fuel pump relay
#31
10-12-2007, 10:14 AM
RE: fuel pump relay
ORIGINAL: rshiver
Lots of good info there cwb, thanks for posting the link.
If the ECM doesn't get a signal from the temp sensor to let it know it's above 100 degrees, I wonder if the cold start injector is activated even though the engine is hot. Wouldn't that cause a rich, and/or hard start condition?
Lots of good info there cwb, thanks for posting the link.
If the ECM doesn't get a signal from the temp sensor to let it know it's above 100 degrees, I wonder if the cold start injector is activated even though the engine is hot. Wouldn't that cause a rich, and/or hard start condition?
Depends on the timing mechanism. If it's electronic, as in controlled by the computer, the only way that's gonna' fail is if the computer fails. If it's mechanical, as in quartz timing, THAT couldn't fail such that it kept runnin' either...
#32
10-12-2007, 11:08 AM
RE: fuel pump relay
What I'm trying to figure out is, where does the ECM get it's info regarding the temperature of the engine at startup. I would assumeit has to have some input from somewhere as to whether the engine is above or below 100 degrees.
I'm wondering if this scenario is even possiable....
If, trying to start an engine that's already at an operating temp of 180 degrees or more, and the ECM "thinks" the engine is cold, wouldthe ECMprovide a rich fuel mixture from the injectors, and, on mine anyway, activate the cold start injector for 8 seconds, in effect,causinga border line flooded condition when trying to crank an already hot engine.
I'm wondering if this scenario is even possiable....
If, trying to start an engine that's already at an operating temp of 180 degrees or more, and the ECM "thinks" the engine is cold, wouldthe ECMprovide a rich fuel mixture from the injectors, and, on mine anyway, activate the cold start injector for 8 seconds, in effect,causinga border line flooded condition when trying to crank an already hot engine.
#33
10-12-2007, 12:01 PM
RE: fuel pump relay
OK, I've found that there's a cold start switch, that disables the cold start injector if the engine temp is over 100 degrees on '85-'88 L98's. Also, the cold start injector can leak too, so that's something for me to check into.
This wouldn't apply to dfwgsx's problem though, he has a '95.
Foundthis info on the cold start injector, but according to it the injector stays on until the engine warms up.
Source....
http://www.corvetteactioncenter.com/...ead.php?t=9073
This wouldn't apply to dfwgsx's problem though, he has a '95.
Foundthis info on the cold start injector, but according to it the injector stays on until the engine warms up.
Since cold starting requires considerably more fuel than a warm engine, it must have some means of enrichening the fuel to air ratio until the temperature of the engine rises to where the fuel will vaporize more readily. The choke systems restricted the air intake so that there was less air moving thru the carburetor while at the same time opening the throttle plate below the choke plate and drawing more fuel. This causes a rich fuel mixture that will enable the engine to run.
The cold start injector (or valve) is mounted in the intake manifold at a centrally located area where it can open and allow extra fuel to enter the engine. This is in addition to the normal fuel injection system. The extra cold start injector is electronically controlled by the computer (ECM) and when the temperature sending units signal the computer that the engine is cold, the computer will send a signal to the cold start injector to inject fuel at the same time as the normal injection system. This makes the air fuel mixture richer to compensate for the cold engine requirements.
The cold start injector delivers fuel to all the cylinders and is controlled by a thermo switch and time control. Thermo switches are located in an area in the engine where engine temperatures can be sensed such as the coolant or head temperature. The temperature sensor has the ability to open the switch when the engine is warm enough to run on the regular injection system or close when the engine is cold and needs more fuel. It activates the cold start injector until the temperature deactivates the thermo switch. (The temperature rating on the switches can be checked in shop manuals).
Whether the sensor is controlling the cold start injector long enough can be felt by cold engine hesitations after the vehicle has run for a few minutes and prior to normal engine temperature. If the temperature sensor rating is too high or staying on too long, there can be some flooding or black tailpipe smoke generated for awhile at about normal engine temperature and also lower gas mileage. It is critical that the correct temperature sensors are used so as not to overload the catalytic converters and foul the oxygen sensors or cause the cold start injectors to work improperly.
