Chasing an intermitent

[Q45tech]

For about 2 years I have had a weird problem that comes and goes every few months, no codes, yet the engine would skip a few beats at cruise for a second [usually about 3-5 minutes after a crank] and in a few cases almost die or not start immediately.

Finally it happened 2 days in a row and yesterday it wouldn't start ..........no fuel pressure.........the pump had been replaced 6 months ago.Fuel pressure was checked at least annually and before and after pump changes.Jury rigged a spare FPCU it cranked immediately!

Examination of the old FPCU show it was orginal: 14 years old and had seviced now 4 pumps..........no external burn marks and examination of board showed nothing out of ordinary except for some very slight discolorations near the power transistors.

Hopefully that's it but only time will tell.

Intermitent problems can drive you crazy, for the past 2 months I've used the Consult daily and nothing showed up.

I accumulated a new MAF, CAS and ecu, Ignitor modules and coils but it is always the thing you don't have or wouldn't thing could be the cause.Many times you just have to wait for a total failure.

[VimyJ]

That's why aircraft have maintenance schedules based upon set amounts of hours of operation. Waiting for total part failure in an aircraft is undesirable to say the least. These maintenace procedures cost a lot of money too so when you hear of airline co.s struggling to stay in business it makes you wonder where the overhead cost savings are coming from. Not the maintenance department I hope!

But even these guys get it wrong. The TWA 800 and the Alaska Airways failures leap to mind. However, most plane crashes are due to pilot error. Over 90%.

[Q45tech]

That why my home garage looks like a dealer parts department. When we strip cars I always get the things that never fail [which are not kept in stock]. Why keep that it never fails! Someday it willI swore I would never let the Q get towed in for anything, again after the stainless steel brake line failure of a few years ago. It may drive into T3 limping a little sometimes. Since I am not the best at replacing things, I always like the assurance that the Master techs are there if needed for advice or to laugh at my contortions with my bag of tools.......I carry around 100 pounds of test equipment, gauges, fluids, bulbs, and spare parts in the trunk. ECU, TCU, FPCU, MAF, CAS, TPS, Ignition modules, coil pack, AC control head, lots of misc and jumper wires, duct tape, and a gallon of distilled water.....etc.

The are so many modules and components that never [at least in 14 years] fail on a Q it is amazing..........I'm sure that will still be the case in a 20 years old unit.

Electronic modules are vibration sensitive so tire wheel balance is important.

2 days ago was the first non crank situation since 1994 when I left it too long at an airport........I've come close a few times [with batteries] but now I just replace them every 36 months on the dot........... early December.

My tire jack has never been used........neither has the spare [rottten by now probably].

[s13sr20chris]

yeah, i carry around somewhere around 100lbs of stuff in my trunk too. ecm, alt, belts, fluids, tools, jack, stands, etc. in my old b12 i had a spare transmission. i was not to sure of how well i had done by rebuilding the stock a/t with an elcheapo trans kit from carquest.

[Q451990]

in my old b12 i had a spare transmission.

Man that's hardcore!!

[90Q45blue]

Hardcore would be storing a VH in your backseat in case your Q croaked.

Nick

p.s. but having a spare transmission is quite high on the hardcore scale.

[greg_atlanta]

For about 2 years I have had a weird problem that comes and goes every few months, no codes, yet the engine would skip a few beats at cruise for a second [usually about 3-5 minutes after a crank] and in a few cases almost die or not start immediately.

Hmmm..... sounds familiar!

[azskygod]

Funny you should mention this topic. My Q started having intermittent stall problems a week ago -- it turned out to be the fuel pump controller. I found a replacement on eBay for $10 and now it's running rock-solid again.

The part number on the original FPC was 17001-60U00 and the part number on the replacement was 17001-60U01. Also, the old unit had a large "03" on the label and the replacement has an "07". Any idea what the differences are?

It seems to be running fine now regardless. This must have been the easiest repair I've done so far...

AZSKYGOD

[Jesda]

I guess thats the downside with having a meticulously engineered vehicle. On my Mazdas and Hondas, if it wasnt electrical (my 929's turn signal would come on when I used the horn), the source of a problem was always pretty obvious.

I imagine could get pretty hairy diagnosting problems on F50 (02+) Qs. Or does it actually get easier because the technology is newer?

