5.7 cutting out at 3k rpms
 

Hello to all! I have a 1996 Shabah z210 with the 5.7l EFI and bravo one. Motor has 97hrs.
I'm going to jump right into this:
While on the water and a load on the motor it will bogg out at about 3k rpms. It will free rev with no problems in neutral.
The motor starts like and champ and idles with no problems, everything sounds great!
So far this is what I have completed:
Drained tank, refilled with 93 and sea foam, removed the pickup from tank and cleaned small screen in side the tube, removes the ball bearing and spring from fitting, replaced fuel hose and all spark plugs..
Put her in the water today and ran great for a few min until the motor warmed up. Bam! Back to bogging at at 3k, never stalls just cuts out big time.

What I did next was very stupid I know but it gave me a good bit of information to narrow down the list. While on the lake I removed the spark arrester, fired up the engine with hatch open and could see a good flow of fuel from both injectors into the ports. I had a friend give it throttle to induce the bogging; when it did occur the fuel from the injectors would almost come to a complete stop, then trigger back on.
So now we know its a fuel delivery issue, or I would think? Here are my questions.. What controls the injectors to keep a continuing flow of fuel? The motor looks to have a throttle position sensor, maybe this? I'm kinda leaning away from the fuel pump just because of the consistent flow. I could be totally wrong.
From the research I have done most people speak of ignition system problems. Could that control my symptoms?

Any ideas guys?
Thanks in advance,
John

Re: 5.7 cutting out at 3k rpms
 

John ,

In my experiences the TPS will usually affect bottom end performance and idling.
Did you change out the fuel filter/water seperator?
I'd do a fuel pressure test on the pump.
Make sure the fuel pressure regulator is good.
With the way she runs good cold , I'd make dang sure the regulator is ok.
I doubt it is in the Ign System.
How much fuel have you run thru her? It could still be a "varnish" issue.

JMO

Larry

I'd say its a fuel delivery problem too. Either a weak pump or plugged filters, lines, etc. If you can, put a gauge on it and watch it. As far as fuel delivery to the injectors, its only the fuel pump. The pressure isn't regulated up or down to coincide with engine speed/load by anything else. If its weak or restricted it will work fine at idle but run out of volume on the big end under a load.

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5.7 cutting out at 3k rpms
 

Yes I did replace the change the FWS I'm going to run by the marina and grab another today just to be on the safe side. As for the pressure test, where do I purchase a tool to measure and does it inline on the fuel rail? I ran it for 30+min in the water yesterday in hope to burn out old crappy fuel. Are there any more filters after the fws?
John.

5.7 cutting out at 3k rpms
 

What I did realize is that the injectors would almost shut off during the bogg. Like something was telling them to stop sending fuel to the motor. I might try to put it in the water this week and video what is going on.

5.7 cutting out at 3k rpms
 

Problem solved! I removed the VST and noticed that the diaphram mounted to the top cover beside the fuel pump was missing two screws which I later found at the bottom of the VST. Looks like that works to pressurize the fuel system. Cleaned everything up, put it back together and ran 55
with out skipping a beat. Thank you everyone who spend time helping me with this issue. I'm very appreciative for this forum.
John.

Big thanks to you for coming back and letting us know what fixed it too!

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Re: 5.7 cutting out at 3k rpms
 

If anyone need's help with anything DC electrical feel free to ask. I'm an Advanced MECP certified installer. I work for the district team of BestBuy, currently over 19 install bays in the south east. I would sure like to return the favor.
John.

Re: 5.7 cutting out at 3k rpms
 

Stored in my memory banks John :)
Thanks for the offer.

Larry

Re: 5.7 cutting out at 3k rpms
 

What is the VST?

5.7 cutting out at 3k rpms
 

Vapor Separator Tank.... Makes sure that there's no air going in with the gas and it IS pressurized so if you didn't have a good seal, you were losing pressure there.....


1998 202 Shabah 5.0L Alpha 1

Re: 5.7 cutting out at 3k rpms
 

The Vapor Separator Tank.