Fuel Pressure

[ric78]

Need some suggestions fellas. Here is the beginning and what we have done. 602 crate engine in a metric chassis. Running on VP CHP since late last season. A couple of weeks ago as the temps have risen the fuel pressure got wacky one night as in continuously dropping throughout the run.Ok the fuel pump is going bad was our first thought, changed it after the heat race. Problem continued throughout the main. So preparing the car the following week here is what I changed to fix or hopefully fix our problem. I changed the pickup tube in the fuel cell. I changed out the entire filter assembly the Fram type that hangs down like an oil filter. I went from the blue fuel line with all the push on fittings #8 to braided line with the screw type pressure fitting still #8. Took the Carter fuel pump I bought at the track and replaced with a new Holley that pumps 7-9 PSI. We also run a by-pass regulator to help prevent the CHP from vapor locking it is in line after the fuel log, replaced it. All fuel lines under the hood are insulated with header wrap to help keep the CHP cool. All seemed fine in the shop after the changes.Back at the track again losing fuel pressure. Not so bad in the heat and practice. In the main though after several kinda lengthy yellows on the restart fuel pressure goes to zero on the restart. Car sputters goes flat until about a lap when the fuel pressure gets back to 3 psi and car again runs and has no issues except low fuel pressure.At this point I know we are having a vapor locking issue. In the shop preparing for the next race I heat the car up to temp and switch it off allowing the fuel pump to heat up to the temp of the block . Fire it back up fuel pressure struggles to reach 3 psi. Pour water on fuel pump pressure immediately returns to 8 psi. At this point I no longer wish to deal with these issues with the CHP and switch to the Ratman. Several drivers suggested this to me as they said they had nothing but issues when trying to run the CHP. Flushed the entire fuel system of CHP and poured in the Ratman. Heated the engine to temp again doing the same steps as above with the CHP except for having to cool the fuel pump. This time no issues I am confident I have fixed my problem. Last night outside temp very similar to last couple of weeks. Fuel pressure fluctuated in the heat between 4 and 6 PSI. Car never stumbled or just not run like the week before but the fuel pressure should remain constant right? Before the main I unhooked the fuel pressure gauge from the by pass regulator and hooked it directly the the end of the fuel log eliminating the regulator from the system. In the main fuel pressure continued to fluctuate but the car never stumbled or went flat like the previous week after a lengthy yellow. So I felt like I gained on my issue but would feel better if the fuel pressure would go back to being consistent. Something I did fail to mention I did check the pushrod for the fuel pump and ran a camera in the hole as I turned the motor to check the lobe on the camshaft all appeared normal. Also I have tried another gauge and no they are not liquid filled. Any suggestions would be very much appreciated.

[Racer96m]

Have you tried a fuel pump insulator? http://www.jegs.com/i/Canton+Racing+Products/074/85-000/10002/-1?CAWELAID=1710932150&CAGPSPN=pla&catargetid=1784155608&cadevice=c&gclid=Cj0KEQjw_42eBRDHqcG1psmtneEBEiQAWPL8WEMF6y_g QeEg0V4X_UPUKNciz4NUBbbCLo0COdnANxwaAsYq8P8HAQ

[ric78]

That is a great suggestion. I was thinking of ways to insulate the fuel pump but thought about the transfer of heat from the block would render that useless. I will give this a try thank you for your help.

[JustAddDirt]

are you running steel, or aluminum line from pump to carb?
how close to the header to the fuel line?
how close is it to the lower rad hose?

Basically have to isolate the heat away from incoming fuel line to pump, then pump to carb.

[26-62 racing]

While you are checking everything, check the vent on the fuel tank also to make sure the tank is venting properly, I have chased problems one way only to fine out I was down the wrong path. Mike

[ric78]

It is now all braided line to fuel pump and up to the carb. After doing a little reading gonna change the fittings in the fuel pump which are 90's to straight. Then change the fitting on the braided line to the more sweeping 90's as I read the 90 fitting in the fuel pump are more restrictive. Just a little concerned with keeping a nice air gap from lower water hose on the out side of the fuel pump with the sweeping 90 on the line. Header clearance the fuel line runs along the front bars so a good bit of space there but those bars get there share of heat from the headers. Line is wrapped in header wrap but if you think I need a better insulator and have a suggestion I am very open to it.On the vent side my hose is a little longer than need be was gonna look at shortening it and trying a little larger filter. I have unhooked it and blew through it with air and it is clear. It is a little long because I like to loop it down to keep water out when washing. I can shorten and still keep down to avoid the water. I have checked the flat plastic washers on the bulkhead fitting they look fine all was tight but may replace just to ensure no air leak.On a side note we run no hole in the nose and keep the nose pinned fairly close to the racetrack. Not a lot of cool air to help cool the fuel pump from the fan. Thought about a 4 inch hole and some of the aluminum type flex pipe such as what you hook your dryer to from the nose to the fuel pump. Similar to what the cup boys do with brake ducts.Thanks for the suggestion fellas.

[ric78]

Man I try to break my post up into paragraphs looks good when typing but when I submit one big long hard to read post. LOL maybe something I am missing sorry fellas. I know it is hard to read.

[JustAddDirt]

just remember heat rises, so try and run the lines below the header if possible ( impossible if you have stock style header though.)

just a thought here, and I may be wrong, but wrapping the fuel line in a header wrap, would that not hold the heat in the line, once it is hot?

I would look at your vent as well. you stated you have a long line, are you sure it is attached to the fuel cell on the vent outlet on tank? (assuming you have a vent, and a return port.)

[skypeseo]

I think there should be lifeguards in the genepool.

[lightening26]

We had the same issue with our mod. We put a return line on to keep fuel moving, moved fuel line away from headers, and put heat wrap shield over fuel line.

[let-r-eat]

Loosen the screws holding the pump together. Compress the pump actuator arm fully. Retighten screws.