how hard to replace fuel pump

[billybob]

well after changing the fpr and the switch relay I still have the same trouble starting up my n/s 96 sts in the am once the temp outside hits below 50. my question is theres a junk yard where im at with a hit parts car 96 deville im thinking of buying the used pump for like $20.00 since its a you pull it place but im hopeing a pump from a 96 deville northstar car will fit. and since i am a backyard repair man im hopeing its not a big job to do myself. local gas station wants $400.00 to replace.

[Bruce Nunnally]

I believe that the fuel pump is in the top of the fuel tank. You have to drain and drop the tank.

[caddyon20s]

ok is there any gas in the tank??? if there is is gonna be very dificult to change you need two people at least to do this job, i did it and it took me arround 8 hours work becuase some of the parts wouldnt losen up and come off and specialy if u just jack the car up and have to do all the work laing on the ground, u can do it but ill rather buy me a new pump cuase u dont wanna take all the time and work just to find out the pump didnt work and then have to drop the tank again you know what im saying, i changed my on my 99 deville the pump was inside the tank good luck.

[BodybyFisher]

Don't mess with the used pump, its way too much work if it does not work or if it dies. Since the Delphi pump is $266.89, if they installed that pump for $400, I would say DO IT.... But its more likely that they will install some aftermarket pump like the Spectra unit for $196. See Rockauto for the prices I just quoted.

My fuel gage is messed up and I need to replace my pump also, I would put a 3/4" piece of plywood under it with my garage jack and jack stands

[steve6]

I have done many in tank pumps, they arnt THAT difficult, just make sure the tank is nice and low on gas... Jack the rear end up as high as you can and secure it. A nice hydrolic jack is good, and a piece of plywood that will fit between the straps, if you can support it that way you can lower/raise it in a controlled fashion and its not too bad. As for rust and bolts hard to get out... I think that goes with every job... some are harder than others. Make sure you have some spare rubber gas line... might break some of the metal lines when lowering the tank etc....

Be prepared to be covered in rust....

[adallak]

Before reconnecting fuel lines with quick-connect, lubrcate the o-rings with clean motor oil so that they would sit properly. Remove just as many bolts holding the straps as you need to remove the tank. It was not easy to put new straps on my car.

[KHE]

Before replacing the fuel pump, why not check the fuel pressure to be certain the pump is bad???? Your symptoms do not indicate a bad fuel pump to me - run the codes and see if anything comes up. It may be possible that the coolant temperature sensor is faulty.

[thu]

Before replacing the fuel pump, why not check the fuel pressure to be certain the pump is bad????

This could be a good idea. A low fuel pressure, although not an indication of a bad pump by itself, could indicate a clogged sock, bad electrical connections, a broken vacuum relief valve, etc. I had what looked like a bad pump, but it would run fine when I pulled the pump out of the tank and hooked it up to +12v. Turns out it may have been broken baffles inside the tank and a malfunctioning vacuum relief valve.

Also, testing a pump out of the tank may not indicate a problem. A pump may exhibit problems only if it is inside the tank, if the gasoline is warm or cold, etc, etc. When I replaced my fuel pump, I tested the old one and it ran just fine. Fuel didn't want to come out smoothly when everything was together. I could have been a lot of things, so I just replaced the pump and the original tank and didn't worry too much about it.

I have had good luck replacing the tank and pump. Instead of replacing just the pump, why not replace the whole tank assembly - pump, sender unit, and all? It cost me $75 total from the junk yard with all the wiring harnesses. My problems disappeared when I did that. Whole thing took me about five hours. It took me a long time because I was really careful. I also had a fire extinguisher within arm's reach. Turns out it was a simple thing. Putting it back in the car took about 20 or 30 minutes.

Also, I drained the tank almost completely before dropping the tank: First, I siphoned out as much as I could. Then, I disconnected the fuel lines at the engine and then turned on the fuel pump (there's a pigtail in the engine compartment that you hook up to +12v to run the pump). I hooked a hose to the fuel line then into a bucket. When the fuel pump runs dry, there is about a quart of fuel in the tank. I used a floor jack to make it easy to lower and raise the tank.

Like KHE said, you might not have a bad pump. You might want to do some more diagnostics to see if you can isolate the problem a little more.

[billybob]

thanks guys for all your input on this job. ill do the presser test first and see what happens. the idea on the buying the whole tank with pump is a good one it would be much so much easy and quicker to do this for a few bucks more thanks.

