 fuel pressure, builds but drops |
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| Gunn1 |
 Nov 18 2016, 11:08 PM
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#1
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Senior Member  Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None  |
After the car sat for a few months (74 2.0 liter factory EFI) the fuel system builds pressure as it should when the key is turned to the on position, but once the system is up to pressure (about 40PSI on the gauge) the pump shuts off as it should but the pressure drops on the gauge. Car will start but barely. Used to build pressure then the pump would shut off but gauge would stay/hold pressure at right around 40PSI until car was started. Do I have a leak somewhere. there is no evidence or gas smell.
what could it be? Up until now the car always started and ran great. |
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| pbanders |
Nov 19 2016, 02:13 PM
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#2
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Senior Member Group: Members Posts: 943 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805 |
QUOTE(Gunn1 @ Nov 18 2016, 10:08 PM)  After the car sat for a few months (74 2.0 liter factory EFI) the fuel system builds pressure as it should when the key is turned to the on position, but once the system is up to pressure (about 40PSI on the gauge) the pump shuts off as it should but the pressure drops on the gauge. Car will start but barely. Used to build pressure then the pump would shut off but gauge would stay/hold pressure at right around 40PSI until car was started. Do I have a leak somewhere. there is no evidence or gas smell. what could it be? Up until now the car always started and ran great. Could be the check valve in the pump, leaky injector, or leaky CSV. Pull off the air box and open the throttle so you can see inside the plenum, if it's full of gas, the CSV is probably leaking. Check your injectors by pulling them and pressurizing the system. If they're not leaking and the CSV is OK, then it's the check valve. According to DD, it's really not a check valve, from a posting of his: "The pump itself acts as a check valve, at least to some extent. There is no specific check valve built in. There is a spring-loaded valve, but its intent is to bleed off overly high pressure from inside the pump back to the tank." |
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| Gunn1 |
Nov 19 2016, 02:25 PM
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#3
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Senior Member Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None |
QUOTE(pbanders @ Nov 19 2016, 02:13 PM) QUOTE(Gunn1 @ Nov 18 2016, 10:08 PM) After the car sat for a few months (74 2.0 liter factory EFI) the fuel system builds pressure as it should when the key is turned to the on position, but once the system is up to pressure (about 40PSI on the gauge) the pump shuts off as it should but the pressure drops on the gauge. Car will start but barely. Used to build pressure then the pump would shut off but gauge would stay/hold pressure at right around 40PSI until car was started. Do I have a leak somewhere. there is no evidence or gas smell. what could it be? Up until now the car always started and ran great. Could be the check valve in the pump, leaky injector, or leaky CSV. Pull off the air box and open the throttle so you can see inside the plenum, if it's full of gas, the CSV is probably leaking. Check your injectors by pulling them and pressurizing the system. If they're not leaking and the CSV is OK, then it's the check valve. According to DD, it's really not a check valve, from a posting of his: "The pump itself acts as a check valve, at least to some extent. There is no specific check valve built in. There is a spring-loaded valve, but its intent is to bleed off overly high pressure from inside the pump back to the tank." What is the CSV? |
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| Bartlett 914 |
Nov 19 2016, 02:35 PM
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#4
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Advanced Member Group: Members Posts: 2,218 Joined: 30-August 05 From: South Elgin IL Member No.: 4,707 Region Association: Upper MidWest |
QUOTE(Gunn1 @ Nov 19 2016, 03:25 PM) QUOTE(pbanders @ Nov 19 2016, 02:13 PM) QUOTE(Gunn1 @ Nov 18 2016, 10:08 PM) After the car sat for a few months (74 2.0 liter factory EFI) the fuel system builds pressure as it should when the key is turned to the on position, but once the system is up to pressure (about 40PSI on the gauge) the pump shuts off as it should but the pressure drops on the gauge. Car will start but barely. Used to build pressure then the pump would shut off but gauge would stay/hold pressure at right around 40PSI until car was started. Do I have a leak somewhere. there is no evidence or gas smell. what could it be? Up until now the car always started and ran great. Could be the check valve in the pump, leaky injector, or leaky CSV. Pull off the air box and open the throttle so you can see inside the plenum, if it's full of gas, the CSV is probably leaking. Check your injectors by pulling them and pressurizing the system. If they're not leaking and the CSV is OK, then it's the check valve. According to DD, it's really not a check valve, from a posting of his: "The pump itself acts as a check valve, at least to some extent. There is no specific check valve built in. There is a spring-loaded valve, but its intent is to bleed off overly high pressure from inside the pump back to the tank." What is the CSV? Cold start valve. It is the 5th injector |
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| pbanders |
Nov 19 2016, 02:56 PM
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#5
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Senior Member Group: Members Posts: 943 Joined: 11-June 03 From: Phoenix, AZ Member No.: 805 |
QUOTE(Bartlett 914 @ Nov 19 2016, 01:35 PM) Cold start valve. It is the 5th injector It's on the back of the plenum on the LH side, fed by a hose from the fuel rail tap on that side. In warmer climates the CSV is rarely if ever actuated, but they can fail and leak, regardless. Its operation is controlled by the thermo or thermo-time switch (depends on what year as to which kind of switch you have), not by the ECU. |
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Posts in this topic
Gunn1 fuel pressure Nov 18 2016, 11:08 PM
Rand :ttiwwp:
:stromberg:
:stromberg:
:stromberg:
... Nov 18 2016, 11:58 PM The Cabinetmaker Admin! Clean up in the garage please. Nov 19 2016, 01:00 AM Gunn1 if you don't have a answer that's ok. I ca... Nov 19 2016, 08:26 AM Gunn1 Thanks going to go out and give the suggestions a ... Nov 19 2016, 03:24 PM Gunn1 plenum is dry, no leaks at the injectors, going to... Nov 20 2016, 05:19 PM Gunn1 Got it running, after looking over everything I no... Nov 26 2016, 06:44 PM Rand Dude, I wish you would give it a rest. Find anothe... Nov 27 2016, 05:57 PM
porschetub
Dude, I wish you would give it a rest. Find anoth... Nov 27 2016, 08:27 PM The Cabinetmaker By now everyone should know who he is. The questio... Nov 28 2016, 07:40 AM tomh Quick question here, in the warm climates would it... Nov 28 2016, 01:58 PM jd74914
Quick question here, in the warm climates would i... Nov 28 2016, 07:01 PM Gunn1
Quick question here, in the warm climates would ... Nov 28 2016, 07:22 PM boxsterfan Who is he/she? I guess I don't spend enough t... Nov 28 2016, 02:20 PM The Cabinetmaker
Who is he/she? I guess I don't spend enough ... Nov 28 2016, 02:48 PM Gunn1 The info in the post is ledgit. Explained exactly ... Nov 28 2016, 05:28 PM Rand
The info in the post is ledgit. Explained exactly... Nov 28 2016, 08:00 PM second wind I am not banned....and for what? Just who the hel... Nov 28 2016, 10:48 PM The Cabinetmaker Once a troll, well you know the rest. Nov 29 2016, 07:18 AM Gunn1 I have no affiliation with "Second Wind" Nov 29 2016, 09:15 AM The Cabinetmaker So you do admit having multiple user names! Yo... Nov 29 2016, 09:23 AM Gunn1
So you do admit having multiple user names! Y... Nov 29 2016, 12:31 PM tomh I was just starting to learn something here about ... Nov 29 2016, 03:55 PM |
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