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Discussion Starter #1 (Edited)
Long cranks only in the morning. Checked fuel pressure and found it between 20 psi and 28 psi primed. The key on/off trick helped a bit. What really surprised me (unpleasantly) the idle pressure was 35 psi with AND without FPR. The gauge needle was fluttering. The vacuum at the FPR port was 18". It used to be 20". No signs of fuel in FPR port. It used to be 44 psi with vacuum removed from FPR. Do you think the FPR is shot or maybe vacuum is too low to make it work?
Checked vacuum at the optispark vent and it was 15" (used to be 18").

I have a replacement fuel pump but it looks as soon as one replaces the original pump, one keeps replacing them again and again...
 

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28 psi for FP is to low...it would very likely have start issues.

have you changed fuel filter?

if so, you need to deal with the in tank pump. Either wiring or the pump itself

FWIW I replaced mine with a Walbro 255 (12-15 years ago) and have not had a problem since. I replaced just the pump, not the whole assembly

Your lower vacuum reading may be because you have a vac leak. Did you plug the FPR vac hose when you took the reading?
 

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Discussion Starter #3
28 psi for FP is to low...it would very likely have start issues.

have you changed fuel filter?

if so, you need to deal with the in tank pump. Either wiring or the pump itself

FWIW I replaced mine with a Walbro 255 (12-15 years ago) and have not had a problem since. I replaced just the pump, not the whole assembly

Your lower vacuum reading may be because you have a vac leak. Did you plug the FPR vac hose when you took the reading?
BALLSS,

The fuel filter is new. I think the pump is a bit weak. I have Spectra Premium pump, which has good reviews. Heard about Walbro 255, but I am on budget, so will try first what I have.

Probably the most common FPR failure mode is leaking diaphragm. Nevertheless, I think it possible to have it stuck, so it does not react to vacuum applied.

I have been monitoring vacuum readings for many years, and they have a tendency to go down. Probably a leak I could never find (so many possibilities!).

I am afraid I need both the pump and FPR replaced. My fuel economy is terrible. It could or could not be related. Yes, the vacuum line to FPR was in place when I checked vacuum on Opti vent harness.
 

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prolonged first start can be due to a leaking FPR diaphragm. That usually shows fuel, or fuel Oder, in the rubber vac nipple to FPR. Could a FPR diaphragm stick...well I guess that is possible but from seeing inside one it looks to me they either get a hole or tear vs sticking in a fixed position.


You could replace the FPR to see if your symptoms, and fuel pressure, improve but I suspect the problem lies in the pump itself.

It's been a long time since I put in my Walbro and I am sure $ have gone up since then but it was cheaper than a whole assembly. My purpose for putting it in was my stock pump no longer kept up with my H/C motor as pressure dropped to zero on dyno pull. Car otherwise ran though


a vacuum gauge can tell quite a bit about a motor. lower, but steady, reading typically means a vac leak somewhere in the car. This usually causes STFT to increase and car to run rich as 02's read more unmetered air and pcm dumps fuel
 

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Discussion Starter #5
As I mentioned, no fuel in vacuum line to FPR. My plan is replacing FPR first and then taking care of the pump when I have a chance to lift the car. I NEVER liked the way my Fleetwood ran. Occasional lack of power, poor throttle response and lately that terrible 10 MPG around the town.

DELPHI FPR is a half of the price for one from ACDELCO. Hope, it will do the job.
 

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fuel pressure test key on engine off 41-47 psi.. now if the pressure drops off like in less than 15min , then most likely the FPReg is bad...



this test if below about 38 psi will cause poor starts and if lower miss fires/stalls.. 28 psi engine runs that is not common..


so if the engine is off and you get 41-47psi and hold but when engine is on it drops down fuel filter or the pickup screen/tube has issues...


also engine on check for volts at the fuel pump connector rear license plate should be 11 volts plus..there is a 2 volt drop because of the long run..
 

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Discussion Starter #7
fuel pressure test key on engine off 41-47 psi.. now if the pressure drops off like in less than 15min , then most likely the FPReg is bad...



this test if below about 38 psi will cause poor starts and if lower miss fires/stalls.. 28 psi engine runs that is not common..


so if the engine is off and you get 41-47psi and hold but when engine is on it drops down fuel filter or the pickup screen/tube has issues...


also engine on check for volts at the fuel pump connector rear license plate should be 11 volts plus..there is a 2 volt drop because of the long run..
The pressure does not drop at all. It is just at 22 psi primed and 34 psi with or without FPR vacuum applied.
I'll test volt drop when I have a chance. Thank you.
 

