2004 G35 Sedan - 336k

Car sat for 3 months without being started. Went to move it, it started, immediately died, and wouldn't start again. Went through FSM diagnosis and found power at IPDM, at pump, and found ECM was triggering pump relay. No pump whine with key in ON position.

Due to the high mileage and previous owner telling me fuel pump was never touched during his ownership, I decided to swap it out. Bought new pump and sock, fuel filter, and pressure regulator from RockAuto (Beck-Arnley stuff, didn't go with economy parts). Rebuilt everything and after a bit of a fight with the VQ I got it started and running. No fuel leaks, took it for a drive and everything felt fine. Did get pump prime whine once again on the new pump.

Had a pile of gaskets and things to install so I didn't drive the G35 very much after I did the pump rebuild. Started it a few times and it started easily enough but I did notice it was taking longer than earlier this year (before it sat for a while). It has always fired up instantly during my ownership until this issue.

Now that i'm driving it more its getting harder to start. Usually 4-5 seconds to finally start and when it does it often runs rough for a second, sometimes lighting oil pressure lamp on cluster, but then it cleans up and runs fine. I observe that in the mornings it starts without any fuss but by afternoon leaving work or after a drive where it can warm up it is a 4-5 second crank to fire it up again. I'm pretty sure I hear the pump whine in the morning, but once its warm outside for the day, or the engine bay is warm, I don't hear the pump whine anymore when I turn the key to the ON position.

I have a CEL on, but its for an intermittent o2 sensor failure. Never have gotten any of the engine codes related to camshaft sensor failure or the cluster lights that show with that sensor failing. Never have had stalling while driving like a crank sensor failure.

My battery maintains good voltage and at worst drops to 10.5 volts while cranking. Just to verify I wasn't testing my battery wrong I took it by an O'reilly and they said it was perfectly fine.

I have new crank and cam sensors ready to install but am not fully convinced this is my issue and I wanted to post here for other ideas before I open those and make them non-returnable.

I feel like my issue this whole time is related to my fuel pump relay but there's a few concerns I have with this assumption as well. My car runs very well once it is started so if my relay contacts were "sticking" when it was hotter outside (or hotter in the engine bay) then I'd think that I would experience some other issues like the relay opening and the car shutting off while driving (or the relay not opening during decel/ ign off and flooding out the motor).

The fuel pump circuit is drawn up in a way that doesn't show any other power circuits being able to feed the fuel pump so my fuel pump relay HAS to be working if my car ultimately starts and the car stays running. I briefly considered that when I don't hear the pump whine, that no high pressure priming occurs and I only get the motor started on the remaining fuel in the supply lines which creates a low pressure moment and causes my rough running. But I can't explain how everything is magically better a second later, unless some other electrical system can run the pump (like my old toyota could).

I also read in the FSM PG section that IPDM integrated relays can't be removed, but I see a fuel pump relay right there in the components layout. I tried to grab a spare fuel pump relay from autozone and advance auto but they didn't even have it in their system. Rockauto doesn't even show it. So can it be swapped? Can I swap it with my high beam relay or something else on the IPDM to test my theory of a sticky relay?

Anyone have any other suggestions that I should chase down before I consider taking it somewhere? I did do the pedal based ecu reset, accelerator pedal position learning, and throttle closed learning that is posted on Nicoclub but I don't think I did it right honestly. But i'm not convinced that would have helped any with this issue.

Thanks for reading and any tips to help me work through this! Hopefully I didn't missing anything obvious before posting here. I tried to take it as far as I possibly could before posting.

 

Take a good look at your intake tubes, maf car need the tubes sealed properly, any cracking will give you rough running and hard starts. Might not be it but a quick check

 

Dropping to 10.5v while cranking is a worn battery. Engine may be struggling to start because the starter can't spin it fast enough.

I'm surprised they said that was ok, it's obviously failed their load bank test.

 

Oh there's a massive rip in the boot for sure. Was waiting for z1 to get ztubes back in stock so I could get one, so for now i've just carefully duct taped it . But I have had a couple moments when stopping at a light when the idle dips really low and it runs rough for a second..and that's probably because of the coupler not being fully sealed. Maybe i'll just get an ebay oem replacement for a few weeks while I wait on z1.

 

maybe they ran the test wrong then. The guy was struggling to input the CCA b/c the bracket was covering the label. I was going to grab a red top for this car anyways and have another car in the driveway with a completely sulfated battery. So i'll just move the G's battery to it and grab a red top I guess. What's weird is that the starter has never been sluggish, always super peppy on cranking. But i've got a lot of road miles for work this summer and plan on taking this car so a new battery is good insurance.

Thanks for taking some time to read and reply ponyryd and cleric670

 

3M Super 33 or 35 electrical tape is a good way to fix a torn boot, the duct tape leaks too much because it's not flexible enough to really get down into those corrugated grooves. The Super 35 though is definitely the right tool for the job, I always keep a role in the trunk, you can repair coolant hoses, air leaks, etc.

Cheap trash electrical tape is NOT the same thing as the real deal, 3M or nothing.

 

so an update to this: intake tube rewrapped with super33 (still debating buying a z-tube), battery replaced, and the problem persists.

The cranking issue now is always fighting me, where a couple of weeks ago it would be fine in the morning and only show up in the hot afternoon.

Yesterday while driving I started to get a fuel smell in the cabin. Not a overwhelming smell that would force driving with the windows down, but it was there. I kept blaming other construction vehicles ahead of me for the smell but it never went away, so it had to be me. Didn't have time to pull the rear seat last night and look for leaks.

