Car struggles to make fuel pressure

jwick

Sub'd just cuz there's good discussion going on here

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Mitco39

Charles, I swapped out the pump with the aeromotive 340 so its got a brand new good pump in it with 10ga running all the way back to the tank.

Its so bad that when heat soaked and hot it struggles to start. Cold it fires up just like stock. I will get another regulator to try while im down here if I can find a place with one. Makes me wonder if I should be mounting it somewhere away from the heat, although there isn't many other choices on our car. The other thing I can try is setting the idle pressure with the system hot. That means however that it will idle at a much higher fuel pressure when colder.

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Mitco39

I found a guy who is having the exact same sort of thing going on. Its weird I am the only Z with this issue. This guy in particular re adjusted his regulator when hot which worked, till it got cold and overfueled hard on cold starts.

https://www.youtube.com/watch?v=q8MO5Ag73oE

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Mitco39

Spoke to Aeromotive just now and the guy knew his ****. Said there is no way its the regulator itself its the heat of the fuel. He said anything over 130F is iffy when your running high flow fuel pumps as the fuel will cavitate while the pump is trying to suck it in and send it back to the engine.

He suggested trying to reroute the lines and move them to the outside of the frame rail at the front then cross over to the engine. Or possibly purchase a fuel cooler with a fan on it to cool the fuel on its way back.

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phunk

Fuel heat can definitely cause problems but considering you are returning before the rails and only running a single pump, you are hardly pushing it as far as fuel system work goes and things that contribute to fuel system heat. I dont know what the weather is like there and if you have a vented hood or not, but you could always try reducing heat in the bay, heat wrapping some things, etc, and see if that helps your case.

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thangcu35

I used to have the same problem regarding fuel pressure dropping after it got hot under the hood. I have a liquid filled gauge and the pressure would build up inside the gauge and lower the reading (actual fuel pressure is unchanged). It dropped up to 10 psi when compared to cold start up. I fixed this problem by draining the oil inside the gauge and left the drain/fill plug open. It fixed my problem completely. It's possible your warm start up problem has to do with uprev start up setting and not with fuel pressure.

Mitco39

So im ready to pull my hair out over this one. Its really cutting into me enjoying the car at this point because I only get one good run down the track before it starts to lose fuel pressure and cut boost (the new innovate boost controller I have is awesome for cutting boost when she starts to go lean).

I upgraded the wiring all the way to the bulkhead of the tank, altho I might cut that apart and go all the way to the pump. There are no leaks and the regulator is set at 58psi cold hooked up with the 1:1 to a boost only source as per reccomendation.

When its heat soaked its hard to start, I have to turn the key to acc let the pump self prime itself for 2-3 seconds then she will fire right up. If I get in and just turn the car on in one button push she does crank for about 4-5 seconds and struggles to start. When the car is cold or cool this does not happen.


What I am starting to think is happening is that basket of fuel is getting warm and fuel is not entering the basket as fast as it needs to under WOT (under wot down the 1/4 mile ive seen it drop to 38psi, at 10lbs of boost thats only a 28psi pressure differential, not good). I am thinking that this 340 pump is just moving to much fuel for that basket to keep up with, and now it is returning hot fuel to that basket and causing cavitation at the pump.

Has anyone ever cut holes in their basket to help with this issue? Ive even thought about adding a fuel cooler to the car but im not convinced that will help me either as its just because the loop circuit is so small.

It all started after doing the fuel return system, and I know its getting hot because that regulator the fuel travels through is cooking (it is installed on my firewall just beside the battery). Normal driving up here its cool enough that it usually doesnt happen, but when we were down in vegas with the cars it really had a hard time.



At a loss....

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phunk

I have run that pump and larger in the factory basket without having to cut holes, along with others. If this problem even occurs when the fuel level is high, than its not likely an issue with fuel getting in the bucket... if the fuel level is higher than the bucket than it will rush in there no problem.

You could try pressure testing your fuel pump module. Perhaps it has an internal leak and when it heats up it leaks more. If you use a leakdown tester and put like 60psi of air pressure into the outlet of the fuel pump module, it should have zero leakage.

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Mitco39

Charles, by fuel pump module you mean the fuel pressure regulator or just the fuel pump itself? It would make sense that its returning to the tank because I can shut off the car for 30 seconds to a minute and you can hear the pump in the tank repriming the system, you can hear the air working its way out.

I was thinking the same about the fuel level, but I'm starting to rack my head on this one. You dont think its that stock line between the pump and the bulkhead do you? If there is a leak there that could do it.

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2007 Chevy Duramax - EFILive Tuned By Me
2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her
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phunk

I mean neither... I am talking about the entire fuel pump module/housing/assembly that is inside the fuel tank. Disconnect the quick connect output on top of the fuel pump module, and apply pressure inward. This will test the entire pressure side of the fuel pump module for leakage. It will check the hose connections, it will check the filter housing for any cracks/leaks, and it will check the regulator delete assembly for leaks (like if it was missing 1 of the 2 orings or something).

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Mitco39

Thanks Charles I will do that this weekend. I did a quick test after driving the car last night I turned the car off with the key on and pulled the fuse to see how fast the pressure would drop. It would go from 58-60PSI down to 0-5 in less than 4 seconds.

IM assuming its supposed to hold pressure much longer than that?

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2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
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phunk

Generally it takes much longer than that, but with aftermarket regulators it can be unpredictable. They do not make it a design intention to hold pressure when the engine is off, its just a side effect that they do... and they are all sort of individuals.

But most will take a lot longer than that to fall so low.

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Mitco39

Got it figured, the regulator delete was leaking, but only at about 40+psi. We swapped out the oring and so far so good. I did notice that when clamping down the regulator I could push it down and bottom it out, which leads me to believe that the spacer used above that oring could be a tad bit thicker to squeeze that oring in there a bit better.

If it starts to leak again then ill probably get a shim to put in there to squeeze that oring in its housing.

Thanks for the info Charles, you were bang on, now the car feels quick again. Has no issues holding 70PSI.

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2007 Chevy Duramax - EFILive Tuned By Me
2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her
My Build --> http://www.the370z.com/members-370z-...39s-build.html

GaleForce

Excellent news! Good job Mitch!

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Mitco39

Going to take it to the track tomorrow night and see what she can do now that I can bump up the boost without going lean again.
im either going to come back with a good trap speed, or a popped engine. lol

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2007 Chevy Duramax - EFILive Tuned By Me
2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me
The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her
My Build --> http://www.the370z.com/members-370z-...39s-build.html