vapor lock heat problems

[milehigh69]

I have a efi system on a 454 with procharger, rock valley tank with 300 lph Deatsch in tank pump.
the car runs at 180-195 degrees normally. I have a aeromotive regulator mounted over the rear axle and is set at 45 psi which is what retrotek wants. I have an inline gas radiator from Barry Grant. The problem I have is after cruising around the fuel gets hot, even without sending it up to the engine bay. I think I know what is happening and wanted to ask you guys to see if you agree and have any ideas on how to fix it. The pump is pwm modulated so it is noy on full bore unless the demand is there. However pumps heat up gas. if the car is mainly cruising, it is returning warmed up gas to the tank most of the time. Eventually the fuel is pretty warm if maybe hot. eventually I get vapor lock. let me know what you think.

[dhutton]

Edit: should have read more carefully....

[CarlC]

If your ECM is controlling the pump via a PWM signal, how does it know what the at-idle and cruise fuel pump speed should be? Is there a pressure sensor at work providing feedback to the ECM?

[milehigh69]

Yes, The retrotek has one in the throttle body.

[CarlC]

So there is a fuel pressure sensor in the throttle body. What is fuel pressure set to on the mechanincal regualator, and what is the programmed set pressure for the ECM? Is the ECM pressure constant or rising rate? If rising rate, what is the pressure range?

[EFI69Cam]

Heat from the return is only part of the problem. How close to the fuel tank is the exhaust ? my BBC EFi 69 would get so hot that the fuel would boil until I insulated the fuel tank and fuel lines with reflective ceramic blanket.

Is the fuel tank stainless? Maybe have it coated with a heat shedding coating such as what is used on brake calipers?

[milehigh69]

the regulator is set around 45-50 psi. The ECM should be about 45 psi. both the regulator and ecm increase pressure with boost. however it heats up just cruising at little throttle. last year I had the exhause turned down after the mufflers. still had problems. this winter I had the tail pipes installed. I really think it is the pump. I looked at Kenne Bells website and he makes a product for this problem. Boost a pump. it boosts the regular pump up yo 50% more on boost. one of the reasons they do this si the overheating of the gas.

[CarlC]

You may have two pressure regulating systems fighting with each other.

If the electronic pressure regulating system is set near where the mechanical regulator is set to bypass, then there is a very good chance that the pump is going to run very fast as it tries to keep up with the ECM commanded pressure. In other words, if the mechanical regulator is set near or lower than the ECM commanded pressure, the ECM will command the pump to run at full speed since it can never meet the electronic pressure setting. Making the pressure rising rate can create more problems as well.

The OE's do not use a mechanical regulator when an electronically commanded pressure (fuel pressure sensor) system is used. It also makes it a single line to the fuel rail setup.

One way to check this it to monitor the voltage at the pump. Though not the actual voltage, it's a good average indication if the pump is running at a slow or higher speed. For example, with the VaporWorx electronic systems both the CTS-V and 5th-gen pumps require less than 6-1/2v at idle and cruise for most applications. The 5th-gen in James Shipka's LS7 Katech OLC uses less than 6v at cruise. With the correctly setup system running a very large pump is possible. The CTS-V fuel module is effectively a 380+lph pump.

[milehigh69]

So the mechanical regulator should be set higher than what the ecm wants. Makes sense. I will try this next. With a PWM controlled pump would the voltage go down or does it just turn the pump on and off to make the pressure? I may be buying one of your tanks sooner or later. Ya never know. Thanks for the help Carl.

[CarlC]

When taking a voltage reading at the pump when using a PWM controller the voltmeter is reading basically an indication of the PWM cycle. The PWM cycle is like a very fast switch. 10ms on, 10ms off, 10ms on, 10ms off, is a 50% duty cycle. The pump only sees it as 12v, on or off. Hence, there is little heat buildup like there would be if a rheostat was used that reduced voltage, but needed a bunch of amperage to just turn the pump.

That is not to say that if the PWM signal is at 50% duty cycle that the voltage at the pump will be 50% of the available battery voltage. It should only be used as a rough estimate. It is very safe to say though that if you're seeing 11v at idle out of 13.5 available, that pump is running pretty hard.

To answer your question, the controller, based on the fuel pressure signals, will increase or decrease the PWM duty cycle in order to maintain the commanded fuel pressure. The actual voltage to the pump does not change since it is either zero or battery voltage. The voltmeter only sees a rough average.