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Long cranks only in the morning. Checked fuel pressure and found it between 20 psi and 28 psi primed. The key on/off trick helped a bit. What really surprised me (unpleasantly) the idle pressure was 35 psi with AND without FPR. The gauge needle was fluttering. The vacuum at the FPR port was 18". It used to be 20". No signs of fuel in FPR port. It used to bt 44 psi with vacuum removed from FPR. Do you think the FPR is shot or maybe vacuum is too low to make it work?
Checked vacuum at the optispark vent and it was 15" (used to be 18").

I have a replacement fuel pump but it looks as soon as one replaces the original pump, one keeps replacing them again and again...
Huf, I'm leaning toward a bad pump or it is also possible that the hose in the tank has a crack or broken and some and some of the fuel is blowing back into the tank. I had the broken hose or lid (can't remember) before and was only seeing about 20 psi at the rail and with the pump running and low fuel in the tank, I could hear fuel falling back into the tank. Sounded like a waterfall.

It could also be voltage or lack of 12v at the pump harness. You really should not see that much of a voltage drop in the circuit past the relay as it pretty much just a wire with no resistors in the circuit. Dirty connections can cause the voltage drop and unplug the 3 wire connector back at the bumper to see what voltage you have there at KOEO. You need to be quick though cause it will only prime for 2 seconds with no oil pressure. Don't forget the FP prime override wire as this will apply voltage directly to the rear connector the entire time you are testing. This also bypasses the FP relay which could be the issue or its contacts.

I can tell you from my experience and with using the racetronix hot wire kit, you will see close to charging voltage (14v) at the fuel pump. This increase in voltage gave me about 3-4 more psi than just the stock wiring alone. So it would stand to reason that lower voltage to the pump could be the issue. You could also have corrosion on the in tank harness before going to the pump. This is a real COMMON issue on our cars especially at the bulkhead connector inside the tank.

Also, when checking for voltage at the back bumper area, the connector will have 3 wires, gray (hot), black (ground) and purple (fuel gauge), try to use the DVM test leads on the pins at the connector for both black and gray wires. If you use the gray wire and then touch body ground with the other lead, this may not reveal an actual ground problem at the pump harness cause you will see a solid 12v. So be sure to use both wires that the pump would be using. Ground wire is also another common fault on these cars.
 

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Discussion Starter #9
Huf, I'm leaning toward a bad pump or it is also possible that the hose in the tank has a crack or broken and some and some of the fuel is blowing back into the tank. I had the broken hose or lid (can't remember) before and was only seeing about 20 psi at the rail and with the pump running and low fuel in the tank, I could hear fuel falling back into the tank. Sounded like a waterfall.

It could also be voltage or lack of 12v at the pump harness. You really should not see that much of a voltage drop in the circuit past the relay as it pretty much just a wire with no resistors in the circuit. Dirty connections can cause the voltage drop and unplug the 3 wire connector back at the bumper to see what voltage you have there at KOEO. You need to be quick though cause it will only prime for 2 seconds with no oil pressure. Don't forget the FP prime override wire as this will apply voltage directly to the rear connector the entire time you are testing. This also bypasses the FP relay which could be the issue or its contacts.

I can tell you from my experience and with using the racetronix hot wire kit, you will see close to charging voltage (14v) at the fuel pump. This increase in voltage gave me about 3-4 more psi than just the stock wiring alone. So it would stand to reason that lower voltage to the pump could be the issue. You could also have corrosion on the in tank harness before going to the pump. This is a real COMMON issue on our cars especially at the bulkhead connector inside the tank.

Also, when checking for voltage at the back bumper area, the connector will have 3 wires, gray (hot), black (ground) and purple (fuel gauge), try to use the DVM test leads on the pins at the connector for both black and gray wires. If you use the gray wire and then touch body ground with the other lead, this may not reveal an actual ground problem at the pump harness cause you will see a solid 12v. So be sure to use both wires that the pump would be using. Ground wire is also another common fault on these cars.
Thank you for a very good advice! For a few hours, I may have a lift in a friend's shop in NJ. I think the best way is dropping the tank and see what is going on inside, check hoses, connectors, etc. I want to be prepared in case some stuff has to be replaced. I have new pump (only pump) and will order new Delphi FPR. Racetronix harness probably great, but money is super tight at the moment. Is this the connector inside of the tank , which could be bad?
 

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Thank you for a very good advice! For a few hours, I may have a lift in a friend's shop in NJ. I think the best way is dropping the tank and see what is going on inside, check hoses, connectors, etc. I want to be prepared in case some stuff has to be replaced. I have new pump (only pump) and will order new Delphi FPR. Racetronix harness probably great, but money is super tight at the moment. Is this the connector inside of the tank , which could be bad?
Not sure what that connector is you have pictured and see you may have a Caddy. I believe thogh the Sending unit is the same or similar as it is on the B-Body car. the connector I was referring to is the Yellow Bulkhead fitting mounted to the Top of the Sending unit that connects the Outside wiring to the Inside wiring. It is pictured here in the Racetronix kit....

https://www.racetronix.biz/product.asp?ic=bcwa-blt1

Pretty sure I remember seeing somewhere that the Caddy may have 4 wires and not just 3 like the B-Body car. But believe that 4th wire was just an extra ground. Think there is info in a thread here that I saw on this topic.

