2003 hamerhead 375 not running under load

[Smokinjo]

What part of Tennessee are you in? Indmar is located 25 mins from MEMPHIS in Millington TN. If you are here in West Tn, I would contact them directly.

[Evans511]

We'll broke down and took it to the dealer, it did not show any codes,they talked to indmar and decided the injectors were not throwing the fuel due to the ecm, they want 1500 dollars for the computer a mefi 4 is about 350 they say it's a mefi 4a anyone gone through this?

[justgary]

My BS flag is at full staff. You can check the injector width with an oscilloscope. You don't talk to someone and decide it, you measure it and know that it happened.

[Evans511]

The boat does not throw any codes on the hose, at the lake it goes into limp mode. Indmar said it was not getting enough fuel, keep in mind this is a 383 long block that they put the 375 componts on indmar says they can flash the ecu to give it more fuel

[Evans511]

Just gray, what is BS full staff?

[toddthelineman]

What he means is he thinks they are full of bs.

[Evans511]

I agree the dealers will blow smoke all day ! I have worked on engines all my life but I have worked on this one sense may, no one wants to man up on putting this long block in and jacking it up! I would be better off if I pulled it out and went from scratch.

[SmoothWaterMan]

Evans,

We have spoken, and it sounds like you took it in and they said the same thing.

I believe it's an issue with the fuel delivery system and ECM designed for a 3-bar 350HH now supplying an air/fuel mixture to a 383 block that is pumping way more air. It needs a fuel delivery system and ECM designed and calibrated for the 383.

Who ever replaced the original 350 block with a new 383 block, and remounted the original external components, did not think through their decision.

Peter

Edited September 24, 2014 by SmoothWaterMan

[Woodski]

@Evans: Could there be a fuel pressure issue also restricting the fuel delivery on top of the 10% displacement fuel demand difference compounding the problem?

[Evans511]

Thanks Peter, you have guided me in the right direction, there is definitely a fuel issue, new ecu on the way, engine going into limp mode due to fuel intake, hopefully the injectors and fuel rails will not have to be replaced

[Evans511]

Woodski, the fuel psi at the rail is 40-45 psi, that is for a three bar reg a 3.5 and 4 bar regulator is for an 8.1 engine which puts out about 65 psi, I just need to figure out if my fuel delivery is right I dont know if the diacom will show it or not.

[SmoothWaterMan]

Evans, the older fuel setup was 3 bar, where the newer setup is 4 bar. The 383 was not offered with a 3 bar setup, so the ECM calibration in my opinion is still not going to deliver the proper fuel mixture, as it will be shooting 40 psi per injector pulse rather than 60 psi per injector pulse.

Diacom will not show air/fuel mixture, fuel pressure, or anything related to Stoichiometric. Back then there were no cats and no sensors showing any part of that information.

pb.

[Woodski]

@Smoothwaterman: For my curiosity, what would be the trigger that indicates it is running lean thus requesting limp mode? It would not have any EGT's either?

[Nitrousbird]

@Smoothwaterman: For my curiosity, what would be the trigger that indicates it is running lean thus requesting limp mode? It would not have any EGT's either?

Not sure how you are going to get EGT's in a water cooled exhaust. I don't think any GM gas motor has an EGT sensor (nor do many production motors in general).

My question is would it have worked had he simply swapped a 3-bar (43.5psi) regulator back in? It wouldn't have ran perfectly, but should have at least ran, though may have been a little lean across the board. Also, a 4 bar regulator (58psi) on a motor tuned for 43psi should have resulted in a rich condition, as there would have been more fuel than intended sprayed into the combustion chamber per injector pulse width.

I'm guessing here, but the reason they went to the higher pressure regulator is that they didn't want to use different fuel injectors from the standard GEN-I SBC offering and the fuel needs for the 383 was maxing out the fuel injectors at high RPM/high load situations, so it was cheaper to go with a higher pressure than larger fuel injectors.

But instead of an ECU swap, the MEFI-4 could have been re-flashed with a new tune and resolved the issue as well.

[oldjeep]

@Smoothwaterman: For my curiosity, what would be the trigger that indicates it is running lean thus requesting limp mode? It would not have any EGT's either?

Isn't it going to knock like crazy if it is running lean and also start heating up due to the lean condition making it detonate and knock even more?

[Evans511]

I would think it would knock also buy its not, just backfiring at about 2300 rpm

[oldjeep]

I would think it would knock also buy its not, just backfiring at about 2300 rpm

You likely wouldn't hear a knock, the knock sensors would keep telling the ecm to try to keep retarding the timing

[justgary]

Isn't it going to knock like crazy if it is running lean and also start heating up due to the lean condition making it detonate and knock even more?

You likely wouldn't hear a knock, the knock sensors would keep telling the ecm to try to keep retarding the timing

I think that is a great way for the ECM know to go into limp mode. Once it backs the timing off all the way to base and the knocks are still coming in, it could compare RPM with throttle setting and decide to limp.

[Evans511]

Justgary, do you think the 375 intake and injectors will ok with the 383 if the emc is tuned right?

[SmoothWaterMan]

- The engine has the 3-bar (low fuel pressure) on it. He needs more fuel, such as the 4-bar regulator, and maybe larger fuel lines (we moved from 3/8" to 1/2" back then) and possibly injectors, along with the ECM.

- The ECM has nothing to tell it that the engine is running lean. It simply runs out of fuel once it gets extremely lean.

- If it knocks, it will simply detune the timing and bleed off any horsepower that should be there. If it bleeds off excessively it will probably set a code.

pb

[Evans511]

Malibu used 1/2" fuel line from 2003 through 2006 the 383 was introduced in 2005, will check the size tomarrow.

[justgary]

Peter speaks sooth. He has the knowledge and experience with this engine. You have a 383 with 375 parts. Which do you want it to be?

[Evans511]

Boat is fixed! I would like to thank everyone that has helped me over the last few weeks! I would also like to give a extra thanks to Peter at smooth water sports for all you help! Thanks Crew!

[justgary]

What did you end up doing to fix it?

[Evans511]

Engine was not getting enough fuel just like Peter said, new ecm programed from indmar. Any idea which prop I need to get 50mph? We are bare footers only or I would not be going through all this trouble with the hammerhead.