Odd and Even Banks on Northstar

[KHE]

If the Carter pump is the same company that produces carburetors, it is probably OK. Is the Carter pump available locally where you can inspect it? If it were me, I would make sure it is US made. It is $76 cheaper than the ACDelco pump on Rockauto.

If you go with the AC Delco pump, make sure to get the dealer part no. so you know you're ordering the correct pump.

Verify the electrical connections to the pump - they may be arced/corroded.

[BodybyFisher]

Thanks, I am reluctant to go cheap here. I went to rockauto also and they have a Delphi pump and to me that is the cheapest I want to go. The Carter pump was from a local Autozone as much as I used to like the Carter AFB, its probably not a good idea to go cheap, as a matter of fact locally that Carter pump is $230, so I am going to try to push him into the Delphi with rockauto delivery less 5% discount if I can get one or the AC Delco.

I suspect that running the fuel low is a good idea huh?

Ill go to the dealer and see what he has for fuel tank hardware. Thanks

[KHE]

The AC Delco part is $251.79 from Rockauto - with the 5% discount, that will just about pay for the shipping. When you include sales tax on the pump purchased locally, the cost is going to be about the same. I'd use the AC Delco pump. Maybe your dealer will match rockauto's price?

You want the tank as close to empty as possible since it can get heavy with fuel in it and it is awkward laying on a creeper wrestling the tank. You can probably siphon most of it out. Another way is to disconnect the supply line and hotwire the pump to run continuously pumping the fuel into gas cans. I don't like the idea of creating sparks with all that fuel vapor around though.

[BodybyFisher]

I am going to let him let it run really low before I do it. I did plan on using a floor jack in the center of plywood to distribute the load guiding it down, sound ok?

The filler neck on my 96 was corroded through, so Ill have a look this one, thanks. I assume there are quick disconnects at the pump?

[KHE]

There should be quick disconnects at the pump. I checked the price of the filler neck on gmpartsgiant.com and it was $272.58!!! I could see $50.00 but $272 is a gouge-job. A seller on ebay has them for the Deville for $53.00 but not the Seville/Eldorado. I wonder if that part is available in the aftermarket? What did you pay for your filler tube?

Using a piece of wood is a good idea to distribute the load. If the tank has only one or two gallons of fuel in it, it won't weigh that much. Is the car even driveable with 25 psi of fuel pressure??

[BodybyFisher]

I never replaced mine, it didnt throw codes but I think it could have easily taken in water.

Oddly enough it can be driven but it misses badly and has no power at all, I would have thought that 25 psi would have rendered it undriveable. Dont get me wrong however it has NO power at all, feels like a clogged CAT and missing

[lothos]

But I have a question, my memory tells me that there was a tiny oring at the bottom of the FPR, I see the screen but no oring, should there be an tiny oring?

From my memory on a 1995 STS with the NS. Yes, there should be an oring on the bottom of the FPR.

[BodybyFisher]

Thanks for that info, I thought I recalled an oring. Let me ask, is it below the screen or above it? I didnt take the screen out, it remained in the FPR body maybe it was below the screen?

[KHE]

It's been a long time since I changed a FPR but it seems to me, the small o-ring was underneath the FPR on a nipple that is inserted into the fuel rail.

[JohnnyG]

Is there an IN TANK fuel filter on this model? We used to call it a "sock" filter, when it would plug (after many years) it would cause the exact same conditions that you are describing. Remember, a fuel pump needs good supply volume as well as good output volume/pressure. Blocking the return line as KHE (?) says may show full pressure...if it does, but takes a little time to get there, the pump itself may be good, but the intake filter may be plugged.

[BodybyFisher]

Thanks Johnny, yes that is a possibility also.

I rechecked the fuel pressure yesterday, and the results were poor

Key On - 27 PSI

Key off

Key On - 34 PSI

Engine idling 34 PSI

Engine Revving drops to 30 PSI

Changed the FPR no change

These fuel pressures seem to be low to me given that my Monte Carlo immediately reads 45 with the Key On

[JimD]

....

I rechecked the fuel pressure yesterday, and the results were poor

Key On - 27 PSI

Key off

Key On - 34 PSI

Mike:

I don't see anything alarming with those numbers.

Here is what I observed on my 2004 Deville several years ago when I was measuring fuel pressure decay at rest.

3/6/07

2004 DTS fuel pressure

Cold engine 0 psi

Key on - off several times = 38 psi

Key off

15 seconds elapsed time = 36 psi

60 seconds elapsed time = 36 psi

2 minutes elapsed time = 35 psi

5 minutes elapsed time = 34 psi

Given the differences in accuracy between your pressure gauge and my pressure gauge there is no convincing difference between your fuel pump pressure and my fuel pump pressure.

[BodybyFisher]

Hmm, and yet my Monte Carlo has 45, so what you are saying is that if my gage is averaging 4 psi low my Monte will have a pressure of 49 PSI. I have actually used a second gage on my Monte Carlo and got 42. I believe my gage is 3 to 4 PSI high as my Monte Carlo is 42 with that gage, RIGHT ON the spec. So if that is the case, given the numbers above and if this gage is 4 PSI high, RUNNING this car doesnt have 34 but 30 PSI dropping to 26 when I rev the engine. I am swapping the gage I got at Harbor Freight for another as the first one I bought leaks and will test again. Ill post the results from the new gage. Thanks Jim

This car idles fine, but as soon as you get on it at all, it misses and has reduced power. I wish this 95 had more info, I am pretty sure I would see a lean code.

