I know it's been asked before, but I could'nt find the right post so here it is. When hooking up an MP-8, which connects to the rail pressure sensor first? The MP-8 or the rp guage. Also the MP-8 goes into the MAP sensor before the TST correct? Thanks RJ.

 

gauge before the mp-8. If the gauge isn't first, it won't work.

 

actually it's the other way around. The MP-8 has to be plugged in first. I tried the other way and it makes the truck runs like a jalopy ! If it's not first it will send false signals. TS is where I got the info from.

 

My gauge does not work if the mp8 is first.

 

I guess maybe we should watch what years the trucks are, for these types of questions then ??? My truck won't run that way. I also have a Diprocol RP gauge and it does work plugged in second... hmm Probably since he has a 03, it will work like yours.

 

That's interesting. I guess try it one way and if it don't work, do it the other way. It won't actually hurt anything if it doesn't work right the first time.

 

I first had the MAP to the TST then MP-8 then factory wiring and pressure sensor to guage then MP-8 then factory. No worky! Now it's MAP-MP-8-TST-factory. And RP-MP-8-guage-factory. Still no worky. I am going to try RP-guage-MP-8-factory and see if that works (leave MAP the way it is now). It's the only option left.

 

Should rail pressure be any higher at idle with the MP-8? I don't see any difference no matter how it is hooked up. Should the engine sound different at all with the MP-8 turned up? Unhooked TST from rail and unhooked RP guage. MP-8 only, no difference. Am I doing something wrong or could I possibly have gotten a bad box/wiring harness?

 

It's not any different at idle. Hook up the rail gauge by itself and go drive around so you see how it acts. Then hook up just the mp8 with the rail gauge - no tst - and see if you can repeat the results, then turn the mp8 up to about 50% and make sure it's giving you an increase. Then you know how things are reading and you go for the tst and know what to look for.