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Low Fuel Pressure


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DamselInDistress
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Nov 19, 2013, 11:15 AM

Post #1 of 32 (2252 views)
Low Fuel Pressure Sign In

Hey guys,

Ok, so we all know the new fuel pump was "a bomb" (sigh) and the fuel pressure is still down.

HT...you mentioned that there is some testing we can do with the fuel gauge pressure tester. (whatever it's called, lol)

I can rent that....I do have about 300 left to my name, and as luck would have it, I have been blessed to have a friends car over these last couple weeks.

Is it the fuel pressure gauge I need??? Or the micrometer thing??? (probably got that one way wrong too Unsure.


DamselInDistress
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Nov 19, 2013, 11:17 AM

Post #2 of 32 (2248 views)
Re: Low Fuel Pressure Sign In

Oh yea, also wanted to let you know that I learned all about the "mass airflow sensor" during this drama. I don't know if it has anything to do with it, but damn it...I know where it is and I did clean it. :)


Tom Greenleaf
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Nov 19, 2013, 11:23 AM

Post #3 of 32 (2244 views)
Re: Low Fuel Pressure Sign In

This is a 96 Buick Riviera, 3.8 that had a suspect fuel pump replaced and instant fuel leak as new gasket wasn't used. Rest of a botched job unknown how bad.

OK - Fuel pressure gauge screws onto fitting on fuel rail Damsel and just key on engine off (KOEO) you should have it up to spec quickly.
Shutting key back off that pressure should hold where it was or mention that.

Sorry to butt in, just had to state the car and the fuel pressure tool. If incorrect say so and I'll edit it to correct,

T



DamselInDistress
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Nov 19, 2013, 11:26 AM

Post #4 of 32 (2239 views)
Re: Low Fuel Pressure Sign In


In Reply To
This is a 96 Buick Riviera, 3.8 that had a suspect fuel pump replaced and instant fuel leak as new gasket wasn't used. Rest of a botched job unknown how bad.

OK - Fuel pressure gauge screws onto fitting on fuel rail Damsel and just key on engine off (KOEO) you should have it up to spec quickly.
Shutting key back off that pressure should hold where it was or mention that.

Sorry to butt in, just had to state the car and the fuel pressure tool. If incorrect say so and I'll edit it to correct,

T


I will take all the "butting in" I can get Tom! Lol So sorry, forget to re-list vehicle. It is a 95 Buick Riviera Supercharged. (you were real close though Wink)

Yea, I have become all to familiar with where this fuel pressure gets tested at....just not sure if that is the unit I need to go rent again. It has a whole lot of other pieces I never used though....maybe that is what I need to rent? I only used the gauge and screwed it to the mainline. (think I used that term right, lol)


DamselInDistress
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Nov 19, 2013, 11:45 AM

Post #5 of 32 (2230 views)
Re: Low Fuel Pressure Sign In

Can't tell I'm bored! Figured I am going to be around these rooms awhile....may as well make myself at home. Sly


Hammer Time
Ultimate Carjunky / Moderator
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Nov 19, 2013, 12:13 PM

Post #6 of 32 (2225 views)
Re: Low Fuel Pressure Sign In

Ok, what you want to do is hook up the fuel pressure gauge and take a reading. Now look for a section of the return line that is rubber (not plastic) and with the engine running, momentarily pinch off the return with pliers and see if the pressure spikes up. If it does, then you have a bad regulator. If not, we are still looking at pump issues. If you happen to have plastic fuel lines, we will have to find another way to restrict the return line because you can't pinch plastic line. It will damage it.

Is there any chance this guy never actually put a new pump in?



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DamselInDistress
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Nov 19, 2013, 12:16 PM

Post #7 of 32 (2219 views)
Re: Low Fuel Pressure Sign In


In Reply To
Ok, what you want to do is hook up the fuel pressure gauge and take a reading. Now look for a section of the return line that is rubber (not plastic) and with the engine running, momentarily pinch off the return with pliers and see if the pressure spikes up. If it does, then you have a bad regulator. If not, we are still looking at pump issues. If you happen to have plastic fuel lines, we will have to find another way to restrict the return line because you can't pinch plastic line. It will damage it.

Is there any chance this guy never actually put a new pump in?


No chance new pump wasn't put in...original is in garage and I had to seal the new one.

Ok, so I will go now and get the pressure gauge. I know there is a return line (rubber) connected to the pump....but is there one under the hood usually??? Or will I need a second pair of hands to do this?

Leaving now for gauge.


nickwarner
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Nov 19, 2013, 12:20 PM

Post #8 of 32 (2218 views)
Re: Low Fuel Pressure Sign In

The fuel pressure spec for this is 41-47 lbs. The pump could be a dud, but I wonder since this guy was a hack that worked on it for you if he even changed the fuel filter. Its on the left side of the car against a frame rail and is has one line with a quick-disconnect that will look like a plastic clip and one end which is threaded. See if it looks shiny. Its about $11 for a new one but you will need a line wrench to remove it without damaging the end. It should've been replaced when the fuel pump was. If it was clogging up with junk, it could've been what killed the last pump. At the very least for the age of the car it is routine maintenance.

