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Discussion Starter #1
Selling my car, have a buyer, suddenly car has problems. Never has had an issue throughout my ownership.

Has complete fuel system including 550's/Lex, AFC Neo, Walbro w/ 12v mod, FPD bypass, etc.

The last week or so when trying to start up, it would run but at 400rpm and barely idle. Sounded like a big block with a monster cam. Moved CPS wires and idle came up some. Pulled codes. Code 12, CPS.

So I had Rajunz rewire the CPS for me. One ground was found to be frayed a bit. That is now fixed. No more CPS code, timing perfect at 10, etc.

Now for the crappy part. Car is learning idle since I pulled EFI fuse to reset codes. It has pulled itself up from 500 to about 750-800 where it should be. Vaccuum is at 17-20 and it idles pretty well considering the following.

A/F gauge is reading three dashes. Completely lean. Fuel pressure is reading 15-20 at idle. Yes I typed that right. No adjustment to the AFPR in or out changes that. Giving any gas at all and car dies.

I remembered the trick to jumper the ports in the diagnostic port to force the pump to run. With the key in On position, engine not running, pump kicks on. Immediately goes to 20psi and within 30 seconds has fallen to 10psi. Pump does not have the usual high pitched whine that I am used to with a 12V modded Walbro.

I have not checked voltage at each of the posts on the relay yet but that is my next option. To me, it all points to the pump or something clogging in a line somewhere. The real problem is my house sells in 7 days and I have nowhere to put the car after that and need this done before that. The potential buyer is being extremely understanding about this, but I'd love to have it running great before then.

Thanks for any help that can be offered.
 

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We had a cheap aeromotive knock-off afpr with a blown diaphragm a while back.
I think the symptoms match what you're describing.
 

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It's the AFPR, fuel filter, or fuel pump.

Try pinching off the return line and seeing if pressure comes back up. If it does, it's the AFPR, if it doesn't, its a fuel filter or fuel pump issue.

Since you say the pump doesn't sound right, my guess is that it's the pump or the wiring to the pump.
 

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Sounds like the fuel pump.
 

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Discussion Starter #5
Finally had a chance to get out to where the car is and test it all this weekend. It would appear the pump is the issue at this point, but I will replace the filter as well just to be sure. I would be surprised if it has ever been replaced.

1. Tested all wiring at the 12 relay that I installed previously to give Walbro full 12V. All terminals were receiving or putting out 12V where/when necessary (i'll spare details)

2. Pump still sounded very quiet and very weak. Pressure again never went above 20psi

3. Pinched off stainless return line off of AFPR as best I could. Made zero difference.

Pump has been ordered and will pick up a filter hopefully locally.
 

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It's your car's way of saying, "nooooo, don't leave me!"

Seriously. Much in the same way that a new-to-you Supra will give you issues that a previous owner never had. Keep us posted though!
 

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I will update when I have more info. At the very least just for search purposes in the future. I hate to see a search for a problem exactly like yours and then never see it updated with results.
I hear ya. My build thread is going to be all sorts of full of what NOT to do haha. ;)
 

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Discussion Starter #9
And the results.......

The pump was definitely having an issue and not working as well as it should. However, I don't believe the last owner replaced the small length of fuel feed line that comes from the pump to the hanger. It was pretty worn out and even had some holes in it from age in a few spots. No wonder it couldn't maintain pressure!

New pump in, car started up and everything is fine again. :)
 
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