When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was visiting with Troy about your issue today. You don't really have to boost the hobbs switch to test the BAP, although it's a more complete test if you do.
You can simply short out the 2 leads on the hobbs switch.
How I would start the testing:
remove the factory relay and create a shorting tool using a fuse link to short pin positions 87 and 30 together. When standing at the passenger fender, facing the driver side, remove the fuel pump relay from the upper left side and short the upper left and lower right pins. The pins are labeled (numbered) and there's a diagram on the side to confirm that 87 and 30 are the pins to short if you forget.
Turn the key on. You'll hear the pump start working.
Short the Hobbs switch wires together and you should hear the pump kick up a notch.
There's an output adjustment dial that comes with the BAP. I always ditch it and short the two wires together to make it go wide open when it's activated.
With the pump running, test the wires at the pump head at the driver side. Without the Hobbs running and without the car running, you should have maybe a 1/2 volt drop at the hot wire from up front. Next, measure the voltage with the BAP activated.
Next, touch your meter lead to the pump head cover and the other meter lead to the frame. It should read less than a few tenths of a volt. If it reads more, you lost your ground path in the plug. make a 10 gauge ground strap and ground the pump head to shiny metal on the frame to solve that problem.
If both the hot and ground show good, then my next suspect is an internal leak bleeding off pressure from a broken or loose line inside your pump assembly. Pull it out and you'll quickly discover that issue.
If the voltage is good outside the pump head and you have no internal leaks, the only remaining items are the connections at the pump itself and a pump that **** the bed.
If you need a better explanation of anything get my # from Troy and hit me up.
I'm working nights, so if you're up really late, hit me up.
Thanks Brett I will check it out. Last night I was able to do some checks before I read this post this am.. I am getting 12v to through the bap with the caspers harness. I am also getting 12v through the caspers harness. I also plugged in the stock fuel pump harness and I am getting 12v. I also shorted the wires from the pressure switch and I got 17v so I know the bap is good. I would like to know how to check the actual switch. Do I just stuff a fitting into the vac hose and use compressed air and check continuity when it closes? Or how do I go about that? I highly doubt that pressure switch is bad but still want to check. And yes I do have the 2 wires from the output adj dial soldered together when I first installed it. I may be giving you a call about checking the voltage on the pump head.
Originally Posted by Milan
Not sure if you checked this yet, how much fuel is in it? Did you start the day at a full tank and then after racing everyone end up with less than 1/4 tank? The way your new pump is setup it might not be getting enough fuel if the tank is low. I know it seems like a "no duh" situation but it's worth mentioning, seen it a million times before.
almost a full tank when it happened
Originally Posted by RoccoC5
Just spitballin here, but I wonder if the pump could be cavitatating? (Is that even possible with an in-tank pump?) If I remember correctly you installed a pump and screen that didn't quite fit right in the oem fuel bucket? Anyway, hope you get it figured out soon!
I thought about that but it would do it all the time I would assume. or idle/drive like crap. Ill get it just didn't know how or what to start with. Im still going to swap that regulator
ain't your BAP activated by manifold pressure (boost)? that's how i understand mine works: takes a vacuum line off the back of my manifold & in positive pressure, it amplifies the voltage to my fuel pump.
if there's a leak in that line, it won't be seeing the expected manifold pressure & therefore won't output the proper voltage to the fuel pump. with less-than-needed voltage, you'll get lower fuel flow/pressure because the engine is using gas faster than the pump can supply it.
maybe i'm out in left field - if so, just say i'm a 'tard & i'll study more before offering suggestions.
ain't your BAP activated by manifold pressure (boost)? that's how i understand mine works: takes a vacuum line off the back of my manifold & in positive pressure, it amplifies the voltage to my fuel pump.
if there's a leak in that line, it won't be seeing the expected manifold pressure & therefore won't output the proper voltage to the fuel pump. with less-than-needed voltage, you'll get lower fuel flow/pressure because the engine is using gas faster than the pump can supply it.
maybe i'm out in left field - if so, just say i'm a 'tard & i'll study more before offering suggestions.
I am using my brake booster for my bov,bap,boost gauge. That vac tube is brand new. I haven't tested it like BLOWNBLUEZ06 suggested that will be the first order of business when I get time hopefully tonight.
Also check your external relay for your BAP and secondary fuel pump... This one got me..
I had 12v at the relay in. I had signal from the Hobbs switch to trigger the relay... The relay was switching/clicking like it should when signaled to switch.... But I had no 12v OUT of the relay going to the BAP/second fuel pump. Turned out the relay had an issue on the out going side (accessory side)...broken contact or internal winding or something... Put a new relay in it and it worked fine.
Just have to go thru EVERYTHING with a fine tooth comb..
