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V6 runs like there is water in the fuel by shurlbert
Started on: 09-01-2014 03:44 PM
Replies: 49 (866 views)
Last post by: tshark on 10-03-2014 07:43 AM
shurlbert
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Report this Post09-01-2014 03:44 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hi everyone,

Some background before I get to the question. I am restoring an 85 GT (V6) that was sitting for an unknown number of years (at least 8 years). I removed and cleaned the fuel tank, replaced the fuel pump and filter, changed all the fluids, and changed spark plugs.

I got it running and it was running smooth for a while, then it started sputtering some on acceleration. It is getting worse the more I drive it. It is acting like there is water in the fuel, but I don't think that is the cause. I've ran a tank and a half of fuel through it with fuel additive (seafoam) each time, to clean injectors and remove water. Therefore, it couldn't be water. Is it possible that the more I drive it, the fuel additive is breaking gunk loose in the fuel system and clogging up injectors?

BTW...I got 12 MPG on the first tank, and it is looking like it will be the same on the second tank. Would a clogged fuel return line cause me to get bad gas mileage?
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tshark
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Report this Post09-01-2014 04:07 PM Click Here to See the Profile for tsharkSend a Private Message to tsharkEdit/Delete MessageReply w/QuoteDirect Link to This Post
...

[This message has been edited by tshark (edited 09-08-2018).]

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85 SE VIN 9
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Report this Post09-01-2014 04:20 PM Click Here to See the Profile for 85 SE VIN 9Click Here to Email 85 SE VIN 9Send a Private Message to 85 SE VIN 9Edit/Delete MessageReply w/QuoteDirect Link to This Post
I have two 85 2.8's. I don't think I've ever gotten as low as 12 mpg. Even with old gas and barely driveable I got 15. Any codes?
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NetCam
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Report this Post09-01-2014 04:46 PM Click Here to See the Profile for NetCamClick Here to visit NetCam's HomePageSend a Private Message to NetCamEdit/Delete MessageReply w/QuoteDirect Link to This Post
If there are no codes, I'd check fuel pressure. Sounds like you may have leaking injectors. If the o-rings are shot they will leak fuel. A leak down test will let you know if this is a possibility. Should hit around 38-40 PSI and stay there for at least about 10 minutes or so.
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gmctyphoon1992
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Report this Post09-01-2014 05:37 PM Click Here to See the Profile for gmctyphoon1992Click Here to Email gmctyphoon1992Send a Private Message to gmctyphoon1992Edit/Delete MessageReply w/QuoteDirect Link to This Post
as said above Check your codes.

If no codes check your fuel pressure. Measuring with a gauge against atmospheric pressure, engine off it's about 42psi (35 to 45psi is acceptable), and with engine idling, high 30s is normal.

The rail shouldn't lose more than just a few psi of pressure in 15-20 minutes with the key off. Much more than that is not normal and indicates a problem possibly a leak somewhere.

I just had a problem where my car would cut out and not run and blow modules because of grounding issues. Even if this is not the source of the problem I would clean all your grounds anyways as a precaution and preventive maintenance step since the car has been sitting. It is very easy and takes just a few minutes and will also make a good running car run better.

[This message has been edited by gmctyphoon1992 (edited 09-01-2014).]

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shurlbert
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Report this Post09-01-2014 10:57 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
There are no codes. The car ran smooth for roughly 30 miles. I was thinking that it might be getting too much fuel, hence the low mileage. Of coarse the low mileage has nothing to do with my heavy right foot.
I checked the cap and rotor, and they are in good order. There is some rust in the distributor though.
I'm sure the injectors and o-rings are as old as the car. I would check the fuel pressure, but I don't know how. I will learn, get it done and report back.

Thank you
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NetCam
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Report this Post09-01-2014 11:04 PM Click Here to See the Profile for NetCamClick Here to visit NetCam's HomePageSend a Private Message to NetCamEdit/Delete MessageReply w/QuoteDirect Link to This Post
Checking the fuel pressure is a piece of cake. Get a pressure guage (They're pretty cheap at places like Harbor Freight), and hook it up to the Schroeder valve, which is located on the fuel rail on the right hand side of the motor. Turn the key on but don't start the motor, you should see pressure in the 40ish range, I think 42 is perfect but 35-45 is reasonable. The big test is let it sit for about 10 minutes and see how much bleeds off. It should hold pretty steady for at least 10 minutes, some say about 1/2 hour. If it goes down fast, you're either leaking fuel into the cylinders, or back to the tank. In order to see if it's going to the cylinders, temporarily block of the return line.

If you look in the picture here you can see the hose going toward the valve. It looks just like the valve on your tires and should have a similar cap on it.



