I surrender

[BarryTurano]

Never thought I would utter those words, but after 4 months of trying to get my new (to me) boat running. I am throwing in the towel. My Volvo Penta 5.0 GI (General Motors Fuel Injected) will be magically transformed into a Volvo Penta 5.0 C (General Motors Carbureted) in the last 4 months we have rebuilt the entire fuel system. Both fuel pumps, cleaned the VST replaced the injectors, cleaned the throttle body, replaced the Temp Sensor, Knock Sensor, IAC, TPI, Map Sensor. We also replaced the distributor, wires, cap, rotor and module. Had the computer looked at and repaired. We have run almost 60 gallons of fuel and 10 hours of diagnostic run time. The motor still runs like crap. No codes show up on the diagnostic computer. Volvo made this particular engine model in 1998 and then 1999. The motor is discontinued and no parts are available. We think we have it narrowed to 2 wires in the harness. But at this point I have lost so much confidence in the system I think it best to stop and go old school.
My feeling is that I will get it running and be 40 miles out and something else craps out. So the throttle body will be coming off along with all the sensors, ECU, distributor and coil. They will be replaced with a Rochester Quadra jet 4 Barrel Carburetor, matching coil and distributor.
So coming soon to slip E22 at Waterfronte in Carolina Beach will be:
?Game Changer? a 1999 Albemarle 24 CC with a Volvo Penta 5.0GC

 

[alldodge]

Sorry to hear about your troubles. For something to run like crud has to be ignition, timing or fuel. Appears you have replaced everything and this may not be the time but did you check to see if the timing chain slipped or was not put on correctly?

Also don't know of anyone here which takes prisoners (sorry had to try for a grin) :behindsofa:

 

[smassey22180]

Out of curiosity, why a Rochester? Would a Holley line up better with factory linkage and fuel lines?

 

[BarryTurano]

Mechanic recommends the Quadrajet says they are virtually bullet proof. They are not as adjustable as the Holly. But I am getting the carb from National Carburetor in Jacksonville who will build it to the specs from my mechanic, as far as air flow etc. So major adjusting should not be necessary (fingers are crossed)

 

[gm280]

I am the opposite to your thinking. That being that I will make that fuel injection system work if it takes everything I can to fix it. Because I can't stand something beating me like that forcing me to give up! Also, I 'd like the fuel injection system better for a lot of reasons. One being, when it is work properly, it is so much better then a carb for a cold engine start and to keeps running as it warms up. But to each their own. If your setup originally worked properly and is now having such problems, then there is something your are missing or looking over. But that is just me and my opinion. You have to do what you think is the best for your boat and needs. Let us know how it all works out with the new carb...

 

[smassey22180]

It's funny you mention National. I am going to be in Jacksonville in January. I was going to stop by ask them for options for my 4 barrel rebuild. There is another internet carb rebuilder in Tampa. http://flyingfishcarburetors.com/

 

[BarryTurano]

I am the opposite to your thinking. That being that I will make that fuel injection system work if it takes everything I can to fix it. Because I can't stand something beating me like that forcing me to give up! Also, I 'd like the fuel injection system better for a lot of reasons. One being, when it is work properly, it is so much better then a carb for a cold engine start and to keeps running as it warms up. But to each their own. If your setup originally worked properly and is now having such problems, then there is something your are missing or looking over. But that is just me and my opinion. You have to do what you think is the best for your boat and needs. Let us know how it all works out with the new carb...

Problem is the motor NEVER ran since I bought it back in August. My own fault I thought it was just a bad fuel issue because the boat was not run in 3 years. I have just lost confidence in it. I could see myself at the stream and the other shoe drops. That's a long run (60 miles) for Tow Boat US. No matter what was done it would not run right. I know that it is a timing issue and a sensor issue. If I disconnect the MAP sensor I can throttle up to about 4200 rpms. After that the timing retards. If the MAP sensor is connnected I can throttle up to 2200 RPMs and then need to increase throttle in steps or else it starts to bog down. At 4200 RPM's I get the same timing issue. I am getting a slight Knock even when the knock sensor is disconnected, how can that be? That is why it has been narrowed down to the harness. Which has been discontinued. I could probably jump the wires that may work. But if it doesn't I have wasted more time chasing a ghost. So at this time my logic tells me go back to old school. I am aware of the limitations, but I need to have faith in my equipment.

 

[bruceb58]

You really aren't losing much switching to the carb other than cold starts. A TBI is not that much better than a carb for power.

 

[alldodge]

Getting a knock leans me to a lean fuel mix. Either way I hope when you get the carb on your running great. I'm sure we would all like to know how it works out.

Good luck

 

[JustJason]

I think you need a new mechanic..... Some engines take longer to figure out than others... but nothing ever "beats me". And in the world of marine engines. The old Gi's were not that overly complicated.

Everything has a test... it comes down to wether you have the tools and knowledge to do them, or not.

