94 3100 gas problems

[jameszach91]

hey everyone, new to the forum, I just got a beretta a month ago, really in good shape, just tryin to fix her up a bit. one problem I notice is that I get really poor gas mileage. I literally go down the street, and I can just see the guage dropping. I have checked for leaks and there appears to be none. I don't know if anyone has had this problem before, so I figured id ask before I go spending the extra money diagnosing. any help would be great thank you!

[Money pit Beretta]

Getting any black smoke out the tail pipe?

[Asylum]

Are you actually losing fuel or is the gauge just acting up?

The gauges in these cars actually move around quite abit as the car moves.

[jameszach91]

gas gauage floats, I have numerous cars that do that, so I don't think that's it, and no black smoke out of tailpipe

[ifixalot]

I had to replace the tank on my 96 because the rear of the tank had pinholes rusted through from the outside in
and it would leak as the gas sloshed back under acceleration but did not leave any puddles under the car
because it would evaporate and dry but I noticed the smell of gas in the garage too.
The porosity was in the upper half as I recall and so until I got the new tank, I kept only 1/4 tank of gas
in the car.
(You mentioned in another post that you actually measured your gas mileage at 10 mpg.)

[jameszach91]

yeah, 15 gallon tank, about 20 miles from full to three quarters. either way maybe not exact, but that's my guestimate. I don't smell any gas tho...
I wonder if it might be an o2 sensor.. also the exhaust leaks near the front, maybe catalytic converter..

[jameszach91]

no smell of gas, tank looks like its been replaced recently, what about an o2 sensor?

[3X00-Modified]

Well in response to what you posted in the FAQ section... You need to do some trouble shooting... FPR does mean fuel pressure regulator... I'd start by checking the vacuum port to that, remove the line and turn they key on and let the pump prime, if the diaphragm is bad fuel will come bubbling out of the port on it. The other stuff you would have to dig in to check/fix, or use a computer data logger to see readings from sensors. You could change the O2 on a whim if you wanted before doing anything else... especially if you have no clue on it's age. The injectors would need to be pulled and tested to see if any one is stuck open. And lastly the coolant temp sensor would have to be logged through the OBD port to see if it's reading properly and doesn't register -40*. The dash gauge may still be working perfectly fine because that is a different sensor than the ECU one that is used for the fan and fueling.

[jameszach91]

ok. to start and clarify, where exactly is the fuel pressure regulator on this engine? ive messed with fuel injectors a little bit, but never had to take them out of the block, im mostly a carb guy, so where would the fuel injectors be located.. and what device should I use/ where is the coolant temp sensor. I know I must sound pretty dumb, just not used to so much electronics...
but I do thank you for your help thus far.

[3X00-Modified]

This is a 3400 but most sensors are in roughly the same locations and it gives you an idea on the the FPR and Injectors.

1. Fuel pressure regulator
2. Idle Air Control Motor (IAC)
3. Mass Airflow sensor (MAF)
4. Throttle Body
5. Throttle Position Sensor (TPS)
6. Fuel Injector
7. PCV Valve
8. Coolant Temp sensor (ECT)
9. Evap Purge Solenoid
10. Egr Valve
11. Intake Air Temp Sensor (IAT)
12. MAP sensor

and a crappy youtube howto on replacing injectors on a 3x00 type engine. I'd save that for the last thing tho... very rarely do they stick open. I betting on a cracked O2 sensor, or bad temp sensor.

https://www.youtube.com/watch?v=lpVY3t-o0yY

[jameszach91]

ok, how many o2 sensors are there? not comparing but my Pontiac 3.4 had two, but where are these located?

[3X00-Modified]

There is only one sensor on a 94, 96 they introduced the secondary post cat sensor, also downstream sensors have no effect on fueling they just read if the cat is doing its job. It is located on the rear manifold pretty much right in front of the steering rack/inner tie rod area. Look right behind the coil packs from the top of the motor.

[jameszach91]

ok, soon as I get home Im def gonna get it replaced. looking forward to restoring, and eventually upgrading this beast. do you have any notes for a v6 rookie? ie brand of spark plugs, and mods?

[3X00-Modified]

I know nothing about the V6's...

Click on the link in my signature... that will give you some idea's and nightmares of what not to do.

[jameszach91]

ok lol I will give it a try thank you