You may also have an issue with the fuel pressure regulator. It is mounted on the fuel rail on the engine and is what creates the pressure in the fuel rail that you are reading with a pressure gauge. They can fail, and there are some tests that can be done to determine if this is the cause that are rather simple. There is a vacuum line on the top of it, and you should pull that line off and see if there is any wetness in it. If so, you have a bad one for sure as it is leaking fuel past its diaphragm.


Hammer Time
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Nov 19, 2013, 12:21 PM

Post #9 of 32 (2218 views)
Re: Low Fuel Pressure Sign In

If you don't have a second pair of hands you can put vice grips on it with the engine off and then cycle the key on. Make sure you only do this long enough to see the pressure spike up because the high pressure is not good for the regulator.



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DamselInDistress
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Nov 19, 2013, 12:50 PM

Post #10 of 32 (2212 views)
Re: Low Fuel Pressure Sign In


In Reply To
The fuel pressure spec for this is 41-47 lbs. The pump could be a dud, but I wonder since this guy was a hack that worked on it for you if he even changed the fuel filter. Its on the left side of the car against a frame rail and is has one line with a quick-disconnect that will look like a plastic clip and one end which is threaded. See if it looks shiny. Its about $11 for a new one but you will need a line wrench to remove it without damaging the end. It should've been replaced when the fuel pump was. If it was clogging up with junk, it could've been what killed the last pump. At the very least for the age of the car it is routine maintenance.

You may also have an issue with the fuel pressure regulator. It is mounted on the fuel rail on the engine and is what creates the pressure in the fuel rail that you are reading with a pressure gauge. They can fail, and there are some tests that can be done to determine if this is the cause that are rather simple. There is a vacuum line on the top of it, and you should pull that line off and see if there is any wetness in it. If so, you have a bad one for sure as it is leaking fuel past its diaphragm.


Fuel filter is new....this is when I learned NEVER to work on a car angry. Blush I was so tired of having "car issues" and was hopeful it was only a filter...I changed it myself. Only to realize that when I was wrenching and it was clearly "unscrewing"....uh, about two inches of my fuel line was attached to it. :( This is actually how I met the "mechanic". I needed someone to come to the house and repair what I did. So, yes...new filter! Lol


DamselInDistress
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Nov 19, 2013, 12:53 PM

Post #11 of 32 (2209 views)
Re: Low Fuel Pressure Sign In


In Reply To
If you don't have a second pair of hands you can put vice grips on it with the engine off and then cycle the key on. Make sure you only do this long enough to see the pressure spike up because the high pressure is not good for the regulator.


Ok, back with the gauge. I just want to make sure I clarify this first. When you say cycle the key on, do you mean not start the engine??? You just want me to turn the key as if I am priming fuel through the new pump right?


Hammer Time
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Nov 19, 2013, 12:59 PM

Post #12 of 32 (2206 views)
Re: Low Fuel Pressure Sign In

Yes, that's exactly what I mean.

Also the spec I have for this car is 333 to 376 kPa (45 to 55 psi) I don't know where Nick got his spec from.



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DamselInDistress
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Nov 19, 2013, 1:09 PM

Post #13 of 32 (2204 views)
Re: Low Fuel Pressure Sign In


In Reply To
Yes, that's exactly what I mean.

Also the spec I have for this car is 333 to 376 kPa (45 to 55 psi) I don't know where Nick got his spec from.


Ok, the only weirdness came when I first clycled the car on and it was only at about 15 again. I noticed if I cycled a few times it slowly climbed back up to like 37psi. (hasn't been above that since all this started over a week ago) So I let it stable out then pinched of the fuel as much as I could. No real pressure change from that at all.


Hammer Time
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Nov 19, 2013, 1:18 PM

Post #14 of 32 (2199 views)
Re: Low Fuel Pressure Sign In

No, you have to cycle again after restricting it.



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DamselInDistress
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Nov 19, 2013, 1:21 PM

Post #15 of 32 (2197 views)
Re: Low Fuel Pressure Sign In


In Reply To
No, you have to cycle again after restricting it.


I did cycle it after restricting the fuel HT. I just waited until the pressure stabled out at 37 figuring it would be more accurate once I cut the fuel off. Was that the right thing to do?


Hammer Time
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Nov 19, 2013, 1:30 PM

Post #16 of 32 (2195 views)
Re: Low Fuel Pressure Sign In

Yes, that would be correct. Are you sure it was the return line and not the feed? If it really was the return, then we are still looking at a problem in the fuel pump. I assume you replaced the entire assembly, right? Not just the motor itself.



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DamselInDistress
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Nov 19, 2013, 1:41 PM

Post #17 of 32 (2192 views)
Re: Low Fuel Pressure Sign In


In Reply To
Yes, that would be correct. Are you sure it was the return line and not the feed? If it really was the return, then we are still looking at a problem in the fuel pump. I assume you replaced the entire assembly, right? Not just the motor itself.


Not sure of anything at this point to be honest. :( I just cut off the only black fuel line I knew of which is attached to the end of the filter. One is the metal line feeding into it, the other is rubber....that's the one I cut off.