HOW TO TEST A COLD START INJECTOR -- when the cold start injector is in a hard to reach area, a pressure drop test with the injector in place can be made. A pressure gauge can be installed at the fuel filter location or at the fuel rail connector. The fuel system can be pressurized by momentarily by-passing the fuel pump relay and then connecting an injector activator to the cold start injector to energize it. This will cause a pressure drop on the gauge if the injector is working. It can also be tested to see if up and then activating the cold start injector. The engine should falter or miss when this is done and possibly black smoke appear from the tailpipe due to the excessively rich mixture.
When the cold start injector is easy to get to and can be removed easily, it may be removed and activated in a container to check the fuel spray pattern. This will enable the injector to be cleaned with a commercial spray cleaner if desired when the spray pattern is not conical or when the injector drips while pressurized.
Loss of electrical power could also be a reason for the cold start injector not working. This can be checked by disabling the engine so it won't start and then connect a test light into the cold start injector connector. The test light should stay on for a short duration when the ignition is turned on. A stop watch can be used to measure the duration of the light staying on. Shop manuals will tell how long each duration of activated injector time is required. The above test should be performed on an engine that is cooled off and prior to start up in order for the injector to work in the time established for proper performance.
The cold start injector (or valve) is mounted in the intake manifold at a centrally located area where it can open and allow extra fuel to enter the engine. This is in addition to the normal fuel injection system. The extra cold start injector is electronically controlled by the computer (ECM) and when the temperature sending units signal the computer that the engine is cold, the computer will send a signal to the cold start injector to inject fuel at the same time as the normal injection system. This makes the air fuel mixture richer to compensate for the cold engine requirements.
The cold start injector delivers fuel to all the cylinders and is controlled by a thermo switch and time control. Thermo switches are located in an area in the engine where engine temperatures can be sensed such as the coolant or head temperature. The temperature sensor has the ability to open the switch when the engine is warm enough to run on the regular injection system or close when the engine is cold and needs more fuel. It activates the cold start injector until the temperature deactivates the thermo switch. (The temperature rating on the switches can be checked in shop manuals).
Whether the sensor is controlling the cold start injector long enough can be felt by cold engine hesitations after the vehicle has run for a few minutes and prior to normal engine temperature. If the temperature sensor rating is too high or staying on too long, there can be some flooding or black tailpipe smoke generated for awhile at about normal engine temperature and also lower gas mileage. It is critical that the correct temperature sensors are used so as not to overload the catalytic converters and foul the oxygen sensors or cause the cold start injectors to work improperly.
HOW TO TEST A COLD START INJECTOR -- when the cold start injector is in a hard to reach area, a pressure drop test with the injector in place can be made. A pressure gauge can be installed at the fuel filter location or at the fuel rail connector. The fuel system can be pressurized by momentarily by-passing the fuel pump relay and then connecting an injector activator to the cold start injector to energize it. This will cause a pressure drop on the gauge if the injector is working. It can also be tested to see if up and then activating the cold start injector. The engine should falter or miss when this is done and possibly black smoke appear from the tailpipe due to the excessively rich mixture.
When the cold start injector is easy to get to and can be removed easily, it may be removed and activated in a container to check the fuel spray pattern. This will enable the injector to be cleaned with a commercial spray cleaner if desired when the spray pattern is not conical or when the injector drips while pressurized.
Loss of electrical power could also be a reason for the cold start injector not working. This can be checked by disabling the engine so it won't start and then connect a test light into the cold start injector connector. The test light should stay on for a short duration when the ignition is turned on. A stop watch can be used to measure the duration of the light staying on. Shop manuals will tell how long each duration of activated injector time is required. The above test should be performed on an engine that is cooled off and prior to start up in order for the injector to work in the time established for proper performance.
http://www.corvetteactioncenter.com/...ead.php?t=9073
#34
10-12-2007, 02:01 PM
RE: fuel pump relay
I understand what yer askin' about if the computer thinks the engine don't ever warm up. And it would then keep the cold start injector pumpin' fuel. But if the thermo switch fails, it's still timer controlled.
So how much flooding could be caused by 8 seconds of unecessary cold start injector fuel?
So how much flooding could be caused by 8 seconds of unecessary cold start injector fuel?
ORIGINAL: rshiver
OK, I've found that there's a cold start switch, that disables the cold start injector if the engine temp is over 100 degrees on '85-'88 L98's. Also, the cold start injector can leak too, so that's something for me to check into.
This wouldn't apply to dfwgsx's problem though, he has a '95.
Foundthis info on the cold start injector, but according to it the injector stays on until the engine warms up.
