2007 8.1 272 starting issue

[Arabian67]

Anyone experience this issue?, boat started and soon as i left the dock it stalled- would restart only to die again. I took my fuel pumps off and brought them to my friend who is a boat mechanic down in my home town in Ma and he tested them out and both the high and low were fine - no paint clog issues etc. I reinstalled and it started up and ran for a bit then stalled out again. Now it turns over but doesn't fire up, i noticed when you keyed the ignition to on position i didn't hear the fuel pump priming the injectors like it use to, it would prime them when i keyed it to the left (accessory) but still no fire up. I figured the ignition switch was bad so i replaced it but still had the same issue with it working backwards in my opinion, I also replaced the two relays and put a meter on the fuel pump power supply and it would only turn hot for a second then nothing. I am on an island so its a not easy to get the boat to a Cobalt dealership and the local mechanic is weeks out with schedule work -any help would be greatly appreciated!

[Big Block Power]

Sounds like you just need a new iac valve

[Arabian67]

Would this be the cause of my fuel pump not priming and not firing up at all?
TY

[AsLan7]

Sounds like you just need a new iac valve

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+1...although it is tough for folks on forums to diagnose from the internet without being in the boat or hooked up to your ECU to read codes. The benefit is sometimes a quick and easy fix. The downside is you can start going down rabbit holes throwing money at things which may be working perfectly fine. ...Just be aware of the possible pitfalls.

It does sound like an IAC valve IMHO as an amateur garage mechanic based upon your description. They’re normally 35-50 bucks on Amazon. You can replace it yourself.
An Idle air control valve allows air to enter the manifold while idling...thus the name. If the plunger is corroded, dirty, or dusty causing it to jam then your engine won't start or idle properly (either too high or not at all).
Many times you can just clean the plunger with CRC. If the servo motor is bad then it’s time to replace. Again, they are about 50 bucks give or take.

A couple of vids which may help you...


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(IAC at the 2 minute mark....)
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Rick I can't remember if your engine is a VP or Merc. This vid is from a 5.0 Merc MPI on a Sea Ray but the principle is the same...
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[Big Block Power]

No the iac is totally diff then the fuel pump prime. Pretty sure you still have a bad iac. The pictures A7 is showing you is a Ford style. You could also have the gm style. I keep spare on my boat. I would recheck the ign cycle to see if the prime started working. If you were just messing around with the key a few times the ecu might have stored priming it. If it still doesn't work your ecu might have taken a crap.

[Arabian67]

Well it sounds like it will need to be towed from the island to a certified Volvo Penta mechanic : ( I did hear a clung when key switch was on the on position coming from the ecu , hopefully it's still good as it looks like a $1800 part.

[Big Block Power]

It's Prob a mefi4 ecu. You can find them cheaper if you want. But yes you may want your dealer to handle this one.

[Arabian67]

Update , I brought my boat to my local marine that works on VP - they checked it over for 5 hrs and couldn't find an answer ,they are reporting no spark . They also don't have the equipment to check the ecu codes and told me without spark you get read codes? Doesn't sound right to me. Local Cobalt dealer 4 weeks out to get in - basically season over.

[Big Block Power]

Update , I brought my boat to my local marine that works on VP - they checked it over for 5 hrs and couldn't find an answer ,they are reporting no spark . They also don't have the equipment to check the ecu codes and told me without spark you get read codes? Doesn't sound right to me. Local Cobalt dealer 4 weeks out to get in - basically season over.

Well I can't resist. They don't diag VP then. They are parts replacers. If they can't check a code they shouldn't be in the business. Sorry even I can check a code. No spark and 5 hours. No comment. Ecu, crank sensor, cam sensor so common things. Wiring, grds. No fuel pump prime. Could be a relay? But really? Sorry man

[AsLan7]

Update , I brought my boat to my local marine that works on VP - they checked it over for 5 hrs and couldn't find an answer ,they are reporting no spark . They also don't have the equipment to check the ecu codes and told me without spark you get read codes? Doesn't sound right to me. Local Cobalt dealer 4 weeks out to get in - basically season over.

Well I can't resist. They don't diag VP then. They are parts replacers. If they can't check a code they shouldn't be in the business. Sorry even I can check a code. No spark and 5 hours. No comment. Ecu, crank sensor, cam sensor so common things. Wiring, grds. No fuel pump prime. Could be a relay? But really? Sorry man

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+1

[Arabian67]

How do I get a wiring diagram for this boat stat?

[Freddie]

I am a month late, but just saw this. I had the same problem, mine was the wiring harness connector right at the high pressure pump. It had some corrosion and would not always make contact. I replaced both sides of the connector, problem solved. Both pumps tested OK off the boat. I checked the pumps for the paint issue, none found. I did clean the screen in the regulator on the fuel rail, but no change. I found it by using a fuel pressure gauge at the test port by the fuel injector rail on top of the engine. Low pressure pump tested good at the lower end of the pump. It may be something else, but I would suggest testing pressure at both locations to verify if it has fuel pressure loss. I was about to change both relays or replace the pumps when I found it. Hard to diagnose without a fuel pressure test gauge.

[AsLan7]

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Thanks for posting your issue Freddie. It may help someone else on this forum.

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