92Q Will start, Not start, Start Again, Die Again

[firstq]

92Q with new pump now around 11K miles ago. I think my current problem is fuel related as well.

These days my Q45 has a mind of its own when it comes to starting. Here are some symptoms:

1. The car will not start at all - does not matter cold or warm. When it happens no point in trying more - it just will not start. If I remove the gas tank cap - I hear no pressure release. Most likely the pump is not engaging.

2. Most of the times it starts with no problem - no hissing or humming sound from the back, just the first couple seconds when the pump primes initially. Works and runs okay - no apparent fuel cut off issues.

Q#1: Fuel Pump Controller Bad? I see no signs of burning on the pins, and as it does start many times - for weeks it works w/o a problem. If the Fuel Pump controller is bad, it should be bad all the time, right?

Q#2: Fuel Pump bad? only 11K miles, I guess things can go bad that early - but again how do you explan that as soon as the car starts, no issues afterwards - the car runs fine.

Q#3: Fuel Pump relay bad? When the car did not start, I asked my wife to turn the ignition on and I was in the trunk and I can clearly hear the "click" around the relay - I can hear it everytime she would put the ignition on "ON" position. No sound in the pump whatsoever.

I think it is the fuel pump relay - any easy check to test the fuel pump relay?

Thanks

[DAEDALUS]

If the Fuel Pump controller is bad, it should be bad all the time, right?

Q#3: Fuel Pump relay bad? When the car did not start, I asked my wife to turn the ignition on and I was in the trunk and I can clearly hear the "click" around the relay - I think it is the fuel pump relay - any easy check to test the fuel pump relay?

Melted solder terminals on the board can cause intermittent problems. If the relay is cheap enough, maybe just replace it without testing. A fuel pressure gauge is a good investment.

[firstq]

I see the test procedure on EF & EC - 220 for Fuel pump relay check. Will try it soon.

If it is the controller (pins burned, intermitten problem) - if the controller is bad, I should have issues while the car is running as well, right? As the controller is to work all the time the car is on to regulate the voltage (so to speak) going into the pump, right?But, the only symptoms are during cranking the car - sometimes starts sometime no start - if starts, the car runs until I stop.

[firstq]

1. Removed the Fuel Controller - everything checked out OK. No burn out terminals, no continuity issues - seems in excellent NEW condition (the inside of the circuit board).

2. The lime green fuel pump relay checked out OK.

The car started again today and ran for 10 minutes before I turned it off. No issues at all. However; yesterday it did not start at all. Once started, the car works out okay.

Can this be the pump (the pump not even has 10k miles on it and the fuel filter was replaced at the same time). I can understand is the controller was on its way out and caused strain from the new pump, but it is not the case - the controller is in perfect condition.

Kind of stumped - I hope it is not the pump again.....

[Q45tech]

Seen similar problems why we always swap fuel pump controllers with pumps............9 out of 10 times it is a funky controller. Over stressed by failing pump.

Pull plug off controller with alligator clip jumper wire ground pump negative lead...........should start then order a new controller asap. Even an hour Wide open will over heat and destroy pump.

[firstq]

Dennis - help me confirm this: are you saying even though the controller seems in pristine condition (I opened up the inside of the controller and looked at the circuit board - there are no signs of heat damage, no burnt up terminals, no circuit board melt down, etc) - it still can be the controller?

Thanks

[maxnix]

Yes, unless you can trace all the electrical components. Dennis spent two years with an intermittent problem finally traced to a perfect looking FCPU.

It really does pay to read all of Q45tech's posts!

[Q45tech]

Every one should carry a working [or mostly working] a junk yard spare FPCU in trunk and a 2 foot wire jumper with tiny alligator clips.

The burned melted discolred units means the electronics probably continued to work so the solder melted.......... repair them check them out by temp swapping and relegate to spare inventory......In Feb 2004 I had to crank on spare and aligator clip for ground and drive 20 minutes to shop before I pulled the rear seat to make a permanent fix.

[firstq]

All right - now to car-parts.com for getting a used FCPU. I will also try to jump the ground to confirm the pump is still OK.

If the FCPU is so unpredictable and cannot be easily checked for correct operations [for intermttent problems - mine looks new inside out, and I am an EE, so I know some PCB stuff], how can one trust the one from the Yard?

Thanks

[Q45tech]

It's much rarer for the FPCU to fail or become intermitent without visable signs but if you look at all the solder joints with a 20x loupe........you see things that eyes alone don't.We see about 90% of them with burned plastic or the solder pad that feeds the pump with signs of melting, reforming, and melting again.

You just swap it and see if it seems to work, better than paying $500 for a new one. Follow the FSM for 3 step voltage change diagnosis of used unit. Most junkyards offer returns if defective. Make then record serial number so there can be no argument.......of course you could swap covers and serial numbers.

Almost all dealers swap both the pump and the FPCU at the same time [take it or leave it the $1000 repair bill]. They've learned the hard way to avoid come backs.

We [T3] only swap if signs are present but warn that they may be back for a FPCU...............so to avoid $570 now they risk $710 later [plus another tow].

[firstq]

Jumping the ground, did start the pump and the car certainly started fine.

I can understand the problem with driving the pump with the ground jumped (full speed all the times) - pump will remain in overdrive.

However; what is the issue with driving the pump all the time under low/medium speed (permanently tie up the ground pin with a appropriate resistance).

I am looking for a used FPCU, but in the mean time - can I set the pump to low mode by using the appropriate resistance?

Thanks

[DAEDALUS]

Lower voltage=less fuel, less pressure at higher flow rates. Once pressure drops below 34-44 psi performance will be unpredictable. Running a car too lean is not good. Might be OK if you baby the throttle everywhere you go.

[Q45tech]

As long as you never try to accelerate much, never more than half throttle and stay out of 1st gear...........keep rpms below 3,000.

Compared to the tiny dribble at idle and 5 times more at steady 60 mph.......AC adds 10-15%.......WOT [at 6500 rpm] can consume 55-60 times more fuel per minute/sec/hour.

You just bought a newish pump hate to see you half it's life in a day or two. Since you probably didn't clean the tank its already stressed anyway.

I learned the hard way 1st pump at 160k, 2nd at 200k, 3rd recently at 240k......FPCU at 262k currently at 264k.

Change the fuel filter every 12 months or 15,000 miles every 800 gallons.

[firstq]

Makes sense folks - I just had a wild thought there perhaps regarding the resistor [but perhaps if one has to drive for sometime [couple hours, few days, etc]before getting the FPCU, it might be a better option than running high during the time].

Does nayone have any recommendations for the yards from the car-parts.com for quality service and good parts history from past experience?

Thanks

[maxnix]

Try autogator. They have a good reputation, but I have never used them.

[firstq]

A used FPCU is on the way, we will see how well it turns out. The guy said no brown terminals - we will see, it is from a 95Q45.

The biggest problem I had is that these stupid yards do not have FPCU in the system as an item - either the pump or the assembly, nada for the controller. Everyone I called, will look into the computer and say no we do not have it - finally found one who was willing to check the car itslef and ofcourse found it inside.

I had jumped the car once with the ground, put back my original FPCU, the car so far has been running fine. I will swap the controller once I get it mid next week.

Interestingly, I bolted back the FPCU from inside the trunk - instead of bolting from inside the rear sundeck, I just screwed the same from inside the trunk - should be an easy R&R from now on within the trunk - has anyone else done that as well?

Thanks