-Jesda

[texasoil]

The intermittent could be caused by a bad connectiont to the FPCU. Had it happen to me on my 94 Q45a. One morning --no start, traced to no fuel, wiggled connector-immediate fuel flow. Happened again cruising down the highway on I-10 between Houston and New Orleans (a durability test of suspension and connections). Just quit running. Had to clean the connector real good--looked VERY closely and found one pin was bent such that it went outside of female pin socket, contactin gon the outside (poorly). Fixed that--no more problems.

How do I post photos? I have some good close-ups of internals of a noisy fuel pump showing the cause.

[maxnix]

How do I post photos? I have some good close-ups of internals of a noisy fuel pump showing the cause.

Look at Rex's signature, or go to Member's Rides, or there is a sticky in the Infiniti Articles forum, I think.

[ardvarkus]

That's why aircraft have maintenance schedules based upon set amounts of hours of operation. Waiting for total part failure in an aircraft is undesirable to say the least. These maintenace procedures cost a lot of money too so when you hear of airline co.s struggling to stay in business it makes you wonder where the overhead cost savings are coming from. Not the maintenance department I hope!

But even these guys get it wrong. The TWA 800 and the Alaska Airways failures leap to mind. However, most plane crashes are due to pilot error. Over 90%.

Totally off topic, but...

I was on an AA flight last week in which there was a problem with a passenger seat. Coach was full (I was up front ) so the flight attendants moved the one passenger in that seat to first.

Fine you say?

No, maintenance was notified. They had to fill out a form to show that the maintenacne item was not significant enough to require immediate repair.

Problem was they could not find the correct part of the manual to cite: they could find 'missing cushion' and 'dirty cushion' but they could not find 'broken setbelt'

Unfortunately, since they had already documented 'broken seatbelt' they couldn't now swipe the cushion and change it to 'missing cushion' and let us go....

1:45 minute delay.

Morons

Ard

[greg_atlanta]

Sounds like FPCU can be a failure item on its own. I'll check the connections and see how it behaves the next week or two. New FPCU is $360 from Scottsdale.... not bad if it guarantees no more fuel problems for a few years.

I'd hate to replace the pump and then have an FPCU fail a few months later. Per an old post from Heath he noticed a lot better performance after replacing FPCU?

[texasoil]

If you are handy with a soldering iron, thae the FPCU out and open it up and resolder the connections to the plug connector. A very easy fix. If you follow the foil, you will see the current flows through a very thin spot next to the power lead, and a large area of that foil is right next to another unused pin connector. Connect the foil to the unused pin and in the wiring harness, connect the now 'live' pin to the original power out wire with a jumper--VOILA-300% more current carrying capacity in the critical location. Why they used a very narrow foil for the main current draw escapes me, especially when a large capacity section is right next to it.

First try wiring the pump direct--bypassing the FPCU speed select.

[greg_atlanta]

I'm not that handy, but will take the unit out and have a look.

I was looking in the service manual and see there's a fuel pump relay nearby. Do fuel pump relays ever fail?

Car ran perfect all day Monday but then tried to stall on me just once today. I doubt it's an electrical issue anymore.

[azskygod]

I can attest to the performance increase after installing a good FPCU. The pump probably was not getting full voltage before, but now -- damn -- it really has a lot more power above 4k RPM. Ive got photos of the pin with the cold solder joint...

AZSKYGOD

[azskygod]

Obvious signs of an overcurrent situation at the connector...

AZSKYGOD

[s13sr20chris]

ouch! we are seeing that same issue with sending units on frontiers and xterras now. its so bad that nissan came out with a recall for them.

[greg_atlanta]

I checked my fuel pump and FPCU connectors and both were perfectly clean. No gunk, no residue. Got about 0.6 to 0.7 ohms on fuel pump, which I guess is normal. Will monitor for a few more days....

[texasoil]

I disassembled and did post mortem on a noisy pump (still working great @ 139K miles)

Cause of noise was 'rust' carbuncles that had formed on outer rim of the pump rotor which were rubbing on the housing. No other wear or deterioration of any kind found. No bearing wear. No armature /brush wear. No pump roller wear--nothing anywhere except the small bumps due to rust? on the perimeter of the pump rotor.

[Q45tech]

People don't know how much water they buy. Every time I change a pump I see water/rust/chunks in the catch pan/sump at the tank bottom...... varies by amounts.......always discolored rusty and black pump pickup sock.

Ethanol States should be real fun.

[greg_atlanta]

It it safe to use 1 bottle of Isoheet every 2-3 tanks? Or in every tank? I think I'll try that.