I was really starting to think that my whole issue here is that the new regulator I installed when rebuilding the fuel pump wasn't holding pressure. This was forcing me to build enough line pressure to start every time. I'm still not hearing notable pump prime whine though.
...but now i'm thinking I just have air getting into the system and fighting me.

Side note, it's really funny how this car is treating me. I started by fixing a bunch of minor electrical quirks and cleaning/rebuilding switches that had failed when I got it in 2019. I gave it a new seat, replaced ALL of the suspension system, rebuilt steering and brake systems, and this little car was quite happy and reliable (even though we've got 336k on the original VQ). Then covid came along and the car stopped getting time and attention. And now it just seems like its after my wallet and threatening to leave me stuck somewhere, which I just don't have time for anymore. I've got enough "problematic project cars" already .

 

Replaced cam sensors today and there was no change.

A friend told me to try cycling my key three times before starting and surprisingly the car started much better. Does this mean my regulator is not providing enough pressure? Or that my new fuel pump is faulty? No issues once the car is running so I'm not convinced it is the pump.

 

I was going to recommend the fuel pressure regulator or whatever it's called in this car but your description sounded like a different problem. I had the long crank problem that's well documented on here. After sitting for a number of hours the fuel pressure in the line would decay and it would take a long crank to start. After cycling the key once to prime it would start fine. But your description that it starts in the morning seems to rule that out. It was so long ago now that i don't recall if it's a regulator or a check valve that caused my long crank but it sounded like you got a new one of those as well when you went through the fuel pump. I didn't have a rough running problem or any dash lights so it doesn't really sound like the same problem.

But if all you have to do is cycle the key multiple times and now it starts fine, it sounds like the same problem I had. I think it was a check valve of some kind on the pump that allowed pressurized fuel line to drain back into the pump/tank and require the line to be primed to start properly. Seems like you should have gotten a new one of these when you bought the new pump.

 

For a couple of weeks now it has ceased starting correctly in the morning. All starts now are difficult. 5-6 seconds each time.
When I rebuilt the fuel pump assembly I put in a new strainer, fuel pump, filter body, and pressure regulator. Not sure if the pressure regulator was faulty out of the box or if my jet pump hose didn't get all the way connected when I put it back in. But that's something i'll be investigating this week.

When I do the key cycling thing it does not run rough when starting.

 

I was curious if this could be related to my fuel dampers? I've found a lot of threads on here that mention noises associated with those failing and I haven't noticed any abnormal noises, but I also am looking at them and seeing they look a lot like pressure regulators of their own.

Anyone have any experience with either of the damper devices contributing to a hard start scenario? I have 336k on this chassis and they are probably the original ones.

 

All they are is a diaphragm that's a little flexible and it absorbs the hydraulic impact of the pulses of fuel that the pump makes. The passenger/right side one is the only one that ever goes bad since it's the first one the fuel hits. I makes a very rapid thumping sound in the cabin when they go bad, I'll see if I can get a recording later because mine is starting to go and I've been too lazy to fix it.

I have no performance issues whatsoever that I can feel though, yes it does cause mild fluctuations in fuel pressure at the injector but there are tons of fuel injected cars that don't even have pressure dampers.

EDIT: They're not going to cause a hard start condition.

 

Sorry Long write up, but worth reading. 05 G35 Sedan that had the dreaded fuel pressure bleed down. Turn key on fuel pump runs for two seconds shuts off (normal). Fuel pressure gauge indicated that pressure went up to around 30 psi, then immediately started dropping to around 15 psi. With engine running fuel pressure was 51 psi, which is normal. Immediately on engine shut down pressure would drop quickly to around 20 then on down to 2 psi within around 3 minutes. Car ran fine no codes, it was just the hesitation on starting. After car sat for awhile crank would be extended even longer. In this case I would turn key on to let pump prime, then turn key off, then back on for another prime. Sometimes this worked for an immediate (normal start), but sometimes it would take extra crank time for engine to start. Verified that there were no external fuel leaks. Replaced fuel pump and rubber grommet that connects fuel pump to fuel filter. Also replaced in tank fuel pressure regulator and new o-ring on pressure regulator. While I was there I inspected the o-ring on pump plastic housing that fits inside of fuel filter. Everything looked good, after all of this there was no change in issue. Suspected fuel injector leak, pulled plenum and fuel injectors. Ran fuel pump relay with scan tool pressure builds to 51 PSI, with no fuel leaking at any of the injectors. Put injectors back in, new gaskets on plenum, torqued to specs. The only thing that I had not replaced was the fuel filter, which I had replaced a couple of years ago with a Beck/Arnley from Rock Auto. I pulled the pump housing out again, for probably the seventh time. Disassembled the pump housing on the work bench. Pressure tested the fuel filter by plugging the hole with the rubber grommet in it. This is the hole that the fuel pump slides into. Also plugged the hole that fuel pressure regulator goes into. I plugged holes with my fingers. Applied 35 PSI from air compressor to filter. One of the seams at the top of the filter had a small seepage. I thought surely this is not enough to cause this issue. Ordered new filter from local Nissan dealership. Part # 16400-2Y505. It took a couple of days to get the filter. Installed the filter, primed fuel system a few times. Started the engine, ran rough until air was purged from system. I let the engine smooth out. Looked at pressure gauge while idling 51 PSI (normal). Shut the engine off, only leaked down to 48 PSI and stopped dropping. After 10 minutes it was still at 43 PSI. Problem fixed, it was only the fuel filter allowing fuel pressure to bleed down. I sure hope this helps someone else that is seeing the same issue.