Technical HELP PLEASE Fuel pressure problem

My stock yblock pump puts out 4 psi dead headed. I run WCFB dual quads and it does not run out of fuel with a 5/16" line at wide open throttle and 90 miles per hour. The racing Holley carbs on both of our race cars ( 1 LSR and 1 circle track) have regulators set at 5 and do not run out of fuel. Both have -8 feed lines. Flow is always the answer not pressure. Good luck.

 

do you have a vented fuel cap?

 

Yes it has the proper fuel cap and you can blow easily though the vent hole

 

When it comes to fuel filters, there are filters and there are FILTERS, some of the stuff on the market simply doesn't have the flow capacity to handle a healthy engine at full throttle. What are you using for filter(s)?

 

We just chased a "vapor lock" issue that turned out to be a ballast resistor on a coil that didn't require a resistor issue.
Just in case that helps.

 

UPDATE: honestly i did not expect the HAMB to be much help but boy was i wrong id like to thank ALL yall for all the imput...
The problen is now solved... And it was soooo stupid... 3 words... CLOGGED FUEL FILTER I cannot believe it... The filter between the stock mech pump and carb... Took it off in the past but i think when i blew through it i blew the wrong way and all the crud just flew off the paper.... I took off the filter... Blew through it the way of flow and it was sooo clogged with crud... (filter came with car... Bought car 2ish years ago).. So i bypassed the filter and ran it straight and blasted down the highway passing pruises with a grin on my face ...
THINGS I LEARNED: 1 fuel pressure gauges CAN read VERY wrong readings when they get hot and theres a reason for the rubber stoppers on the side of them
2 Sometimes the solution to problems can be really STUPID easily overlooked things (fuel filter)
3 I learned that i should of joined the HAMB AGES ago

 

We give you shit to make you think! We really love you though. (quote from my Dad). LOL. Lippy

 

Had a similar liquid filled gauge reading problem a few years back. Finally wrapped an ice pack around it and watched the reading come up to normal. Relocated it to a cooler spot and no more problems.

 

Welcome to the wonderfull world of the car hobby, find a spot on the wall to beat your head on and paint your name on it!!

 

put a filter back on or we will be diagnosing a clogged carb or stuck float.

 

Is that really nessesary if im running a filter before both the electric and stock pump?

 

I've had exactly the same problem with a tree leaf inside the filter acting as a flapper valve when there was any demand for fuel much beyond a gentle cruise. That took some chasing down. The biggest problem is that we typically look for the most difficult solutions before eliminating the simplest. I'd had the cylinder head off looking for warpage when hot. We live and learn.

 

no probably not. did you cut it open to see what was clogging it?

 

Yeah correct, but note "pressure is pressure" and "volume is volume"
Both your examples the pump can supply enough volume to maintain 4psi

The OP should have a decent high capacity pump with a bypass regulator if he is concerned about vapor lock.
And ditch the mechanical pump
If he used a Bosch 044 pump off an EFI system with a quality bypass regulator and a decent fuel and return lines the fuel delivery problems will be a thing of the past.[mount the regulator close to the carb]

This is a very common method on Fox Body Mustangs when converting to a Carb [ I am doing the same with my Road Racing Falcon]

 

Glad ya got it fixed, but I would still listen to a couple of the answers on here and get rid of the 2 different pumps. Remember the KISS theory. The car company spent a lot of money to get the original fuel system to work, why reinvent it.
Tony

 

First I like to that the original poster for reporting how he solved the problem.

I'm glad the problem was solved but I had to comment on the above post about using a fuel pump without a pre-filter.

It sounds like there is no screen in the tank like the factory used so a filter between the tank and the pump is essential. Some electric pumps have a screen incorporated like some Holley pumps and Carter made one with a screen in a cup, but most do not. I've seen many people try to run without some type of filtration prior to the pump and wonder why the pumps continually fail. Most blame it on a bad pump when it is a bad installation. You don't need as fine of a filter before the pump but you do need something.

Whenever a topic comes up related to vapor lock I like to remind people that GM recognized this problem and designed fuel filters and systems to solve the problem. They added a small port to the filter and a line to return some fuel to the tank so the cooler fuel from the tank is constantly flowing through the system even when the needle valve is closed.

 

I'm going to use that part of your post, but this is directed to everyone who's ever been stumped or tried to help those are stumped.

" When you see horse tracks why look for a zebra ? "
I first heard that as a young man, it stuck. It was said to me that because I to was looking for the most difficult solutions paying the price of frustration. In the realm of auto mechanics these exercises in of tail chasing are nearly eliminated by simply following a finely honed list of hierarchy in a troubleshooting chart and not deviating from it.

These charts or tables (published 1000s of times and within reach of everyone) are laid out so they are elementarily simple when taken one step at time. However they do assume the user to possess both simple testing equipment and basic working knowledge of how to use them. That's the only prerequisite.

