? about Q45 fuel pump

[ahardb0dy]

I know from previous posts that if the FPCM goes bad that you can bypass it using a jumper wire or the 3 way switch as suggested in a previous post ( which I have in my 94 Q), so If while driving the engine stalls and I bypass the FPCM shouldn't that let the engine run so the car could be driven home ( or where ever)?

Is it possible that even after bypassing the FPCM that the fuel pump got so hot that it wouldn't allow the engine to stay running?

Yesterday while on our way home from a wedding the RPM's started to drop and the engine stalled, The FPCM was already bypassed as the day before the car was acting up and I switched the switch over to bypass.

The engine would start but wouldn't stay running, even after an hour it wouldn't run. Today the car started fine with the switch allowing the FPCM to function but if you revved the engine it would pop thru the air filter and bog down, Bypassing the FPCM would let the engine rev fine.

I had a friend pick me up a FPCM out of a 91 will get it tomorrow he said their were no burnt marks at all on any of the pins hopefully this module will let the car run better until I can get a new fuel pump.

So why would the engine not run with the FPCM bypassed?

[Q451990]

If you've been running the FP in "high" mode, it may have finally burnt out - or be so diminshed in capicity from the damage as to cause the car to shut down from low fuel pressure. At this point be absolutely sure that you replace the pump and fuel filter with NEW OEM parts before you plug that FPCU in. Putting it in place with the old pump will just fry it too. The bypass trick is for moving the dead Q from the failure point to the shop, saving the towing charge... not as a semi-permanant "fix"

EDIT: Just re-read your post. The "popping" through the air filter comment is scary! See the other thread about an intake fire! Maybe you have an injector or o-ring issue (caused by the high pressure)?

Heath

[ahardb0dy]

I installed the FPCM from the 91 Q I got from the junk yard, the car still would not rev and was still making that "popping " sound, I took it for a ride around the block and it was running worse than it was with the original FPCM,I put it into the "bypass" mode and it still ran like garbage.Took it back home and parked it, I'm lost at this moment.

When we first bought the car it hesitated from a stop but never made that popping sound.

I recently replaced the plugs and removed the TB and cleaned it.

I guess it's fuel pump & fuel filter time.

I'll probably put the original FPCM back in tomorrow just so I don't burn up the new/used one.

[Q451990]

I'll probably put the original FPCM back in tomorrow just so I don't burn up the new/used one.

If you haven't already.

- If you're hearing popping in the intake, pull the hose or filter housing and see if you have fuel in there. As I mentioned earlier, I would suspect that you have an issue more serious than fuel delivery at this point. See the thread below by "senatorjames" about the intake fire entitled "Multi-Faceted Q45 Problem"

Heath

[maxnix]

Dumb question time: Timing Chain Guides?

[ahardb0dy]

the new/used FPCm is fine, I put the original one back in today, also checked for codes, only one coming up is the knock sensor code.

I checked some things the service manual said too,

" when disconnecting -IACV-AAC valve harnbess connector doesengine speed drop" - It didn't

"when pinching blow by hose does engine speed rise?" - no

I'll check in the air box housing tomorrow for fuel and I'll read the post you said too.

[Q451990]

Dumb question time: Timing Chain Guides?

It's a 94... must have signatures turned off?

Heath

[Q451990]

I checked some things the service manual said too,

" when disconnecting -IACV-AAC valve harnbess connector doesengine speed drop" - It didn't

If they AAC valve has been adjusted upward to cover up rough/low idle (typical as the intake gets gunked up with carbon) it won't drop when you unplug the connector. The base idle is above the ECU's target at that point...

Heath

[ahardb0dy]

don't know about the IACV-AAC valve being adjusted, the idle has always been normal,

but since I removed the TB to clean it the idle seems like it has been slightly higher than it used to be, could an air leak cause this?

[maxnix]

It's a 94... must have signatures turned off?

Heath

Yup, too much repetitive noise drowned in useless information in most signatures. Saw the 1991 reference.

