Fuel Pump Vapor Lock - Team Camaro Tech
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post #1 of 16 (permalink) Old Apr 15th, 12, 01:43 PM Thread Starter
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Fuel Pump Vapor Lock

1968 Camaro 396, has vapor lock caused by the heat in the pump. Car has new tank, lines, pump. All lines were insulated with reflective heat tape and a reflective sleve over that. Has a see through filter befor carb. When the car is cold the pump works, as the car heats up at idle and gets to 160 to 175 the pump stops working, got a new one Oreilly brand, and it does the same think, if I hold a towel with ice on the on the pump, Bam it starts working, remove it and it stops. The gas is supposedly only 10 percent alcohol, almost impossible to get it without alchol.
So... My question is how to fix it, will a good pump like a Edelbrock Victor help?
Do I just have to put on an electric pump.
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post #2 of 16 (permalink) Old Apr 15th, 12, 02:15 PM
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Re: Fuel Pump Vapor Lock

I would question your engine temps if a failing mechanical fuel pump starts working when you cool it with ice. Start by filling us in on your car, why did you insulate the fuel lines? What's different about your car compared to a stock '68 BB car?

Maybe you can pull the fuel line right before the filter (think safety when doing this) and crank the engine over right after the pump seems to fail from being hot. If the pump pushes fuel out the line without you cooling it off it will prove the pump isn't the problem.

Again an engine running 180 or below should not be heating up your fuel so hot that it causes a problem in the fuel lines are run properly.

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post #3 of 16 (permalink) Old Apr 15th, 12, 02:59 PM Thread Starter
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Re: Fuel Pump Vapor Lock

1. I insulated the line trying to figure out why the pumps would stop pumping. 2 pumps do the same thing. I thought it was heat from the exhaust causing tha vapor lock, it was not.
2. Engine temp verified by new gauge and non contact infra red temp gun.
3. Two new pumps do the same thing? Engine is not overheating!
4. 1968 Camaro, iron block, mostly stock but big cam, iron heads, new valves, springs, pushrods, pistons 10:1. I think it has to do with the cheap pumps from the parts stores or alcohol in the gas helping to boil the gas. Alcohol boils around 78C, that is around 172 degrees F.
I am sure there are people having the same issue I am.
I was wondering if they solved this issue with a different pump, or had to go Electric.
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post #4 of 16 (permalink) Old Apr 15th, 12, 03:10 PM Thread Starter
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Re: Fuel Pump Vapor Lock

DjD
Wondering why you moved this to troubleshooting?
I already know what the problem is and wanted to find out if a different pump would work or if I had to go to an electric pump. Currently there are no registered users in this forum. So I doubt I will fing my answere here.
Thanks
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post #5 of 16 (permalink) Old Apr 15th, 12, 04:14 PM
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Re: Fuel Pump Vapor Lock

Ed I moved the thread here because you are trouble shooting a problem. You know the symptoms, if you knew what caused them you would know what the problem was!

It's still visable and active in the Engine forum for 1 week so you get your post accessed from 2 forums! As for how many people are reported active in a forum, it's a statistic that is collected over a period of time and is not a real time indicator of who is in the forum...

...Dennis

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post #6 of 16 (permalink) Old Apr 15th, 12, 04:20 PM
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Re: Fuel Pump Vapor Lock

Are you running a return line?

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post #7 of 16 (permalink) Old Apr 15th, 12, 04:32 PM
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Re: Fuel Pump Vapor Lock

Ed I doubt the problem is the over the counter fuel pump! You can throw money at this and buy another more expensive pump or even switch to an electric if you want. I'm sure there are plenty of classic's and hotrods running around Kansas with parts store fuel pumps and using the same blend of fuel without issue.

The fuel pump is a mechanical cam driven device and if it is heating up to the point it is causing the fuel to boil you need to figure out what the source of the heat is. When it heats up the pump itself isn't stopping or you would be destroying the lobe on the cam that runs it. I made a suggestion that you should test the pump when it apears to be failing, give it a try, pull the line from teh filter and crank it over into a coffee can and see if the pump is still working...

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post #8 of 16 (permalink) Old Apr 15th, 12, 05:18 PM Thread Starter
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Re: Fuel Pump Vapor Lock

No return line (part of problem) Has single line to pump.


Ok, got engine to normal heat 170, when we see the filter start to emty out, shut off, then with the line pulled off before the fuel filter , start up, the pump intermittantly spits a bit of gas , nothing like it is supposed to, then we reconected it and cooled it off with ice, start engine, refilled float bowls, shut off disconnect line, cool with ice, and start up, it pumps pretty good.
I have never seen this. I have however in the past few years been geting parts from the local parts places that have been failing and not very good quality made in a different country, and having a hard time finding gas without alcohol. This is why i suspect a issue with the pumps or the alcohol.
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post #9 of 16 (permalink) Old Apr 17th, 12, 03:32 AM
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Re: Fuel Pump Vapor Lock

Does the pump have an insulation block between it and the motor? Bit of thick plastic the same shape as the gasket..
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post #10 of 16 (permalink) Old Apr 17th, 12, 03:40 AM
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Re: Fuel Pump Vapor Lock

I'd also be tempted to put a makeshift filter on before the pump to see if that empties out too. Just to totally rule out everything else on that side of the system.
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post #11 of 16 (permalink) Old Apr 17th, 12, 05:10 AM
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Re: Fuel Pump Vapor Lock

There is no heat insulator for the f/pump.
If you were to remove the fuel filler cap, does engine continue to run?
You could add an inlet filter for troubleshooting purposes.

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post #12 of 16 (permalink) Old Apr 17th, 12, 11:16 AM Thread Starter
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Re: Fuel Pump Vapor Lock

Thanks Guys, No Insulation Block, just gasket.
will order a phenolic heat spacer and use a test filter before the Fuel pump to see if issue is before the pump, or the pump.
Also the muffler is mounted between the tank and rear differential, I was going to try and put some type of heat shield there. This is one area where we tripple insulated the fuel lines. The tank does build lots of pressure from the muffler heat.
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post #13 of 16 (permalink) Old Apr 17th, 12, 05:54 PM
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Re: Fuel Pump Vapor Lock

I don't think you'll find a heat isolation block/panel. If you do, let us know.
The tank gets heated from not only the muffler, but from road heat and the natural flow of heat from the front of the car while moving.

You might end up running a return line. Moroso sells a return tube fitting/replacing the hose between the filler neck and tank right behind the license plate. A 1/4 OD tube for return would be a good size.

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post #14 of 16 (permalink) Old Apr 19th, 12, 11:07 AM Thread Starter
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Re: Fuel Pump Vapor Lock

http://www.summitracing.com/parts/CTR-85-010/

I was going to try this,
But now i think I will do a return line, and the spacer, then the fuel will not be in the line and pump for so long.
Question,
On the return line do I just T in the line between the carb and the pump a regulator with a return port and return it to the tank?
And should I go with a pump thats 10psi and regulate it to 6?
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post #15 of 16 (permalink) Old Apr 19th, 12, 04:29 PM
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Re: Fuel Pump Vapor Lock

What size fuel line from the tank to the pump? You will want the suction tube as large as possible. 3/8" tube at least. and not running close to the exhaust.

Mat

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