Lack of power with problematic Volvo Penta GXI-J....now backfiring at 3000rpm

[saltymoff]

Hi new to this forum but it seems to be full of information so Im posting to see if it can help me...

I bought a 2008 Chap 215 with VP 5.0 GXI @ 270hp at the start of the years and it has never run right for me, when I first bought it was fully serviced by the local Poole Marina (yeah right...) I got the boat home and ran it only to discover 180L of dirty 2 year old fuel in the tank....Which I ran through the engine, breaking down with me and wrecking the fuel pump (dreaded whine). I had too flush out tank, fuel lines and replaced the fuel pump and the boat seemed to run at its best for a day or so after this......

......Then slowly over the past few outings (I go out 4-5 times a month) the engine performance has been decreasing...first month I couldn't get past 4200rpm & 37mph, so I changed the prop as I knew the current prop had been damaged and thought it was causing the lack of top rpm. I went from a 19 pitch 3 blade to a 20 pitch 4 blade...it came recommended by some people with the same boat/engine

I then ran worse @ 3700rpm max where I then changed out the spark plugs as I thought it may be down a cylinder...the 8 month old spark plugs were very clean and looked perfect.
Today it wouldn't even plain and struggled to go past 3000rpm where the engine then popped (i presume back firing). I haven't tried to repeat the problem yet...will do soon with a set of fuel pressure gauges....the fuel pump had not been giving any concern as its operation was quiet...no dreaded whine

After the engine back firing today do you think my timing may be out...do the VPs have a timing chain? Some mentioned to me it may be slightly out....first time the engine has back fired but the exhaust did smell gas rich today but usually I don't get this problem..

Previously when the engine runs it sounds sweet, never stales, cuts out or back fires until now.....

I regularly change the fuel filter and have checked the regulator both which were clean...I would hope a new fuel pump would last longer than 3-4 months but I will check the pressures at the weekend to rule out.....the fuel pump hasnt been noisey at all whilst trying to achieve WOT
My local VP mech/dealer has been involved in the whole process but has brought nothing to the table and only seems to look at what I steer him too??? Happy to take my money but not interested in fixing the problems..

Any advice appreciated .....Cheers

 

[jerryjerry05]

Check fp pressure.
Then check the coil.
Too hot to keep your fingers on it?
Then it's bad.
Do a compression test.

If it's running at lower rpm's then the timing chain should be ok.
If the chain slips/ then it's run crappy through out the curve.

Any crud in the filter?
Check the pickup in the tank and the anti-siphon valve.
It could be clogging just enough to cause this.

 

[saltymoff]

Thanks for that...Im convinced its to do with the dirty diesel the first time...i don't think my marina mechs have properly cleaned through the fuel system...going to strip it right down myself tomorrow and clean it thru....maybe pull the injectors and get them tested...Filters have been changed previously and were always found to be clean..
Compression check was meant to have been carried out in March..i have the figures there but im beginning to only trust what I see and do myself...

 

[jerryjerry05]

Never trust what someone "said" Unless that someone is you.
Where'd the diesel come from? I didn't see that in the top post?

 

[saltymoff]

Sorry dirty petrol...it was what was sitting in the tank when I bought it fully serviced....I late found out the boat hadn't run for 2 years, apart from the service prior to purchase..
This morning I Stripped the fuel system from the tank to the injectors....no signs of any real restrictions although it wasn't as clean as I would like. The injectors seemed clean enough but I did notice the o-ring on fuel flexi supply line from the HP pump to the fuel rail was severely perished....wouldn't reckon it would offer much of a seal..... Also my anti-syphon valve was 100% sealing on the return side...will order a new one.... fuel filter was spotless though...
I cleaned everything through, re-built it and then went for a brief test run (have to wait to source an or-ring) an I could clearly hear the engine drawing air via the fuel when increasing throttle, I ran it to 2500rpm where it started to back fire again.....I'm hoping/wishing that this o-ring is the cause of my problems but seeing as it is after the HP pump would it draw that much air from there it effect performance ??? I would maybe expect to see fuel leaking from it if its that bad??
Can anyone advise where the screens are on the fuel pump....there weren't any on my supply, discharge or return ports??
Once I get a set of O-rings this week I will try another test run with the gauges on....

 

[jerryjerry05]

I don't think there are any screens on the pump.
http://www.volvopentastore.com/mall/image/view/7/6/23924_4.png

 

[saltymoff]

↵OK so ended up cleaning the injectors out, took a fair bit of dusty dirt out of them, this then solved the back firing issue and put the engines performance up to 4400 rpm @ WOT with a 20p 4 blade prop, the problem being the speed on the GPS was only 37 mph so still well short of the sort of top end speed it should be capable off??

I have a new 18p prop coming which should then give me an extra 400rpm and take it to its max range off around 4800rpm but I very much doubt it will give me the extra 10-12mph I should have..

 

[saltymoff]

The Fuel system was checked and pressures were as they should be, on the first run we didnt have the GPS speedo and with the engine going up to 4400rpm with a possible overside prop we though we had nailed it.

Next day we went out with​ the GPS to have our hearts broken at the 37 mph @ 4400 rpm....whats next to check...compression test

 

[saltymoff]

If an engine is running @ its designed max revs the is it a gearing/prop issue??

