Potential fuel pressure issue
#1
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Car: 1991 Z28
Engine: L31-R 350 w/ EBL P4
Transmission: 700R4
Axle/Gears: 2.73
Potential fuel pressure issue
I've got the stock 305 TPI in my car. Around June of last year, I noticed my car acting weird - especially on hills. When I start to give the car more throttle (to climb a hill or accelerate quicker), sometimes the engine drops a few hundred RPMs. The more gas I give it, the lower the RPMs drop. Sometimes, letting off the gas and getting back on the gas fixes the issue. Other times, the engine will correct itself and raise about 500-600 RPMs in a matter of seconds without me changing the amount of throttle I'm giving the engine.
On even more rare occasions, the car will jump between about 1800 and 2000 RPM's while climbing hills every second. Giving more throttle bogs the engine down more, so usually I just keep the throttle constant while I make my way up the hill bouncing between those two RPMs. Once I reach the top of the hill, the car usually corrects itself and raises about 500-600 RPMs to where the engine should be running at.
So after almost a year of this, I'd like to fix this. It's a sporadic issue that doesn't happen every time time I climb a hill or give the car a lot of throttle, but it happens often enough that it's getting annoying. And every time it happens I wonder if the car will die while I'm climbing a hill or merging onto the freeway. I'm thinking it's a fuel pressure issue (fuel pressure regulator maybe), but I thought I'd come and ask about it on here before I start tearing into my car.
On even more rare occasions, the car will jump between about 1800 and 2000 RPM's while climbing hills every second. Giving more throttle bogs the engine down more, so usually I just keep the throttle constant while I make my way up the hill bouncing between those two RPMs. Once I reach the top of the hill, the car usually corrects itself and raises about 500-600 RPMs to where the engine should be running at.
So after almost a year of this, I'd like to fix this. It's a sporadic issue that doesn't happen every time time I climb a hill or give the car a lot of throttle, but it happens often enough that it's getting annoying. And every time it happens I wonder if the car will die while I'm climbing a hill or merging onto the freeway. I'm thinking it's a fuel pressure issue (fuel pressure regulator maybe), but I thought I'd come and ask about it on here before I start tearing into my car.
#2
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Car: 91' Firebird SOLD
Engine: 350 TPI +bolt-ons
Transmission: 700r4
Axle/Gears: 3:42
Re: Potential fuel pressure issue
I've got the stock 305 TPI in my car. Around June of last year, I noticed my car acting weird - especially on hills. When I start to give the car more throttle (to climb a hill or accelerate quicker), sometimes the engine drops a few hundred RPMs. The more gas I give it, the lower the RPMs drop. Sometimes, letting off the gas and getting back on the gas fixes the issue. Other times, the engine will correct itself and raise about 500-600 RPMs in a matter of seconds without me changing the amount of throttle I'm giving the engine.
On even more rare occasions, the car will jump between about 1800 and 2000 RPM's while climbing hills every second. Giving more throttle bogs the engine down more, so usually I just keep the throttle constant while I make my way up the hill bouncing between those two RPMs. Once I reach the top of the hill, the car usually corrects itself and raises about 500-600 RPMs to where the engine should be running at.
So after almost a year of this, I'd like to fix this. It's a sporadic issue that doesn't happen every time time I climb a hill or give the car a lot of throttle, but it happens often enough that it's getting annoying. And every time it happens I wonder if the car will die while I'm climbing a hill or merging onto the freeway. I'm thinking it's a fuel pressure issue (fuel pressure regulator maybe), but I thought I'd come and ask about it on here before I start tearing into my car.
On even more rare occasions, the car will jump between about 1800 and 2000 RPM's while climbing hills every second. Giving more throttle bogs the engine down more, so usually I just keep the throttle constant while I make my way up the hill bouncing between those two RPMs. Once I reach the top of the hill, the car usually corrects itself and raises about 500-600 RPMs to where the engine should be running at.
