Got a problem. Probably fuel supply issue.

[Curly1]

I have Enderle hat on 760 HP SBC I had been making changes to try to get it to footbrake with little success. Now car has developed a bad problem and will not come up on converter. The data logger is showing fuel pump pressure drops like a rock, all O2 sensors read lean and car just lays over.
My first thought was loose fuel line and dirty filters causing pump to suck air and not fuel. Drained fuel cell, checked and cleaned filters and checked all fittings (they were tight). Fuel filters had a few little bit of trash but it was not much and filter was not clogged. Nothing more than I consider normal.
I checked the belt and the pulleys are good. The nozzles are clean and flowing and all O2 on all 8 cylinders are consistent so it is not a clogged nozzle.

I looked in the fuel cell for paper or plastic or anything that could float around and block outlet. Nothing, yet it sounds to me like it is a fuel supply problem. Car has been running very good with same system for several years. I do see a few things I could improve to make system better but it was working good before and I need to fix the issue here.  Most of the hoses are one year old and in good shape.

I will probably put my old tune up back in it and I have a new pump that I may try but I seriously doubt that is the issue. It is acting like it is starving for fuel and sucking air.  Note I am not that far off of old tune up now and it should be way fatter. Basically I am right now one size smaller nozzles and way smaller main so it should if anything be very fat right now but it is not and in my opinion it is somehow running out of fuel.

I have two large Summit stainless filter elements that go into a tee fitting and one -10 line to bottom of pump. No sharp turns or anything like that. Returns go into top of cell near the back. I am thinking of making a manifold to return the fuel back into inlet line near pump to reduce aeration of fuel. I think it would also help to keep inlet fuel flowing and pump covered with fuel. Now I found two larger filters and will probably get them and put them on, anything I can do to increase flow and lower restriction should help but the current filters are not the problem as they have been working well and were clean.

It is not ignition as logger is not showing any missing etc.

Any suggestions? Hope I gave you enough information to give me a direction to look. Thanks,

[Spud Miller]

 What has changed since it DIDN'T have the problem?

 Some ideas...

 Are you running a blank pill in the barrel valve? You didn't forget it, right?

 A hose flapper on the supply side. Either on the suction line or pressure side of the pump ahead of your pressure sensor. Turn your hoses around the other way (swap ends) if the fittings allow it to troubleshoot. Hose flappers are the main reason I quit using "cutter-style" hose fittings and only use push-lock now.

 Fuel tank vent...to troubleshoot, remove the fuel tank cap and see if you still have the problem.

 Barrel valve spool is in wrong or turning the wrong way (assuming your pressure sensor is on the nozzle side of the barrel valve).

 Fuel shut-off isn't open all the way?

 I hate filters on the inlet side. Troubleshoot by removing the elements from those and see if you still have the problem with just the empty housings installed.

 That's all I can think of at the moment...

 Spud

 

[Curly1]

I did turn the inlet hose around and checked it. Hose seems good but turned it around anyway. Note, when I removed the hose the fuel flowed out like a water hose confirming to me the filters were not restricted. Just the same I put two HUGE stainless filters on there.
Tomorrow I plan on changing out the pump. I am very confident it is not the problem but I have it and will not hurt to try it.
I did check the vent and it is clean and open. May be able to put car up on jack stands, pull low RPM chip out and try it against transbrake to see if it is better.
I did not remove the barrel valve so it could not be turned around.
I went back to my original tune up and will see what happens on Sat.
Fuel shut off is closed, I have got into the habit of checking and double checking the fuel shut off and make sure transmission is in low gear before I stage. I also occasionally check operation of fuel shut off to make sure it completely closes.
Found a small leak on one of the fittings going into the tank and fixed it.

Thanks for the good  ideas and suggestions. Saturday is my first points race and I hate going into it blind and unprepared but I will do what I can. Hoped I would find and resolve the problem but right now have not seen anything firm as to what the problem is.  At least nothing definitive so far.

[32bantam]

If the pump is good......sounds like a poppet could be open...maybe stuck or broken/weak spring?

[Curly1]

Okay for the latest. I changed the pump, the line and put two huge filters and the supply problem is gone. That is the fuel pump pressure is staying good but I am still having same issue I had last year. When I leave off transbrake for the .400 Pro Tree with 4400 chip it leaves good and hard. But when I foot brake it the car will not run, it will stumble and bog. Even on the dyno this motor did not want to take a load at lower RPM. We ended up starting our pulls at 5500 RPM. When I footbrake if I leave from dead idle the car will run good but reaction times are terrible. When I bring it up to 2500 reaction times are good but motor is not happy right there. I know mechanical injection does not have squirters to enrichen it when you open throttle so it is set up fat to cover, I know it is asking a lot from injection to make it work clean through out the RPM range. Most are idling or wide open most of the time and I can make it work good at both but not 2500 RPM. Still I think something is not right and it could be better.
Now I have noticed something and need to verify. The pressure is on the main pill bypass is 18 or less. On the idle bypass it is very little probably less than 1 PSI you can easily blow through it and I can not get my leakdown tester to measure that low. Any air at all and it is leaking. I believe Enderle told me that should be 8 to 10 PSI. Do not have any idea what main should be? Note this is naturally aspirated and not a blown motor.