 

[Silvertip]

So you had a poorly performing engine and you thought going from a 19P three blade prop to a 20P 4 blade would increase performance? If any assumptions can be made, it would be that the boat performed properly with the original 19P so at this point I would not be buying propellers until you have the engine situation sorted. You can also easily determine if it is gearing issue. Count the engine revs (manually) to see how many it takes to make the prop turn once. I also feel there is something wrong with speed and RPM numbers. You should not be able to keep the same rpm and speed with two very different props -- especially considering the big difference between these two.. Timing does not change over time with an electronic ignition system unless the distributor is not bolted down tight.

 

[ericga]

You may have more than one problem.

Check your firing order from A-Z with no assumptions.

Inspect the distributor cap and rotor.

Make sure you have the right spark plugs. Your engine requires the Iridium 0.06 I believe.

 

[Silvertip]

Fully serviced can mean many different things to different people. If it was a sales guy that said it was fully serviced they maybe checked the oil level and that's it. They obviously never did an on-water test. Since that part of this is now history, it is up to you to do the "full service". Cap, rotor, plugs, oil and filter change, outdrive lube check and change. And while you have the plugs out, do a compression test -- at least for historical purposes. Be certain to mark the plug wires or do one plug/wire at a time so you don't screw up the firing order (which may be part of the current problem). Yes, GM V8's have timing chains and it is highly unlikely that's an issue. Timing can be an issue but it really sounds more like a fuel issue than timing or it would bark at you more often. 1-8-4-3-6-5-7-2 is the proper firing order. It take two minutes to verify this.#1 cylinder is the front cylinder on the right side looking at the engine from inside the boat. 1-3-5-7 are on the right side, with 2-4-6-8 on the left.

 

[jerryjerry05]

If??? He's getting 4400 then I really doubt he's got a plug wired wrong???
Dropping the pitch will bring up the revs. But the tops speed probably won't change.
Compression?

What does the boat weigh? How much of a load are you carrying?
You using the trim and tabs correctly?

 

[everharta07]

The backfire issue you were having is EXACTLY what's going on with my boat. 2000 Chris craft 210, 5.7 Volvo penta. At first, it would backfire at 4700rpms. Then 4300, then 4000, and progressively worse all the way to 2900rpms. It's making a popping, or grinding, or backfiring noise. And the last time I took it on the water, it wouldn't start, but you can Clearly smell fuel, so it's getting gas. I've got it with the mechanic now. He thinks it's the carburetor. He thinks it's dirty and needs to be rebuilt, that there's a "flap" or something that opens and closes, letting gas into the motor, and that it's stuck open and just flooding the motor. Waiting for a kit from Holley right now. Hoping that's the problem and nothing worse. He claims that if its not just the carb, that it's the fuel line. But he "sure" that it's one or the other. I guess we'll find out!

 

[Scott Danforth]

check the distributor cap, a bit of slight corrosion and you can get cross talk at higher RPM's

 

[Scott Danforth]

The backfire issue you were having is EXACTLY what's going on with my boat. 2000 Chris craft 210, 5.7 Volvo penta. At first, it would backfire at 4700rpms. Then 4300, then 4000, and progressively worse all the way to 2900rpms. It's making a popping, or grinding, or backfiring noise. And the last time I took it on the water, it wouldn't start, but you can Clearly smell fuel, so it's getting gas. I've got it with the mechanic now. He thinks it's the carburetor. He thinks it's dirty and needs to be rebuilt, that there's a "flap" or something that opens and closes, letting gas into the motor, and that it's stuck open and just flooding the motor. Waiting for a kit from Holley right now. Hoping that's the problem and nothing worse. He claims that if its not just the carb, that it's the fuel line. But he "sure" that it's one or the other. I guess we'll find out!

Everhart, welcome aboard. please do not hijack threads. Please start your own thread on the subject.

 

[saltymoff]

Thanks for all the replies....a late update..

I Dropped two pitch sizes to an 18p prop (I know throwing money away) and gave the boat a clean bottom as it had a fair build up of fresh water weed....there was no difference in performance....still topping out about 4400rpm and 39mph...something holding this boat back? I thought dropping the pitch would increase my revs sufficiently
Still trying to find the mechanical problem??
I am currently trying to locate someone with a diagnostic software for the engine...
Going to check the fuel pump pressures again tomorrow ...I only have a fitting for the HP side but at least that will give me an indication that the final pressure is sufficient @ 50-60psi
Compression test, plugs, rotor all changed out at the start of the season...new fuel pump fitted aswell
Haven't confirmed gear ratio yet , will do once it's out of the water this winter...but looking at the serial number its the same drive as the original which was 1.6...
The boat was bought privately and serviced by an independent engineer shop in Poole...I have all there receipts and they carried out the compression test for me when I purchased...but yes I will re-check all these things....
I did notice a kink flexi fuel hose on the return, seems to have been like that for a long time, we re-routed it and it's much better but still a slight link there..didn't think it would matter as its in the return but I will order a new one this winter...
Cheers

 

[saltymoff]

Oh...the back firing was cleared after we plugged the injectors , cleaned them and functioned them...
I'm sure it's a fuel issue not allowing me to pass 4400rom, also at the Rev range I should be going faster than 39mph??
Could the injector still be slightly blocked affecting the spray pattern slightly...would this be enough to effect my speed...
This boat did see very very old petrol, although it the tank has been flushed through, filters changed regularly....the fuel rail looked pretty clean when we stripped it..


Cheers

 

[saltymoff]

Thanks again for all your advice...
Boat weight I'm unsure but I would expect it to be as per design...its 2008 and has laid on a beach for most it's days (which is part of the problem)...
No trim tabs yet but I am trimming...
Cheers

 

[ericga]

Have you inspected the anti-siphon valve for clogging?