" I Need some help I have a TPI system from a 88-89 5.0 Camaro installed in my 40 chevy. In the beginning it would not run after it warmed up. Checked the fuel pressure and it was only 20 PSI. Replaced pump and that cured 85% of my problems. Now it runs great under 2800 RPM. Anything above that it backfires and bogs down. I thought it might be the vacuum advance, but the distributor does not use a vacuum advance. Anyone with an idea want might be causing my problem??"
If youve got an early year TPI , thats designed to use a 9th cold start injector,check the cold start injector as its a potential problem source if its not working correctly.The cold start injector is between the front and rear pairs of runner tubes on the driver-side.on early TPI engines if its not working or loose causing a vacuum leak starting the engines much harder, later versions did not use these
verify the fuel pressure with a fuel gauge connected to the shrader valve on your TPI fuel rails,
during all rpms it should remain constant between 38psi min and 44psi max,
if its not stable the fuel pump, restrictions in the lines or fuel filter or a defective fuel pressure regulator are most likely at fault
fuel pumps produce fuel flow, usually measured in gallons per hour of flow ,at the expected operational resistance. resistance to flow is measured by pressure between the pump and the restriction to flow, on a TPI thats usually measured at 40 psi, so a pump may be rated at 120gph at 40psi-200gph at 40psi.
if the pressure remains constant at the fuel rail (AS ITS DESIGNED TO DO!) that indicates the fuel pressure regulator is preventing fuel flow back to the tank thru the return line untill the pressure exceeds 40psi or if its an adjustable fuel pressure regulator at what pressure its adjusted to let the fuel flow at.
IF the pressure varies either the fuel pressure regulators defective (easily tested) or theres a restriction to the feed lines or the pumps defective.
if the return lines blocked off, back to the tank, the fuel pressure should go up and stay at the max pressure the fuel pump can produce, in the case of most TPI fuel pumps thats in the 42psi-50psi range, if the fuel filter and feed lines allow the pump to supply the engines fuel requirements
The stock fuel pressure for 1985 to 1987 C4 engines with TPI was 36 to 39 psi with the fuel pressure regulator vacuum hose connected, and 47 to 48 psi with the vacuum hose disconnected. For the 1988 to 1996 C4 corvettes, the stock fuel pressure is 40 to 42 psi with vacuum hose connected and 47 to 48 psi with the vacuum hose disconnected.
swapping out the stock non-adjustable fuel pressure regulator requires removing the plenum but takes only about 20 minutes and its easy to do, it allows some minor tuning adjustments which tends to help power.ESPECIALLY if the stock FPR is leaking
http://www.summitracing.com/parts/ATM-3275/
http://www.summitracing.com/parts/SUM-800199/
viewtopic.php?f=44&t=366&p=448#p448
viewtopic.php?f=55&t=5307&p=15751#p15751
be VERY SURE you order a adjustable fuel pressure regulator that comes with a NEW matching diaphragm as many kits assume youll re-use the stock diaphragm
if you swap to an adjustable fuel pressure regulator on your TPI fuel rails it makes sense to install a small fuel pressure gauge on the fuel rail so you can easily verify your fuel pressure, keep in mind raising the fuel pressure tends to richen the effective fuel/air ratio slightly while reducing the pressure tends to lean it out slightly, but remember the computer and the oxygen sensors try to maintain the emission friendly 14.7:1 fuel air ratio
http://www.jegs.com/i/JET-Performance/5 ... ProductId=
READ THE LINKS AND SUB LINKS
viewtopic.php?f=55&t=1241
viewtopic.php?f=80&t=728
viewtopic.php?f=32&t=596
viewtopic.php?f=55&t=635
viewtopic.php?f=55&t=606
viewtopic.php?f=32&t=33
viewtopic.php?f=32&t=168
If youve got an early year TPI , thats designed to use a 9th cold start injector,check the cold start injector as its a potential problem source if its not working correctly.The cold start injector is between the front and rear pairs of runner tubes on the driver-side.on early TPI engines if its not working or loose causing a vacuum leak starting the engines much harder, later versions did not use these
verify the fuel pressure with a fuel gauge connected to the shrader valve on your TPI fuel rails,
during all rpms it should remain constant between 38psi min and 44psi max,
if its not stable the fuel pump, restrictions in the lines or fuel filter or a defective fuel pressure regulator are most likely at fault
fuel pumps produce fuel flow, usually measured in gallons per hour of flow ,at the expected operational resistance. resistance to flow is measured by pressure between the pump and the restriction to flow, on a TPI thats usually measured at 40 psi, so a pump may be rated at 120gph at 40psi-200gph at 40psi.
if the pressure remains constant at the fuel rail (AS ITS DESIGNED TO DO!) that indicates the fuel pressure regulator is preventing fuel flow back to the tank thru the return line untill the pressure exceeds 40psi or if its an adjustable fuel pressure regulator at what pressure its adjusted to let the fuel flow at.
IF the pressure varies either the fuel pressure regulators defective (easily tested) or theres a restriction to the feed lines or the pumps defective.
if the return lines blocked off, back to the tank, the fuel pressure should go up and stay at the max pressure the fuel pump can produce, in the case of most TPI fuel pumps thats in the 42psi-50psi range, if the fuel filter and feed lines allow the pump to supply the engines fuel requirements
The stock fuel pressure for 1985 to 1987 C4 engines with TPI was 36 to 39 psi with the fuel pressure regulator vacuum hose connected, and 47 to 48 psi with the vacuum hose disconnected. For the 1988 to 1996 C4 corvettes, the stock fuel pressure is 40 to 42 psi with vacuum hose connected and 47 to 48 psi with the vacuum hose disconnected.
swapping out the stock non-adjustable fuel pressure regulator requires removing the plenum but takes only about 20 minutes and its easy to do, it allows some minor tuning adjustments which tends to help power.ESPECIALLY if the stock FPR is leaking
http://www.summitracing.com/parts/ATM-3275/
http://www.summitracing.com/parts/SUM-800199/
viewtopic.php?f=44&t=366&p=448#p448
viewtopic.php?f=55&t=5307&p=15751#p15751
be VERY SURE you order a adjustable fuel pressure regulator that comes with a NEW matching diaphragm as many kits assume youll re-use the stock diaphragm
if you swap to an adjustable fuel pressure regulator on your TPI fuel rails it makes sense to install a small fuel pressure gauge on the fuel rail so you can easily verify your fuel pressure, keep in mind raising the fuel pressure tends to richen the effective fuel/air ratio slightly while reducing the pressure tends to lean it out slightly, but remember the computer and the oxygen sensors try to maintain the emission friendly 14.7:1 fuel air ratio
http://www.jegs.com/i/JET-Performance/5 ... ProductId=
READ THE LINKS AND SUB LINKS
viewtopic.php?f=55&t=1241
viewtopic.php?f=80&t=728
viewtopic.php?f=32&t=596
viewtopic.php?f=55&t=635
viewtopic.php?f=55&t=606
viewtopic.php?f=32&t=33
viewtopic.php?f=32&t=168