Stalling on freeway

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May 4, 2015 | 12:08 AM

#16

tomwhatley

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Quote:

Originally Posted by Blue and White

The 5/16" pickup may not be helping... Fix was a small electric fuel pump as booster added on the frame rail just in front of the rear axle..

This may be something I need to look into further. I'm not too keen on dropping the tank again. I think the only place I could mount something like this is at tank switch (which is by-passed). That's about half way down the line. Do you think it would be more effective closer to the tank? I was looking at this:
Mr. Gasket/Fuel Pump 12S at AutoZone.com

May 4, 2015 | 09:18 AM

#17

84espy

Fleet Mechanic

Joined: Nov 2009

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If that is the way you are going, you should bring in a 12v line to the fuel pump. The pump should be installed just after the tank switching solenoid. You are going to want to use that 2nd tank at some point. Once the pump is primed, you should be ready to go. Make sure to put in the block-off plate for the mechanical unit. BUT....After re-reading your original post, you said that the issue started BEFORE you put in your gas tank. A clogged supply/suction line with a weak fuel pump could have been the issue. Also, you stated that the supply line was 5/16", so the suction line could possibly be 5/16". I'm thinking that I would just change the stock fuel pump and then jump back at the fuel tank when it is near empty.

Last edited by 84espy; May 4, 2015 at 09:29 AM. Reason: Additional info

May 4, 2015 | 09:53 AM

#18

Jdeshler

Fleet Mechanic

Joined: Jun 2013

Posts: 1,895

Likes: 32

Quote:

Originally Posted by tomwhatley

I have a vacuum leak somewhere that I can't find but I've had that for a year and it's run ok in the past, though I have to keep the fuel mixture screws out about 6-7 turns, and I assume it's like that to compensate for the vacuum leak.

Again, any ideas are welcome.

Thanks

I say this is your problem, you know it IS a problem so get that fixed and out of the way first so your not chasing rabbits!

I have always had bad luck initially with creating vaccumm leaks whether I'm servicing a my carburetor or changing an air breather

Your mixture screws are turned WAY too lean.. Those leaks lean towards erratic idle, dying, bad road manners, crappy mpg's and the feeling of a few fouled spark plugs..

When no leaks, and in this Alabama elevation I usually find my truck very happy with the mixture screws set at 1 3/4 turn out..

May 4, 2015 | 09:19 PM

#19

Blue and White

Postmaster

Joined: Nov 2011

Posts: 2,553

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Quote:

Originally Posted by tomwhatley

I mounted mine at the same location of the (removed) fuel tank selector switch. Just in front of the rear axle on the frame rail. I think that is the spot you are thinking of. Closer and lower is always better... but that location is cool and seems close enough. It fixed it.

Mr gasket offers two fuel pumps with two pressure settings (7-9 and 3-4 PSI from memory). An OE carb and I think Holly can take the higher pressure, an Edelbrock or Carter or similar cannot. Either pump should work fine in booster application but don't exceed the max pressure rating of your carb. I went for the higher pressure rating as my OE carb could handle it.

May 5, 2015 | 03:45 AM

#20

somethingclever

Cargo Master

Joined: Dec 2008

Posts: 3,221

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From: SW PA

put a pressure gauge and line into your fuel system at the carb and start driving and watch the gauge...make sure it is indeed loosing pressure post pump while driving.

I agree that it sounds like the pump needs replaced....fuel demand is low at idle/rev. The current worn out pump may be able to adequately support it...but nothing more.

May 16, 2015 | 12:00 PM

#21

tomwhatley

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It finally stopped raining so I'm putting in a new fuel pump today. The local parts stores don't have the OE part in stock and I'd have to wait for it to be shipped, but the DO have the one with the filter attached. It looks like there's room for either kind up there, but it's a little tight. And the parts website claims it fits my truck/engine. I think it will but I thought I'd ask the experts here if that's a correct assumption.

May 17, 2015 | 11:05 AM

#22

tomwhatley

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Dadgummit

Put in the new fuel pump (the filtered one will replace non-filtered I found), but we died half a mile from the house. Took 2 or 3 minutes and half a dozen tries but we started back up and got home. I sat it the driveway idling/revving and it died again. Started back after 2 tries. Died again after revving for about a minute. Starts up, dies after a second. Starts up idles rough and if I rev up and down I get a little backfire.

Jul 17, 2015 | 08:25 AM

#23

tomwhatley

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My wife has put a moratorium on working on my vehicles myself. She seems to think it interferes with our time. I told her if she put a wrench in her hand we could spend all day together. She didn't think that was funny. So, I've put my truck in the shop. It's not very encouraging when the mechanic goes through all the troubleshooting steps I already did, and comes to the same conclusion I did, but I guess he can't just take my work for it. He wants to be thorough.

I have replaced every part of the fuel system. Tank, sending unit, all the rubber lines, fuel pump, filter, rebuilt carb, blew out hard lines with air compressor, installed an auxiliary electric pump. Still, when running off the tank, the damn truck only runs for a minute and then dies. If I run off a gas can, it's fine. The conclusion I came to was that somehow, someway, I did something weird when I put in the new tank and sending unit. It's got to be something there. The guy at the shop even hooked up an electric fuel pump with a little foot long piece of fuel line directly to the sending unit, and it just dribbles out, with intermittent healthyish spurts. Same pump running out of a gas can shoots a steady solid stream.

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Jul 17, 2015 | 08:56 AM

#24

HIO Silver

Fleet Owner

Joined: Dec 2009

Posts: 20,678

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From: NorCal

Simple physics.... vented vs non-vented gas cap?

Jul 17, 2015 | 09:00 AM

#25

tomwhatley

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it's vented, though it does't need to be because its evaporative emissions control and has a vent line running off the top. That's not hooked up to anything. Also, it does the same thing with the gas cap off anyway.

Jul 17, 2015 | 09:42 AM

#26

tomwhatley

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I thought at first maybe I installed the sending unit upside down. But I think I would have noticed if that was even possible, and would have been careful about that. It's been several months so I can't remember. Also, I read on another post here that it's not possible to install it upside down. Figured that was the case. So now I'm thinking that something fell in the top of the tank from the vent hole. I used the same rubber grommet that came off the old tank, and it was in pretty bad shape. Maybe a chunk fell off and got sucked into and stuck in the pickup tube?

Jul 17, 2015 | 10:03 AM

#27

redroad

Lead Driver

Joined: Nov 2006

Posts: 5,217

Likes: 506

From: Pa.

It sound like you've eliminated everything down stream of the gas tank .. With the quality of aftermarket parts today and the many reports of new out of box parts not functioning you are left with but one choice and that's to drop the tank and inspect the new pickup and sending unit you put in along with the other in tank things you've mentioned .. What a major PITA this has turned out to be for you .. I feel for you man!

On a side note be careful putting an electric fuel pump in without it being wired through an oil pressure switch otherwise a possible scenario exists where the key is left on accidentally and fuel pressure overpowers the needle and seat and the oil pan fills up with gas .. This thread will give you an idea on how to do the wiring ..