But that Bulkhead fitting on the inside the tank side can get corroded especially on the Ground wire. that's what got me once while on vacation. Replaced the pump only to discover the burnt connection when it failed again and after closer inspection.

EDIT - BTW on that plug you have pictured, do you know what that was from or the description? the shape of that connector makes me think of a Square Plug that is mounted in the LR Footwell area of my 95 caprice. Not 100% certain what that plug is for but I know it's on my car and it is shaped like that. Maybe this is the Plug that brings the wiring from the front of the car to the back area?
 

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Discussion Starter #11 (Edited)
Huf, I'm leaning toward a bad pump or it is also possible that the hose in the tank has a crack or broken and some and some of the fuel is blowing back into the tank. I had the broken hose or lid (can't remember) before and was only seeing about 20 psi at the rail and with the pump running and low fuel in the tank, I could hear fuel falling back into the tank. Sounded like a waterfall.

It could also be voltage or lack of 12v at the pump harness. You really should not see that much of a voltage drop in the circuit past the relay as it pretty much just a wire with no resistors in the circuit. Dirty connections can cause the voltage drop and unplug the 3 wire connector back at the bumper to see what voltage you have there at KOEO. You need to be quick though cause it will only prime for 2 seconds with no oil pressure. Don't forget the FP prime override wire as this will apply voltage directly to the rear connector the entire time you are testing. This also bypasses the FP relay which could be the issue or its contacts.

I can tell you from my experience and with using the racetronix hot wire kit, you will see close to charging voltage (14v) at the fuel pump. This increase in voltage gave me about 3-4 more psi than just the stock wiring alone. So it would stand to reason that lower voltage to the pump could be the issue. You could also have corrosion on the in tank harness before going to the pump. This is a real COMMON issue on our cars especially at the bulkhead connector inside the tank.

Also, when checking for voltage at the back bumper area, the connector will have 3 wires, gray (hot), black (ground) and purple (fuel gauge), try to use the DVM test leads on the pins at the connector for both black and gray wires. If you use the gray wire and then touch body ground with the other lead, this may not reveal an actual ground problem at the pump harness cause you will see a solid 12v. So be sure to use both wires that the pump would be using. Ground wire is also another common fault on these cars.
I just tried to make measurements at the connector you described and it has FOUR wires: Black, Blue, Gray and Black with gray stripe. This is Cadillac vs Chevy difference, I guess.
I can ask my GF to turn the ignition key on and off so I would be able to measure the voltage between Black and Gray, Black and Blue and Black and Black with stripe. They all are supposed to be close to whatever I have at the battery terminals.
Here is one thing I must mention. I have unresolved battery issues. So, in the morning the voltage can be some 12.10 -12.20 V and less than that at the pump. That could cause the pump provide less pressure than expected when PRIMED. When I do manage to start the engine and the alternator kicks in, the pump gets more power and may provide more pressure, so I get 34 psi at idle. Now, if I only knew why pressure does not jump a few psi when I pull the vacuum line off FPR. There is no fuel/fuel smell in that line, so the diaphragm is still intact.

The resistance of FP winding (plus wires and connectors) is 7.3 Ohm. Seems to be very close to new Spectra Premium (6.1 ohm).

The voltage at the connector is practically equal to one at the battery. After the battery got a bit of charge from alternator, the pressure primed increased to 28 psi (at 12.55 V). Still low. Pressure at idle was 34 psi. Disconnecting vacuum line from FPR did not make any difference.

My plan is dropping the tank to see what is going on inside and go from there. Will keep you updated. Will order new FPR anyway since replacing is not a big deal.
 

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Given the FPR does not react to vacuum in terms of fuel pressure changing (it should get higher by 5-8 psi without vacuum) could mean a bad FPR which is WAY easier to replace then in tank pump.

Might want to do that first to see if that is all you need to do.

The pressure should immediately snap to around 44 and drop to around 38 with KOEO

It should then be around 38 with engine on and increase some on acceleration (vacuum hose on)

weak battery could affect some but your slightly lower battery voltage is not that low
 

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I just tried to make measurements at the connector you described and it has FOUR wires: Black, Blue, Gray and Black with gray stripe. This is Cadillac vs Chevy difference, I guess.
I can ask my GF to turn the ignition key on and off so I would be able to measure the voltage between Black and Gray, Black and Blue and Black and Black with stripe. They all are supposed to be close to whatever I have at the battery terminals.
Here is one thing I must mention. I have unresolved battery issues. So, in the morning the voltage can be some 12.10 -12.20 V and less than that at the pump. That could cause the pump provide less pressure than expected when PRIMED. When I do manage to start the engine and the alternator kicks in, the pump gets more power and may provide more pressure, so I get 34 psi at idle. Now, if I only knew why pressure does not jump a few psi when I pull the vacuum line off FPR. There is no fuel/fuel smell in that line, so the diaphragm is still intact.

