Fuel pump

Post by **deputydriver** » Tue Jan 21, 2003 4:25 pm

I've read some of the past threads and surmise my fuel pump is nearing it's end. My 94Q has ~84K miles on it and the noise from the rear has begun to increase.

What I am wondering is whether this is a DIY job for a junior mechanic like me or better left to professionals. If I take it in, how much labor should I expect?

This forum has been very helpful to me and I appreciate any advise. I love my Q but I'm also on a budget...

Post by **DAEDALUS** » Tue Jan 21, 2003 4:25 pm

No special tools required for this one, and you can expect to pay at least a few hundred bucks at a dealer in labor alone. It's easy enough to tackle on your own. The most important thing is to remember you're opening a gas system, so take extra precautions. Wear a ground strap if you have any ESD problems. Next most important thing is to release the pressure of the system first. Pull the fuel pump fuse and run the car till it dies. Then crank it a few more times.

http://www.nissaninfiniticlub....=6268

When you get to the flare nuts on the gas tank, loosen them slowly. If fuel starts to leak out of the first one you loosen, then close it back up gently and loosen the other one. One is a vent, the other's a liquid line. You want to vent first. Have a lot of shop towels around to catch any spills and minimze clean-up time.

Post by **DAEDALUS** » Tue Jan 21, 2003 4:25 pm

Don't be tempted to buy a cheap non-Infiniti pump. It'll last 1/4 as long as a factory one, and probably take your pump controller out with it.

Post by **deputydriver** » Tue Jan 21, 2003 4:25 pm

Daedalus,

Thanks for the advise. I plan to get an OEM part and wait for a nice-weather Saturday. Hope I don't wait too long...

"I removed the rear seats and deck cover, and it made access a bit more convenient, but does anyone know if the job can be done without removing the rear cover? Seems the recessed tray would prevent removal of the pump."

Did you ever get an answer to this question?

Post by **DAEDALUS** » Tue Jan 21, 2003 4:25 pm

I'm pretty sure the answer is that the rear deck has to come off. It wouldn't cost you more than 5 minutes to verify, though. After bleeding/venting the system, go straight to the fuel pump and try to remove it first. You can always stop and remove the seat/deck if needed. Not sure if you've seen the recommendations, but a few dealerships offer great discounts on parts. infinitipartsusa.com has your pump for less than $250 if I remember right. Their number's on the website--call them and tell them you're a NICO member.

Post by **911/Q45** » Tue Jan 21, 2003 4:25 pm

I would add that you remove the gas cap before you begin and have the tank mostly empty.

Post by **landtodd** » Tue Jan 21, 2003 4:25 pm

Removing the rear deck cover is what makes it possible to remove the pump without moving or tilting the fuel tank. When you remove the pump, it goes up through the hole in the metal which is normally occupied by the bin behind/between the rear headrests. That bin comes off as part of the rear deck cover.

That said, this is a great job for a do-it-yourselfer! Low effort, high payback. It's also a job which pays mightily to do before the pump actually fails. My dealer's price was in excess of $1000 to replace the pump because they wouldn't replace the pump without replacing the $450+ controller. Understandable since most people wait for pump failure, by which time the controller can be fried.

Echo comments about venting the tank by removing the fuel cap and grounding yourself. Also replace the engine-compartment fuel filter!

Post by **911/Q45** » Tue Jan 21, 2003 4:25 pm

My storage bin wasn't part of the deck cover, but just a couple additional Phillips screws.

Post by **mzarkowsky** » Tue Jan 21, 2003 4:25 pm

I am experiencing some fuel pump "hum" that wasn't there before. I changed the fuel filter last weekend and it seemed to diminish a bit. My Q45t has 98,000 miles and the pump has never been replaced. From what I've just read here, I should get to this ASAP. How much noise is too much? Does it realy have to be noticable or is even a little doing something that may effect the controler?

Post by **landtodd** » Tue Jan 21, 2003 4:25 pm

As the pump deteriorates and slows down, it begins to draw more and more current from the controller. The controller then overheats at some point. Very difficult to say "that's the point" until you've passed it. I suppose you could install an ammeter and watch the change in the current it draws, but it would be easier to replace the pump. (Besides, even if you installed an ammeter, we don't know how much is too much.)

80,000 seems like a reasonable life for this unique three-speed fuel pump. Just go ahead and replace it every 80K and be done with it.

