Greetings!

Using scan9495 I see STFT's near the normal 128 for both banks at idle as well as under load (70 mph). The LTFT for bank 1 is near normal (130) but the LTFT for bank 2 is consistently high (hovering around 155) at all speeds, loads, and RPM's.

What I've done:
1) Replaced fuel filter
2) Cleaned throttle body
3) Replaced spark plugs
4) Checked fuel pressure

All spark plugs look the same; no signs of any problems.

When turning key to run to prime the system the pump runs for about 2 sec, brings the pressure to 37 psi then falls to 5 psi in about 5 sec.

The engine starts easily if I prime the system once then immediately turn key to start before the pressure drops. While running the pressure is maintained at 37 psi.

When I remove the vacuum hose to the pressure regulator the pressure increases by 8 psi to 45 psi so I think the regulator is good.

From what I've read this kind of narrows it down to the either the fuel pump or leaky injectors. Knowing the LTFT on bank 2 is high while the LTFT on bank 1 is near normal I'm leaning (no pun intended) towards the bank 2 injectors being the culprit. My logic being that if it were a weak pump both sides would have high LTFT's.

Is there an easy way to isolate the pump from the injectors to test the pressure provided by the pump? My thinking is that if an injector(s) is/are leaking then by taking the injectors out of the equation I could determine if I have a weak pump and faulty check valve if the pressure is still low and the pressure still drops rapidly. If it does: replace the pump. If not, get the injectors serviced.

I'm a union electrician by trade, not a mechanic. I'd appreciate any feedback with my issues. If my thinking is faulty please set me straight!

Thanks for reading and please don't hesitate to reply,

Philip

 

sounds like the fuel pressure regulator and/or the fuel pump check valve are failing.

 

I just wanted to bring some closure to this thread. After adding a bottle of techron/chevron fuel system cleaner to a nearly empty tank, letting it sit at the pump for about 15 minutes, then filling up, my KOEO fuel pressure rose to 44 psi (must've cleaned the inlet sock of varnish). I used a $15 borescope to look in the gas tank to see if there was a bad varnish problem...couldn't see the inlet sock but the tank and fuel pump look brand new! After replacing the horribly clogged fuel injectors (which solved my lugging/no power under load issues, the fuel pressure still dropped to zero with KOEO in seconds. Rather than spending $200+ on a new fuel pump and the labor involved with either droppng the tank or using the hatch method (when the original pump supplied spec pressure) I opted to install an inline check valve in the nylon supply line in the engine bay. Now the engine starts on the first rotation of the first crank and the LTFT's and STFT's are normal throughout all speeds and loads. I'm proud to say that my 1994 Camaro now starts, runs and handles like new (well, like a new car with 20K miles on it)! The power and acceleration are what one would expect from a 160 HP engine and the fuel economy (with about 75% hwy/25% city) over the last 3 fill-ups is averaging 27.5 mpg!

Stay Frosty!

 

Im glad you figured the problem out here was my suggestion: If Bank 1 is staying at a good PSI Check your bank 2 injectors. I would Change the plugs on the whole engine just because it wont hurt and if you want to Cross your T's and dot your I's change your injectors on both banks just to keep them copacetic. It may cost a little more but if you have a 1994 with 15K original miles that is your baby and I would treat it like one. It wont hurt to put a K&N air filter system on it to give a little more breathing room for your V6. Plus I would dump two bottles of fuel injection cleaner through the pump to clean the system out. Sounds like you have a nice car there. Again Im glad you for her fixed. ZIGGZ

 

Thanks, Ziggz, for your reply. Here is what I've actually done to Dot to get her to perform as she does now.
1) New AC Delco fuel filter
2) Added approx. 3oz. Valvoline High Performance 80W-90 gear oil
3) 5 oz. Lucas Oil Fuel System Treatment to full tank
4) New AC Delco transmission filter and trans fluid change
5) 6 New AC Delco spark plugs
6) Built an OBD1 adapter cable and used Scan9495 software
7) Bought HEI spark tester, checked for spark at all plug boots
8) Chevron/Techron fuel system cleaner to full tank
9) Cleaned throttle body w/ CRC throttle body cleaner
10) Chevron/Techron fuel system cleaner to another full tank
11) Used 1 can Seafoam Spray Cleaner in throttle body w/ engine @ 1500 rpm
12) Installed 2 new AC Delco O2 sensors
13) Installed 6 new SMP 17 lb/hr fuel injectors
14) Installed McMaster-Carr inline check valve in engine bay
15) Installed front seat covers
16) Replaced 4 stock speakers w/ Pioneer TS-A1686R 6.5" 350-Watt 4-Way Speakers
17) Replaced stock stereo w/ Pioneer DEH-X5800HD head unit

She sure is fun to drive now! I just looked up the K&N Performance Air Intake System you mentioned...No funds now but maybe next year. Thanks for pointing it out!

Stay Frosty,
Philip