[ahardb0dy]

spoke to a friend of mine tonight he said that the popping sound could be caused by the fuel not being burned completely , he said one of the ignition coils may not be on properly or one may be bad and is arching against the plug tunnels, (not sure if that's what the area the plugs go down into is called).

Anyone hear about anything like this?

[Q451990]

I agree on the source of the popping sound...

Only way to find out is to pull the plugs and see. I still suspect that the unburnt fuel is related to an injector or o-ring failure. Also seriously suggest that you replace the fuel pump first. You know there's a problem there... eliminate that cause first!

Heath

[maxnix]

Also seriously suggest that you replace the fuel pump first. You know there's a problem there... eliminate that cause first!

Heath

This is the mantra of preventative maintenace.

It is very difficult to diagnose simultaneous multiple failures. Much easier when the possibilities are reduced to one or two components.

Fix what you know is failing first, then analyze the resultant change in behavior.
Modified by maxnix at 5:42 PM 6/15/2006

[ahardb0dy]

left work 3 hours early today so the wife could take my car to go to the doctor, figured it was a good time to replace the fuel pump ( recevied my order from Joe yesterday, fuel pump, O-ring, 2 knock sensors and the KS harness).

Anyway, installed the new fuel pump took about an hour, hardest part was getting it back into the tank, the fuel gauge is reading low not sure if the fuel level is that low or I messed up the sender, couldn't get gas at the time as I was watching my wife's handicapped sister.

Started the car and it actually stayed running!!! Revved it a few times no more popping sound thru the air filter, took it for a ride no hesitation at all, RPM's climbed smooth and steady, downshifted perfectly, actually feels like it might have 310 horse power!, Friday is Knock sensor day.... I can't wait, can you tell how much I'm looking forward to doing them! Thanks to all for their assistance.

[Q451990]

That's good news! If the gas gauge is off, then you probably bent the arm on the float...

You'll notice yet another substantial "increase" in horsepower when you get those new knock sensors installed!

Heath

[ahardb0dy]

well it was a relief to me when I put gas in the car and the gauge moved up!! I was worried there for a minute! I guess it really was almost empty.

I drove the car last night for about an hour and it runs pretty good, I noticed a slight hesitation after about 45 minutes but it goes away quickly, I think their may be an exhaust leak some where as I can hear it on the drivers side under the car, I'm sure that doesn't help the engine running smooth. I may swap the FPCM to see how the one out of the 91 works.

Going to attempt the knock sensors this weekend, have to change the pcv valve, fuel filter and clean the IAC valve also.

[ahardb0dy]

got the plenum off today ( without cutting any hoses) and installed the new knock sensors, had to stop at that point since everythinginfiniti.com sent me the wrong KS harness, they're overnighting me the correct one for tomorrow. Turns out their was a split in the production at 2/93 and the KS harness they sent me was for Q's made before that date. Good thing is the wrong harness cost $96 the right one cost $31, $31 is closer to the original price of $26 they originally gave me, plus the price increase I guess.

I cleaned the IAC valve and the plenum, (TB was clean from spark plug replacement earlier), I found that the EGR passage in the plenum was just about clogged, cleaned it all out also, PCV valve tomorrow,

On a side note while re-instaling the fan blade and clutch after determining the one I got out of a 91 wouldn't fit, I leaned on the upper radiator hose and snap broke the top hose mount about 1/2" out of the radiator!! Now I have to find a radiator tomorrow. It probably would have broke on it's own if it was that fragile.

So I have a like new fan blade for a 91 available if anyone is interested

[ahardb0dy]

I forgot I ohmed the injectors also and they were all within spec

[ahardb0dy]

replaced intake plenum with the one I got from poppop, car started right up and is running very good had the rear end sideways during a quick power brake test, only thing I notice now is the engine light will come on once in a while, shutting the key off will make the light turn off, going out to check the codes in a few minutes.

[Q451990]

Sounds like you're making progress!

Heath

[ahardb0dy]

got code 55 today, engine light still comes on, was thinking possible bad gas cap gasket maybe?