Pump Cavitation and fuel temps

[96dreamer]

Anyone have issues with fuel temps and possible pump cavitation? A few weeks ago the car died and I had to push it to the side of the road and let it set for the afternoon. Luckily it was in my parent neighborhood right in front of someone's house. Ambient temp was 99° and the fuel temp got up to 115° when the fuel pressure started getting erratic before it stalled and wouldn't build pressure or idle. After sitting for a few hours I was able to get it to my parents house about a mile away. Let it sit over night and it drove home fine the next day. Fuel temp didn't seem to be an issue but it was only about 85° out and I drove it straight home.

After that incident I ran the return line further from the pickup in the tank, I had it ran to inside the pickup area which was a mistake, and wrapped all of the fuel lines from the control arm mount back in heat insulation sleeve in addition to pulling the filters to check for restrictions. Both the pre and post filter looked great.

Took it on a test drive last Friday when temps were about 90° ambient and although it took much longer the temps eventually got up to 115° again and it started having erratic fuel pressure again.
I'm thinking the first time I had the issue it may have caused permanent damage to the pump which is now causing the issues to continue even though I believed I solved the initial issue. Currently debating sending the pump back to Fuelab

The fuel system is a glenn's performance sleeper tank, fuelab 42401 pump with fuelab pre and post filters, -10 feed, fuelab regulator in the passenger fender feeding the rails deadhead and a -8 return from the regulator. I have the pump running via pwm from the MS3Pro .

 

[01yellercobra]

I can't say anything about cavitation. On the Fore set up it dumps the return right by the pumps.

Can that pump handle PWM? Or are you running it through a SSR?

 

[96dreamer]

It has a built in controller which is one of the reasons I went with it. Fuelab verified that it shouldn't have any issues with frequencies down to 200hz even though their documentation states min of 500hz. MS3 only supports up to 250hz on their pump driver.

 

[01yellercobra]

Could it be vapor lock?

 

[96dreamer]

My theory is the first time the temps jumped up to 115°+ it caused the pump to cavitate and boil the fuel vapor locking itself. Now the damage from the first instance is driving the fuel temperature up which is again causing the pump to cavitate/vapor lock. I know there are a ton of guys running the pump on the front/exterior of the tank that don't have issues with heating up the fuel or if they do are not posting about it.

 

[96dreamer]

Something that just crossed my mind was the tank vent/evap system. If that were clogged/ restricted it may cause cavitation issues leading to heat building. I'll probably blow all those lines out before sending the pump in.

 

[01yellercobra]

I can't see one time cavitation/vapor lock damaging the pump that much. I've driven my car in 100+ ambient temps with no fuel issues. But I'm not monitoring temps so I can't help in that regard. A friend of mine ran the Glenns set up on his GT and it never skipped a beat.

It might be worth giving the pump the full 12vdc for a couple trips and see how it acts.

 

[96dreamer]

I can't see one time cavitation/vapor lock damaging the pump that much. I've driven my car in 100+ ambient temps with no fuel issues. But I'm not monitoring temps so I can't help in that regard. A friend of mine ran the Glenns set up on his GT and it never skipped a beat.

It might be worth giving the pump the full 12vdc for a couple trips and see how it acts.

I admittedly have no experience with cavitation first hand. This article from Fuelab lays it out pretty good though.

Understanding cavitation and it

The most common failure of high flow fuel systems is cavitation, or lock. The combination of too much heat or too much inlet restriction can create this operating condition, where the liquid fuel literally vaporizes (boils) inside the pump assembly.

www.fuelab.com

I think at a full 12v all the time it would increase the issue im having. It is rated at 640lph and tested at over 700lph in the cert sheet that came with it which is significantly more fuel than I need on 93. I can run it at half speed by just jumping a wire which i may try .

 

[MG0h3]

I don’t think hot fuel is the problem, but maybe contributing to it.

Never heard of anyone having trouble when running deadhead.

I also don’t think you caused damage with 115* temps but maybe the pump already had an issue. A cup of coffee is upwards of 150*.

I’d def take a look at your evap system like you are. If you’re running evap, you shouldn’t have a vent. The system on our cars, and likely most, will throw a code if there is a leak the size of a pin hole. Not sure how often the system monitors for leaks though.

