90 Corvette Hesitation and Missing
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Joined: Apr 2007
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From: Montgomery Alabama
Way too low. I'll bet that under load it will drop even more. There is only so much increased pulse width can compensate for that. Tape the gauge to the glass and do a WOT run. I'll bet it will drop a lot more than the 45 psi it should be at.
3 things you need. Air (unless you have a blockage somewhere, it should not be a problem. Spark (need a solid blue flame with no heat soak of the coil and other ignition components). Fuel (pressure and pulse width).
Can you have more than 1 problem? Sure. One way to see is to take a good spark plug and ground the threads. Disconnect a wire when it is running and connect it to this plug. Better yet, get a spark tester. You should see a strong blue flame at night.
Fuel. You need to have enough pressure. 45 psi is nice to have. Why is your's so low? Maybe there is an obstruction like a dirty filter, either in the tank sock or the actual fuel filter. Another problem is the fuel pump. Is it getting enough current? Is it weak?
3 things you need. Air (unless you have a blockage somewhere, it should not be a problem. Spark (need a solid blue flame with no heat soak of the coil and other ignition components). Fuel (pressure and pulse width).
Can you have more than 1 problem? Sure. One way to see is to take a good spark plug and ground the threads. Disconnect a wire when it is running and connect it to this plug. Better yet, get a spark tester. You should see a strong blue flame at night.
Fuel. You need to have enough pressure. 45 psi is nice to have. Why is your's so low? Maybe there is an obstruction like a dirty filter, either in the tank sock or the actual fuel filter. Another problem is the fuel pump. Is it getting enough current? Is it weak?
Spark, im not too sure about how to test, can you specify or send me somewhere that has instructions.
Fuel, I'll be putting a new fuel filter in tomorrow and maybe fuel pump if i remove it and it wont respond to 12 volts.
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From: Liberty Twp OH
Same problem on my 1990. Leaky injector makes that cylinder too rich to ignite and results in the stumble at low RPM's. At WOT the air/fuel mixture gets more correct and so it will ignite and run perfect. The leaky injectors clogged the hell out of my cats in the process and clogged up my EGR valve so I deleted them. Ford makes a good but cheap injector M-9593-A302 it is a 24lb injector so you need to chip tune afterwards but the are considered very high quality and are match flowed from Ford. If you look it up you'll find alot about them.
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From: Hartford WI
http://findarticles.com/p/articles/m...2/ai_n9206860/
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
Same problem on my 1990. Leaky injector makes that cylinder too rich to ignite and results in the stumble at low RPM's. At WOT the air/fuel mixture gets more correct and so it will ignite and run perfect. The leaky injectors clogged the hell out of my cats in the process and clogged up my EGR valve so I deleted them. Ford makes a good but cheap injector M-9593-A302 it is a 24lb injector so you need to chip tune afterwards but the are considered very high quality and are match flowed from Ford. If you look it up you'll find alot about them.
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From: Montgomery Alabama
I appreciate the help.
Another question, If it was the spark why would the fuel pressure at the rail prior to being cranked be at 30psi?
I guess i'll replace the filter tomorrow, because I haven't heard of it being replaced since we've owned it and go from there. Next step I guess is the fuel pump and check the spark.
Another question, If it was the spark why would the fuel pressure at the rail prior to being cranked be at 30psi?
I guess i'll replace the filter tomorrow, because I haven't heard of it being replaced since we've owned it and go from there. Next step I guess is the fuel pump and check the spark.
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From: Hartford WI
I appreciate the help.
Another question, If it was the spark why would the fuel pressure at the rail prior to being cranked be at 30psi?
I guess i'll replace the filter tomorrow, because I haven't heard of it being replaced since we've owned it and go from there. Next step I guess is the fuel pump and check the spark.
Another question, If it was the spark why would the fuel pressure at the rail prior to being cranked be at 30psi?
I guess i'll replace the filter tomorrow, because I haven't heard of it being replaced since we've owned it and go from there. Next step I guess is the fuel pump and check the spark.
Unless you have a law that states you can only have one problem at a time, I am stating that you MIGHT have more than 1 problem. So, if this doesn't fix it, something else you can look into might. Don't think you can fix one problem and solve all. BTDT. I too had problems like you mentioned. It was BOTH the pump and spark quality. Make sure you have good spark so you can eliminate that. It shouldn't take you more than 5 mins.
http://www.racetronix.com/RX-C44-FPWHG-2.html is something to look at. They run a wire from the alternator to the tank and a separate ground too. This gives them both the voltage and current to make sure that the pump runs like it should. In the MB world, they test the pump by checking amperage draw, FYI. You don't have to get that sophisticated. Run current from the battery to the pump and a separate ground. Check pressure.
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From: Montgomery Alabama
Where are you at? It doesn't show up.
Unless you have a law that states you can only have one problem at a time, I am stating that you MIGHT have more than 1 problem. So, if this doesn't fix it, something else you can look into might. Don't think you can fix one problem and solve all. BTDT. I too had problems like you mentioned. It was BOTH the pump and spark quality. Make sure you have good spark so you can eliminate that. It shouldn't take you more than 5 mins.
http://www.racetronix.com/RX-C44-FPWHG-2.html is something to look at. They run a wire from the alternator to the tank and a separate ground too. This gives them both the voltage and current to make sure that the pump runs like it should. In the MB world, they test the pump by checking amperage draw, FYI. You don't have to get that sophisticated. Run current from the battery to the pump and a separate ground. Check pressure.
