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Hey guys,

I reported awhile back about my vapor lock problem and the fact that my Holley mechanical fuel pump has been acting weak lately. Yesterday I redid my fuel line out of the carb, eliminating the filter I had at the carb outlet, and installing one of those Summit Brand high-flow fuel filters and fuel pressure gauges at the Holley 4160 (600CFM) inlet on my 289. I also installed a 1/2" phenolic carb spacer and gaskets.

I fired up the car and got 5 1/2 psi at the carburetor...nice and steady. So, I figured there wasn't any problem with the pump. However I had a little drippy fuel leak so I went ahead and spent 10 minutes or so tighting that up and checking everything else out...including by float levels, etc. with the engine running. When I got done checking all that stuff I looked at the fuel pressure again...and it was gone.

It was reading right at 1 psi. I tried hitting the throttle, running the engine fast, slow and everywhere in between and the thing just sat there on 1 psi.

Frustrated, I went inside and told the wife it needed a new fuel pump. However, since it was running OK even at 1 psi, I decided to take a drive in the car. I fired it up and drove it about 10 miles to a restaurant with the family for dinner and then drove home. When I got in the driveway, I popped the hood and checked the fuel pressure again...and it was back.

The gauge showed between 6 and 7 psi.

Does this make sense to anyone...because I'm at a loss.

Phil
 

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Is it a liquid filled gauge? If a liquid gauge is mounted in the engine bay, it can give false readings when the liquid temp increases do to the radiant heat.
 

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Any hole in the fuel line that will allow air to enter the line between the tank and the fuel pump will cause the fuel pump to stop working.

However, it's probably your fuel pump.....
 

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I still say bad fuel pump. Tony had a similar problem... intermittent fuel pressure. We also thought it was vapor lock. Ended up being the fuel pump arm... the pin that holds it in and acts as the pivot kept popping in and out, and so it wouldwork, not work, work, not work...

BB uses same fuel pump as SB right?
 

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Discussion Starter #7
Interesting. I guess I can take it off and take a look at it. I'll try to do that tomorrow.

Phil
 

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Dont dismiss the advice of a liquid filled gauge problem. XRP gauges especially, the liquid expands with heat, and then the differential pressure makes the fuel pressure look like zero. If you have a liquid filled gauge, and the car runs good, try an old shaky-needle gauge, I bet there is no problem.
 

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Not to steal your problem, But mine is doing the same thing. In fact, it left me and my wife stranded last night. I just put a holley HV fuel pump on it about 2 weeks ago, and last night it would only pump enough to idle. Had to get a trailer to bring it home. :(
 
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