just installed p600b and having tuning questions!

[RI lx]

The line from the side of the FMU should have a femail input on the end, and conect to the fuel rail (FMU INPUT), the line from the bottom of the FMU should have a male end and go to the frame/return line (FMU OUTPUT).


Here's what the install manuel says:

1. Conect the supplied high presure line to the FMU, ensuring that the line with a female fitting conects the the SIDE of the FMU, while the line with a male fitting conects to the BOTTOM of the FMU.


You can see how yours is conected, and most likely swap them at the FMU, since the ends only fit the car one way.

[K.C.90gt]

im pretty sure thats the way its hooked up.. but how do I know if i connected those lines to the right one? there are two lines on the intake and two on the frame..

here is the best pic i have of the fmu.. its not good but i will definetly check it out once I get home

http://images.cardomain.com/member_i...79_15_full.jpg

[RI lx]

The other two are the supply lines. JUst reverse the lines on the FMU itself, ignore all other conections. The FMU has 1 vacumn lines, and two fuel lines. Its plumbed into the return line.

The guy who sold it to you probably had the lines off the FMU when he took it off his car, and put them back on wrong.

[WA2FAST]

Yes. Check those lines... hopefully that is the problem (I'm sure it will end up being something simple to fix)... also, what about your gauge?... I have the same gauge, accurate as hell... but if you hook the 3 wires up wrong on the back, the sender will either fry the gauge or make it work all wierd as yours is doing.

[Nasty Notch]

What's the word on this fmu problem?? It has got to be the problem. If not, it's the guage and that is easily checked by just throwing on a mechanical guage right there at the shrader valve. If that guage reads 100psi, then you know the electirc one is good.

[K.C.90gt]

ok I checked out the fmu last night.. the line on the side of the fmu was hooked up on the return line on the lower intake and the line on the bottom was hooked up to the return line on the frame.. the guy had upgraded steel braided fuel lines on the fmu too that he never took off of the fmu when he took it off his car...
.. so the fmu IS hooked up right.. FOR SURE

as far as the fp gauge being wrong.. it could be but I really think its accurate because the car is running super rich and I can smell the fuel while its running and blowing out the exhaust.. it wont stay running while idleing because its getting too flooded.. plus I checked the brand new plugs and they are pitch black.. also there is only one way to plug in the wire harness on the back of the gauge.. then a positive and ground for the bulb.. so i highly doubt the gauge is hooked up wrong...

If the o-ring on the AFPR somehow fell off than do you think it would cause this problem?? because the guy I bought it off of who helped me install it said he found what looked like a fpr o-ring in his driveway.. it could've just fallen off of the old stock one though.. i still have to check it out..

anyway I'm going to take the fmu off completely and see if its that first and ifs not than I'll take off the AFPR... hopefully its one of those causing this problem or else I wouldn't have a clue what to check after that...

thanks again everyone and hopefully I can get this thing worked out so I can drive this thing!! its killing me not being able to :(

[WA2FAST]

Originally posted by WA2FAST
In reply to your last attempts..


Disconnecting the fmu vacume line takes out the possibility that the line could have been hooked up wrong in any way.

Adjusting the regulator would be the next step... you said you adjusted it all of the way out... did you try the other way?

Rotating the MAF has nothing to do with fuel pressure... fuel pressure is strictly mechanical.

Again, fuel pressure is mechanical. Resetting the computer would do nothing.

You having the FMU hooked up to the vacume tree is just fine.

Kinks in the vacume line wouldn't make it sit at 100psi. all of the time, but always good to check that anyway.



I'm still trying to figure out why you would "hammer it" when it is working as odd as it is, but whatever... either way, it sounds to me that something is hooked up backwards or simply malfunctioning.

The way that the regulator works is it lets a certain amount of fuel through the return line back into the tank and that is what creates the pressure. The more you press the accellerator, the less vacume there is in the intake no matter weather it is forced or naturally aspirated. The less vacume present in the intake, the more "pinched" the return line to the tank becomes... causing the fp to go up. Fuel pressure regulators only work off of vacume (except for special "boost sensative" regulators)... and that is where FMU's come in. They aren't effected by vacume at all... only by boost (they work exactly the same, just opposite eachother). So when pressure is present, it respectively "pinches" the fuel line even more. That is why FMU hooks up to the return line for the fuel. It restricts fuel flow back into the tank even more under boost to up the fuel pressure above what the regulator can do.

I don't think it is possible to accidentaly hook the FMU to the send line from the tank, or if that would even effect it how it is, but that is something to look at. I beleive the send and return use different size connectors anyway to eliminate that possibility, but it's worth looking at.

I don't think it is possible to install a regulator wrong either, I am pretty sure they only install one way, but that is something else to look at.

My first guess would be that something with either the fmu or especially the regulator is screwed up. It sounds to me like the regulator for some reason is working backwards from what it should be.