Unless you have a law that states you can only have one problem at a time, I am stating that you MIGHT have more than 1 problem. So, if this doesn't fix it, something else you can look into might. Don't think you can fix one problem and solve all. BTDT. I too had problems like you mentioned. It was BOTH the pump and spark quality. Make sure you have good spark so you can eliminate that. It shouldn't take you more than 5 mins.
http://www.racetronix.com/RX-C44-FPWHG-2.html is something to look at. They run a wire from the alternator to the tank and a separate ground too. This gives them both the voltage and current to make sure that the pump runs like it should. In the MB world, they test the pump by checking amperage draw, FYI. You don't have to get that sophisticated. Run current from the battery to the pump and a separate ground. Check pressure.
Yeah how would I run a wire from the battery to the fuel pump if the pump is in the tank? Is there an easier way to go about it or?
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From: Hartford WI
The pump is in the tank. I wouldn't suggest you go clamping wires to it just like that. http://www.ecklers.com/product.asp?p...7&dept_id=1268 is a good picture. See the "square"? That is the top. There is a plug on that top that is connected to a harness. That is where the fuel pump wires are at. There is also a sender connection. It would be easier if you had a helms manual or a FSM. I have both and if you wanted to, I might be able to scan the page to you
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From: Montgomery Alabama
Something else I forgot. Check your fuel pressure regulator. http://forums.corvetteforum.com/1569662603-post2.html
The pump is in the tank. I wouldn't suggest you go clamping wires to it just like that. http://www.ecklers.com/product.asp?p...7&dept_id=1268 is a good picture. See the "square"? That is the top. There is a plug on that top that is connected to a harness. That is where the fuel pump wires are at. There is also a sender connection. It would be easier if you had a helms manual or a FSM. I have both and if you wanted to, I might be able to scan the page to you
The pump is in the tank. I wouldn't suggest you go clamping wires to it just like that. http://www.ecklers.com/product.asp?p...7&dept_id=1268 is a good picture. See the "square"? That is the top. There is a plug on that top that is connected to a harness. That is where the fuel pump wires are at. There is also a sender connection. It would be easier if you had a helms manual or a FSM. I have both and if you wanted to, I might be able to scan the page to you
Ohhhh I see what it is. So I just connect the leads to those terminals and it should send 12v straight to the fuel pump?
Thanks for all your help man, I really appreciate it. I work at advance auto thats about .5 miles from the house so I can always go check the book there
.
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From: Hartford WI
Whenever I start and run the car it has a strong smell of gas. I noticed the guy from FIC stated that in the post you referenced. Maybe it is the injectors? I guess we'll see when we check the fuel filter/pump issue.
Ohhhh I see what it is. So I just connect the leads to those terminals and it should send 12v straight to the fuel pump?
Thanks for all your help man, I really appreciate it. I work at advance auto thats about .5 miles from the house so I can always go check the book there.
Ohhhh I see what it is. So I just connect the leads to those terminals and it should send 12v straight to the fuel pump?
Thanks for all your help man, I really appreciate it. I work at advance auto thats about .5 miles from the house so I can always go check the book there
.Yes. Here is the trick. You have to be very careful when doing this. IF your injectors are leaking, you could be sending fuel down and hydrolocking the thing. So, take out the plugs when you are done testing should you suspect that it is the injectors. Crank motor over so it blows the gas out instead of hydrolocking the motor.
The helms manual is a start. Get a set of FSM to be really sure.
Last edited by aklim; Apr 28, 2009 at 12:03 AM.
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From: Montgomery Alabama
Maybe. Again, it could be your injectors leaking. I can't tell from here. I would think that if you clamped off the return line, the fuel pressure has to either build up or drain somewhere. That somewhere is the injectors into the cylinders. Clamping off the line should force it to build up pressure. If it cannot even do that, your problem is pump related. If it can, it might be the regulator or the injectors leaking.
Yes. Here is the trick. You have to be very careful when doing this. IF your injectors are leaking, you could be sending fuel down and hydrolocking the thing. So, take out the plugs when you are done testing should you suspect that it is the injectors. Crank motor over so it blows the gas out instead of hydrolocking the motor.
The helms manual is a start. Get a set of FSM to be really sure.
Yes. Here is the trick. You have to be very careful when doing this. IF your injectors are leaking, you could be sending fuel down and hydrolocking the thing. So, take out the plugs when you are done testing should you suspect that it is the injectors. Crank motor over so it blows the gas out instead of hydrolocking the motor.
The helms manual is a start. Get a set of FSM to be really sure.
Also after turning off the car for awhile it takes awhile for the pressure to go back down.
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From: Near Lockport NY Black 1986 Coupe
It's threads like these that make me happy I went to the dark side.. no offense to the OP, I hope you get your problem solved - it does sound like injectors. But all of this talk of error codes, leaky/fault injectors, bad sensors, etc. erases the guilt of taking off the fuel injection.. damn.
Well anyway, keep us posted. I'd like to know for sure what turns out to be the problem, incase I ever switch back to the faithful EFI.
Well anyway, keep us posted. I'd like to know for sure what turns out to be the problem, incase I ever switch back to the faithful EFI.
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From: Hartford WI
That makes me thing it is your pump.
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From: Hartford WI
It's threads like these that make me happy I went to the dark side.. no offense to the OP, I hope you get your problem solved - it does sound like injectors. But all of this talk of error codes, leaky/fault injectors, bad sensors, etc. erases the guilt of taking off the fuel injection.. damn.
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From: Montgomery Alabama
Yeah I think it maybe the pump. I'm replacing the filter today and if i need the pump i can always get it. How hard are they to install?
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From: Hartford WI
Very easy to get to. Take the fuel lid off and take the rubber thing off, several bolts (9 IIRC) and the pump comes out.