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Print in friendly format Send this term to a friend  Regular Production Order
Commonly known as RPO. These are the codes that GM uses to identify options.

For example, LT1 is the RPO for the engine used from 1992-1996.

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istter1 Check Valve in fuel system
Elite Guru
Bakersfield Ca
1619 Posts
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2011/7/4 17:23



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Questions is there a check valve on the fuel pump or the fuel tank. When the cap comes off there hasn't been any pressure built up in the tank for about a month. I have been try to see if I can find the reason my 87 is losing fuel pressure when it sits.
Posted on: 2012/7/20 14:54
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Matatk Re: Check Valve in fuel system
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There is a check valve in the fuel pump assembly. I removed mine and replaced it with fuel hose with my new pump.

Fuel pressure will drop when it sits for an extended period of time. One of the reasons the fuel system primes with the key on before firing.
Posted on: 2012/7/20 14:59
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1989 Corvette...custom 383 stroker, superrammed and cammed, NEWLY BUILT trans! with PeteK 2800 stall.
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Woodstock Re: Check Valve in fuel system
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Bremen/Germany
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Loosing pressure over time is totally normal!
Just last week I did a pressure test on my 91. After I had the engine running, pressure stayed at 43 PSI for a few minutes and dropped off to 39 at the 30 minute mark. At 1 hour it was down to 26 PSI, after 90 minutes at 21 and in 3 hours down to 8 PSI.
With a cold engine pressure seems to drop off a little quicker.
If I let it sit for a couple of weeks,I still get a few drops out of the Schrader valve when pushing in the pin.

Here's a picture of the check valve of the pump. The right valve is the feed line. The left must be a high pressure relief valve.

Attach file:



jpg  Benzinpumpe-Ventil.jpg (83.88 KB)
1024_5009b70b8830c.jpg 800X492 px
Posted on: 2012/7/20 15:54
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Woodstock Re: Check Valve in fuel system
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Another pic of the pump for better orientation:

Attach file:



jpg  Benzinpumpe-Ummantelung.jpg (138.45 KB)
1024_5009b7da0437b.jpg 800X615 px
Posted on: 2012/7/20 15:56
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bogus Re: Check Valve in fuel system
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San Pedro, CA
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and on hot days, expansion will cause the pressure to go up all by itself.
Posted on: 2012/7/20 17:28
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istter1 Re: Check Valve in fuel system
Elite Guru
Bakersfield Ca
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Is the first the check valve on the tank from the return line?
The Diaphram was replaced pic 2

Picture 3 new fuel pump

picture 4 return line filter new


No leaks in fule lines and before the fire the fuel pressure stayed up so when you fired it up in the morning it fired right up.

I don't know what the mechanic did that worked on it at the shop did wrong as I don't think the injectors and the heads can all have problems at the same time. Sudden head gasket blowes and water in the jackets . Wasn't that way before it went in. Intake runners dented up.

Running presure before fire was 40-45 or so

engine off 38-45 would hold for hours.

I will double check every thing before I hopefully run down to LA Sunday.

Will run test with fuel presure tester again to see where I am.

Attach file:



jpg  check valve.jpg (145.95 KB)
5144_500a220fb45d3.jpg 2048X1536 px

jpg  dia.jpg (275.54 KB)
5144_500a225e1dc9b.jpg 2048X1536 px

jpg  fp6.jpg (310.42 KB)
5144_500a230c884da.jpg 2048X1536 px

jpg  Filter.jpg (136.54 KB)
5144_500a234eaeb11.jpg 692X546 px
Posted on: 2012/7/20 23:42
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Woodstock Re: Check Valve in fuel system
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The fuel return line is next to the pump, no check valve there!
On your first pic is the fuel gases line, going to the charcoal canister located under the left headlight.
Posted on: 2012/7/21 5:36
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Matatk Re: Check Valve in fuel system
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If you are holding 38-45 psi an hour or later after you shut down that is better than most systems out there, including mine, and everything I have is brand new. I don't know if you were referring to how it used to be, or how it is now. But if everything changed after you had work done, I'd be suspect of the quality of that work.

Matthew
Posted on: 2012/7/21 7:51
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"Prius is the Latin word for impotence" (30 Rock)
1989 Corvette...custom 383 stroker, superrammed and cammed, NEWLY BUILT trans! with PeteK 2800 stall.
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istter1 Re: Check Valve in fuel system
Elite Guru
Bakersfield Ca
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Quote:

Matatk wrote:
If you are holding 38-45 psi an hour or later after you shut down that is better than most systems out there, including mine, and everything I have is brand new. I don't know if you were referring to how it used to be, or how it is now. But if everything changed after you had work done, I'd be suspect of the quality of that work.Matthew



Went back through everything. My gut feeling is that it was the fuel pressure Diaphram again. First I checked pressure would not hold.

In side the fpr I found a small 1/8 piece of hard plastic.
A half inch of SS line the type my hoses are. Waited till my son showed up. We blue out both lines more crud. Put it back together it holds pressure and starts as it first cylinder fires like it was before it was being repaired by another Mechanic.

Running down to LA in the morning and we will see how it runs.
Posted on: 2012/7/22 1:00
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Matatk Re: Check Valve in fuel system
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That's strange. I wonder if the lines had some debris in them from when they were cut and fitted.

Glad you got it resolved.
Posted on: 2012/7/22 7:33
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"Prius is the Latin word for impotence" (30 Rock)
1989 Corvette...custom 383 stroker, superrammed and cammed, NEWLY BUILT trans! with PeteK 2800 stall.
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istter1 Re: Check Valve in fuel system
Elite Guru
Bakersfield Ca
1619 Posts
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2011/7/4 17:23



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Quote:

Matatk wrote:
That's strange. I wonder if the lines had some debris in them from when they were cut and fitted.

Glad you got it resolved.


When I put the lines in before we hooked every thing up we cleaned the lines with air. Something I learned repairing Internatiol Harvester in the field when I started as a Mechanic at age 16 in Buttonwillow.. When they removed the heads they let the lined go any where. When they came back in the morning half the gas tank drained on the floor.I beleive if you have a shop it needs to be clean everyday not once a month.
Posted on: 2012/7/22 10:37
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