.Fuel Pump and FPCU Problems

[Jesda]

This is regarding a friend's 1990 Q45 with 145k.

I sold my rebuilt 1992 FPCU to him on eBay (rewired per Tangalora's method). I tested it for 100 miles prior to putting it up for auction, and it worked perfectly. But he continues to have starting problems. I'll paste his e-mail below:

Quote »Jesda:

Again, thank you very much for your help.

We bought the Q45 in 1996 when it had 75,000 miles on it. From the paperworkI received from the Infiniti dealership, the fuel pump had not been replacedwithin this 75,000 miles.

The fuel pump has been making a humming noise which I can hear from thefront seat almost since we purchased the car. A couple of years after wepurchased the car the electrical connection (I now think I can identify itas the ground connection - the same one which looks burnt on the rebuiltfuel pump control unit you sent me) on the fuel pump control module and thesame one on the harness looked burnt and the Infiniti dealer installed a newharness and it worked well with no more burning signs from then on.However, I later had to replace a fuel pump control module and it lastedabout 1 year and 8,000 miles. and then I replaced the fuel pump controlmodule a second time and it lasted 3 years and 25,000 miles. Now I am upto the present date when I purchased your rebuilt one.

The possible key is that I don't think the fuel pump was replaced before Ipurchased it in 1996 and I know it has not been replaced after I bought it.It presently has about 145,000 miles on it.

The only electrical tool I have is one of those 12 volt screwdriver devicesthat has a light in it to see if there is current. I know I have current tothe fuse for the fuel pump. I held the fuel pump relay (the lime greenrelay located near the antenna) and felt it click when my wife turned on/offthe car. The fuel pump used to make a clear discernible hum when I turnedon the car and know there is absolutely no noise indicating the fuel pump ison.

There is no gas coming from the fuel pump. Is there a method in which I cantell:1) the fuel pump is receiving voltage?2) whether or not the fuel pump is definitely bad?

I wanted to post on the forum you suggested, and I registered to do so, butI have not received the password yet. I was instructed they would send mypassword to my email address. That was a very helpful forum.

Thank you very much

David[/quote]Quote »Jesda:

Another comment, my gut feeling is that voltage is not getting to the fuelpump and the fuel pump may not be bad. I feel this way because I hearabsolutely no sound from it and my 12 volt electrical tester picks up nocurrent in the fuel pump relay (although I do feel it click) the harnessesboth to the fuel pump control unit and fuel pump. Could it be a short or aground wire?

Thanks

David[/quote]Quote »Jesda:

Thank you very much for your help.

This is what I have done:1) - Based on what I read in the forum, with the fuel system otherwisecompletely intact, I filed an alligator clip's teeth so that it fit into thesmall female tab on the bottom left (terminal side, with the clip up) of thewhitefuel pump control unit harness connector (this is the terminal which hadbeen burnt prior to you having the fuel pump control module being rebuilt).I connected the other side of the wire to a ground. My wife turned on theignition while I was in the trunk. I heard a one second low volume noise(like someone clapping their hands almost silently) and I felt somethingever so slightly move inside the fuel pump for a second (my hand was on topof the fuel pump). There were no other noises or movements.

I then returned inside my house and read your email. I then applied thealligator clips to the ground of the fuel pump and a ground on the car. Iheard the same noise which I heard when I grounded the female tab on thebottom left of the fuel pump control unit harness. Nothing else occurred.

Does this give you information to diagnosis the problem? I know believevoltage is going to the fuel pump or else it would not have made the onesecond noise and one second feeling that something moved. Is this a correctimpression?

Do you think this provides reason enough to conclude it is a bad fuel pump?I read the forum about fuel pumps and they cost $250.00. I read one shouldonly buy an Infiniti fuel pump. However, I must be economically driven, sois a pump from a salvage yard or a new off-brand from Autozone a second-bestalternative?

Thank you again for your help.

David[/quote]
Modified by Jesda at 10:51 AM 10/24/2004

[Jesda]

Also, he sent his two old FPCUs to an address in Spokane where someone I know is rebuilding/wiring them. They'll be shipped to me here in St Louis soon, and I can test them on my Q to see if they were actually bad.

[Q45tech]

A bad crankangle sensor [loss of 1 degree rotation signal] connector or unit will signal the ecu that the engine has or is stopping. The ecu will quit supplying the minimum 5.6 volt signal or any signal [to keep alive the FPCU] as a safety method to turn pump off when engine ceases running............if it happens fast enough for short enough period code may not be set. As the engine/ecu tries to keep running on the 90 degree signal.

Just another one of the things that can cause the pump to quit momentarily.

It is dangerous to assume you can use another used REPAIRED FPCU with a used replacement pump as the pump may just take out another section in the FPCU.

New oem pump, new oem FPCU, and new oem Relay AND new 15 amp fuse just to be sure is the only way............that way all that is left is ECU and wiring [never seen either fail].

Worse thing we ever did was explain about FPCU and repairs as who knows how many are being done correctly or completely [especially by those without a Q to test them on afterwards].

A simple AMMETER in place of the 15 amp fuse will show you the pumps speed and when it starts and how it stops [reads both pump and FPCU combined currents].

[Jesda]

Quote »Jesda:

I'm again going to take you up on your kind offer to post on the forum(since I do not have a password yet). Would you please post the following:

"Would like to purchase a used Infiniti fuel pump for a 1990 Q45. I am onlyinterested in buying the fuel pump if you personally know it is a GOOD usedfuel pump. An added bonus is if you also have the fuel pump o-ring (if not,I will purchase one at the local Infiniti dealership. I know there are noguarantees with used parts, but I would like to know if you have personalknowledge that it is a good fuel pump. I need this ASAP so I will paythrough PayPal. Please contact me at [email protected]. Thank you.David"

I would appreciate if you could post this.

Thank you

David[/quote]

[elwesso]

Just so you all konw, he plans on buying one of my fuel pumps..

[Jesda]

...and whats up with his registration? He still hasnt received a confirmation email.