5.7 GI Knock and surge loss of power

[efdog]

Hi and thanks in advance to anyone who can point me in the right direction. First off, let me say that I am new to this engine and inboards in General. I have just acquired a 2002 Four Winns 248 Vista with this 280 hp 2002 VP 5.7 GI and a VP DP-SM drive. Aside from a sea trial prior to purchasing (no survey done), I had it out for the first time this weekend. I will try to be as detailed as possible to describe what has happened in hopes that someone can point me in the right direction as to where to start looking for my problem.
Engine started right up and ran great for approx 2 hours at various speeds and RPM's, then the engine surged for about 1 second twice. I throttled down and killed the engine immediately. Checking the engine showed no obvious sign of trouble, but I noticed the battery cables were all loose (hand tightened only). After tightening the cables, I started the engine back up and got underway. Ran smooth for a couple minutes at around 4000 RPM's then came a backfire and gradual loss of RPM's down to approx 2500 or so. I put her into neutral, then very gradually applied throttle. At approx 2100-2500 RPM's I now have a knock (sounds to me like the engine is struggling) The more throttle the louder the knock gets. Under 2100 RPM's and there's no knock and appears to engine be running fine. I should also mention that the knock does not exist in neutral even with throttle bursts. A friend of mine who was with me and is more mechanically inclined than I thought the sound was coming from the top part of the engine, and suggested possibly a stuck valve? He also admittedly was not familiar with the fuel injected engines.
Oil pressure is great (over 40psi) and temps are in normal range (around 175 or so)
I had about 3/4 tank of gas, some from last season.

Any help is greatly appreciated. This forum has saved me thousands over the years!

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

Does anyone have any ideas? Fuel related? Could last seasons gas or a fuel pump issue cause this? I'm sure I'll have to get a mechanic to it for a water test to diagnose, but while trailering home from the dock that day, I blew a bearing, which ruined my spindle / brakes / drum etc...almost caught on fire...yes it was a bad day and bad situation...made it home, but not going anywhere until I get the trailer fixed.
In the meantime I thought there might be something I could check myself that might be an obvious cause to my problem with the engine.

 

[Joeboatva]

Re: 5.7 GI Knock and surge loss of power

On the front of the engine you should see two fuel pumps along with your filter. Do you hear one of the pumps wine louder when you run? Also check the water line coming from the risers to the fuel pump canister. It might be clogged causing your fuel to get hot and have vapor lock

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

On the front of the engine you should see two fuel pumps along with your filter. Do you hear one of the pumps wine louder when you run? Also check the water line coming from the risers to the fuel pump canister. It might be clogged causing your fuel to get hot and have vapor lock

I'll check this out tonight. After the backfire, I did notice a bit of whine that I don't think was there before. I'll run on muffs and have a good listen. Where it only ran good for 2 hours in my ownership, it's hard to compare the "then and now" sound of the engine.
Is it significant that there is no knock at all if the engine is not under load?

Cheers

 

[Bondo]

Re: 5.7 GI Knock and surge loss of power

Ayuh,... I'd start with a compression test, 'n inspection of the fuel filter contents....
A close look at the sparkplugs during the compression test might be tellin'...

 

[Boater1951]

Re: 5.7 GI Knock and surge loss of power

I had simular problem but not identical. Same engine 5.7 GXI. Throdle body fuel injection. Engine ran normal until ~2600 rpms than no power above that. There are 2 fuel pumps in the assembly: one high pressure and one low pressure pump. One of these pumps failed (it did start to make a high pitch noise). I replaced the assembly with OEM parts because that's what my dealer had. It solved my problem. The bad news is the assembly cost $690. They appearently don't sell the individual parts for this assembly.

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

Thanks everyone.

Listening to the engine on muffs didn't really tell me much last night. I cant hear anything abnormal. Starts and idles very smoothly. Exhaust drowns out a lot of the little noises though. Unfortunately there's only 1 VP mechanic in my area and it will be weeks before I can book him for an in water diagnosis.

I'll do the compression tests and plugs first (probably would have been very wise of me to do this prior to purchasing but I'll leave that for another day)...and then go from there with the fuel filter, then pump etc. Obviously I would rather not dump $700 into a pump assembly, but hey it's better than a blown engine which is my fear right now!