The fuel pump is the complete assembly, not just the motor and/or wiring harness. If that is bad I can have new one sent and do it myself at this point. Honestly, seeing what I saw in the fuel pump....I promise I will do a better job than any of these guys who have crossed my paths recently. Ugh

It's more the waiting that bums me out. Again, because of money I bought it online at the same company I purchased my new PCM and Supercharger from last year. They manufacture and warranty their own parts and are MUCH cheaper than O'Reilly and Autozone. The new assembly cost me 125.00 with free shipping instead of 250 before tax.

Is there a way to test the pressure at the pump itself HT??? I have the unit here with all these handy dandy little "attachments." Lol


Hammer Time
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Nov 19, 2013, 1:49 PM

Post #18 of 32 (2188 views)
Re: Low Fuel Pressure Sign In

That could have been the vapor line The is another line the runs from the fuel rail back to the tank as a return. It's usually one size smaller hose than the feed line. The fuel pump- has 3 lines going to it. A feed, a return and a vapor that carries no pressure.





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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Nov 19, 2013, 1:50 PM)


Hammer Time
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Nov 19, 2013, 1:58 PM

Post #19 of 32 (2184 views)
Re: Low Fuel Pressure Sign In

You know, I think you are going to have a hard time finding any portion of rubber on this line. I'm pretty sure they use plastic which means youb are going to have to find another way to block it off.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



DamselInDistress
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Nov 19, 2013, 2:03 PM

Post #20 of 32 (2183 views)
Re: Low Fuel Pressure Sign In


In Reply To
That could have been the vapor line The is another line the runs from the fuel rail back to the tank as a return. It's usually one size smaller hose than the feed line. The fuel pump- has 3 lines going to it. A feed, a return and a vapor that carries no pressure.




Gotta stop you there real quick. So, I do have three ports on the new pump, only return and feed are hooked up. The middle one is bare and I seen no accessible hose that could attach.

Now I had idiot number two come by yesterday from parts store (yea, I just roll like that... Tongue) who wanted to help, but was truly honest to God...."not the one" and I knew that so he went away.

He said he installs these for a hundred, I told him I am not paying anyone else to do this again. About that time the first mechanic surfaced on the phone and I let those two guys talk, I just wanted to know about the house that belongs in the middle port. Guy that did the job SWEARS (whatever thats worth) there wasn't one, and the other guy was in agreement, but we know my opinion of his knowledge.

I am going to try and upload photo of my original pump....it does look as if the middle port has never had anything attached. See how short the stem is on it?

[URL=http://s1288.photobucket.com/user/pjones19691/media/pump_zpsa9ad7836.jpg.html]


Hammer Time
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Nov 19, 2013, 2:12 PM

Post #21 of 32 (2182 views)
Re: Low Fuel Pressure Sign In

That looks like it might be broken off but is should have a line going from there to the charcoal canister. Either way, the return should be attached to the tank but it will be made up of a combination of steel and plastic, just like the feed. If you can rig a way to run the feed directly into the gauge with no outlet, it would tell us the same thing.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



nickwarner
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Nov 19, 2013, 2:27 PM

Post #22 of 32 (2179 views)
Re: Low Fuel Pressure Sign In

Got my spec from AZ website. I'll go with your Alldata one. Looks like its not just AZ employees that don't know what they are talking about, huh?


Hammer Time
Ultimate Carjunky / Moderator
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Nov 19, 2013, 2:42 PM

Post #23 of 32 (2178 views)
Re: Low Fuel Pressure Sign In

Their data base is wrong 50% of the time



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DamselInDistress
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Nov 19, 2013, 3:19 PM

Post #24 of 32 (2177 views)
Re: Low Fuel Pressure Sign In


In Reply To
That looks like it might be broken off but is should have a line going from there to the charcoal canister. Either way, the return should be attached to the tank but it will be made up of a combination of steel and plastic, just like the feed. If you can rig a way to run the feed directly into the gauge with no outlet, it would tell us the same thing.


Sorry....life got in the way for a sec.
Ok, trying to keep from being "so" confused. I did some research and from what I understand the line I used was the fuel return.

Sorry, since I know I am being such a HUGE pain in your ass trying to help me, I really do want to get this right. There are three fuel lines sitting beautifully on top of my engine. :) But I don't have a CLUE which one is "return."

So I am really trying to "help you help me" and I took this picture and numbered each one. If you can tell from the image which one is the return, I would be able to test this and know that the results are 100% dead on accurate. Wink

[URL=http://s1288.photobucket.com/user/pjones19691/media/lines_zpscd659651.jpg.html]

Thanks TONS


Hammer Time
Ultimate Carjunky / Moderator
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Nov 19, 2013, 3:34 PM

Post #25 of 32 (2171 views)
Re: Low Fuel Pressure Sign In

Number 2 is definitely vapor. I can't see where the other lines go but i would suspect the one with the repair is the feed. It will be larger line than the return usually. As you can see, these lines are plastic and cannot be pinched. You will have to find another way. Our fuel pressure kits come with a lot of adapters than can usually be used.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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