575 sci acting up
 

I have a low hours 575sci in my Scarab 26 and just recently it has started to cough when I throttle up, then when I return to idle it revs up and down a few times on its own and then dies. My mechanic is checking the fuel pressure but were not sure what it should be on the 575. Does anybody have any ideas as to what the problem is or what the fuel pressure is on these? Thanks for any help!!!

I believe it should be 35-38 pounds on idle.....check the pressure its extremely important on these motors or anything with a supercharger (I learned it the hard way)....I melted two pistons due to a bad pump and no fuel preesure guage....

They have 28 to 30 PSI @ Idle.
Have you checked the IAC?

35-38 is way too high. Don't forget these are still TBI units. That kind on fuel pressure will hold the injectors shut. I was told 26 psi at idle w/vac disconnected. Or 28-30 psi wot under load. Mine studdeded and misfired when my fuel pressure was spiking up at 33 psi wot. Good luck and keep up posted Mike

I say IAC

you could be right, I have to check with Lupe from Tnt again, him and my builder Steve from Progressive racing engines were in contact and maybe I heard wrong...........

checked today with my builder and yes 28-30 is correct......

It is easy to put a mechanical gauge in line to measure fuel pressure.
I'll bet it is the IAC. Set it @ 14-16 and it should run great.

Also doubt this is the cause - but DO check the timing as well.

575sci question
 

I'm having the same symptoms with my 575 in a 27 baja. Did you figure out what the problem was? I've had a fuel pressure gauge on my dash since I installed the used motor. It always reads 28 at idle and 26-28 at full throttle. My fuel pressure never changes when this problem occurs. I pulled the IAC motors and checked them with a ohm meter like the 575 service manual states. They both check out perfect. Any help would be appreciated. I just ordered a MAP sensor because it did not check out on both readings. One was fine 1.4Kohms, the other .50 ohms was reading 4.5mohms. I have a mercury scan tool and it shows no codes.

Thanks,

Dale

What is the IAC value @ idle from the scan tool?
Should be 15 or REAL close.