Source....
http://www.corvetteactioncenter.com/...ead.php?t=9073
OK, I've found that there's a cold start switch, that disables the cold start injector if the engine temp is over 100 degrees on '85-'88 L98's. Also, the cold start injector can leak too, so that's something for me to check into.
This wouldn't apply to dfwgsx's problem though, he has a '95.
Foundthis info on the cold start injector, but according to it the injector stays on until the engine warms up.
Since cold starting requires considerably more fuel than a warm engine, it must have some means of enrichening the fuel to air ratio until the temperature of the engine rises to where the fuel will vaporize more readily. The choke systems restricted the air intake so that there was less air moving thru the carburetor while at the same time opening the throttle plate below the choke plate and drawing more fuel. This causes a rich fuel mixture that will enable the engine to run.
The cold start injector (or valve) is mounted in the intake manifold at a centrally located area where it can open and allow extra fuel to enter the engine. This is in addition to the normal fuel injection system. The extra cold start injector is electronically controlled by the computer (ECM) and when the temperature sending units signal the computer that the engine is cold, the computer will send a signal to the cold start injector to inject fuel at the same time as the normal injection system. This makes the air fuel mixture richer to compensate for the cold engine requirements.
The cold start injector delivers fuel to all the cylinders and is controlled by a thermo switch and time control. Thermo switches are located in an area in the engine where engine temperatures can be sensed such as the coolant or head temperature. The temperature sensor has the ability to open the switch when the engine is warm enough to run on the regular injection system or close when the engine is cold and needs more fuel. It activates the cold start injector until the temperature deactivates the thermo switch. (The temperature rating on the switches can be checked in shop manuals).
Whether the sensor is controlling the cold start injector long enough can be felt by cold engine hesitations after the vehicle has run for a few minutes and prior to normal engine temperature. If the temperature sensor rating is too high or staying on too long, there can be some flooding or black tailpipe smoke generated for awhile at about normal engine temperature and also lower gas mileage. It is critical that the correct temperature sensors are used so as not to overload the catalytic converters and foul the oxygen sensors or cause the cold start injectors to work improperly.
HOW TO TEST A COLD START INJECTOR -- when the cold start injector is in a hard to reach area, a pressure drop test with the injector in place can be made. A pressure gauge can be installed at the fuel filter location or at the fuel rail connector. The fuel system can be pressurized by momentarily by-passing the fuel pump relay and then connecting an injector activator to the cold start injector to energize it. This will cause a pressure drop on the gauge if the injector is working. It can also be tested to see if up and then activating the cold start injector. The engine should falter or miss when this is done and possibly black smoke appear from the tailpipe due to the excessively rich mixture.
When the cold start injector is easy to get to and can be removed easily, it may be removed and activated in a container to check the fuel spray pattern. This will enable the injector to be cleaned with a commercial spray cleaner if desired when the spray pattern is not conical or when the injector drips while pressurized.
Loss of electrical power could also be a reason for the cold start injector not working. This can be checked by disabling the engine so it won't start and then connect a test light into the cold start injector connector. The test light should stay on for a short duration when the ignition is turned on. A stop watch can be used to measure the duration of the light staying on. Shop manuals will tell how long each duration of activated injector time is required. The above test should be performed on an engine that is cooled off and prior to start up in order for the injector to work in the time established for proper performance.
The cold start injector (or valve) is mounted in the intake manifold at a centrally located area where it can open and allow extra fuel to enter the engine. This is in addition to the normal fuel injection system. The extra cold start injector is electronically controlled by the computer (ECM) and when the temperature sending units signal the computer that the engine is cold, the computer will send a signal to the cold start injector to inject fuel at the same time as the normal injection system. This makes the air fuel mixture richer to compensate for the cold engine requirements.
The cold start injector delivers fuel to all the cylinders and is controlled by a thermo switch and time control. Thermo switches are located in an area in the engine where engine temperatures can be sensed such as the coolant or head temperature. The temperature sensor has the ability to open the switch when the engine is warm enough to run on the regular injection system or close when the engine is cold and needs more fuel. It activates the cold start injector until the temperature deactivates the thermo switch. (The temperature rating on the switches can be checked in shop manuals).