 

[aspeck]

Sorry to hear your engine and mechanic have beaten you into submission! Good luck with the new carb! Let us know how it all works out!

 

[BarryTurano]

Getting a knock leans me to a lean fuel mix. Either way I hope when you get the carb on your running great. I'm sure we would all like to know how it works out.

Good luck

See that's another bit of strangeness. The motor is running VERY rich. Black smoke and soot from the exhaust. Even after warm up on the hose or under load. Why would the diagnostic show a knock if the knock sensor is disconnected? Why does it run better with the MAP disconnected? Why does my timing retard after 4200 rpms? So many questions and no answers. It's not the mechanic who want to convert (all though he should) it's me. The mechanic has not charged me for any time trying to figure this out. He says he has not gotten a result therefore he can't charge for his time. He is of the mindset that a machine cannot and will not beat him. I on the other hand am just weary of this and as I said I have lost confidence.

 

[alldodge]

See that's another bit of strangeness. The motor is running VERY rich. Black smoke and soot from the exhaust.

Appears your running rich

Even after warm up on the hose or under load. Why would the diagnostic show a knock if the knock sensor is disconnected?

If the knock sensor wire runs along a sparkplug wire it could pick up a knock signal. This has happened to others when they use items to make the wires look neat.

Why does it run better with the MAP disconnected?

When the engine is running at idle there is high vacuum and low voltage output from the MAP to the ECM. Under high RPM the voltage output increases as RPM increases telling the ECM the engine needs more fuel. If you disconnect the MAP no voltage will go to the ECM which in turn reduces the fuel going to the engine.

Why does my timing retard after 4200 rpms?

It retards because it is trying to save it self because something is telling it there is pre-ignition happening (knock)

So many questions and no answers. It's not the mechanic who want to convert (all though he should) it's me. The mechanic has not charged me for any time trying to figure this out. He says he has not gotten a result therefore he can't charge for his time. He is of the mindset that a machine cannot and will not beat him. I on the other hand am just weary of this and as I said I have lost confidence.

If your willing we could try to help figure this out. I would start with the basics.
Compression test and leak down test to check the health of the engine.
Then pull the valve cover on the port side and bring 1 to TDC, paying close attention to the valves as it comes up.

 

[bruceb58]

I agree with what AllDodge is saying, especially checking the basics like compression. You never mentioned that this was checked. As far as you know has any major mechanical work been done on this engine?

I also would take a look at the ground connections for the ECM and I would also make sure the ECM is getting full voltage so that there is no voltage drop gong to it.

I am curious, has your mechanic actually measured the MAP voltage?

Also, by removing the MAP sensor, the ECM may get thrown into a default mode which may then ignore all of sensors. I don't know that for a fact. Just a hypothesis.

 

[BarryTurano]

Thanks for the response. All of the tests were done, compression, leak down, etc. Voltages have been checked at different RPM's the mechanic has it all in charts and graphs. Everything checks out on paper. But paper is not the real world. Like I said I feel as if I am chasing a ghost.

 

[alldodge]

Thanks for the response. All of the tests were done, compression, leak down, etc. Voltages have been checked at different RPM's the mechanic has it all in charts and graphs. Everything checks out on paper. But paper is not the real world. Like I said I feel as if I am chasing a ghost.

Can you provide the results of the test accomplished?

 

[Fun Times]

Also it seems you never mentioned what your fuel pressure is at all speeds?

Before switching to a carb, it would be a really good idea to run an engine vacuum test to see if you have an engine problem somewhere.
http://www.tuneruniversity.com/blog/2011/05/check-your-engines-health-with-a-vacuum-gauge/

One thing to try would be to remove the MAP sensor, plug the hole in the intake then use a vacuum pump on the MAP sensor and bring the vacuum up somewhere around 12 - 15 Hg and see if the engine runs better. By doing this test, you'll be telling the ECM the engine vacuum should be within normal working range provided the MAP sensor is not actually faulty. http://www.harborfreight.com/mityvac-vacuum-pump-39522.html

Here's a way to clean the inside of the engine if desired. http://forums.iboats.com/forum/engi...drives/9076459-decarb-a-mercruiser-7-4-lx-mpi

 

[smassey22180]

Since you probably are going to get a new one anyway, have you considered peeling apart the wiring harness with a razor blade? I hate my carbs mostly for hard starts when hot. I would love a FI engine that started first time, every time. That way my wife could actually drive the boat herself

 

[bruceb58]

My carbed boat starts first time every time.

 

[keith2k455]

A finely tuned carb should run as good as TBI/EFI but then try telling that to my wife as the battery let's off its last crank.

Does the motor ever backfire? How many hours? It sounds like you may have a bad distributor...when they wear out the spark suffers, makes it appear rich, timing issues, etc. A good mechanic can test the distributor (notice I say distributor, not just cap).

If not the distributor I would ask if the ecm has the correct and unmodified program in it.