Fuel Pump/Control Unit question

[Highway Q45]

I haven't been here in quite awhile but the ugly side of 1st Gen Q ownership has raised it's ugly head for the 1st time in years. I had the Q towed to the stealership today after an intermittent stall problem, no start problem. Using the FSM I was able to track it down to no fuel pump operation. I had it towed this morning for a Consult. They ran the Consult and said the fuel pump was bad. I got a call later saying that the new fuel pump ran for a few seconds (enough to start the car) and the fuel pump control unit, they used the term 'modulator', gave out and the ground path through the control unit was bad due to the high current draw of the old fuel pump? My thoughts are the old fuel pump is fine and the control unit is bad. I talked to the tech who worked on the car and he said after injectors that this was a very common problem on the 1st gen Q's. I've always done my own repairs (chain guides, under plenum hoses,trans cooler) and feel like I might be taken for a fool. For those of you in the know, is it best to replace both the fuel pump and control unit together? This is on a 91 with 140K miles. Sorry for the question, but I know there are some really good techs here. I'm looking at about $1200 between the 2 items at the dealer and the car won't move without another tow.

Thanks if you can help.

Steve

Modified by Highway Q45 at 4:32 PM 10/13/2005
Modified by Highway Q45 at 6:32 PM 10/13/2005

[elwesso]

Hey steve, how are things, definitely has been a while since youve been onthe boards...

Replacing the fuel pump was not a bad move, probably indeed necessary. The old fuel pump is what caused the module to die..

What you can do, if you dont have far to drive, is ground the fuel pump control unit, drive it home, and then replace the control unit later on your own time. Thats what i would do

[Q451990]

In this case the dealership is right... very, very common issue. You might find a used FPCU to save some $$. Could be worth your while to have it towed home and install it yourself - or even see if they'll let you order one from Joe. The other option is to ground the pump directly (which would bypass the controller and put the pump at max. pressure) for the drive home.

The high current draw from a worn Fuel Pump kills a lot of FPCU.

Heath

[Highway Q45]

Hey steve, how are things, definitely has been a while since youve been onthe boards...

Replacing the fuel pump was not a bad move, probably indeed necessary. The old fuel pump is what caused the module to die..

What you can do, if you dont have far to drive, is ground the fuel pump control unit, drive it home, and then replace the control unit later on your own time. Thats what i would do

Hey Wes,Yeah, Long Time Huh? I would love to tow it home but the dealer is already into me for $250 in labor and Consult time. Joe at Scottsdale has the parts at 33% less but can't ship to another dealership. I'm trying to work a deal with the service writer at Infiniti of Elk Grove to discount the parts a bit and that might fly. I hate to give up on this car but AC work and this fuel problem will set me back $2K in the last year. I'm hoping I'm not on a downward Q spiral at 140K miles because the car is near perfect and still so nice to drive. It's funny, I can diagnose anything on a Porsche 944 but these early Q's are a tough nut to crack when it comes to garage electronic repairs without a Consult. Thanks Wes for the response. OT: So who is still around from the early Forums?

Steve

[Highway Q45]

I'll probably just bite the bullet and have them finish it at the dealership. I thought about the ground bypass but I had a fuel pressure regulator fail on my Turbo and I don't won't to go through any potential fire issues ever again..a very close call. Again, thanks for the responses, I thought the tech was being square with me but wasn't sure since it was the first time the Q had to go to the dealer for anything. I'm having them reset my TPS using Consult while it's there also; I stupidly moved the TPS during my plenum pull/injectors/hose replacement job 2 years ago. The finite TPS postion and AAC adjustment I did was done only with a voltmeter and I have felt it in the trans shift points ever since. Oh well, live and learn.

Steve

[q45tech2]

The number 1 reason Q45/300zx were [are] ever towed into dealers is fuel pump/controller-modulator failure. Number 2 is short move flooding [not letting engine run A FULL 5 minutes after each crank cycle in cool weather].

Fuel injector failures are only the result of buying BAD [non standard or watery] Gasoline.....................299,000 miles on mine [made Jan 1990] and still clicking as new.........ohms and power balance.