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shurlbert
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Report this Post09-02-2014 02:39 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
So I borrowed a fuel gauge kit from Auto Zone. Took the plenum off, found the schrader valve, and checked the pressure. There was no measured pressure. I could not get the fuel gauge to engage the valve. I will return the kit tomorrow to Auto Zone and borrow a different one.
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shurlbert
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Report this Post09-02-2014 02:48 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the picture NetCam. I didn't realize you could access the schrader valve without taking the plenum off. It is ok though, because I wanted to check the EGR pipe and the various vacuum hoses for breaks and blockages anyway.
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shurlbert
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Report this Post09-02-2014 02:52 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post

shurlbert

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Member since Feb 2014
BTW...is it normal for the inside of the plenum to be coated with oily soot?
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Report this Post09-02-2014 11:12 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
I guess you could say it's normal for a high mileage motor, but not ideal.
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shurlbert
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Report this Post09-02-2014 02:12 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
The car only has about 60K miles, and judging from the great visual condition of the motor, I don't think it has been replaced.
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Report this Post09-02-2014 03:01 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Possibly a stuck ring would blow by some oil, and the PCV system would scavenge that back into the intake....The best cure for that is to drive the car.
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shurlbert
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Report this Post09-02-2014 04:11 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks Gall757,
I did notice that the tube from the pcv valve was really oily, which I think is normal. Nevertheless, I replaced the pcv valve.
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shurlbert
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Report this Post09-03-2014 10:27 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
I checked the fuel pressure. When I turned the key on and primed the pump, the pressure hit 42 PSI and then within 5 seconds dropped to 20 PSI. The fuel injectors are dry and there is no external leaking. I believe all that fuel is going into the engine, which explanes the poor MPG and the bad performance.

What should I do next?
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gmctyphoon1992
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Report this Post09-03-2014 01:09 PM Click Here to See the Profile for gmctyphoon1992Click Here to Email gmctyphoon1992Send a Private Message to gmctyphoon1992Edit/Delete MessageReply w/QuoteDirect Link to This Post
It should stay pressurized and not drop off like that so quickly.

your fuel pressure regulator isn't keeping the rail pressurized maybe?

A vacuum line runs to the regulator to provide extra pressure against the spring. check to see if there is any fuel in the vacuum line that runs to the regulator. What happens usually when the regulator goes bad is the diaphragm develops a leakage and the fuel enters the vacuum hose. check to see if that hose has any cracks also while checking for fuel in them.

The car will run very rich as well which would explain the poor fuel mileage.
Your spark plugs will look degraded and blackened from the extra work due to the extra fuel.
You will also could blow a little black smoke ..

If a bad regulator was the case.
my thought is..
Even though you have low fuel pressure what happens is since this is a return line fuel system the regulator pressures the rail through a loaded spring and keeps the pressure constant allowing a certain amount of fuel in and back to the tank but when it goes bad the spring either gets weak or the diaphragm leaks and the car pushes too much fuel through the rail and floods the engine because of that lack of resistance from the regulator. The reason why you cant keep pressure also is because the regulator isn't holding the pressure constant anymore at the rail and allowing the fuel to return to the tank too quickly. This is why you get 42psi right away but get a huge drop off after a few seconds.

someone correct me if I am wrong?

[This message has been edited by gmctyphoon1992 (edited 09-03-2014).]

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Lou6t4gto
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Report this Post09-03-2014 01:11 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
if you believe all that fuel is leaking into the engine you should Check and Change your OIL !
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Report this Post09-03-2014 06:32 PM Click Here to See the Profile for NetCamClick Here to visit NetCam's HomePageSend a Private Message to NetCamEdit/Delete MessageReply w/QuoteDirect Link to This Post
Does the car start really well when cold, but take some effort after it's warmed up a bit? If so, probably fuel sitting in the cylinders that leaked from your injectors and needs to blow off before it will start. Do you smell any gas right after you start it up?
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shurlbert
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Report this Post09-03-2014 11:13 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
I don't think there was fuel in the pressure regulator vacuum line. I'm not positive about that because I didn't know about that symptom when I took it off, and I was't looking for it.

The car starts well at all times (hot or cold), and I do not smell gas. It starts acting up during acceleration. It will loose power (bog down) temporarily, like there is water going through the system. However, if I let off the accelerator, it will recover. Seems like it's flooding, right?

