Problems starting lately
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 8,740
Likes: 2
From: Minneapolis MN
Problems starting lately
As of the last week I have noticed if the car sits for a few hours when I try to start it again it cranks for quite a bit longer before firing, where before it used to fire right away.
If the car only sits for say a half hour instead of a few hours it fires right up.
When the problem does happen sometimes right after it fires the rpm's will drop low for a second and then rebound and runs fine after that.
Any ideas what could cause this? Leaky injector(s) maybe?
If the car only sits for say a half hour instead of a few hours it fires right up.
When the problem does happen sometimes right after it fires the rpm's will drop low for a second and then rebound and runs fine after that.
Any ideas what could cause this? Leaky injector(s) maybe?
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
I was thinking what you said, leaky injector(s). First thing to do is put on a fuel pressure gauge, ignition on to prime the fule rails, ignition off, and see if you observe noticable pressure bleed down in a short amount of time.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
N1kki6, I followed the thread a few weeks/months back about the bad gas thing. Did you end up replacing the injectors or just cleaning them? From what we discussed I figure you know how to test the fuel system. A possibility it could be leaky injectors.
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 8,740
Likes: 2
From: Minneapolis MN
Originally Posted by RRT vette
N1kki6, I followed the thread a few weeks/months back about the bad gas thing. Did you end up replacing the injectors or just cleaning them? From what we discussed I figure you know how to test the fuel system. A possibility it could be leaky injectors.
Must be a leaky injector. Upon clicking the key over I get 31 psi and within 5 minutes it dropped to 20 psi.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Originally Posted by n1kki6
Didn't end up doing the injectors, just used some techron in the gas.
Must be a leaky injector. Upon clicking the key over I get 31 psi and within 5 minutes it dropped to 20 psi.
Must be a leaky injector. Upon clicking the key over I get 31 psi and within 5 minutes it dropped to 20 psi.
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by n1kki6
Nope, How can I test it?
There's a good tech tip on fuel system diagnosis, very easy to do. I'd have posted the link but I'm too lazy, drunk and tired.
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 8,740
Likes: 2
From: Minneapolis MN
Found the tech tip
... Here are the sure fail tests for the fuel system to save you time and money.. Take a fuel pressure gauge attach it to the schraeder valve.. turn the key on and off a few time to build up the pressure in the system... If you are having starting trouble the pressure will probably drop as soon as it hits 38 or 40 and the pump turns off it will probably leak back to zero within a few minutes. Ok now right after you prime the system pinch off the return line near the tank if the pressure drop stops it is a bad fuel pressure regulator.... Next pinch off the feed line if the pressure holds then the leak is before the point where you pinched the line IE fuel pump check valve..hole in the metal line on the sending unit caused by it rubbing on the inside of the tank you should visibly be able to see this if you pull the pump and the sending unit...(this was my problem) or the pulse dampener which is the piece between the pump and metal line on the sending unit.. the diphragm tears.. and last if you pinch both the feed and return line near the tank and the leak down of the pressure continues then a fuel injector is your problem.. This is the GM test.. saves time and money..
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Large Impressive Member
Joined: Jul 2003
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by n1kki6
So is the FPR in the tank? Also are the stock injectors 22lb in a 94'?
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 8,740
Likes: 2
From: Minneapolis MN
I think I may have lucked out. Just by chance that my battery was going I threw the charger on early this morning, went to start it about 8 and it fired right up. I don't think its the alternator because I am still at 14.3 -14.5 volts while driving. I was kind of wondering this because if I have my hood open for even 10 minutes it doesn't seem the car wants to fire normal unless I have something thats slowly draining the battery as the car sits.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Attach the fuel pressure guage and turn the ignition on (don't crank). Observe the pressure and turn the key off. As you stated the pressure drops which could point to leaky injector(s), ruptured diaphram in FPR, check valve not holding, or pulsator leak. For the FPR take the vacuum of and look for signs of gas. For injectors you will need to pinch off the fuel return line at the tank and see if pressure falls. Check valve and pulsator are in tank. More likely one or more of the injectors are not holding pressure. They are very easy to change on a LT1 compared to a L98. You can also remove the fuel rail assembly bolts and pull up the injectors still attached to the fuel rail and the fuel lines will have some slack so that you can hold the injectors above the holes and pressurize the system and visually check for leaks in the injectors. You can also ohm the injectors one by one using a ohm meter and touch the injector terminal with the black and red leads to get the reading and should be around 16 ohm. This just tests the resistance of the injectors and bad resistance can mean poor operation.
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 8,740
Likes: 2
From: Minneapolis MN
Originally Posted by RRT vette
Attach the fuel pressure guage and turn the ignition on (don't crank). Observe the pressure and turn the key off. As you stated the pressure drops which could point to leaky injector(s), ruptured diaphram in FPR, check valve not holding, or pulsator leak. For the FPR take the vacuum of and look for signs of gas. For injectors you will need to pinch off the fuel return line at the tank and see if pressure falls. Check valve and pulsator are in tank. More likely one or more of the injectors are not holding pressure. They are very easy to change on a LT1 compared to a L98. You can also remove the fuel rail assembly bolts and pull up the injectors still attached to the fuel rail and the fuel lines will have some slack so that you can hold the injectors above the holes and pressurize the system and visually check for leaks in the injectors. You can also ohm the injectors one by one using a ohm meter and touch the injector terminal with the black and red leads to get the reading and should be around 16 ohm. This just tests the resistance of the injectors and bad resistance can mean poor operation.
To test the injectors I shouldnt pinch both lines like the tech tip said, or doesnt it matter.
Thread Starter
Le Mans Master
Joined: Dec 2000
Posts: 8,740
Likes: 2
From: Minneapolis MN
Also before I started having this problem upon clicking the key foward I would be in the upper 30's, now its at about 30, would this leak also cause my pressure to be down right away. I will check the pressure at idle on my lunch break.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by n1kki6
Also before I started having this problem upon clicking the key foward I would be in the upper 30's, now its at about 30, would this leak also cause my pressure to be down right away. I will check the pressure at idle on my lunch break.