[KHE]

Post back your findings on the pressure test. Have you checked for codes using the onboard diagnostics yet? If so, were there any codes? I am starting to think there is something wrong with the coolant sensor or intake air temp sensor since the problem seems to be thermal related.

[billybob]

Just a quick update I have set up a date with my local repair shop for tuesday. after giveing it much thinking you guys are right it could be anything besides the pump doing this my shop even said it even could be a leaky injector doing so ill post there finding once fixed to help others out on this type of trouble.

[rmac-etc]

Keep in mind that the pump can be intermittent. As to the replacement, it's not too difficult. I described my experience here:

http://caddyinfo.ipbhost.com/index.php?sho...0pump&st=15

Just scroll down a bit ...

[billybob]

Just found out today from my repair shop It is the fuel pump not holding. hes willing to replace pump change oil which it needs and replace fuel filter all with the labor $540.00

[BodybyFisher]

I believe that Logan and others have said that they have never seen fuel pumps hold pressure after the key is off. I don't know if 'holding' is a good indication of a pumps condition. What are the pressures at idle, high idle, etc?

[thu]

It is the fuel pump not holding.

Not "holding"? What does that mean?

[BodybyFisher]

It is the fuel pump not holding.

Not "holding"? What does that mean?

Given that he is complaining about hard starting, I assumed that he meant that when the key was off, it lost pressure, I believe it is suppose to hold pressure when the key is off, if I am not mistaken Logan has stated that he has never seen one hold pressure and it did not seem to affect its performance.

I am curious now, what billy means by not holding pressure

[billybob]

hi guys, what I mean by not holding pressure was like you guys said with key off. he said the pressure was like 20 pounds or so at cold start and not much more when running which red flagged the pump replacement. I did pick the car up today and WOW!!!! it moves like a dam rocket so much more power. Only bad news is when he dropped the gas tank he seen some of my brake lines that are rusty and will soon need replacement. I think $540.00 total with a oil change was not bad what do you guys think,?? he said he put in a good new pump not the cheapee one thats out there.

[JimD]

Given that he is complaining about hard starting, I assumed that he meant that when the key was off, it lost pressure, I believe it is suppose to hold pressure when the key is off, if I am not mistaken Logan has stated that he has never seen one hold pressure and it did not seem to affect its performance.

I am curious now, what billy means by not holding pressure

The ability to hold fuel pressure with the key off is a measure of the health of the check valve located in the pump plumbing. This subject came up 6 months ago and I made the following fuel pressure observations on a '04 model Northstar:

Cold engine = 0 psi

Key on - off several times and then off = 38 psi

15 seconds elapsed time = 36 psi

60 seconds elapsed time = 36 psi

2 minutes elapsed time = 35 psi

5 minutes elapsed time = 34 psi

[Logan]

"Logan has stated that he has never seen one hold pressure and it did not seem to affect its performance."

I grabbed this too...out of the GM service manual.

"Important: The fuel pressure may vary slightly when the fuel pump stops running. After the fuel pump stops running, the fuel pressure should stabilize and remain constant."

For years, GM service manual have information that, the way it is written, implies the fuel pressure should be able to hold constant psi overnight.

I've never seen one. 100's of GM cars. Typically after a hour the pressure is gone, or a very noticeable drop in psi.

If you see one that drops in 5 seconds or so. You do have a problem.

JimD's one is pretty tight..

Cold engine = 0 psi

Key on - off several times and then off = 38 psi

15 seconds elapsed time = 36 psi

60 seconds elapsed time = 36 psi

2 minutes elapsed time = 35 psi

5 minutes elapsed time = 34 psi

On a hot engine, you can sometimes actually see the pressure go up a bit. Due to heat soak of the fuel and the fuel rail.

But it would be 0 psi or close to it in a hour or 2. I have never have seen one that could 'remain constant' psi per GM speak.

[BodybyFisher]

Given that he is complaining about hard starting, I assumed that he meant that when the key was off, it lost pressure, I believe it is suppose to hold pressure when the key is off, if I am not mistaken Logan has stated that he has never seen one hold pressure and it did not seem to affect its performance.

I am curious now, what billy means by not holding pressure

The ability to hold fuel pressure with the key off is a measure of the health of the check valve located in the pump plumbing. This subject came up 6 months ago and I made the following fuel pressure observations on a '04 model Northstar:

Cold engine = 0 psi

Key on - off several times and then off = 38 psi

15 seconds elapsed time = 36 psi

60 seconds elapsed time = 36 psi

2 minutes elapsed time = 35 psi

5 minutes elapsed time = 34 psi

Thanks Jim, that is great to know, Mike