06-5.7 mpi mag starts,, stalls, starts stalls. ran fine last fall

S

svb165

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• Saturday at 6:57 AM

• #1

I just replaced the fuel pump and regulator and still the same. 43 lbs while it primes 39ish sitting. could this be from a bad IAC valve valve??

 

alldodge

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• Saturday at 7:06 AM

• #2

If you can keep it running by giving it a slight bit of throttle, than most likely it is the IAC. The IAC might need cleaning

 

S

svb165

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• Saturday at 7:11 AM

• #3

I can ,, somewhat. if I pump it some it will rev up, then it wants to quit again if I let off the throttle. or it will poof pop and want to quit..

 

alldodge

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• Saturday at 7:31 AM

• #4

What's your serial number?

 

S

svb165

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• Saturday at 7:42 AM

• #5

OW359972 as I said it ran great all last season. it did start hard the last couple times I had it out but that's it. this is why I went and did the fuel pump and regulator. this is a cool fuel system also.

 

alldodge

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• Saturday at 7:52 AM

• #6

Thanks
Your motor can have a mechanical or digital throttle body, Ill assume it's mechanical and there is a cable connected to the TB.

https://www.mercruiserparts.com/bam/subassemblydetail/43949004/28193894

The IAC (item 16) has 2 hoses connected to it. Remove the IAC and look inside, does it need cleaning, are the hoses tight? Next turn key ON to see if it moves

 

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svb165

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• Saturday at 7:59 AM

• #7

yes it is mechanical although the parts look up pages I use(merc) shows a second fuel pump near the filter, for serial # over 330000 this does not have one. just the cool fuel pump.

 

alldodge

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• Saturday at 8:32 AM

• #8

The boost fuel pump was an add on when Merc was trying to fix the vapor lock issue

 

S

svb165

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• Saturday at 8:40 AM

• #9

I just removed the IAC module, its pretty spotless inside. when I turn the key on while its plugged in holding the valve, it does NOT move at all. there iS power getting to it. this motor has about 100 hrs at most

 

alldodge

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• Saturday at 8:51 AM

• #10

Looks like it's bad, when key is turned ON it should move in/out one time and stop. Only way to make 100% sure is with a scanner

Part number 8M0181068

 

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svb165

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• Saturday at 9:03 AM

• #11

Thanks that's what I was reading also. there's no movement tho.. what's your take on using the Ford replacement module??

 

alldodge

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• Saturday at 9:05 AM

• #12

Many have used the Ford IAC and they have worked fine, I've just don't have first hand knowledge

 

alldodge

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• Saturday at 9:08 AM

• #13

The old part number was 862998 and Sierra makes one
https://www.amazon.com/DEF-Control-...ff-9597-ee81ef051b0e&pd_rd_i=B07RXQBV4Y&psc=1

 

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svb165

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• Saturday at 9:14 AM

• #14

Thank you for the link. I'm tryyyying to make it to Boston for "sail 250" this weekend so I'm trying the Ford part today. from all I've read its identical.
? much like the fuel volume control valve the NR-1 is used in many applications and not 200$ thru auto parts dealers.

 

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svb165

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• Saturday at 12:54 PM

• #15

Yes I need to have it scanned for sure. I replaced the iac module and it iis better. it still stalls out and needed to be re started and revved a little, then it tryyys to idle. I got my hand near the open intake and cut a little air entering the TB, it stalled immediately. it did idle a couple of times for a minute, after a little rev/clear up (60sec) then stalled out again. done for today/
I found the oil line to the outdrive is in baaad shape and now leaking,,,the rubber back there is all original,,,,,, so its time change the bellows . oil line, water hose and both trim switches since I see cracked insulator on the position sender.

 

alldodge

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• Saturday at 1:57 PM

• #16

In post 6 link
Look at item 6 the IAC muffler and item 8
Pull the muffler out (it's foam) and see if it needs cleaned. Also check the hose and fitting that it's clean

 

alldodge

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• Saturday at 2:00 PM

• #17

Does the fuel pressure stay close to 40 when motor is started and when it's stalling?

 

S

svb165

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• Saturday at 3:15 PM

• #18

yes the filter WAS pretty dirty even down into it a bit. I pulled it. as far as pressure maintaining 40 I will check that again tomorrow. I left the gauge on for a couple of hours today while I was running errands and it dropped to about 31 from 38. that didn't seem terrible for 2 plus hrs ?

and I need to check the vaccume line from the cooler / reg to the manifold as well

 

alldodge

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• Saturday at 3:24 PM

• #19

No issue with it dropping some over time, just trying to rule out that we're not loosing power to the pump after it starts

 

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cwella

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• Yesterday at 2:44 PM

• #20

svb165 said:

I just replaced the fuel pump and regulator and still the same. 43 lbs while it primes 39ish sitting. could this be from a bad IAC valve valve??

Click to expand...

No, the IAC valve won’t cause low or incorrect fuel pressure. It only controls idle air. Your 43 psi prime and 39 psi hold look normal. Check for vacuum leaks, MAF/MAP issues, injector problems, or regulator vacuum line issues instead.