k/cp unit question

[carsonmx114]

i've got a 951 that's been whipping me for quite a while now and i could use some help. my car started cutting out under boost when my boost controler would open, i eventually found that the wastegate hose had split behind the motor. before i found this i think i managed to damage my k/cp unit because after replacing the hose and testing many different things the car still does the same thing. i'm almost certain the car is in some kind of safe mode and the dme is cutting fuel under boost because the k/cp unit is damaged. i think this because there is no ground signal to the cycling valve under boost conditions. does anyone know the symptoms of a dead k/cp unit? i have a aftermarket boost controler so i'm not using the cycling valve and i have a autothority maf kit also. any help would be appreciated. thanks!

[nize]

what non-stock mods does the car have other than the boost control?

what boost control are you using?

what boost were you running?

[carsonmx114]

i got the car in 96' with a bad head gasket. i had the head polished and flowed while i had it off for a gasket. i wasted the clutch at a track day in 2000 so while i had the trans out i went ahead and pulled the motor to inspect it. two of the cylinders had a couple of small scratches in them so i went with 1st over porsche pistons and new rod and main bearings. this is when i installed the autotority hot wire kit with new dme and k/cp chips. i also installed a sks electronic boost controler. at this point i was running 18psi and the car worked great. last summer the hose at the wastegate broke, so the car would pull like normal down low and as soon as the boost controler opened up it was like you turned off the key. i the process of test runs trying to find the problem i managed to separate my throwout bearing so i was forced to do exploratory surgery. well when i removed the crossover pipe i found the broken hose. while i had the car down this time i had the hybrid 26/27 turbo upgrade done and to my suprise when i got the car back together it still did the same thing. i think i shorted the wires to the cycling valve before i tore up my clutch and now the k/cp unit is offline, sorry this post is so long and i appreciate your response. do you think i'm on the right track?

[nize]

assuming everything else is working properly, with the wastegate hose disconnected, the car should be overboosting.

so it does sound like the klr could be fried. if you open the klr box, check resistors r125 to r128 and see if they appear burned.

[carsonmx114]

thanks! i've got the unit apart now and i did see at least one resistor that had the ceramic burned off, it was right next to another resistor that, judging from the stripes still visible on the ends of the burned one, is the same value. i ohmed them out and they read the same, but they were still in circuit so that's probably not a acurate test. i'll check in the morning and see if they are 125 and 128. have you had any luck replacing these and bringing a klr back from the dead? thank you for your help.

[nize]

it's r125 THROUGH r128. that means;
r125
r126
r127
r128

those are the resistors that most commonly burn out, it doesn't mean that other parts of the circuit won't fail though.

i know two guys who have tried to repair these by replacing the burned out resistors and they never worked. it seems the only way is to replace the whole klr. you can probably find one for sale on rennlist, or buy a rebuilt+tested unit.

i'm curious, and you might have to think back carefully about this. before this issue started, have you ever shut off the ignition (via turning the key) while the car was moving?

has the car ever shut off on its own while moving?

one of the most common (and perhaps the only) way these resistors get fried is through this process.

[carsonmx114]

i don't remember turning the ignition off while the car was moving. i think i shorted the cycling valve wires in the process of testing output voltage with wires run into the car and a test light. my problem started as a broken hose at the wastegate. in retrospect it should have been an easy fix, but i started testing ignition and fuel presure and injector pulse, spark plugs and boost presure. so i think the dme was cutting fuel because of the boost leak to start with, and before i found that problem i managed to fry my klr unit so now the dme is cutting fuel because of the klr problem. i've got a friend in town that just got a 86' 951 also and he's got new chips coming in tommorrow so i told him i would install his chips for him and in the process we are going the plug his klr into my car and see if it fixes the problem.

[nize]

sounds like a plan. let us know how it works out.

[carsonmx114]

update, i found the probem. it was a burned trace in the DME unit not the klr unit. i put my friends klr in with my chip in it and it did the same thing. i put my chip in his dme and all the way to the redline without so much as a skip. thank you all for your help!

[nize]

glad to hear.

you wouldn't happen to know which specific trace and/or have photographs of it for future reference would you ?

[carsonmx114]

it was a large trace under the bottom board right under the plug socket. it was very noticable. there is a small trace right at the edge of the board and the one that burned was the next trace in. thanks again for your help.