To troubleshoot which one is the problem... removing the FMU from the fuel line will tell you right away which one it is. That would be my first mode of troubleshooting.

Please keep us updated as to what you find out.

Just like I said before... do these things to troubleshoot. Also, if you KNOW that there is something not right and your car isn't running right (missing O-Ring)... fix it. I don't think that would cause anything like this, but you never know. If there are known missing parts or things that are not right and you are having problems... first things first, fix what you KNOW is wrong (1st rule of troubleshooting anything) then go from there to further troubleshoot as neccessary. Do what I said above and you will have troubleshot everything.

P.S. I didn't realize that your fuel pressure gauge has a plug... mine doesn't. I know that I got it when it first came out, so they might have revised it, but I have 3 wires with eyelettes on the harness (gauge side) and 3 studs/wahsers/nuts that they go on. So it is very possible with mine to hook it up wrong. On the control box side of it... there are a bunch of different screw-pots that could easily be hooked up wrong too.

[K.C.90gt]

I agree that I should fix something that I know is wrong but thing is I don't know if the o-ring fell off or anything... I really doubt it and I'm almost positive that the o-ring was still on the new one when I installed it.. Im about 95% sure it had the o-ring on it.. like i said its most likely the one off the stock fpr or an o-ring to something else.. anyway I pretty sure I have the newest model of that gauge because the shop I got it from said they just got it in and I read from a few others who bought that gauge earlier and they said that they hooked up different.. It was real easy with mine though.. all I had to do was plug in a wire harness into the sending unit and into the back of the gauge.. also the a-pillar doesn't use double sided tape anymore either.. it came with black plastic rivets that you just drill a small hole for in each corner.. works out pretty good..

thanks for all your help too way2fast.. I'll do what you said to troubleshoot and keep you guys informed on whats going on.. HOPEFULLY I'll find the problem soon... PEACE

[K.C.90gt]

ok PROBLEM IS SOLVED!!.. I took off the fmu and bingo! fuel pressure dropped right to 38psi while idleing and vacuum off..
the fmu must be bad or something but i think Ill run without it anyway since I have 36lbs inj and 255lph intank..
whats a good base fuel pressure to run with 12 or so lbs of boost with the setup I have?? right now its at 40psi w/vacuum off... is that about good?

Thanks for your help!

[WA2FAST]

More than likely you are going to need more injector (#42) to run that boost with no FMU, but you might be able to get away with it... the ONLY way to tell is to throw it on a dyno with a wideband a/f and see what it is... otherwise you are playing a mean guessing game that could end up costing you thousands of dollars. Was the FMU hooked up backwards? Did you try it the other way to see?

[K.C.90gt]

the fmu was definitely hooked up the right way... how much do they cost to rebuild anyway? Its the fmu that comes with the kit from ATI...

So far I haven't heard any detonation but I also haven't run it real hard.. only up to like 4800 rpm or so because I still need to get rev limiter modules for my msd 6al... you don't think 36 lbs injectors are enough? I'm only seeing around 10-12lbs of boost right now... but than again I haven't gone past 5000rpms yet either so who knows...

another thing is it costs $500 out the door for a dyno tune at my local speed shop... and I just dont have that money for that right now...

[SnakeIs]

I don't think the 36's will be enough without the FMU either, it will be really close if they are. But to be safe and go without the dyno tune you will need 42's. if you are seeing 12psi of boost at just 4800-5000 then at 6000 you will probably see 13-14+ so you will most likely need more injector. I wish I could get over 10psi out of my P600!

PS I have a perfect ATI adjustable FMU that I'll let you have cheap if you want it. Just email me Racin4ds@yahoo.com

[WA2FAST]

Same here (about the FMU)

[K.C.90gt]

well actually I have only seen around 10psi from what my passengers have said.. I am too busy watching the rpms and road to have looked at the gauges yet.. but like I said I have to push it a little more as soon as I get those rev limiters put in.. dont want to chance over revving the motor & supercharger...

Im going to see how it goes without the fmu for a while until I get to really test it out at the track.. but If I decide to go with a fmu than I might buy one of your guys...

by the way SnakeI's, how do you like that dss pro bullet?? because I was thinking about getting that as soon as more money comes around my way...

another question.. The pulley on the blower is about 2-3/4" and the crank is stock size.. supposed to put out 17psi before IC and 14 after... should I put a bigger pulley on the blower to lower boost a little? how can you tell if the blower belt is slipping? will it make a noise or boost jump up and down or something??

Thanks again!!

[SnakeIs]

I love the DSS! I have built a ton of motors and for a mail order short block, it was one of the nicest, well built pieces I have ever seen. It was very clean and everything fit perfect. I just bolted my oil pan and heads and stuff on and it all went together great. The motor has about 10K on it and hasn't had a single problem with daily beatings, it is a daily driver and has been blown since the install.