Hey guys,

I am trying to diagnose an issue with my KB boost a pump. After searching the forum here, I read how to test voltage etc etc....but what I am finding stumps me.

All tests with car idling.

Idle voltage at the fuel pump plug(down stream of BAP)
13.00 (warm)

Next I jumped the wires at the pressure switch with a fuse so it "should" be activating the BAP thus raising voltage to 16 ish and raising fuel pressure. This is where it gets weird. I tested this thing atleast 20 times.... Most of the time I see no increase in voltage or FP. Then every down and then, the voltage will raise to 14.5v and I can hear a slight slight hum from the BAP. No noticeable jump in FP..... This was very sporatic and inconsistant. Then occassionally, I could keep the DVM probes on the fuel pump wires and watch them for a while....if I shut the engine off and restart it a few mins later, I only twice saw the voltage jump to 16.56v, I could really hear the BAP humming and the FP jumped to about 62 psi or so at idle. It would only stay like this for a few seconds, then it drop back to 13.0v and 58 psi, with no audible humming from the BAP....I only saw this twice the whole day of testing.

So to me, it seems like whatever tells the BAP box to kick up voltage is not working consistantly.. All tests were with the pressure switch either disconnected or jumped so that takes it out of the mix. The gain **** on the controller is wide open... Is there something else in the BAP system that tells the BAP box to ramp the voltage? Is the BAP box just going awol? I did check the ground wire for the BAP box. Its grounding in the fender well where the factory ground strap to the filler neck is connected. I hit it with a wire wheel but it made no difference.

This thing is inconsistant at best but its definitely not working. The whole thing may have 2000 miles on it...

Any help is greatly appreciated!

 

Sounds like your BAP is flakey.

Might be the gain controller is int or a bad connection.

With the switch jumped you should be able to vary the output up to 20 volts.

 

Thanks.... Yeah I think the BAP is flaking..... From the schmematics, there can only be a problem with the box or the gain control....I cant see where the problem could be anywhere else.... There is only 4 wire connections and they are all soldered well.....


Anyone else? Surely some of you pro-builders that use a lot of KABs have seen screwy problems with them before?

 

Just a comment: You should not see a change in fuel pressure when/if the pump receives increased voltage. The regulator should do its job in maintaining the pressure.

 

If the **** is cranked up all the way and you are not seeing a jump in voltage, I would say the BAP is toast.

 

Not true at all.

 

Interesting. Why wouldn't it?

 

Under boost I could turn my **** on BAP box and watch my pressure go up and down instantly with more/less voltage from BAP. This showed fuel pressure was instantly bumped up with more volts to the pump itself which it is suppose to do. This was only with 550 rwhp also which is about the limit for a BAP. Now at 752 rwhp I of course had to get rid of the BAP which was the smartest thing I ever did and should have done even with only 550 rwhp..

I just left the **** on to test the BAP occasionally to see if it was actually working. I eventually soldered ends together and got rid of the **** tho cause iot got hit once and I didnt know it..

 

KB told me to try removing the gain **** box all together. I'm just going to cut the cable and solder to the two wires together bypassing the gain control and see if it makes it consistant. Other wise its the BAP box itself crapping...

 

We solder them together on our installs as well. Leaves no chance of accidentally turning the ****...

 

Andy told me one time that he actually has to hide all the ***** in the shop because you like turning them so much!