Even a few tanks of bad product won't kill them if you use BG44K regularly [ever 90 days with oil change] to wash the crap out.

[elwesso]

Steve

First off ive diagnosed everything on my car and ive never even seen a consult besides in pictures. Under my ownership of Q45s neither of them have been "under consult"..

Anywho, what im trying to say is.. well first off, they already replaced the pump, yes? If so, then you can do as I said, by grounding the FPCU... what this will do is the pump runs in full speed mode. You want to have a ful tank of gas to do this, and not drive more than 15mins or so because the fuel pump will get too warm...

This will at least let you get the car home so you can replace the FPCU, which only takes a few mins to replace...

[elwesso]

Also steve, im going to merge this thread with your other thread and it will be moved inot the online mechanic.....

[Highway Q45]

Steve

First off ive diagnosed everything on my car and ive never even seen a consult besides in pictures. Under my ownership of Q45s neither of them have been "under consult"..

Anywho, what im trying to say is.. well first off, they already replaced the pump, yes? If so, then you can do as I said, by grounding the FPCU... what this will do is the pump runs in full speed mode. You want to have a ful tank of gas to do this, and not drive more than 15mins or so because the fuel pump will get too warm...

This will at least let you get the car home so you can replace the FPCU, which only takes a few mins to replace...

Wes,I would love to have done all the work myself if I had been sure what the exact issue was. I had it narrowed down to fuel delivery related. Even the Consult at the dealer didn't turn up any fuel related error codes. At first it was intermittent then finally wouldn't start at all. Not being on this Forum for a long while I never had heard of the fuel pump/FPCU issues...my bad.

I also requested that my TPS/AAC be adjusted using the Consult . Ever since my plenum job I did 2 years ago the trans would have a glitch and felt like the shift points were sort of floating while driving around town. I had used the voltmeter method to try and set the TPS and did the best I could. I remember Dennis saying years ago the Consult is by far the best way to dial in this critical TPS adjustment. As usual he was dead on. The dealer was good enough to split the parts price difference between Joe's price and theirs and knocked 10% off the diagnostics labor charges. Even then the repairs were over $1K...ouch. I figure I could have done it myself for $650 but still would have been charged $110 to set the TPS. It was more a matter of time and convenience than money; my wife needed her 'baby' back and I was concerned her driving the turbo around town was going to get her in trouble...boost comes in at 2700rpm making it kind of impractical for stop light to stop light driving.

Anyway the Q runs absolutely fantastic now, better than ever actually! The tech did say it looks like the higher current draw from the fuel pump caused some heat damage to the harness connection at the FPCU; he made a temp repair but recommends I find a new/used harness section and replace it. Now I need to get in the trunk and see which harness he was talking about. Anyone parting a 1st Gen car that might have this harness?

Thanks again for all the help guys, I see it's still a great forum for tech input. Another cool thing was as I was picking up the car I had 2 people come up to me and ask me what year it was, I told them it was 15 years old and their jaws dropped...I do keep it spotless and shined...anyway that was the only good thing that happened that day. Steve

[Q451990]

Another cool thing was as I was picking up the car I had 2 people come up to me and ask me what year it was, I told them it was 15 years old and their jaws dropped...I do keep it spotless and shined...anyway that was the only good thing that happened that day.

That's what makes it all worthwhile sometimes

I was taking a break from painting at our new house and was out near the road when my wife drove up in Q1 unexpectedly. My first thought was - there's a Q!... man, that's a nice looking car. Then I realized it was mine... weird but it really did work that way.

Heath

[elwesso]

That's what makes it all worthwhile sometimes

I was taking a break from painting at our new house and was out near the road when my wife drove up in Q1 unexpectedly. My first thought was - there's a Q!... man, that's a nice looking car. Then I realized it was mine... weird but it really did work that way.

Heath

LOL!!!

Steve,

Glad you got it back going again.. At least the dealer sounds VERY honest... For dealership prices, i dont think you got ripped off at all!!!

at least you know your Q is in good hands and its now running great again!!! Maybe now we can get you to stick around a little bit mroe so you dont have to go through this again! And i think it is true that wives never need boost, that can only mean bad things!!!!