Whether the sensor is controlling the cold start injector long enough can be felt by cold engine hesitations after the vehicle has run for a few minutes and prior to normal engine temperature. If the temperature sensor rating is too high or staying on too long, there can be some flooding or black tailpipe smoke generated for awhile at about normal engine temperature and also lower gas mileage. It is critical that the correct temperature sensors are used so as not to overload the catalytic converters and foul the oxygen sensors or cause the cold start injectors to work improperly.
HOW TO TEST A COLD START INJECTOR -- when the cold start injector is in a hard to reach area, a pressure drop test with the injector in place can be made. A pressure gauge can be installed at the fuel filter location or at the fuel rail connector. The fuel system can be pressurized by momentarily by-passing the fuel pump relay and then connecting an injector activator to the cold start injector to energize it. This will cause a pressure drop on the gauge if the injector is working. It can also be tested to see if up and then activating the cold start injector. The engine should falter or miss when this is done and possibly black smoke appear from the tailpipe due to the excessively rich mixture.
When the cold start injector is easy to get to and can be removed easily, it may be removed and activated in a container to check the fuel spray pattern. This will enable the injector to be cleaned with a commercial spray cleaner if desired when the spray pattern is not conical or when the injector drips while pressurized.
Loss of electrical power could also be a reason for the cold start injector not working. This can be checked by disabling the engine so it won't start and then connect a test light into the cold start injector connector. The test light should stay on for a short duration when the ignition is turned on. A stop watch can be used to measure the duration of the light staying on. Shop manuals will tell how long each duration of activated injector time is required. The above test should be performed on an engine that is cooled off and prior to start up in order for the injector to work in the time established for proper performance.
http://www.corvetteactioncenter.com/...ead.php?t=9073
#35
10-12-2007, 02:23 PM
RE: fuel pump relay
So how much flooding could be caused by 8 seconds of unnecessary cold start injector fuel?
One things for sure, something is causing a rich, hard start condition when the engine is hot, after it sets for a little while.
#37
10-12-2007, 06:54 PM
RE: fuel pump relay
Well, O2 readings are sometimes obscure, but at idle it should be cycling between .2 volt (lean) and .6 to .7 volt (rich) and a good O2 will have high crosscounts, which are how many times the O2 switches from rich to lean. The O2 doesn't actually control fuel mixture readings as the ECM responds to the readings from the O2. So, if the O2 is switching actively, the ECM has better fuel control. Actually, GM uses whats called a bias voltage to the O2. If you unplug the sensor and turn the key on, you will have somewhere around .2 volts and it measures the return voltage based against the bias voltage. A little theory for ya there! Cruise speed should be similar to idle on a warmed up engine.
#38
10-12-2007, 07:04 PM
RE: fuel pump relay
One of the best places I found for injectors is @ 5-O Motorsports, www.fiveomotorsport.com . Some of you might be aware that TPI Chevys and Port injected Fords (Trucks & Mustangs) use the same injectors. 5.0 Camaro's in the 80's and 5.0 Mustangs use a 19lb injector and Corvette 5.7 and Ford 5.8 use a 22lb injector. You can give them a try. Just Google them to find their web presence.
#39
10-14-2007, 06:34 PM
RE: fuel pump relay
ORIGINAL: dfwgsx
cause once my car gets heated up after i let it sit for about 30 minutes or so it takes a couple turns of the key to get it to finally start, then once it starts i get this big whiff of fuel, someone told me it could be the fuel pump relay
cause once my car gets heated up after i let it sit for about 30 minutes or so it takes a couple turns of the key to get it to finally start, then once it starts i get this big whiff of fuel, someone told me it could be the fuel pump relay
Does it start instantly when cold? I mean instantly - turn the key and let it go, and it runnin'?
#40
10-15-2007, 08:06 AM
RE: fuel pump relay
Do a fuel pressure check , the gauge is not expensive and it could be several things from regulator to fuel filter weak pump and my favorite one, but relay either works or not.
My favorite one is I replaced an electric fuel pump in tank in my sons car and about a year later it would start but not run long.
I bought the pump at a discount auto supply and it worked fine for a year then the hose which came with the pump turned to mush and was leaking more than feeding the engine.
I would have never guessed but a fuel pressure check found the problem.
My favorite one is I replaced an electric fuel pump in tank in my sons car and about a year later it would start but not run long.
I bought the pump at a discount auto supply and it worked fine for a year then the hose which came with the pump turned to mush and was leaking more than feeding the engine.
I would have never guessed but a fuel pressure check found the problem.