Fuel injector Prob. 77 280z

[jagnew3]

Fprgot to say it will idle all day long with only a brief stumble from time to time...How loud should the fuel pump be, because I can really hear this baby whirring...almost moaning..

[sblake01]

The sound seems to vary from pump to pump. The one on my Z is very quiet and the one on my 810 can be heard but it's not really what you'd call loud. But I have sound louder on other Zs. Do you have a pressure guage? If so, hook it up and watch the fuel pressure while it's idling. Should be about 37 psi. Also, it should hold when you turn the engine off rather than dropping. If it drops, it could be the check valve, the fuel pressure regulator, the fuel pump relay etc. Any of those could cause the problem you describe as well as the things your Sea Doo friends mention.

[jagnew3]

AAAAAAAAAHHHHHH! ! I can tell you it does hold pressure..how much I'm not sure, but I can tell you I learned a tough lesson the first time I changed the fuel filter..ba boom! Glad no spark or open flame were present. I was wondering about the thermotime sensor...and the (I'm not sure of the termonology here) fuel temp sensor. The onlt thing I can even remotly notice resembles a reoccouring event is that It always runs good when it is cold, and the fuel is really abundant..It runs good at temp. What I notice is that right around the time the temp gauge shows the thermostat should be opening is when I have this problem, and right after it should be closing it begins to subside...It could be just imagination, But it always seems to be around that point.

[sblake01]

Have you checked the connections at all of the sensors/switches/valves? You may have mentioned that earlier in this thread but that is crucial to everything working right. You mean 'thermotime switch' and 'temperature sensor'. If the car starts quickly and runs good with a faster than normal idle when cold, the your cold start valve, thermotime switch, air regulator, are all functioning properly. The temperature sensor doesn't kick in until the engine is approaching operating temperature. I would check the connection there as well as the operation of that sensor. It should have continuity from about 125 degrees up.

[jagnew3]

I know the contacts there are clean, But the connector does not look too good., Infact there could be an arch at that location, the connection is tight..but the connector may not seperate the two sides...would this allow for an intermittant (spell) problem? HMMM You know the connections all look good save this one connection...What exactly is it's function..I'm reading the manual at the link you provided...make sure I'm getting very simple english..and please act like I'm four, because this is nre to me, and I won't be offended.

[jagnew3]

Okay, Replace the temp.sensor and #6 cyl. inj. connectors. ..didn't help, but the symptoms are very clear, and are happening in a particular way. Start car (cold) runs great, car warms...runs great, idles great etc,then (for reasons unknown)idle begins to flutter, it begins to have hesitation,bog, followed by backfire as I begin to stump it, and feeather it and pump it....right after this begins I notice that the whine from the fuel pump has stopped..I hear the engine continue to stublbe, backfire etc...finially it starts to clear, the engine revs up, and once again I hear the whine of the fuel pup..idle is back to normal again The whine always goes shortly after the symptoms begin...and is alwys back when they stop.

Also, If I turn on the lights, or hazzards or heater blower..I can hear a big change in the whine's pitch..so voltage to it really but be getting tweked. It the hazzards are on you can really see em dim the dash lights as they blink. Anyhow the above is exactly the sequence it follows everytime. And it never does it below operating temp., while the mix is fat.

[jagnew3]

man I can't type.. fuel pup..

[sblake01]

The water temp sensor basically takes over control of the air fuel mixture after the cold start circuit as the engine warms up. If you have a pressure guage, hook it up between the fuel filter and the fuel rail and see if the pressure fluctuates when the problem occurs.

[jagnew3]

Okay here's fuel pressure readings....34 constant at idle...42 while reving...30 as the trouble starts...20 and then recovery, back to 34..

[jagnew3]

oh and as I typr it's running at 32...a little rough, and when I stomp it..it goes down to 28-30 and hesitates real bad....then idles back at 32 though rough

[jagnew3]

if I hold the throttle at about 2500-2800 the fuel gauge settles at 29-30, earlier it was continous 34

[jagnew3]

problem seems to cycle..it just went through one of those 30 down to 20 backfire spells..the as it bottomed out at 20psi..with me feathering it..it powered to 34 and runs great...