the error codes?
1) use a small gauge wire to short the 2 pins
2) turn your ignition to "ON", but don't start engine
3) first code you will see displayed is C12, this is not error code but indicates the start of error code dumpage
4) write down any subsequent codes that may display. If all you see are dashes "---------", that is good. Takes about 2-3 minutes to run through the error code log. An example of a stored History error code would be something like H64.( You can clear error codes from your cars computer by disconnecting the battery Neg. terminal for ~30seconds, and then reconnect.....
)5) Ignition Off
6) Remove the shorting wire.
cross relerance any error codes with your engine type and this chart:
http://www.troublecodes.net/GM/
