Pump or filter. When you rev it, the pressure should go up.
Fuel Pressure an Easy one?
Thread Starter
Instructor
Joined: Apr 2008
Posts: 240
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From: Peachtree City GA
Fuel Pressure an Easy one?
I connnect A fuel Pressure Gauge to 85 C4, I have 40 PSI with key on, I crank, I have 40psi at Idle, when I rev the motor for more that 2 seconds It drops To 35 PSI. the I
let off it comes back Can anybody help?
let off it comes back Can anybody help?
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
according to the specs I have the running rail pressure on a 85 should be 36.. they went to 3 bar in 86. Am I right?
Thread Starter
Instructor
Joined: Apr 2008
Posts: 240
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From: Peachtree City GA
I bought this car about 6 month ago From a friend who does Rebuilds ( totals). The car was bumped in the left front fender Just cracked the glass. It was repaired. And then sat for 9 years, Utill I got it. The fuel pump had rusted off Inside the tank. I replace the Pump with a new , After cleaning the tank and blowing out the lines. I ran seafoam thru the tank with the new gas, replace Plugs wires, cap ,rotor cleand and re oiled the K&N filter. And it seem to run fine Really strong for this motor (TPI.) The car has a B&K 48mm Throtle body And an Adjustable fuel pressure reg. It has a relocated air temp sensor and from what I can tell the Knock sensor has been unplugged. I guess they turned up the pressure for the changes. This is my 3rd vette My 1st was 95 LT1, 2nd ws a 98vert, This buy far has been the most work of the 3. I will try the Fuel Filter again. I will let you know if that works.
Supporting Vendor
Joined: Mar 2008
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From: Cumming Ga
here is the product we recommend.
http://fuelinjectorconnection.com/sh...&productId=166
Thread Starter
Instructor
Joined: Apr 2008
Posts: 240
Likes: 0
From: Peachtree City GA
the 85 uses a 24lb injector stock because of the reduced fuel pressure, they act like a 22
here is the product we recommend.
http://fuelinjectorconnection.com/sh...&productId=166
here is the product we recommend.
http://fuelinjectorconnection.com/sh...&productId=166
Are you in Atlanta?
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Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
the running rail pressure should be 36 you are at 35. sounds right to me. The computer does not control fuel pressure on these. after the car was sitting for 9 years did anyone service the injectors
Last edited by FICINJECTORS; Sep 27, 2008 at 07:11 PM.
Thread Starter
Instructor
Joined: Apr 2008
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From: Peachtree City GA
Well It sounded to me, and felt like it was all of a sudden lacking in power, almost as if it were running on 7 1/2 clyinders. It was hard to start after a couple of days of sitting and would throw a code 54. It starts and idles at 40, rev the motor and hold at 3500 and it goes up 2psi the instanly drops to 35psi, relase the rpms and it goes back up to 40psi. Someone change out the TB and FPR to a 48mm B&k and Adjustable FPR, I assume they were tring to make more power by turning up the FP. I dont know if the motor had any other mods. Also When driving at 55mph or any other crusie speed it seem like it misses intermitently.
I do want to buy some Injectors from you. But I must get any other issues cleared first, I dont wont to screw up a new set of injectors if something else is going on too.
I do want to buy some Injectors from you. But I must get any other issues cleared first, I dont wont to screw up a new set of injectors if something else is going on too.
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
Well It sounded to me, and felt like it was all of a sudden lacking in power, almost as if it were running on 7 1/2 clyinders. It was hard to start after a couple of days of sitting and would throw a code 54. It starts and idles at 40, rev the motor and hold at 3500 and it goes up 2psi the instanly drops to 35psi, relase the rpms and it goes back up to 40psi. Someone change out the TB and FPR to a 48mm B&k and Adjustable FPR, I assume they were tring to make more power by turning up the FP. I dont know if the motor had any other mods. Also When driving at 55mph or any other crusie speed it seem like it misses intermitently.
I do want to buy some Injectors from you. But I must get any other issues cleared first, I dont wont to screw up a new set of injectors if something else is going on too.
I do want to buy some Injectors from you. But I must get any other issues cleared first, I dont wont to screw up a new set of injectors if something else is going on too.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
ECM/PCM has no control.
Thread Starter
Instructor
Joined: Apr 2008
Posts: 240
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From: Peachtree City GA
It does, When I rev the motor It goes from 40 to 45psi Then Drops to 35 Untill I release the throttle, Guess I will pull the vacum line and note what that does, If that dosnt help I will pull the Pump, Cause I have used sea Foam in the tank. 1 Can to a full tank. and to top it off Im driving yesterday and the Front left brake calipers starts locking up,I just replaced both fronts about 4 months ago for the same Problem,CrapOLA does it ever end!!!, Why did I buy this car!
CrapOLA does it ever end!!!, Why did I buy this car!
Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
I think it's ALL normal. the regulator is connected to vacuum in the intake manifold.
example:
You start the engine: It idles at 700 rpm and the pressure is 50 Kpa and you have 40 psi of fuel pressure.
you apply gas in P or N: the rpm increase to 1000 the pressure decrease to 45 Kpa (the vacuum INCREASE).
If the vacuum increase, the pressure regulator acts to reduce the pressure of the fuel. you read 38 (instead of 40)
you apply more gas (again in P or N) the rpm increase to 2000 and believe me in N or P you need a very low throttle openings: the pressure decrease to 40 Kpa (the vacuum INCREASE more).
the vacuum increase more, the pressure regulator acts to reduce more the pressure of the fuel. you read 36 (instead of 40).
When you are in gear (under load) and apply (say... 40% TPS) and you are in acceleration at 3000 rpm, the pressure INCREASE -say..85 Kpa- (the vacuum DECREASE) and you see the fuel presuure increase.
-Beppe-
example:
You start the engine: It idles at 700 rpm and the pressure is 50 Kpa and you have 40 psi of fuel pressure.
you apply gas in P or N: the rpm increase to 1000 the pressure decrease to 45 Kpa (the vacuum INCREASE).
If the vacuum increase, the pressure regulator acts to reduce the pressure of the fuel. you read 38 (instead of 40)
you apply more gas (again in P or N) the rpm increase to 2000 and believe me in N or P you need a very low throttle openings: the pressure decrease to 40 Kpa (the vacuum INCREASE more).
the vacuum increase more, the pressure regulator acts to reduce more the pressure of the fuel. you read 36 (instead of 40).
When you are in gear (under load) and apply (say... 40% TPS) and you are in acceleration at 3000 rpm, the pressure INCREASE -say..85 Kpa- (the vacuum DECREASE) and you see the fuel presuure increase.
-Beppe-
I guess my preformance lag may be related to the Injectors