So after almost a year of this, I'd like to fix this. It's a sporadic issue that doesn't happen every time time I climb a hill or give the car a lot of throttle, but it happens often enough that it's getting annoying. And every time it happens I wonder if the car will die while I'm climbing a hill or merging onto the freeway. I'm thinking it's a fuel pressure issue (fuel pressure regulator maybe), but I thought I'd come and ask about it on here before I start tearing into my car.
#3
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Car: 1991 Z28
Engine: L31-R 350 w/ EBL P4
Transmission: 700R4
Axle/Gears: 2.73
Re: Potential fuel pressure issue
I have not. I checked the technical articles and didn't see anything about testing fuel injectors. I Googled "how to test fuel injectors" and found a few that said check the resistance of the fuel injectors with an OHM meter. Is this a good method? If it is, what kind of resistance would tell me if the fuel injector is good or bad?
#4
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Car: 91' Firebird SOLD
Engine: 350 TPI +bolt-ons
Transmission: 700r4
Axle/Gears: 3:42
Re: Potential fuel pressure issue
I have not. I checked the technical articles and didn't see anything about testing fuel injectors. I Googled "how to test fuel injectors" and found a few that said check the resistance of the fuel injectors with an OHM meter. Is this a good method? If it is, what kind of resistance would tell me if the fuel injector is good or bad?
#5
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Car: 1991 Z28
Engine: L31-R 350 w/ EBL P4
Transmission: 700R4
Axle/Gears: 2.73
Re: Potential fuel pressure issue
Alright, I got out there today and got these readings:
Cylinders 1,2,3,4,5,7 all had readings of 16.3 or 16.2 (they jumped between the two)
Cylinder #6 had a reading of 15.3 and cylinder #8 had a reading of 15.9.
Is the 1 ohm difference on cylinder 6 giving me issues?
Cylinders 1,2,3,4,5,7 all had readings of 16.3 or 16.2 (they jumped between the two)
Cylinder #6 had a reading of 15.3 and cylinder #8 had a reading of 15.9.
Is the 1 ohm difference on cylinder 6 giving me issues?
#6
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Re: Potential fuel pressure issue
Alright, I got out there today and got these readings:
Cylinders 1,2,3,4,5,7 all had readings of 16.3 or 16.2 (they jumped between the two)
Cylinder #6 had a reading of 15.3 and cylinder #8 had a reading of 15.9.
Is the 1 ohm difference on cylinder 6 giving me issues?
Cylinders 1,2,3,4,5,7 all had readings of 16.3 or 16.2 (they jumped between the two)
Cylinder #6 had a reading of 15.3 and cylinder #8 had a reading of 15.9.
Is the 1 ohm difference on cylinder 6 giving me issues?
Cold they look good, check them hot to see if the readings are the same
#7
Sponsor
Re: Potential fuel pressure issue
Alright, I got out there today and got these readings:
Cylinders 1,2,3,4,5,7 all had readings of 16.3 or 16.2 (they jumped between the two)
Cylinder #6 had a reading of 15.3 and cylinder #8 had a reading of 15.9.
Is the 1 ohm difference on cylinder 6 giving me issues?
Cylinders 1,2,3,4,5,7 all had readings of 16.3 or 16.2 (they jumped between the two)
Cylinder #6 had a reading of 15.3 and cylinder #8 had a reading of 15.9.
Is the 1 ohm difference on cylinder 6 giving me issues?
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#8
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Car: 1991 Z28
Engine: L31-R 350 w/ EBL P4
Transmission: 700R4
Axle/Gears: 2.73
Re: Potential fuel pressure issue
I went out for a 10 minute drive today and got the car up to temperature. Came back and took some measurements.
Cylinder #1: 17.1
Cylinder #2: 17.7
Cylinder #3: 17.2
Cylinder #4: 17.5
Cylinder #5: 17.0
Cylinder #6: 16.2
Cylinder #7: 17.1
Cylinder #8: 17.2
Cylinder #1: 17.1
Cylinder #2: 17.7
Cylinder #3: 17.2
Cylinder #4: 17.5
Cylinder #5: 17.0
Cylinder #6: 16.2
Cylinder #7: 17.1
Cylinder #8: 17.2
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