Mechanics

CAR NEEDS GAS?

1991 Infiniti Q45

Engine Performance problem
1991 Infiniti Q45 V8 Two Wheel Drive Automatic 172000 miles

When driving my car it will suddenly stop getting gas to the engine. Sometimes I'll drive all day with no problems in other cases I have to restart my car half a dozen times just to get off of my block.

The car gives no warning and will just cut out mid drive. Sometimes it will just bounce between getting no gas and some and hover between dying and running. I was thinking the fuel pump, but after 2 months I figured it would have completely quit already.

Any advice?
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Dukethompson
April 15, 2010.




Your's does sound like a fuel system related problem, but don't assume without testing. It could also be your ignition system.

Also, you could have a plugged filter, clogged injector (or more).

What you need to do is first check your ignition system. The fastest way to do this is to let your engine idle and pull the plug wire for one cylinder at a time. If there's a noticable change in how the engine runs or a drop in r.P.M.'S, then that cylinder was firing correctly. If there's no change in how the engine runs, then that cylinder was not firing.

But that's not the end of the test. Now you must use a stethoscope to listen to the injector for that cylinder. (They sell them at AutoZone for 5 bucks)

You should hear a steady clicking while the engine runs. If you hear the clicking, then that plug wasn't firing. If you don't, then that fuel injector wasn't firing.

If you have an ignition problem, then you'll need to correct that before you go any further.

After you've either ruled out the ignition system or repaired that system, then test the fuel system, beginning with a static pressure test. (Key on, engine off) Compare the fuel pressure to specs. If it's not at spec, then your pump is bad. If it specs out good, then do a operating pressure test. (Key on, engine on) If pressure drops, then you either have a clogged filter or bad fuel pressure regulator.

Next, if your fuel pressure checks out ok, then you'll want to do a balance/drop test on each injector. They could be bad or clogged.

Finally, if both your ignition and fuel system checks out ok, then you'll need to test you computer sensors and the computer itself. Good luck.

Ernest Clark
Apr 25, 2010.


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