My Vote is low voltage while running. Our alternators do a poor job and they get hot while running. When they are hot they really do a poor job of producing voltage. Add to that when the car gets warm the cooling fans come on.... set up your DIC with the voltage displaying, start the car on a warm day and let it idle, you can watch the voltage drop .1 at a time. eventually it will get to the point where even the boost a pump can't give you the pressure you need. Add to that you don't have a boost reference regulator with a return, so subtract the boost psi from your fuel psi.....
I have experienced a lot of this in the past, not just a theory. Keep checking, you will find it,
Good Luck
Steve, I thought that may be it but voltage checks out after the multimeter tests..I will keep an eye out though..
Well here is the update. Looks like the issue is resolved. I did all the checks Bret had suggested the only issue I did have was .5 drop of a volt from the frame to pump hat. So Ill get a 10awg wire and run that. Looks like I'm getting cavitation???? I swapped back to the stock pump and fp is now at 55-60 at idle/start up as opposed to 74-76psi with the aem one. I got on it for awhile fp never dropped below 50. Possible that fuel was getting to hot with that pump? Fuel pressure gauge liked to dance around also with that aem
So what exactly was happening then? That thing should just be pumping out some pressure being a 320. What exactly makes it drop like that when the fuel gets hot? Why doesn't that happen with a 255?
Steve, I thought that may be it but voltage checks out after the multimeter tests..I will keep an eye out though..
Well here is the update. Looks like the issue is resolved. I did all the checks Bret had suggested the only issue I did have was .5 drop of a volt from the frame to pump hat. So Ill get a 10awg wire and run that. Looks like I'm getting cavitation???? I swapped back to the stock pump and fp is now at 55-60 at idle/start up as opposed to 74-76psi with the aem one. I got on it for awhile fp never dropped below 50. Possible that fuel was getting to hot with that pump? Fuel pressure gauge liked to dance around also with that aem
So what exactly was happening then? That thing should just be pumping out some pressure being a 320. What exactly makes it drop like that when the fuel gets hot? Why doesn't that happen with a 255?
My opinion after discussing all of this with you and based on the results of all your tests is that your AEM pump is too big and trying to pump too much, overwhelming your existing regulator and overheating your fuel. That overheated fuel causes what's known as EFI vapor lock and pump cavitation. The cure is to use a PWM controller to slow the pump down with decreased demand and increase the pulse width with increased demand. It's not really worth spending all that money to cure the issue with your AEM pump, considering your current power arrangement. When it's time to increase power, get a second pump to run off a WOT Hobbs switch so that it doesn't cook your fuel.
That's makes sense Bret and once again thanks for all the help and phone call yesterday. I was trying to explain what you where telling me to someone but it wasn't close how you told me. I left alot of details out was teying to do other things at the same time while talking with you. All is now lovely sci wonder if sdcp will let me return that pump.
So finally some good news!! For the first time ever my fuel pressure jumped up under boost about 10-15 psi maybe more(gotta focus on the road) usually it would just stay at 58-60 psi even after my hotwire, 255, bap, secondary, bigger fuel rails, return style it just would not do anything it would just stay at 58-60psi. I got around 550 miles on the clutch and let it rip. Boost went up 2psi(smaller pulley) so hitting about 11psi on the D1 and saw my fp gauge go from 58-60psi like it always had no matter what I did to 75+ I think it's finally working like it's supposed to. I need a tune so I dont want to do back to back runs but so far things are looking great. I think my stock line that i replaced may have been the culprit. I need to see where i tossed it to see if I can at least find root cause of the issue this whole time. Feels great!! lets hope it works out but it's looking very good so far..
here is the new setup up. I got rid of the stock lines had someone make me a special fitting for the small orifice that goes to the main feed..
Booooooooooooooo.. Guess I didn't drive it long enough but it happened the other day. Same symptoms like before..Drive around for awhile get on it and 30-45 mins after you been getting on it fuel drops down into the teens. Gonna have to take it to someone I cant figure this one out boys I'm out of ideas.
__________________
Offering products from A&A Superchargers, East Coast Superchargers, Mechman Alternators, Mantic clutches, RPS clutches, Kooks Headers, Lakewood, LG, Brian Tooley Racing, Comp Cams, FAST, ARP, UPP Turbo systems, Wiseco, Callies, K1, MAST Motorsports, Haltech and many more. PM me for details.
Booooooooooooooo.. Guess I didn't drive it long enough but it happened the other day. Same symptoms like before..Drive around for awhile get on it and 30-45 mins after you been getting on it fuel drops down into the teens. Gonna have to take it to someone I cant figure this one out boys I'm out of ideas.
03-31-2014, 07:46 AM