If you get that sorted out I have another suggestion. Once you get the pump slowed down now you are going to heat the fuel in the pump up since very little will move at idle. On the pressure side of the pump put in a small bleed that can return to the tank. Say a 0.015-0.020" hole restrictor. This will allow some fuel to bypass and keep cooler fuel circulating through the pump. This is another one of the big advantages of the fuel module, the venturi pump design uses bypassed fuel to keep cool fuel circulating through the pump at all times.

If you try the higher mechanical regulator setting and it works, don't be surprised if you see a pressure spike when you turn the key off. The pump will keep spinning once the power is removed due to inertia. Since the injectors close at the same time, now there's basically an incompressible fluid in a solid vessel but the pump is still spinning due to inertia. The pressure will spike. Set the mechanical pressure regulator to 15psi higher than you maximum anticipated fuel pressure. Now the mechanical pressure regulator is a safety poppet valve, assuming that your pump has a functional check valve.

[milehigh69]

Great info Carl. Best information I have received on this topic. Last summer I was unable to drive my car much because of this problem. I am bound and determined to get it running soon. I will adjust the regulator well above the set point of the fuel pressure on the PWM control. What would you think of putting in a 190 LPH walbro instead of the 255? I dont think I had a problem with the 190. However it was not supercharged. Kenne Bell has a product called boost a pump and it boosts the output when the procharger is putting out.

[CarlC]

1) How much boost?
2) What is the flywheel horsepower?
3) What is the injector rating? (#/hr @ psi)
4) Is the electronic fuel pressure rising rate? At idle fuel pressure?

Let's make sure first that the 255 is enough pump for your application. There is not much difference in heat generation between a 255 and 190lph pump. At full output @ 50psi there is only a few amps difference between them.

The BAP is a good option in some cases. However, it adds more complexity, cost, and won't solve the root cause of your problem.

No guarantees that raising the bypass pressure on the mechanical regulator will work, but I can see where if the electronic and mechanical components were arguing with each other, it could cause problems. Did the ECM manufacturer have any suggestions?

I also suggest wrapping the tailpipes with insulation if they are close to the tank.

[milehigh69]

11psi at WOT
430 at the wheels.
92 lbs/ hr at 50 psi
I think it rises on boost. The regulator is referenced to the boost.
ECM manufacturers is of little help. The tech guy left and doesnt respond to e-mails. He is on this forum. Dr. EFI.
I can wrap the tailpipes.
Thanks again.
BTW my latest pump is a Deatsch 300 lph pump.

[67zo6Camaro]

Carl, Good stuff here.

Do you know if this is the same on an older 98 style ECM for an LS6 with the older Street and Performance style modified fuel rail so that you have a full 2 lines front to back? The reason I'm asking is that I get a hot fuel line at the back near the tank, I still need to use a mirror to see if it is the return line or pump line.... most likely the pressure out, pump line. I don't seem to get any vapor lock. As I read more of these similar cases, with in-tank pumps for EFI, I'm starting to wonder if I have the correct and/or best set-up.

Brett


When taking a voltage reading at the pump when using a PWM controller the voltmeter is reading basically an indication of the PWM cycle. The PWM cycle is like a very fast switch. 10ms on, 10ms off, 10ms on, 10ms off, is a 50% duty cycle. The pump only sees it as 12v, on or off. Hence, there is little heat buildup like there would be if a rheostat was used that reduced voltage, but needed a bunch of amperage to just turn the pump.

That is not to say that if the PWM signal is at 50% duty cycle that the voltage at the pump will be 50% of the available battery voltage. It should only be used as a rough estimate. It is very safe to say though that if you're seeing 11v at idle out of 13.5 available, that pump is running pretty hard.

To answer your question, the controller, based on the fuel pressure signals, will increase or decrease the PWM duty cycle in order to maintain the commanded fuel pressure. The actual voltage to the pump does not change since it is either zero or battery voltage. The voltmeter only sees a rough average.

If you get that sorted out I have another suggestion. Once you get the pump slowed down now you are going to heat the fuel in the pump up since very little will move at idle. On the pressure side of the pump put in a small bleed that can return to the tank. Say a 0.015-0.020" hole restrictor. This will allow some fuel to bypass and keep cooler fuel circulating through the pump. This is another one of the big advantages of the fuel module, the venturi pump design uses bypassed fuel to keep cool fuel circulating through the pump at all times.

If you try the higher mechanical regulator setting and it works, don't be surprised if you see a pressure spike when you turn the key off. The pump will keep spinning once the power is removed due to inertia. Since the injectors close at the same time, now there's basically an incompressible fluid in a solid vessel but the pump is still spinning due to inertia. The pressure will spike. Set the mechanical pressure regulator to 15psi higher than you maximum anticipated fuel pressure. Now the mechanical pressure regulator is a safety poppet valve, assuming that your pump has a functional check valve.