[JimD]

Hmm, and yet my Monte Carlo has 45

You are clouding the issue by comparing the fuel pressure of a totally different vehicle with a Northstar Cadillac. Apples and oranges.

...,so what you are saying is ....

I am saying nothing except the observed fuel pressure values I stated earlier.

This car idles fine, but as soon as you get on it at all, it misses and has reduced power. I wish this 95 had more info, I am pretty sure I would see a lean code.

Spend some quality time looking and listening for a vacuum leak.

[BodybyFisher]

As I said, Ill check the pressures again today, I have a new gage.

[Logan]

The pressure is too low. I do not have a 1996 manual...but I do have a printed 1994 book and 1998 and newer hard drive version.

The 1994 printed service manual suggests 40-50 psi. (note: 1994 is OBDI)

The electronic manual for a 1998 Eldorado and 1998 Seville "the fuel pressure indicated by the fuel pressure gauge should be 333-376 kPa (48-55 psi)".

Also, GM service manuals suggest that fuel pressure should hold after shut down for 'x' amount of time. You rarely actually see the system hold pressure for very long on any GM vehicle with any age or mileage. If it drops most the pressure over 5-10 minutes or so I would call that normal.

[Cadillac Jim]

The 1997 model year FSM has the Fuel System Pressure Test on pages 6-676 and 6-677. Key numbers:

• With the key on and the engine NOT running, the fuel pressure should read 333-367 kPa (48-55 psi). Turn the key off an on several times to get the highest possible reading (the fuel pump will run about two seconds each time).
  
• The fuel pressure should not drop more than 5 psi in ten minutes. If it does, there is a leak. Places to check include the fule pump check valve, the fuel pump flex pipe, the FPR, and the fuel injectors.
  
• When the engine is idling, the high manifold vacuum causes the FPR to reduce the fuel pressure. This keeps the pressure across the fuel injectors constant, meaning that the PCM uses the same PWM signal to the injectors to maintain a given fuel flow in gal/hr without compensating for vacuum, because the fuel pressure regulator compensates for vacuum by bleeding just the right amount of fuel to the return line.
  
• Low fuel pressure on acceleration can cause a lean condition that causes poor performance or misfiring cylinders.
  
• Fuel pressure above 55 psi can cause a rich condition.
  
• "A lean condition may result from the fuel pressure being below 333 kpa (48 psi)." This is part of item 15, page 6-677.
  
• Fuel pressure over 60 psi will damage the FPR.
  

[BodybyFisher]

Thanks Logan, that is what I was feeling also, I also never saw the pressure DROP 4 psi when I revved an engine, it usually stays steady.... thanks

Jim, this statement seals it for me, this is what I have

Low fuel pressure on acceleration can cause a lean condition that causes poor performance or misfiring cylinders

[Cadillac Jim]

Also, the peak fuel pressure when turning the key off and on without starting the engine should be 45-48 psi. You are reading half that. The first thing I would do is to try a new FPR.

[Logan]

It should be noted...different GM vehicles will have a different psi depending on the fuel/intake system. Examples...some GM trucks run about 13 psi..have seen readings as low as 3 psi. Other GM truck systems run 60 psi with no-starts happening at 56 psi on those.

[BodybyFisher]

Also, the peak fuel pressure when turning the key off and on without starting the engine should be 45-48 psi. You are reading half that. The first thing I would do is to try a new FPR.

Jim, a new FPR made no difference

[Cadillac Jim]

According to the 1997 FSM, all the Northstars for that year have 48-55 psi; see post 57. Since that's set by the FPR, I looked at the selection on Rock Auto. According to the buyer's guide for the 1997 Eldorado part, the same part is used for all 1996-1999 Cadillacs. Depending on vendor, the specified fuel pressure is 44 psi to 54 psi. Looking at the 1995 model year, the only pressure number I see in the listed parts is 47 psi; the part buyer's guid lists only the 1995 model year. For the 1993-1994 model years, the FPR range is 30-40 psi, according to the buyer's guides I see for parts on Rock Auto's online catalog.

Bottom line: For the 1995-1999 model years, the peak fuel pressure, obtained by turning the key on and off until the maximum pressure is obtained without starting the car, is 48-55 psi. For the 1993-1994 model years, it's 30-40 psi.

[Cadillac Jim]

Also, the peak fuel pressure when turning the key off and on without starting the engine should be 45-48 psi. You are reading half that. The first thing I would do is to try a new FPR.

Jim, a new FPR made no difference

Then we are looking at the fuel filter, fuel lines, and fuel pump. Ouch.

[BodybyFisher]

Oh by the way, the oring is below the screen. The screen detaches from the FPR, and typically when you pull the regulator out, the screen stays in the cavity. Upon pulling the screen out, you will see a tiny oring.

[navion]

Mike,

I would replace the inline fuel filter before I did anything else.

If the owner got one tank of contaminated fuel, it could be partially plugged. It does not matter if the filter was changed last year or last month.

A partially plugged filter would still allow the pressure to be read, but the restriction may contribute to the lean conditions that you describe.

I would do this first as it is relatively cheap and easily changed.

I had a similar problem on my '94 SLS Nstar. When I removed the inline filter, I found that it was full of fine sand.

Take Care,

Britt