The resistance of FP winding (plus wires and connectors) is 7.3 Ohm. Seems to be very close to new Spectra Premium (6.1 ohm).

The voltage at the connector is practically equal to one at the battery. After the battery got a bit of charge from alternator, the pressure primed increased to 28 psi (at 12.55 V). Still low. Pressure at idle was 34 psi. Disconnecting vacuum line from FPR did not make any difference.

My plan is dropping the tank to see what is going on inside and go from there. Will keep you updated. Will order new FPR anyway since replacing is not a big deal.

my battery voltage is 12.6 volts .. when key on NO crank , the voltage at rear fuel pump connector external under the trunk is about 11.2 volts .. so a voltage drop of perhaps 1.4 volts.. fuel pressure is in the spec of 42 psi. .
new pumps are another part crap shoot ... also many with pump issues did have the pickup tube and or the electrical in tank connections fail..


if you solder the wires on the pump use silver solder ..
 

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Discussion Starter #14
BALLSS and J cat,
Thank you. I will no better when I drop the tank and see what is going on inside. I am not even sure the FPR is bad. Probably, the pump just does not provide more than 34 psi, so taking off the vacuum hose does not make difference.

Is the fuel return hose under the hood is plastic? I was thinking of chocking it to see if the pressure increases to check FPR.
 

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BALLSS and J cat,
Thank you. I will no better when I drop the tank and see what is going on inside. I am not even sure the FPR is bad. Probably, the pump just does not provide more than 34 psi, so taking off the vacuum hose does not make difference.

Is the fuel return hose under the hood is plastic? I was thinking of chocking it to see if the pressure increases to check FPR.

the regulator does reduce pressure when the vacuum is high idling .. when you floor it the vacuum drops and the pressure will rise like when engine is off..since the pressure is so low then the regulator will not do anything ..
 

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I just tried to make measurements at the connector you described and it has FOUR wires: Black, Blue, Gray and Black with gray stripe. This is Cadillac vs Chevy difference, I guess.
I can ask my GF to turn the ignition key on and off so I would be able to measure the voltage between Black and Gray, Black and Blue and Black and Black with stripe. They all are supposed to be close to whatever I have at the battery terminals.
Here is one thing I must mention. I have unresolved battery issues. So, in the morning the voltage can be some 12.10 -12.20 V and less than that at the pump. That could cause the pump provide less pressure than expected when PRIMED. When I do manage to start the engine and the alternator kicks in, the pump gets more power and may provide more pressure, so I get 34 psi at idle. Now, if I only knew why pressure does not jump a few psi when I pull the vacuum line off FPR. There is no fuel/fuel smell in that line, so the diaphragm is still intact.

The resistance of FP winding (plus wires and connectors) is 7.3 Ohm. Seems to be very close to new Spectra Premium (6.1 ohm).

The voltage at the connector is practically equal to one at the battery. After the battery got a bit of charge from alternator, the pressure primed increased to 28 psi (at 12.55 V). Still low. Pressure at idle was 34 psi. Disconnecting vacuum line from FPR did not make any difference.

My plan is dropping the tank to see what is going on inside and go from there. Will keep you updated. Will order new FPR anyway since replacing is not a big deal.

If you found you have a good/Solid 12V and Ground back at the connector, then it has to be an issue in the Tank. If dropping the tank, I would most certainly just replace the Pump and replace the intank wiring and double/triple check those connections. GL
 

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Discussion Starter #17
I was trying to disconnect fuel lines at the tank (managed to do only 5/16" one so far) and found this... see the picture. That is evap line. The part of the hose still attached to the pump assembly is quite rotten... the hose, which goes to evap canister is solid and has a nylon tube inside. Question: was there something connecting these two parts, or it was the same hose? What if I leave it as is for now?

As for quick disconnect tool, I use a set of plastic ones. Any tricks to get that stubborn 3/8" line disconnected?
 

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you can spray wd40 in the fitting that is stubborn and try again with the fuel line disconnect tool

Pushing the line towards the tool some, I find, helps

The vapor line goes up to the charcoal canister...I would suspect you would throw one of the EVAP codes if it is disconnected
 

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Discussion Starter #19
Okay. The tank is off and pump assembly is out. Surprisingly, all the wires, connectors, etc. look wonderful... Shall I replace the original pump with Spectra Premium? I think I will. I have no replacement strainer. Any way to get the original strainer off the pump and use it with new pump?

I'll fix that failed evap line.
 

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