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

Engine ran normal until ~2600 rpms than no power above that.

Boater1951, When you say "no power above that". Did the engine surge, misfire, or simply stay at 2600 rpms? In my case the engine will surge as if struggling and begin a constant knocking like a cough.

Cheers

 

[Boater1951]

Re: 5.7 GI Knock and surge loss of power

Boater1951, When you say "no power above that". Did the engine surge, misfire, or simply stay at 2600 rpms? In my case the engine will surge as if struggling and begin a constant knocking like a cough.

Cheers

My boat is a 2002 Colbalt. The engine continued to run but the air/fuel ratio was way wrong as I increased the throttle and no additional fuel was not provided. I opened the engine compartment and removed the flame arrestor so we could watch the throttle body injectors in operation. At ~2600 rpm as I increased the throttle a change in the fuel pattern was visible but no additional fuel flow was apparent. We concluded the injectors were functioning but the fuel pump was not. I called the dealer and he told me there are 2 pumps in the fuel pump assembly one for high and one for low fuel flow/pressure. It was easy to replace and we did it our self in an hour. I'm going to attach a link to a Video we made during our evaluation so you can exactly see and hear what was happening. Watch the ending closely.

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

Thanks for the video...WOW! You got me like one of those ghost spook pictures!
All in all this doesn't seem to match what I have going on at all as I have no symptoms in idle. I've been crazy busy, but am hoping to do the previously suggested tests tomorrow. I also obtained the EFI Diagnostic Manual from another thread thanks to Don S which should be helpful. I'll post my findings.

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

Compression test shows 0 compression on #4 and #6. Hoping it's just a head gasket at this point. It's now laid up at the shop and my mechanic will be tearing in to see what's going on. I'm getting ever closer to my worse case scenario!

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

Verdict in...It was the head gasket which now has a 1 inch gap between 4 and 6...however there's also a 1/4 inch wide bore between the 4 and 6 as well (block and head). It's bad. I will need a repower. I guess my question now is why? Manifolds are a bit crudded up, but will be reusable once cleaned and machined. My volvo rep thinks it could be fuel related. Lean running perhaps that caused this? I would hate to put a new block in, then have the same thing happen.

 

[Bondo]

Re: 5.7 GI Knock and surge loss of power

My volvo rep thinks it could be fuel related. Lean running perhaps that caused this?

Ayuh,... He's probably Right,... Detonation does alota damage, Quickly...

 

[HORN X 4]

Re: 5.7 GI Knock and surge loss of power

Unfortunetly this is a common issue with the Vortec engines, make sure your mechanic checks the intake and exhaust valves, they will usually tulip (try to pull into the valve seats). good luck

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

Unfortunetly this is a common issue with the Vortec engines, make sure your mechanic checks the intake and exhaust valves, they will usually tulip (try to pull into the valve seats). good luck

Thanks for the tip. I'll be sure that the entire exhaust and fuel system gets full diagnostics. We found the factory ignition coil was completely bypassed to a new aftermarket coil that was dangling in there freely. Factory coil still mounted in it's original spot...so the previous owner either had a shabby mechanic or friend do his work, and I'm sure that is a sign that no proper maintenance has been performed either. As I've said before, it's my own fault for not having it surveyed, and a hasty buying decision was made after what seemed to me to be a successful sea trial.
Think I've learned my lesson? Probably not

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

So after reading up a bit on cleaning my Manifolds and Risers, it seems as though that's a gamble, and a bad gamble at that. Now it looks like I'll be replacing em. Volvo rep says about $1000 for both Manifolds and Risers. Anyone know how I can save money here? Advise on going aftermarket?

 

[efdog]

Re: 5.7 GI Knock and surge loss of power

I think I'm being punished. New engine ran for half an hour before a rocker stud in the new head popped out sending the push rod flying. Another big bang and knock. Closer inspection of the rocker studs show on one head the studs held in place with a roller pin and in the other head...NOTHING...hence I guess why it came loose almost immediately...Now waiting again for new heads this time.