1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Fuel pump is cavitating.

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Old Apr 15, 2009 | 12:50 AM
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Fuel pump is cavitating.

profanity, obscene language, vulgar words and well...crap.

well i went to get the start up process going tonight and low and behold, the fuel system is going to be an issue. Originally, i had this problem with fuel flow to the engine. I had dropped the gas tank and saw that the pick up tube was mostly blocked by the orange crap the they inside gas tanks when they refurbish them. Though i had cleared it out.

Turn the pump on and i get the obviously sucking air noises from the pump, the fuel pressure will read around 45 (with some variation and its not very smooth). Then if i shut it off the gauge will extremely quickly plummet to 0 psi. Seems like its pushing a lot of air. Now i dont think i have anything wrong other than something still kicking my *** with the gas tank's pick up tube.

Now, my options are pretty much try and drop the tank and see if i can clear the pick up, or perhaps tap for a new connection. Money is tight and i have only 12 days til i leave for the Air Force basic.

stupid car.
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Old Apr 15, 2009 | 04:41 AM
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i'd drop the tank and go that route... seems like th better alternative to ensure you arent picking up anything that need not be picked up and it may help you determine why you are sucking in air..
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Old Apr 15, 2009 | 05:28 AM
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You can only do one thing, drop the tank and look!

One thing I have found is that you cant put a rotary on a dead line! Didnt work for Jesse James on Monster Garage, didnt work for me when I wanted to get to deals gap. Hasnt worked for my buddy when he drops of his car at the tuners lol

Hopefully you will break this cycle though!!!
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Old Apr 15, 2009 | 05:44 AM
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i already dropped the tank previously. im just worried the orange stuff is bad news bears. But its probably the only route i have.

also, not sure i follow on the dead line
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Old Apr 15, 2009 | 07:13 AM
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Well when you said that you where leaving for boot camp, I just guessed that you were trying to get it done b4 then, thus having a deadline

When you drop your tank, if there is still alot of debris in there, you can throw in a chain and toss the gas tank around, then chain inside will knock loose most of the crud that is peeling off the inside of the tank, so you can scoop it out or vacuum out. I used this on my pinto with a rusty tank and it worked great.

I would let it air out a little as it may cause sparks, but I have never heard of anyone blowing them selves up, but I dont want you to be the first.

EDIT: I just remember that you will have baffles inside the tank, so that might be tricky but not impossible, also make sure you pull the sending unit out, that should be a given though
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Old Apr 15, 2009 | 07:40 AM
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well from when i dropped it before, the inside of the tank is fresh with the orange sealer stuff. It was refurbed recently. No crud or anything. What it looks like is the orange sealer was improperly done, so it accumulated at the sump area. Runs of sealer from the tube where connected to the sump itself. So basically, there is some issues that im not sure if i CAN fix.

i am hoping to have it start before i leave. And really, i dont see why it can't. Just need to work around this.
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Old Apr 15, 2009 | 08:24 AM
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Remove the fuel filter and cut it open. This should tell you the state of your fuel system and help narrow things down for you...
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Old Apr 15, 2009 | 08:30 AM
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it was brand new. I didnt even see a speck of dust in the gas tank when i had it down before. Ill take a look at it though. I am kinda tempted to drop the tank, run the hose from the intake pipe up to a funnel and fill it will gas or maybe MMO and see what the fuel is like. Then compare it to just the same diameter hosing (that is obviously not blocked).
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Old Apr 15, 2009 | 09:38 AM
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If you have an air compressor, you could loosen the lines under the hood and try blowing them out while you have the tank down.
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Old Apr 15, 2009 | 09:45 AM
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Originally Posted by ported12at
If you have an air compressor, you could loosen the lines under the hood and try blowing them out while you have the tank down.
i tried that before and i think its misleading. Since it can get SOME fuel its not completely blocked. And 300 psi will make a small opening seem like its flowing just fine.
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Old Apr 15, 2009 | 01:00 PM
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can't hurt to drop the tank and look. maybe takes 20 mins. if its nasty, you can have it cleaned at a radiator shop and hopefully they'll have it ready for you in a short time frame...
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Old Apr 15, 2009 | 03:49 PM
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I know theres been some controversy as to whether its supposed to exist or not, but my car had a small conical screen in the inlet side of the fuel pump that was clogging up and caused these symptoms. IF your car has it, this could very well be the problem.
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Old Apr 15, 2009 | 05:47 PM
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on the pump itself? The pump is a external pump and is new. The tank IS clean on the inside. No crud at all. Im going to drop the tank out, maybe tonight, or worse case, tomorrow, then see what i can do. Maybe ill attempt to get a picture.
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Old Apr 15, 2009 | 10:58 PM
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Fuel systems don't suck air, if they're sound. You mentioned sucking air, check your hoses and connections. An air leak will also account for the quick drop in fuel pressure.
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Old Apr 16, 2009 | 07:21 AM
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Originally Posted by Gravity Fed
on the pump itself? The pump is a external pump and is new. The tank IS clean on the inside. No crud at all. Im going to drop the tank out, maybe tonight, or worse case, tomorrow, then see what i can do. Maybe ill attempt to get a picture.
yes, i know its external. on the drivers side of the pump (inlet side), after removing the fuel line there was a small screen slide into the fuel pump fitting. apparently not all of our cars have this.
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Old Apr 16, 2009 | 08:34 AM
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It might suck to have to do, but you may want to run all new fuel lines. Your hard lines up front could be clogged as well. I had the same problem with the pickup tubes being blocked on mine. It's a pain!!!
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Old Apr 16, 2009 | 12:29 PM
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dropping the tank tonight. We shall see what happens.
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Old Apr 16, 2009 | 12:43 PM
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keep us posted with what you find. i wonder if some muck that you didnt see the first time got stirred up...
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Old Apr 25, 2009 | 03:32 PM
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Originally Posted by Gravity Fed
profanity, obscene language, vulgar words and well...crap.

well i went to get the start up process going tonight and low and behold, the fuel system is going to be an issue. Originally, i had this problem with fuel flow to the engine. I had dropped the gas tank and saw that the pick up tube was mostly blocked by the orange crap the they inside gas tanks when they refurbish them. Though i had cleared it out.

Turn the pump on and i get the obviously sucking air noises from the pump, the fuel pressure will read around 45 (with some variation and its not very smooth). Then if i shut it off the gauge will extremely quickly plummet to 0 psi. Seems like its pushing a lot of air. Now i dont think i have anything wrong other than something still kicking my *** with the gas tank's pick up tube.

Now, my options are pretty much try and drop the tank and see if i can clear the pick up, or perhaps tap for a new connection. Money is tight and i have only 12 days til i leave for the Air Force basic.

stupid car.
your problem i dont think is in the tank if you hooked up the lines correctly. the tank is good. trust me my tank had rust piled up and i used muneric acid and a couple of hours and have it looking NOS. and now it runs fine. try cleaning it. but its probably the lines how much gas is in it? if you just dropped the tank and only put in a small amount of fuel say a gallon or so, it wont pick it up. try putting more. Mines didnt start with that little in it. most often the simplest answer is the right one. just my 2 cents.

Last edited by Rotor_Venom08; Apr 25, 2009 at 03:39 PM.
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Old Apr 25, 2009 | 03:35 PM
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turn out to be air trapped in the gauge line causing lots of fluctuation. Bleed it all out, pump runs better and pressure holds steady. Thank god for an easy fix.
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