[CarlC]

11psi at WOT
430 at the wheels.
92 lbs/ hr at 50 psi
I think it rises on boost. The regulator is referenced to the boost.
ECM manufacturers is of little help. The tech guy left and doesnt respond to e-mails. He is on this forum. Dr. EFI.
I can wrap the tailpipes.
Thanks again.
BTW my latest pump is a Deatsch 300 lph pump.

How many injectors are there?

Assuming 20% drivetrain loss you have 520FWHP. 520 * 0.6 = 312gph. If the fuel pressure is rising-rate then you're looking at 60-61psi at WOT. A GSS340 255lph pump @ 13.5v will supply 61GPH @ 60psi. @ 6lbs/gal that's 366lbs/hr. The 255lph is plenty.

If the mechanical regulator is set to 45psi and the electronic is 50psi, the pump is running at full speed since the mechanical regulator is set lower than the electronic. Attaching a voltmeter to the pump is going to be the best indicator of what's happening unless the ECM has a method to show how much voltage, duty cycle, etc. is being fed to the pump.

Having too big a pump without a method to control the speed = lots of heat.

[CarlC]

Carl, Good stuff here.

Do you know if this is the same on an older 98 style ECM for an LS6 with the older Street and Performance style modified fuel rail so that you have a full 2 lines front to back? The reason I'm asking is that I get a hot fuel line at the back near the tank, I still need to use a mirror to see if it is the return line or pump line.... most likely the pressure out, pump line. I don't seem to get any vapor lock. As I read more of these similar cases, with in-tank pumps for EFI, I'm starting to wonder if I have the correct and/or best set-up.

Brett

Nothing that early used fuel pressure feedback. The ECM has no input for it.

The earlier LS cars had a full return system, meaning that the pressure regulator was on the engine. Hence, there was a return line. Even the later cars, like the GTO, still did not use fuel pressure feedback to control the pump. GM just moved the regulator to the fuel module inside the tank.

It was not until the later model cars, like the 5th-gen, C6, etc. that PWM and fuel pressure feedback systems come into play on a mass scale.

[milehigh69]

carl
i have 4 injectors in a TBI. I will try the adjustment this weekend. I think I have seen your new set up available with a weldable ring . could I weld it into my rock valley tank, And use your pump set up? can I buy from you or do I go to Ricks? also, would the dc control controller help this problem?

[67zo6Camaro]

Thanks, wizard of tanks.

[CarlC]

carl
i have 4 injectors in a TBI. I will try the adjustment this weekend. I think I have seen your new set up available with a weldable ring . could I weld it into my rock valley tank, And use your pump set up? can I buy from you or do I go to Ricks? also, would the dc control controller help this problem?

This may be what you're thinking of. It's everything needed mechanically to mount the either the Camaro or CTS-V fuel module in a tank. If the tank is between 7" - 8-1/2" tall, it should work. If using the PWM kit you won't need the fuel pressure adapter. This kit can be purchased from me, as well as the electronics, pumps, etc. I don't sell or manufacture the tanks.

https://static1.pt-content.com/images/noimg.gif

[milehigh69]

Carl
Does the pwm kit include the Dc controls PWM controller. What I am thinking is buying that and trying it on my existing set up. If all else fails go to your set up. Will the PWM from Dc Controls work with my Deatsch pump?
http://www.deatschwerks.com/fuel-pumps/300+-lph-high-flow-in-tank-fuel-pump

[CarlC]

It should work. I've tested it with a 255lph and it worked fine, but I still suggest the 0.015" bypass as mentioned above. I'd exhaust all options with yours first.

The kit does come with the DC Controls PWM controller and my signal conditioner. Wiring for either a CTS-V or 5th-gen pump is also included, but you won't need unless you go with the fuel module. The OE wiring connectors, pressure sensor, etc as well. Final pricing will depend on if you want a fixed pressure (FlowWorx) or rising-rate pressure (PressureWorx).

I tried clicking on that like and it sent my computer into a spastic fit.

[milehigh69]

What is difference between Flowworx and pressureworx? I guess I dont understand what you mean exactly by a bypass in the pump. My fuel exits the tank, goes thru a regulator and returns to the tank in about 1.5 feet. So it is sending fuel back into the tank ut it is heated up. I adjusted the regulator up and it doesnt seem like the PWM is working because the fuel pressure just keep going up. I stopped at 60 psi. Fuel injection works fine though.

