600SCI Gurus Needed -- No BOOST
 

I was trying to help a buddy with a problem he's having. A little background... 2008 600SCI with Whipple kits. They have had the IAC circuit repaired. Motor ran fine but suddenly after a restart failed to build boost. The motor on cold start will NOT go into high idle/enrichment and sounds weak. It is firing all cylinders, and there are no codes. It will idle all day without issue, albeit it has no "crispness". Boost gauge shows vacuum at idle and when rev'd will get to no vacuum and build absolutely zero boost as it falls on its face. So far my friend has swapped IAC, TPS, MAP, IATs, ECUs, and pretty much anything else that will go motor to motor without help. He has also swapped the boost relief solenoid (not sure if that's the proper term) to no avail. Any ideas?

[QUOTE=Jpzaluski;4177603]I was trying to help a buddy with a problem he's having. A little background... 2008 600SCI with Whipple kits. They have had the IAC circuit repaired. Motor ran fine but suddenly after a restart failed to build boost. The motor on cold start will NOT go into high idle/enrichment and sounds weak. It is firing all cylinders, and there are no codes. It will idle all day without issue, albeit it has no "crispness". Boost gauge shows vacuum at idle and when rev'd will get to no vacuum and build absolutely zero boost as it falls on its face. So far my friend has swapped IAC, TPS, MAP, IATs, ECUs, and pretty much anything else that will go motor to motor without help. He has also swapped the boost relief solenoid (not sure if that's the proper term) to no avail. Any ideas?[/QUO

i believe the whipple that is on the motor has a bypass valve,,now what controls it might be temperature related..

Have you pulled the belt and checked to see if the snout shaft has broke? Just happened to me this weekend on a 4.0 Liter

With no codes and no boost, I'd be looking into the blower. Smartcraft keeps an eye on pretty much everything else.

Ran a 700 one time with the blower belt off ( due to a seized blower ) and it idled low/weak as you have described.

replace the boost control valve

Boost control valve or the fuse that controls it on the back of the engine.

As mentioned, check the snout of the blower and the coupler that drives the snout. They have a tendency to fail.
Eddie

Thanks for all the info guys I appreciate it. I had already changed the boost control valve and other parts exchanged from other motor. Brett I just got done checking fuse. It was bad. I pulled the other motors same fuse and it created the identical problem so I know I am working on the correct circuit. Even with the boost control valve unplugged it still blows the fuse when started. I pulled the fuse and check both fuse plug in terminals with an ohm meter to ground and got no reading. It has 14volt on the red wire side fuse plug when running nothing on the red wire with blue stripe of course with no fuse installed. There must be a short to another wire on the red with blue stripe that goes to the boost control plug or something. Looks like same wire from fuse to boost control plug but travels into wiring harness loom so I am not sure. Do you know if that wire goes through another control or sensor before going to boost control? I guess its time to source a wiring diagram to check circuit route on red with blue stripe wire maybe? Again thanks for everyone's help and Jason for starting this thread. Any other suggestions are welcome. There is no one in my area locally that work on these type of engines. Also I pulled both super charger belts and both blowers spin and feel the same with no noise, no play in shafts or binding etc. Supposedly the only have 100 hrs on them.

you may want to give whipple a call,,they might have a solution for you..

If I cannot get it fixed I will call Dustin sooner or later he and mercury HP put me on the boost control valve. He is a busy guy to try and get a hold of and right now is not the time to be calling him with what happen at LOTO. Now that I know its blowing fuses I can call back Merc HP back and run that by them. Thanks everyone for your help and comments. Any more info is appreciated.

Boater I can have you talk to one of our techs tomorrow. My cell number is on our website. Dustin Whipple has his hands full. If we can help. We will

Brett

Performance Boat Center

Very nice of you!

Thanks Brett. I may have to do that. I am trying to get my hands on a wiring diagram for motor. Called Merc HP today. Tech said he had not heard of that problem before and did not have a wiring diagram there. Not much help. I just picked up a service manual tonight and will see If there is a diagram in it. If I cannot make any progress on it I will give you a call next week after the holiday. Again thanks for the offer I know you guys are very busy.

Check the resistance across the leads of your IAC, it is probably shorted which will cause the fuse to keep blowing. The IAC and boost control valve are on the same fuse so this could be the source of your low boost issue. Be careful swapping parts because a failed IAC (very common on these engines) can damage the ECU so check both IACs if you've been swapping parts back and forth. I recommend installing a 1 AMP fuse inline with the hot lead of your IAC to prevent damage to the ECU. Dustin is the best person to talk to and has been really helpful and responsive on this issue with me in the past but as we all know this is bad timing. R.I.P. Mike Fiore.

If you find that your ECU was damaged by the failed IAC then your only options are to have Dustin repair it or purchase a new one from Mercury$.

Brett, I stayed at Red Head Yacht Club for the Shootout and attended your party on Thursday night. You guys are awesome and your facility is fantastic!

GF?

Thanks for the info GF? I will compare the ohms reading between the two IAC . That is the info I was trying to get out of Merc to determine what else was in the circuit. The IAC was the only thing I did not swap out. Dustin had done an IAC repair on the other motor ECU in 2010 he wrote it on the back of the Starboard motor ECU. You may have solved my problem. Man I really appreciate you pointing that out. Starboard motor is still running as normal so hopefully I have not damaged anything. I will check it out in the morning. Thank you!

Where exactly is that fuse ??for me to check - i have the same problem on a 700sci .tks

Rear of starboard side valve cover on top, attached to black bracket. 2 black plastic fuse holders side by side . Says fuse on top of cover. Its the one closest to the header. Has four fuses in it. It is the first yellow 20 amp facing rear of motor on right of fuse block. Has red/green stripe wire and red with small blue stripe wire connected to fuse female sockets.
Fuse pack C27 - Position CD- powers IAC, boost by-pass, Driver power

thank you sir !

Makes perfect sense. If that fuse is taking out the boost control AND the IAC then you're not going to get the idle enrichment/high idle as the IAC opening is what's needed to get the motor idled up

Thanks everyone for your help and comments. Just compared IAC resistance readings. I have a bad IAC. Good IAC read twelve on digital ohm meter with a tone. Bad IAC read 290 which is high resistance and will cause a higher amp draw and blow fuse. I have one on order will be here tomorrow. I will let you know what happens after install. Hopefully I did not damage anything else and it fixes problem. This problem did not trip a code as stated that it would in other thread about IAC ECU repair. Again thank you all and Brett your offer was very over the top and appreciated.

You can buy the IAC at just about any car parts store. AC Delco part number AC423. Same exact part.

GF?

Thank you GF? Your posts have moved my progress forward in the right direction along with other posts and hopefully other members in the future with this problem.