I apologize if posted this in the wrong area. Just offering some info through my experience and hoping it helps someone else.
I have an 1986 TPI setup in KITT with a modified 350. Ever since I can remember, I've been questioning my fuel pressure. At idle (650 rpms), I set my fuel pressure at 42 psi. When I hit the gas, the pressure would drop to 30 psi. Seemed I was always adjusting it, cause it was never consistant.
When I'm driving, I would floor it from a stand still. Most of the time it would hesitate for a second, then take off like a rocket. Rarely backfiring through the intake.
When the engine was cold after sitting all night. Outside temp above 70 F. It would take a few attempts to fire up. I would have to keep my foot on the gas for a minute to keep it running.
I bought a Factory 1986 Pontiac service manual. So I checked my cold start injector and TPS (Throttle Postioning Sensor) circuit. All were fine.
I Replaced the MAF (Mass Air Flow), IAC (Idle Air Control) and O2 sensors. Always adjusting my timing. I even replaced the Ignition module and Ignition coil. And since I am the one who programmed my own ECU chip. Was the programming at fault? I'm a Novice at best with chip tuning. All this cause I'm trying to resolve these issues. But the car does run and is very trustworthy for road trips. I just have these hiccups that I noticed and want resolved.
Then this year .... Its April 2013. I drive my KITT to work and never got on the throttle. As I coming home I decided to floor it, WOT (Wide Open Throttle). There was no power!! I could have been passed by a lawn tractor. Backfiring through the intake badly, until I let off the gas. I pull into a gas station. Advanced the timing a slightly. While in PARK and hit the gas. KITT was very responsive, until I put him in DRIVE. I can accelerate gradually to reach 60 mph but not by flooring it. I get him home and in the garage. I call a buddy over who is an ASE GM Mechanic. He plays with the timing and adjust fuel pressure and gets him going somewhat well. He said he found the sweet spot with adjustable fuel pressure and I should replace it. It seems to be the failing compontent. Since I have to remove the upper intake anyways. I decided to also swap the EGR vale too, its 25 years old. I put it back together and still the same results. No power when floored and backfiring throught the intake.
Since the fuel pressure regulator was new, I had to reset it. The fuel pressure was peaking at 35 psi. So I took vice grips to clamp the return fuel line and see that my peak fuel pressure was 38 psi. Not good. At some point after summer of 2012, my fuel pump started pumping low pressure.
I did some google research. Factory 1985 - 1991 TPI fuel pumps offer around 140 LPH (Liters Per Hour). 1991 Corvette around 160 LPH. 1994 Buick roadmaster around 190 LPH. People with slightly modified TPI setup should run 255 LPH.
A Walbro fuel pump are said to be noisey. Holley fuel pumps are also said to be repackaged Walbro Fuel pumps. (On the actual Holley Fuel pump, its stampped WALBRO on one side. Holley on the other.) Walbro pumps do NOT come with a warranty and many people have stated their Walbro pump failed within a year. The factory AC Delco pumps have been reported to be very successful. I would recommend keeping the in tank style pump. And don't put a 2nd fuel pump under the car.
I came across a pump brand called Tre Preformance. They offered 155 LPH, 255 LPH and 255 HP LPH (High pressure). I ordered the 255 LPH. NOT High Pressure. I dropped my tank and installed the fuel pump. I clamped the returned fuel line to see the pressure from the pump and the gauge max out. I removed the clamp and adjusted my fuel pressure to 45 psi. KITT started right up!!!!
All those symptoms I stated I was experiencing. Hard to start with a cold engine, inconsistant fuel pressure, fluctuating fuel pressure when accelarating and backfiring through the intake occasionally. Since this new pump, I have not had those problems!!!! When I hit the gas now. That fuel pressure needle barely moves.
If you are having similar issues with your TPI, modified or not. I would recommend swapping the pump. What brand is up to you.
I'll list my engine mods so it my be comparable to others looking for help.
Throttlebody - I had my OEM Throttlebody machined from stock 47mm to 52mm with an Holley AirFoil. (The butterfly in my throttlebody were sticking. Not allowing for the car to always return to idle. All throttle bearings were replaced fixing the high idle problem.)
Injectors - I have 24 lbs Bosch stage II injectors. (Stock 305 come with 19 lbs, 350 come with 21 lbs.)
Cam - Comp Cam 12-262-4
Block - Late 70s 4-bolt main 350 SBC, punched .030 over.
Fuel regulator - Holley Adjustable with a big Thumb wheel, 512-501. (I first tried Jet Adjustable Fuel Regulator, 61501. The Jet version is a pain to adjust. You have to use a 3/8 open end wrench to adjust it in a tight area. Good news about the JET, you can use stock diaphrams. Easy to find and replace if it blows. The Holley use a special Diaphram in theirs. Not able to find quickly. But the Big Thumb wheel allows for quick easy adjust for your fuel pressure. I do recommend adjusting when the engine is cold. I've had blisters on my fingers from the Holley being so hot.)
Fuel Pressure Gauge - Accel Fuel Pressure Gauge Kit, Part No. 74745. (I have gone through 3 of these in 10 years. The meter it self started leaking and I only replaced the gauge. I have a liquid-filled fuel pressure gauge now. Its lasted the longest and because its liquid filled, the needle doesn't bounce so much.)
Heads - Stock cast iron heads from the late 60s. Nothing special.
Cooling fans - I found 87 and up TPI dual fan setup which I put in.
Cold Air - I found a stock 89 formula cold air set up. (It allows for a cone shape K&N filter, with a 3" mounting end, to fit nicely on the right (Passenger) side. It fits over the right side battery tray and I'm wanting to cut out that battery tray to allow better air flow. I did have to move the Stock charcoal canister by only securing it with 1 bolt instead of 2.)
Exhaust - 2 1/2 from the cat to the muffler. Muffler is an Flowmaster American series 2.
Headers - Flowtech 16102FLT. Comes with y-pipe.
Computer - Self modified tuner chip. (I DID MY OWN RESEARCH. Look into to it before you buy stuff you will never use. I ended up going craig moates and ordering a USB programmer, G1 package and chip extension cable. I wasn't about to constantly remove the KITT dash to swap out preformace chips. The 24 inch extension cable is nice.)
Fuel Pump - TREPERFORMACE Fuel Pump 255 lph, TRE-343. (This pump really beefed up my line pressure. If you have a weak part of your fuel system. O-ring, rusted lines, worn hoses, etc. You might want to replace those componets too.)
Rear End - Posi Drum brake 10 bolt with 3.73 gears. (I wish I did 3.42. Easier on the gas. )
If its not listed, then presume its not modified. I hope this helps someone.
Joined: Tue Oct 23, 2012 7:01 am
Joined: Tue Oct 23, 2012 7:01 am