Is there an easy way to test the pressure regulator? Should I assume from the symptoms that it is damaged, and just put a new one in to eliminate it as a suspect?
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shurlbert
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Report this Post09-03-2014 11:20 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Oh yes, I just remembered something. I removed one of the spark plugs, and it was blackened and had gas on it.
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army_greywolf
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Report this Post09-04-2014 04:03 AM Click Here to See the Profile for army_greywolfClick Here to Email army_greywolfSend a Private Message to army_greywolfEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm about to junk a fiero motor that's beyond repair actually. It has a known good regulator and set of injectors on it if your interested.
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shurlbert
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Report this Post09-04-2014 12:01 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
I replaced the regulator and changed the O-rings on the injectors, and no change. I think the injectors are bad.

Is there is anything else I should consider before I replace the injectors?
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shurlbert
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Report this Post09-09-2014 01:42 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
So I replaced the fuel injectors and I am still getting the fuel pressure drop within five seconds of powering up the fuel pump. Could the cold start injector be the source of this pressure drop?
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Report this Post09-09-2014 08:08 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is there a thermostat in the cooling system? The car could be running too cold and staying in closed loop.
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Gall757
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Report this Post09-09-2014 08:49 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Fuel pressure drop can be happening inside the fuel tank.....either with the pump or the line.
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phonedawgz
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Report this Post09-09-2014 09:08 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
The fuel pressure regulator is designed to hold the fuel pressure at 42 psi minus the intake manifold vacuum in psi.

Rather than follow a bunch of whatever let's stick to the problem. What is the fuel pressure when this problem IS OCCURRING. If it's 42-manifold vacuum (which will be pretty low at WOT) then move on and look at something else.

How is your timing?

Try running it with a piece of rubber hose directly from the intake manifold port to the MAP sensor. See if that makes a difference. If so suspect cracked vacuum lines running to the FPR.

[This message has been edited by phonedawgz (edited 09-09-2014).]

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Alex.07.86GT
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Report this Post09-09-2014 01:39 PM Click Here to See the Profile for Alex.07.86GTSend a Private Message to Alex.07.86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by shurlbert:

Hi everyone,

Some background before I get to the question. I am restoring an 85 GT (V6) that was sitting for an unknown number of years (at least 8 years). I removed and cleaned the fuel tank, replaced the fuel pump and filter, changed all the fluids, and changed spark plugs.

I got it running and it was running smooth for a while, then it started sputtering some on acceleration. It is getting worse the more I drive it. It is acting like there is water in the fuel, but I don't think that is the cause. I've ran a tank and a half of fuel through it with fuel additive (seafoam) each time, to clean injectors and remove water. Therefore, it couldn't be water. Is it possible that the more I drive it, the fuel additive is breaking gunk loose in the fuel system and clogging up injectors?

BTW...I got 12 MPG on the first tank, and it is looking like it will be the same on the second tank. Would a clogged fuel return line cause me to get bad gas mileage?


exactly what Spark Plugs did you install??
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Report this Post09-09-2014 04:13 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Spark plug wires and fuel filter replaced?
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shurlbert
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Report this Post09-09-2014 10:44 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thank you everyone for your input on my problem.

The fact remains that I am getting a major fuel pressure drop after the fuel pump is primed. After the pressure regulator and injectors were replaced, it slowed somewhat, but remains a drop from about 45 PSI to 20 PSI. This happens when the car's ignition is cycled with the motor not running. Therefore it can't be a vacuum leak, nor a spark problem.

My thoughts are that it could be from two remaining possibilities; fuel pump, or cold start injector.

When I started this project, the first items that I addressed was the fuel pump and the fuel filter. I dropped and cleaned the gas tank and changed both filter and pump. After some research I think that it is entirely possible that I purchased a pump with a faulty check valve. With the check valve malfunctioning, the fuel will return to the tank, which results in a loss of pressure. I am unclear on how to troubleshoot this condition. Does anyone know how without droping the gas tank?

The cold start injector is original. I have no idea on how to troubleshoot it. Please help.

Thank you,
Steve

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shurlbert
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Report this Post09-09-2014 11:59 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ok, so I have been thinking logically about what I just posted regarding the fuel pump, and it doesn't add up. I am getting too much fuel to the engine, causing horrible gas mileage and a flooding condition. If the fuel pump check valve was not working, or the hose connected to the pump inside the tank had a hole in it; I would be getting less fuel to the engine, or at worst case no fuel. Therefore, am I correct to rule out the fuel pump?
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Report this Post09-10-2014 09:06 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
That's pretty good thinking, but you can always have more than one problem......

but you should pursue the cold start injector first.....rather than drop the tank again.

http://www.fiero.nl/forum/Forum2/HTML/131210.html

[This message has been edited by Gall757 (edited 09-10-2014).]

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Report this Post09-11-2014 12:52 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks Gall757 for the link. I'll temporarily close off the cold start injector and see what happens.