[CarlC]

EFI it very forgiving with fuel pressure at idle. Mine will idle just fine from 20-90psi.

The FlowWorx system is a constant pressure system, similar to a non-manifold referenced mechanical fuel pressure regulator. Think C5 Corvette fuel filter/pressure regulator. For yours, set it to 50psi and forget it.

The PressureWorx system has a rising rate fuel pressure, similar to a manifold referenced mechanical fuel pressure regulator. As manifold pressure increases, so does the fuel pressure. This setup requires that additional wiring be used to tap into the MAP ground and output wiring. I would need to know what the BAR rating is for your MAP (1bar, 2bar, 3bar, etc.)

Don't go by the sound of the pump to determine if the thing is running really fast. The slower it runs, the higher the pitch, which some people interpret as the pump running faster. The pump input voltage is the best way to determine if the pump is slowing down or speeding up.

With either system above the mechanical regulator now in your car is removed. With yours there would be only a single pressure line going to the fuel rail. Unlike a fuel module, there is very little fuel flowing through the pump at idle. This means that the pump can get hot since very little cool fuel passes through it. My suggestion is to make a controlled leak that would allow pressurized fuel to return to the tank and take the pump heat with it. The PWM speed control is the first line of defense, but adding this small amount of fuel bypass to help keep the pump even cooler is a good thing.

So....

1) Somewhere after the pump but close to the tank, put a "T" in the pressure line.

2) Reconnect the fuel pressure line to the "T".

3) For third leg of the "T" connect a hose that will return to the tank. In this hose will be a restrictor. The restrictor will have a hole that is 0.015 - 0.020" diameter. This hole will allow a small amount of fuel to pass through the pump, helping it to keep cool, and then return to the tank. It's a controlled leak.

The fuel modules have this feature built in. In order to drive the venturi pumps high-pressure fuel is bled off to power them. If the pump is running, so are the venturi pumps. So, even at idle and/or very low engine fuel demand, there is additional fuel passing through the pump to power the venturi pumps working, keep the pump submerged, and cool fuel flowing.

EDIT:

More pondering. If you wanted to take the time and effort you could make this bypass happen in the tank. Most of the time the pumps are hung on or attached to a stainless tube. Drill a 0.015 - 0.020" hole in the tube. This would do the same thing as above but keep it all in the tank with no external hoses needed.

[milehigh69]

So effectively I have a pressureworx system now since I have a boost regulator 6 inchs outside the fuel tank returning fuel to the tank right. Doesnt this do the return and boost the pressure upon boost? I think my only option left short of getting a whole new system is to use the dc control PWM control. Its the only thing going to slow my pump down. I am wondering how all the guys with Fuel injection out there don't have the same problem. These pumps cause lots of heat. How much for the controller from you? PM me with the info. Thanks again. You have been very helpful.
BTW, where abouts are you in LA? My daughter works for CHP.

[CarlC]

I'm in Newbury Park.

It sounds like your ECM may have the same system, but using two pressure regulating systems won't work together. If the rising-rate fuel pressure is controlled by the mechanical regulator how does the electronic side know what to do? There are two non-compatible components are work.

Let's look at it from the viewpoint of the ECM.

The ECM sees a feedback signal from the fuel pressure sensor, and likely, the MAP sensor IF the ECM has rising-rate capability.

There is a programmed fuel pressure in the ECM. For simplicity say it's 42psi at idle, so approximately 50psi across the injector.

Start to accelerate. Manifold pressure increases. The ECM increases fuel pressure the same amount, assuming it is rising-rate.

If the at-idle fuel pressure commanded by the ECM is higher than the mechanical regulator setting then the mechanical regulator is going to allow a lot of fuel to bypass and return to the tank. That equals heat.

If the mechanical regulator is manifold referenced then its bypass pressure will increase as well. But, if the ECM has a rising-rate as well, nothing has changed. The EMC commanded pressure is still higher than the mechanical. The ECM will command the fuel pump to run very fast.

If the mechanical regulator is not manifold referenced, but the ECM is rising rate, the mechanical regulator will still be bypassing a lot of fuel. The ECM will command the pump to run very fast.

In both cases above the mechanical regulator is operating at a pressure lower than the ECM commanded pressure. Since the ECM commanded pressure is higher than the mechanical, the mechanical will bypass fuel and return it to the tank. That equals heat.

If the ECM commanded fuel pressure is higher than the mechanical at any point, the ECM will command the pump to speed up in an attempt to match the commanded pressure. It can't do it since the mechanical regulator won't let it. It will only take approx. 3-5psi difference before the ECM will command the pump to run at full speed.