I want to check basics, does anyone really know what idle and main bypass should be set at?  Once again Thank you for your help and suggestions.

[BK]

 Your idle pressure is too low. I think Spud suggested 3-5 on the idle I set mine 5-7 either is fine you just compensate with the barrel valve. Once you get idle pressure up if that doesn't help your problem check your  secondary  / pump saver bypass if you have one.  If that's still in play at 2500 and set too low that could be a problem.
 

[Curly1]

So it does sound to me like idle pressure is too low. I set up one at 9 PSI and going to try it. Now on the main mine is at 18 PSI. Makes me wonder if at some point someone got them mixed up? What is main supposed to be? Also with idle bypass basically set at zero that may explain why this motor has always been hard to start.

Going to try one thing at a time starting with raising idle pressure as it makes sense and data logger appears to back it up. Sure makes me think the main is off to.

[BK]

 I'm not sure what you mean by main. You have to have the idle check that should includes your main jet. You should have a secondary / pump saver but not everyone runs one. And sometimes you need a High speed. The link should take you  to pretty good setup diagram
http://goodvibesracing.com/Tunnel_Ram_Injection.htm.

[Curly1]

I'm not sure what you mean by main. You have to have the idle check that should includes your main jet. You should have a secondary / pump saver but not everyone runs one. And sometimes you need a High speed. The link should take you  to pretty good setup diagram
http://goodvibesracing.com/Tunnel_Ram_Injection.htm.

THANK YOU!  My main was set at 18 PSI according to that drawing should be 2-5 PSI. The SECONDARY is the one I was calling idle was set at less than 1 PSI and that drawing says it S/B 17-25 PSI.
Now I am not sure what the secondary does I thought it was idle?

[Curly1]

Okay, now it is making more sense. The secondary check valve was around 1 or even less. I thought that was idle. What is the idle check valve I thought was the Main and it was set at 18. So I think at some point someone got them mixed up. It ran well up top but is hard to start and did not run good low RPM. Now I will put them in proper place and start tuning from there. That drawing helped. Thank you

[BK]

The secondary can do two things. When the throttle shuts at the end of a run the fuel pressure wants to spike because the fuel has nowhere to go. The secondary stops that by giving it a path back through a return. It can also be used regulate part throttle pressure. Say if you where driving it back, and it was real rich you could bleed a little fuel off with the secondary. After the barrel valve rotates about 20 degrees the passages don't line up and it becomes inoperable until it goes back below the 20 degree point again.

[coupemerc]

Now that your poppets are sorted out, you may need to adjust your barrel valve leak down for a proper idle.

[Curly1]

Now that your poppets are sorted out, you may need to adjust your barrel valve leak down for a proper idle.

I am pretty sure will have to adjust barrel valve and expect it will help my low RPM performance.

[Curly1]

This is a drawing that came with the hat, I guess it is from Enderle? Anyway this is why I thought the lower front bypass was the idle. But I think we have it right now and look forward to testing ASAP. I will let you know how it works. Thanks,

[Curly1]

Okay, I finally got it out to test and learned quite a bit. The car would NOT footbrake with out bogging or stalling. After doing some research asking some questions and checking some things we determined the Idle and secondary check valves were backwards. The secondary was probably less than 1 PSI you could easily blow through it or unseat it simply by tapping bottom of check valve. To low to determine leakdown but it was very little. I set it at 18 PSI. Then the idle was at 18 PSI and I set it at approx 7 PSI. Car footbraked good but performance was off from 60 foot all the way down track. Made 7 passes checking things and finally got most of performance back. Secondary set at 26 PSI and idle is around 9 PSI.

Only thing that bothered me was to get it to lean down enough to idle I had the set barrel valve almost as short as it could go. I even tried lowering idle bypass down to around 1.5 PSI and it still was almost out of adjustment.

7 Test passes is not enough testing to have all of the answers but it appears that 26 on secondary and 9 on the idle works well for footbraking on my car. Need a little more testing but I am now much closer and can get it from here.  Only issue is I have a race next Saturday and will not be able to test any more between now and then but it is what it is and I will go out there and do my best. Make small changes and hope it works.

Thanks to everyone with all of the suggestions and ideas.