If you think it’s vapor lock, try driving without the cap on. Should set an evap code though.


Sent from my iPhone using svtperformance.com

 

[96dreamer]

I don’t think hot fuel is the problem, but maybe contributing to it.

Never heard of anyone having trouble when running deadhead.

I also don’t think you caused damage with 115* temps but maybe the pump already had an issue. A cup of coffee is upwards of 150*.

I’d def take a look at your evap system like you are. If you’re running evap, you shouldn’t have a vent. The system on our cars, and likely most, will throw a code if there is a leak the size of a pin hole. Not sure how often the system monitors for leaks though.

If you think it’s vapor lock, try driving without the cap on. Should set an evap code though.


Sent from my iPhone using svtperformance.com

From what I had read some additives can start boiling off around 95°F and Fuelab says anything around 120 is excessive which i suspect it was around 120 at the pump. I am getting the temp from my flex fuel sensor that is just behind the passenger front tire so it has ~6ft of line to cool off in after the pump.

To be clear it is a return system but the rails are fed in a deadhead loop from the regulator.

I'm also running an ms3pro stand alone so the factory evap system doesn't really do anything. I kept the factory lines up to the charcoal cannister and vented to the atmosphere to help control the fumes. Running without the cap is a good idea though. I may give that a try.

 

[01yellercobra]

I admittedly have no experience with cavitation first hand. This article from Fuelab lays it out pretty good though.

Understanding cavitation and it

The most common failure of high flow fuel systems is cavitation, or lock. The combination of too much heat or too much inlet restriction can create this operating condition, where the liquid fuel literally vaporizes (boils) inside the pump assembly.

www.fuelab.com

I think at a full 12v all the time it would increase the issue im having. It is rated at 640lph and tested at over 700lph in the cert sheet that came with it which is significantly more fuel than I need on 93. I can run it at half speed by just jumping a wire which i may try .

FWIW, I'm running twin 450's and still have my full evap system in place even though it's not working. The pumps run full time whether I'm on 91 or E85 and my system is in a dead head configuration. The regulator should be able to handle the excess fuel.

 

[96dreamer]

Checked the evap lines tonight. All seemed clear and air passed through all of them fine.

Going to try letting it idle at half speed with no pwm controller next. Thinking I might pull the pump and send to fuelab to check out if that doesn't work. Not sure what else to look at.

 

[MG0h3]

Is this the first summer that you’ve had this setup together?

Trying to determine if this is a design issue (since it’s entirely aftermarket) or a component failure.

There’s a lot of us that have been out in higher temps than that without issue running return systems but still the factory tank.


Sent from my iPhone using svtperformance.com

 

[96dreamer]

Is this the first summer that you’ve had this setup together?

Trying to determine if this is a design issue (since it’s entirely aftermarket) or a component failure.

There’s a lot of us that have been out in higher temps than that without issue running return systems but still the factory tank.


Sent from my iPhone using svtperformance.com

I got the fuel system buttoned up last April 2021 but I couldn't tell you how much it was actually driven on hot days. My son was born in July so I don't think it got driven much before or after then. I would have to go back and see if I have any logs over that time. I am pretty sure that earlier this summer when i first had the issue and it was 99 ambient with 90% humidity was the hottest day I have driven it with the new fuel system.

I know there are quite a few guys running the pumps/filters in the same location as me and either they are not having issues or i was not able to find posts where they were.

The only thing I can think would be a flaw in the system was where I had the return line running originally. It was dumping directly into the sump pickup area. My initial reasoning behind this was to prevent starvation in low fuel situations but fuel heating/aeration/cavitation hadn't crossed my mind. Since I started having issues I moved the return to the driver side of the tank pointed away from the pickup. However I am afraid having it there caused damage to the pump that is now giving me issues.

 

[96dreamer]

Wanted to follow up on this. Fuelab looked at the pump and it checked out fine. He suggested I remove the heat shielding on the return line and/or run hard aluminum lines where possible. I haven't done either of those yet but have looked into running hard lines under a portion of the car. I also adjusted my pwm control table to reduce the amount it was flowing as I previously had it set up wrong. Went on a 100+ mile cruise Sunday and temps never got above 95°F. Crossing my fingers that it's somewhat resolved now.