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No high end power after HVS change


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2010 Indmar 5.7L GM MEFI 5a on Axis A20

Got service required msg - turned out to be the CAM sensor on the HVS.  The plastic body of the HVS wasn't in great shape with the screw holes worn out so decided to replace the whole HVS.  

My mechanic fitted it.  Found we had no power above 2500rpm and a knocking or detonation noise every 5 to 10 seconds.

I bought the Diacom software and set the Cam Angle to 705 degrees as per the manual - same problem.

Worked with our mechanic to take the HVS back out and re-install it ensuring we had top dead centre on C1 before installing - connected water - run it at 1200rpm and set cam angle to 705..  Back on lake - same problem.

Next, I changed the leads (spark plugs are new this season) - the lead from the coil was a bit shot with part of the mental connector missing I noticed when doing this leads change so I was hoping I'd found the problem.   Back out to test - NOPE - same problem.  empty boat, no ballast - full throttle pauses at 2500, struggles to get on plane - give it more throttle - starts to plane at about 3000rpm - more throttle - bang bang bang.  Urgh - missing some mega sunny days from all this.

I'm a bit locked into the idea that the HVS is the problem because the boat was running fine before we changed it.  We've definitely installed it correctly so maybe it's a faulty HVS?  It's an after market one but my mech assures me it's better than original because it's alu rather than plastic body so won't disintegrate like the Indamr one and he's used it many times before.

Ideas to move forwards:-

change spark plugs for some iridium ones I have

change the coil module

put the old HVS with the cam senor fault code back on (maybe swap the cam sensor from the new one if that fixes it)

Be grateful if anyone has any other ideas on how to proceed.

Thanks,
B

 

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The only thing I would change at this point is going back to the old HVS and see if the problem duplicates or not.

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On 8/15/2021 at 6:09 PM, Steve B. said:

For giggles, plop a fuel pressure test kit on that bad boy.

Steve B.

Bought a new Indmar HVS and fitted it - same problem.  Fuel pressure showing 50psi on gauge all the way through..  Going to refit the HVS again - the cap pointer went a bit too far past the 8 so maybe it's on the wrong tooth - but when I rotated the body so the 8 lined up with the pointer, the idle on trailer sounded great..  Cam angle was 630 initially, I rotated the body to get 702 and went for a run..   Same problem - no real power from 2500rpm and then a loud metallic knock as I advanced towards WOT :-(

Desperation move to save what's left of the season (my time is worth more than the money at this point), replacing all the injectors.  Let's see.

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On 8/15/2021 at 5:02 PM, formulaben said:

The only thing I would change at this point is going back to the old HVS and see if the problem duplicates or not.

thanks - yeah thought of that - but the old one is kind of toast - cam sensor fault and screw holes for rotor and cap damaged..  

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2 hours ago, csleaver said:

Your fuel pressure may be a bit low, it should be 58-62 PSI.  Have you done a compression test?

yep - 125 to 135 dry and wet in all cylinders..  Indmar manual says ok above 100psi

I don't think it's compression because we had a great session just before changing the HVS..  It's gone in 3 times now on 2 different HVS but can't help feeling it hasn't gone in exactly right even though 2 of those were by our mech..   I'll have another go tomorrow and just do it again and again until the rotor tab lines up on the 8 or as close as possible to it.

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2 hours ago, csleaver said:

Your fuel pressure may be a bit low, it should be 58-62 PSI.  Have you done a compression test?

our mech thinks 50psi is ok - brand new regulator and we had some repairs done to our fuel pump over winter so it is a suspect area..  injectors being changed tomorrow.

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6 hours ago, Baz787 said:

our mech thinks 50psi is ok - brand new regulator and we had some repairs done to our fuel pump over winter so it is a suspect area..  injectors being changed tomorrow.

It may be worth your while to listen to @csleaver.  A 4 Bar injection system needs 4 Bar pressure to work correctly, and any less will eventually starve it for fuel.  The block learn table can probably adapt enough at low power, but you will run low on fuel at high power.

4 Bar * 14.7 PSI/Bar = 58.8 PSI.

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Sounds an awful lot like the plug wires are on wrong.  But my .02 is, if "your mechanic" can't figure it out, try another one.  Seems like they are tossing parts at it.

Edited by oldjeep
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Running great now but new fault code on injector voltage..  I swapped the injector so seems to be on the harness.

 

Injector Fault: current below normal or open circuit

 

Thanks

 

 

Screenshot_20210828-173450_WhatsApp.jpg

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1 hour ago, Baz787 said:

Running great now but new fault code on injector voltage..  I swapped the injector so seems to be on the harness.

 

Injector Fault: current below normal or open circuit

 

Thanks

 

 

Screenshot_20210828-173450_WhatsApp.jpg

It is interesting that you got an injector fault with the engine off.  Did you have the key on while you were swapping the injectors?  Did you clear the code and have it return?  Did you carefully examine the harness and connectors for that injector (that means at the ECM end also)?

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