You'll find a quite few threads where mysticism is thought to be and blamed to be the likely culprit for a mechanical issue.

Here's a personal story of tail chasing, money flushing and complete loss of faith in my abilities from 20 years ago. At that time I'd been at this mechanical stuff for quite some time already with a vast experience base. As the story unfolds keep track of the number of hands in it.

I purchased a old 1979 Harley Davidson motorcycle that was recently rebuilt, beautiful bike. After about 200 miles (1st weekend) it developed a horrible vibration in 3rd gear. I ripped it apart, took the Trans to my buddy and the insides were new but toast. He suggested the likely culprit was an alignment issue when he gave me Trans back along with the bill.

So I carefully put it back together using the factory service manual and minding all of the procedures to obtain the correct alignment. It was close but something was off just a smidgeon. I tried everything I knew and I reached the end of my knowledge base. I hauled the disassembled bike to a local custom pro bike shop and had them check for the issue and put it back together . They called and said the bike went back together great and I shouldn't have any more troubles as they gave me bill.

Now of course 200 miles later the bike eats 3rd gear and I'm back at square one. I quizzed the bike shop and asked if they found anything suspicious or encountered the same issue I had with it being just a bit off? They told me "no, it went together like every other bike they've ever put together." So I have the WTF moment and begin doubting my sanity. I take the bike apart and try to reassemble it following the correct alignment procedure and I experience the same issue I had before, it's off by just a little. It's a very small amount ant the bolts will pull it in but that slightly deviated from the factory service manual procedure. Taking that hands on info, my experience leve and the bike shop at its word - combining all of that I decide it must be something off in the transmission case itself.

So I figure it must be within the Trans I buy a brand new one, and paid that bill. I set out to put it together and experience the same issue. Ok Trans is not the problem, humm. The next likely culprit is the inner primary case, so buy a brand new one and pay that bill. I go thru the assembly process and and and and get the same damn place again with the same damn issue. WTF is going on- it must be me fucking something up or over thinking this crap. The only other parts it could be are the primary drive so I get a new one and pay that bill. I'm sorta pissed off and disenchanted with whole mess now so the parts and bike sit till winter.

I get the bike together and head down to Daytona in March. Have a great time until my new primo belt drive belt shredded, it looked like chicken feathers shooting out of the bike. Another defeat and I've just given up. Take the bike to a Daytona shop and had them put on a new belt, payed that bill and finished my vacation staying in close and not riding much at bike week, whoo hoo big fun.

I get the bike home and parked it, Ohio riding season come and I need to get something going here. There must be a problem here>> , well I get a new mounting plates, a factory one, a fancy adjustable one, and some other bullshit. Put it all together and For the 49th time and off I go and shred another belt after a few hundred miles. Fuckit, no bike for me but my buddy needs some help so I help him with his 1959 pan head. By know I've asked everyone who'd listen and bored them to death with this bullshit.

Just by happenstance we were at the dealer and I was browsing the "Factory parts catalogue" which is different the the "Factory service manual". In the parts book is every single part and part number. In there I see the transmission bolts are special for 1979 with their very own part number. So I had the guy order them and was suprised they were still available.

The bolts came in and what they were was basically a round head carriage bolt with one side ground flush to the flat on the shank. The pair of bolts was under $5.00 but any hardware store carriage bolt could have been ground to match it in a few mins. So I set out on time number 50 to reassemble the bike with the correct bolts. Low and behold the previous alignment issue disappeared and the problem fixed. nice huh?

Harley changed Trans styles for 1979 and they required those "special" bolts.
A journey like that will make you stronger if it doesn't kill you.

 

Were these filters designed for the stock mechanical pumps ?

 

The type of filter also matters in that a paper filter, or one referred to as "cellulose", which is glorified paper, should never be placrd inline so that it is in suction, only under pressure. It may come apart and send particles on downstream to the pump and clog it.
If a filter is upstream of the pump, or IOW between the tank and the pump, it must be a screen type pump.
And be sure that the filter can withstand ethanol

 

This has been a great thread! Good information on fuel system configuration--something I'm working on now--and a good refresher on troubleshooting best-practices.

I'm grateful the OP did not use the seach function, but instead created an opportunity for engagement on the forum. Stumbling on threads like this is one reason why I love the HAMB.

 

They used them on Pontiacs in the 60s. The one pictured is for the GTO tri power setup which might have had more of a problem because the filter is so close to the radiator.

It's the same as a 33041 Wix. Chevrolet used it in the 71s and up to counter the vapor lock problems encountered as vehicles had to be capable of using unleaded fuels and running hotter to meet emission standards.

 

This was my first post and i already love the HAMB

 

Boy I sure missed that sorry 31 vicky, now it makes sense.

 

I have one gauge on the inlet side of the regulator and a second gauge at the front 3x2 carb.

Ref gauge reads constant 5-6 carb gauge starts at 4 drops to almost zero.

Shut it off 10-15 min and it Repeats the same crap.


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