 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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| Rand |
Nov 18 2016, 11:58 PM
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#2
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Cross Member Group: Members Posts: 7,410 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
(IMG:style_emoticons/default/thisthreadisworthlesswithoutpics.gif)
(IMG:style_emoticons/default/stromberg.gif) (IMG:style_emoticons/default/stromberg.gif) (IMG:style_emoticons/default/stromberg.gif) Wait, Stromberg got his own turd emoticon, I think 0U812/Gunn1/and all his fake accounts need one too! No, I take that back. Stromturd was just a rip off artist who sold bad shit. Gunn1 has no substance at all. poof |
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| TheCabinetmaker |
Nov 19 2016, 01:00 AM
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#3
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I drive my car everyday Group: Members Posts: 8,335 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
Admin! Clean up in the garage please.
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| Gunn1 |
Nov 19 2016, 08:26 AM
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#4
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Senior Member Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None |
if you don't have a answer that's ok. I can figure it out.
Thanks |
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| pbanders |
Nov 19 2016, 02:13 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(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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#6
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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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#7
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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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#8
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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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| Gunn1 |
Nov 19 2016, 03:24 PM
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#9
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Senior Member Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None |
Thanks going to go out and give the suggestions a try.
Will report back |
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| Gunn1 |
Nov 20 2016, 05:19 PM
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#10
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Senior Member Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None |
plenum is dry, no leaks at the injectors, going to try a different pump off of one of the other cars to see if its pump/check valve related. Although I do not like to do it, the car starts right up with a little starting fluid, until it burns it off. whatever it is I don't believe it to be to serious. will get back with the final results.
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| Gunn1 |
Nov 26 2016, 06:44 PM
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#11
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Senior Member Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None |
Got it running, after looking over everything I noticed a crack in the fuel supply line just before the square inline filter by the fuel pump. There wasn't any fuel dripping, but it did smell like Gas. Now the Gauge pops right up to 45psi and doesn't leak down over night. Runs like a champ, or at least well enough to move it in and out of the shed under its own power, so I guess I got that going for me.
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| Rand |
Nov 27 2016, 05:57 PM
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#12
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Cross Member Group: Members Posts: 7,410 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
Dude, I wish you would give it a rest. Find another forum, we aren't amused anymore. 45psi to a cracked hose you can see visually, but not a drip? (IMG:style_emoticons/default/bs.gif)
Glad you got your fuel pressure figured out though. (IMG:style_emoticons/default/wacko.gif) The point of this post isn't to bait the troll, but to expose him to people who seem to not realize who he is. (IMG:style_emoticons/default/stromberg.gif) |
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| porschetub |
Nov 27 2016, 08:27 PM
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#13
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Advanced Member Group: Members Posts: 4,806 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
QUOTE(Rand @ Nov 28 2016, 12:57 PM) Dude, I wish you would give it a rest. Find another forum, we aren't amused anymore. 45psi to a cracked hose you can see visually, but not a drip? (IMG:style_emoticons/default/bs.gif) Glad you got your fuel pressure figured out though. (IMG:style_emoticons/default/wacko.gif) The point of this post isn't to bait the troll, but to expose him to people who seem to not realize who he is. (IMG:style_emoticons/default/stromberg.gif) (IMG:style_emoticons/default/agree.gif) what a load of bs |
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| TheCabinetmaker |
Nov 28 2016, 07:40 AM
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#14
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I drive my car everyday Group: Members Posts: 8,335 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
By now everyone should know who he is. The question is, why has he not gone the way of freeky, megaturd, and the rest of his aka's? And a few new aka!s too.
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| tomh |
Nov 28 2016, 01:58 PM
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#15
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Member Group: Members Posts: 322 Joined: 28-February 10 From: san jose Member No.: 11,412 Region Association: None |
Quick question here, in the warm climates would it be ok to just compleatly disconnect the csv.
What would be the drawbacks on doing that. |
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| boxsterfan |
Nov 28 2016, 02:20 PM
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#16
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914's are kewl Group: Members Posts: 1,776 Joined: 6-June 03 From: San Ramon, CA Member No.: 791 Region Association: Northern California |
Who is he/she? I guess I don't spend enough time here to know anymore.
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| TheCabinetmaker |
Nov 28 2016, 02:48 PM
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#17
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I drive my car everyday Group: Members Posts: 8,335 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
QUOTE(boxsterfan @ Nov 28 2016, 03:20 PM) Who is he/she? I guess I don't spend enough time here to know anymore. She/he/it(say that real fast) is a troll that uses the alias' of megalug, ou812, gunn1, second wind, and others who have been banned already. |
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| Gunn1 |
Nov 28 2016, 05:28 PM
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#18
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Senior Member Group: Members Posts: 1,021 Joined: 14-February 16 From: Minnesota Member No.: 19,670 Region Association: None |
The info in the post is ledgit. Explained exactly how it happened.
Isn't it a wonderful thing and very telling that some people need to tear down others for their enjoyment. I have never overcharged , misrepresented a car or a part to anyone on this site, but yet I'm the one that gets treated like the criminal. You say things like "don't feed the troll", then why do you even comment? Others have weighed in to help in an honest fashion and I appreciate it. "if you can't say something nice don't say anything at all" |
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| jd74914 |
Nov 28 2016, 07:01 PM
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#19
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Its alive Group: Members Posts: 4,841 Joined: 16-February 04 From: CT Member No.: 1,659 Region Association: North East States |
QUOTE(tomh @ Nov 28 2016, 02:58 PM) Quick question here, in the warm climates would it be ok to just compleatly disconnect the csv. What would be the drawbacks on doing that. Yes, you do not need a cold start valve to start, but it does make starting easier. Without that large start pulse you'll likely be cranking a bit longer. |
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| Gunn1 |
Nov 28 2016, 07:22 PM
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#20
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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(jd74914 @ Nov 28 2016, 07:01 PM) QUOTE(tomh @ Nov 28 2016, 02:58 PM) Quick question here, in the warm climates would it be ok to just compleatly disconnect the csv. What would be the drawbacks on doing that. Yes, you do not need a cold start valve to start, but it does make starting easier. Without that large start pulse you'll likely be cranking a bit longer. My 74' has the cold start valve but it is not wired, or connected to the fuel supply. the car actually starts pretty good without it, but you have to treadle the throttle a little to keep it going . Question (IMG:style_emoticons/default/confused24.gif) Besides helping start a cold engine does the Cold start valve also act like a idle enrichment circuit and help regulate fuel delivery to create a more stable idle. |
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