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fuel pump problem today.. figure THIS out


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Okay, configuration... I am running triple webers on an L28, fueled by a Mallory Comp Pro Series 70 (P/N 4070LP) fuel pump set at 4 psi. I was getting 2.75 psi to the fuel rail under the hood. This setup has worked flawlessly since 2010, and the webers loved it. Well I finally finished getting the dash back in the roadster and took her out for a pleasure drive for the first time in 4 months, and had to back up the Z.  I just drove the Z 2 weeks ago and I swear she was running better than ever.  Car has been rock solid for years.  However, the thing would not start, and smelled like it was getting way too much fuel.."How can this be I thought, I have everything dialed in!" Still smelled like fuel. 

 

I got out and noticed a STRONG fuel smell and my fuel pressure gauge on my fuel rail, which is normally happily at 2.75 or so reading, well it was not reading anything as the needle was pegged past 18 psi and my beautiful webers were streaming fuel out at an alarming rate. Guess I know the floats cannot stop 18+ psi. :)

 

So I took the pump out and pulled off the bottom off to see the seal and expose the gear. I cannot see anything that would lead to this happening. I have never touched the tensioner spring inside the bottom of the pump.

 

Any ideas?

 

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Just went over this pump with jxq.  That pump uses a bypass port to regulate pressure.  I'll bet there's something blocking it.  Not sure exactly where the passages are but the instructions describe screwing a bolt in or out to get some variation of pressure, probably by shrinking or enlarging the port.  I'd remove that bolt and see what's in there. 

 

Here's the instruction sheet - http://www.jegs.com/InstallationInstructions/600/650/650-4070LP.pdf

Edited by Zed Head
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May have found it.

I undid the locking nut and the allen bolt and the spring loading the bypass plunger onto the seat in the body just fell out. This piece moves to regulate the pressure output by the pump. Very simple design. However, the brass cylinder was stuck against the fuel body and would not move a bit. I had to pry it out. Apparently a piece of sludge or something got in there and held it up hard.  I took it out and ran a brass 9mm gun cleaning brush through it and it slides in nince and falls out easy.  It actually operates.  I would be willing to bet this was my issue.  I will install it back into he car and see what I can get.  It may be time to install a new filter in there. I have been running the same one for years.  

 

 

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Yeah, it could, but it was on the bottom of the cylinder bore horizontal to the ground.  I think it was accumulated junk from the fuel and the fact the car is not driven enough. Either way, I am going to replace the fuel filter as it is a few years old, Just to be sure.  I would hate to have this happen while I am driving.

 

 

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Yeah, that would be really bad for that thing to stick while driving. You might not even know about it until it's too late.

What kind of fuel filter are you running? The ubiquitous G3, or something different? Seems weird that anything "visible" could make it through a filter like that, even if it was a couple years old.

How about a liquid contamination issue maybe? Ethanol in the fuel reacting with the aluminum or the brass inside the pump? Water maybe? Something like that?

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