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Report this Post09-11-2014 02:31 AM Click Here to See the Profile for thesameguyClick Here to Email thesameguySend a Private Message to thesameguyEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'd take a second look at what phonedawgz is saying - I would not worry about the fuel pressure dropping off after the pump stops running. It's not ideal, but has about zero to do with poor gas mileage and engine stumbling. The only thing you should really be concerning yourself with right now is what fuel pressure looks like when the stumbling is happening. If pressure is dropping off while the engine is stumbling, then you've got something to actually worry about. Frankly, I think the fuel system is a boondoggle.

On an engine that's been sitting, I would be concerned about the state of wiring (corroded or even eaten) and rubber parts (especially vacuum hoses). A weak electrical system will cause your problems, as will vacuum leaks. You could have a sensor out of whack (perhaps MAP or coolant temp or O2) that's causing issues only once the engine is warmed up. Might be worth hooking up a scanner to it and watching those sensors before and after the problem occurs.
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Report this Post09-12-2014 10:48 AM Click Here to See the Profile for Alex.07.86GTSend a Private Message to Alex.07.86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Alex.07.86GT:


exactly what Spark Plugs did you install??


My question is what brand of plugs, cap & wires did you install?

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lordbg0205
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Report this Post09-13-2014 12:33 PM Click Here to See the Profile for lordbg0205Click Here to Email lordbg0205Send a Private Message to lordbg0205Edit/Delete MessageReply w/QuoteDirect Link to This Post
Lets get down to it, whats the pressure like when running? I had the same issue years before and it ended up being the pump check valve not holding pressure in the line, possibly even the pulsator leaking as well. If you deadhead the pump and block off the return line does it hold pressure? If it doesnt then it isnt the injectors or regulator, its the supply from the pump. Deadhead the pump without the car running. I just had a chevy the other day with the same problem, pump was bad. Good luck use common sense.
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shurlbert
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Report this Post09-18-2014 01:11 PM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm sorry for the delayed response. Haven't had a lot of time to work on the car.

Thank you everyone for your input. I closed off the cold start injector. PSI started at about 45 and dropped slowly to about 38 and leveled off. This is not what I believe to be normal, but is a huge improvement from the previous span and immediate drop from 45 to 20 PSI. My next proceedure will be to clamp off the fuel suppy line and test what is going on in the tank. Then on to electical issues as was suggested. When I first started this project I replaced the spark plugs; but not the wires, cap and rotor. I will address that as well.

Any thoughts about plugging up the cold start injector permanently?

If I am having a problem with the fuel pump, what brand replacement do you recommend?

I will check what plugs I installed (I don't remember and can't find the reciept). What plugs and wires do you recommend?

Thanks again for your help
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Report this Post09-23-2014 01:37 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
I checked the fuel pressure at the gas tank with both lines closed off. The needle pegged the gauge at 100 PSI, then quickly dropped and settled at 60 PSI where it stayed. Is that normal pressure, or did I purchase the wrong fuel pump (one for a turbo charged engine) three years ago? I'm thinking that the fuel rail is getting too much fuel, and the return line can't handle it.
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Report this Post09-23-2014 07:13 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
I think you are right, normal fuel pressure is in the low 40's
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Report this Post09-24-2014 01:27 AM Click Here to See the Profile for shurlbertClick Here to Email shurlbertSend a Private Message to shurlbertEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have been racking my brain trying to solve this issue and I realized something today. I dropped the engine to replace the freeze plugs. I also wrapped the cross-over pipes and the exhaust with insulation at the same time. Prior to this the car did not have this problem. Yes it did lose the coolant a few times, but there was always plenty of power. This may be a coincidence, I'm not sure.

[This message has been edited by shurlbert (edited 09-24-2014).]

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phonedawgz
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Report this Post09-24-2014 07:54 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by shurlbert:

The car starts well at all times (hot or cold), and I do not smell gas. It starts acting up during acceleration. It will loose power (bog down) temporarily, like there is water going through the system. However, if I let off the accelerator, it will recover. Seems like it's flooding, right?


No, that is not a symptom of a flooding car. No that is not a symptom of water in the gas either.

Does this problem only occur when there is a load on the system and you are pressing the accelerator down further? Doesn't happen with the car in neutral? When it is happening is there an exact place where the missing occurs in the throttle, lift up a hair and the miss goes away, press slightly from there and the miss returns? And that spot happens earlier (at less throttle) when there is more load on the engine?

Replace your plug wires and replace your ignition coil. Do not install the new coil until you have replaced the wires.

[This message has been edited by phonedawgz (edited 09-24-2014).]

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