Buy genuine Nissan for this application. Rebuilders apparently don't understand the peculiar demands on this pump. Most likely they build just expensive enough to last the 6/6 warranty.

Post by **Tgvince** » Tue Jan 21, 2003 4:25 pm

Can someone in the know explain how this three speed controller works? I sell alot of Walbro fuel pumps and have a few applications that I have custom made because Walbro doesnt have an install kit for them. Albeit none of them use speed controllers. I doubt the motor on the pump has three tap settings, guessing I would say the controller varies the voltage to the pump? In away emulating a VFD. So whats the purpose of this and does the 97+ have this as well?

Thanks!

Terry

Post by **landtodd** » Tue Jan 21, 2003 4:25 pm

Yes, the pump operates at three different voltages, controlled by the FP controller.

Why did they do that? It's just my guess that Nissan wanted finer control of the fuel going through the injectors at low rpm, but needed to flow more than those injectors were capable of at that pressure at high rpm/load.

No idea how long they kept doing it.

Post by **Tgvince** » Tue Jan 21, 2003 4:25 pm

I got in contact with the tech i deal with at Walbro...The consensus is that they do it for noise and finer control of low speed pressure...which would help with evaparotive emmissions as well. The walbro pumps will work great unless the lower voltage is below 7Vdc. Has anyone ever tested the voltage?If theres any interest i can look into putting a kit toghter for any of the models...Id be glad to test the 97+ out on my car. As for the Pre-97 anyone in AZ with a Pre-97 up for experimentaion?

Terry

Post by **landtodd** » Tue Jan 21, 2003 4:25 pm

According to the '92 factory service manual (page EF & EC-25), the voltages the pump sees from the controller are as follows:

Low: ~5.6V Medium ~7.8V High 11-14V (battery voltage)

Post by **Tgvince** » Tue Jan 21, 2003 4:25 pm

Hmm...Well that doesnt look promising. Ill look at my 97 to see if it has a 3 speed setup as well.

Thanks!

Terry

Post by **landtodd** » Tue Jan 21, 2003 4:25 pm

When you look at the overall cost of Q45 ownership, $269 for a brand new Nissan-built pump that will last 80,000 miles doesn't look bad at all.

Post by **Obsydian** » Tue Jan 21, 2003 4:25 pm

Tgvince wrote:Ill look at my 97 to see if it has a 3 speed setup as well.

Any news on this yet, T?

Would there be any notable compromises made if you were to replace the variable speed system with a single high capacity pump, other than pump noise?

Were the low RPM resolutions on injector pulses extremely finely tuned on the VH motors, Technical Dudes?

Regards,Obzai

Post by **landtodd** » Tue Jan 21, 2003 4:25 pm

I am also curious whether or not they continued the multi-speed pump in the 4.1.

Post by **Q45tech** » Tue Jan 21, 2003 4:25 pm

Yes a multispeed pump is derigour in most lux cars!

The 97 and later added a large resistor [low ohm] across the fuel pump controller to take some of the stress off the unit when the pump current increases so that a controller failure would not occur and cause the car to die but we are still replacing noisey 97 pumps on high mileage units.

The resistor lets the pump run at say 33% but a worn pump will still slow down and may still fail at the same age.

Newer returnless fuel system require a variable speed pump as this system has no return fuel line to regulate pressure......hopefully the pump is fast enough [responding] to always provide the required rail pressure ???????????

Post by **Tgvince** » Tue Jan 21, 2003 4:25 pm

Well it looks like the 97 has a three speed setup as well...Im still waiting to find out if any of the Walbro units can operate on the lower voltage levels. Ill let you all know when i find out.

Terry

Post by **Tgvince** » Tue Jan 21, 2003 4:25 pm

As for the returnless systems...Walbro has yet to address the aftermarket issues with these pumps as the units they have now cannot handle the "deadhead" that occurs on the returnless systems...Most guys that modify returnless system cars with Turbos have to convert back to a return system in order to get enough fuel as the stock ECU controls the pressure....Just an FYI.

Terry

Post by **landtodd** » Tue Jan 21, 2003 4:25 pm

What's the advantage to a Walbro pump? Cost?

Post by **Tgvince** » Tue Jan 21, 2003 4:25 pm

Yeah cost i can usually put a custom kit together for about $120.These pumps are top quality not the crap you get from Checker or Autozone.

Terry

Fuel pump

Fuel pump

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