Volvo Penta 50Gi running rich and soot buildup

"Deewayne: Do you have a part

"Deewayne: Do you have a part number for the injectors, either from Volvo or GM? Any one else agree that they are the same injectors as '88-95 GM trucks? Thanks, Ron"

I pulled my injectors and sent

I pulled my injectors and sent them out to be cleaned and serviced. They tested O.K. before and after. One injector was a bit dirty giving an injector inbalance of ~3.3% Lower than the other. Not bad but now they are balanced within .8% of each other. From the flow calculations (static) 916cc/min @ 43.5psi it looks like these are running ~88lbs/hr. Maybe I'm not calcluating these correctly. I little help here from anyone a bit more versed?? Part # stamped on the injectors removed from the TBI are 25170301 ACR. I contacted AC delco who said these have been Xcross ref'd -> 5235206 -> 17113080 -> 217348 -> 217-2282 Oh boy! But I think these injectors are 55lbs/hr so I'm a bit confused.
If I calc out fuel pressure from 43.5psi (tested pressure) to 31psi (my actual fuel pressure) the flow is reduced from 916 cc/min to ~773cc/min (static flow). Calculations @ 29psi brings the flow down ~25cc/min to ~748cc/min. Maybe just enough to stop the soot. I will try to set the fuel pressure to 29psi and see what happens. Spec is 29 +/- 2psi. I'm not certain this will help though. Boat is winterized so this won't happen till next spring. Any Comments??? Progress??? Thanx in advance.

"Dear All,

I have almost th

"Dear All,

I have almost the same problem in my 5.7 Gi 1996 MY. While at idle some times the engine revs up and down and there is a sound from the fuel pump, the same happens when trolling at 1000-1200 Rpm. When I accelerate a litle not more than 1500 Rpm everything is ok but after a while the same starts to happen again. All fuel pumps are new, fuel lines are new so are the filters.
I read that a faulty fuel regulator may be the problem do you know were it is located because I can not find it in the parts book they have it as kit.
Any other suggestions what is happening is very iritating.
Thanks a lot."

"The pressure regulator is bui

"The pressure regulator is built into the Tbi and mounted into the injector pod assy, under the fuel meter cover. You can find an after market regulator which ususally is an adjustable one. Or, rebuild the one that is there as long as the spring is in good shape. Finding the spring rate used to maintain 29 psi may be tricky. So hopefully it's in good shape. When I rebuilt mine (it held pressure steady at 31psi, the diaphram looked a bit beat up but it still worked) there was some corrosion on the spring. I left that alone. You can pick up a TBI gasket rebuilt kit at Autozone or any decent parts shop. Tell them you have a GM Rochester 220 TBI and need a rebuilt kit. If they know what they are doing, thy won't even need to look in the book. This is a common rebuilt kit for early year GM's from probably the 80's-96. The kit should cover 4.3l to 5.7l and possibly 7.4l Tbi engines as well. The main difference here is the injectors on the 4.3l and the 7.4l. The kit come with the Diaphram and gaskets (no springs). I would check the fuel line presure while that noise is heard. It sounds like an obstruction causing the pump to squeal. Or the low presure side is having trouble feeding from the tank. You could have reduced flow from the tank. What size filter(s)and how many do you have installed?? New filters can get clogged quickly esp if the tank is drawn down. If you find that this is the case, you may need to clean the fuel tank. The pickup tube inthe tank could also be clogged. I've also seen new pumps out of the box noisy and still function O.K. I remember reading somewhere that paint breaking down inside the pumps was the culprit. I think that was finaly figured out and fixed a few years back after many failures.

Oh, and if you do get as far as rebuilding the regulator yourself, could you please report the part # stamped on the injectors. They should be the same as the one I listed above for the 5.0l Gi. Go figure, same injectors and fuel pressure. The Xcross ref'd number 5235206 is a 55lb injector and definately not the correct one. The others may be O.K."

"BTW, to shed some light on a

"BTW, to shed some light on a few questions back.....The same injectors are used from the GM Truck/car line but they are typically sized way up (and fuel pressure increased) to produce the HP needed. Typically a GM 305 5.0l(auto/truck) produces ~180hp. A Marine GM 5.0l produces ~250hp. I have recently found that the injectors used in my TBI are used in the 454. These are 80-90lb/hr injectors. So some xcross matching needs to be done...."

"Dear Peter,

Thanks for you

"Dear Peter,

Thanks for your feedback. I removed the sensor and tried to compress the spring but no luck. It is completly stuck. So I have to change the sensor. For your reference the fuel tank is new.
I will try with a GM dealer because volvo sells this sensor 350 Euros in Europe. I will go there with the sensor to be sure I get the correct part"

"I have replaced the IAC valve

"I have replaced the IAC valve and the engine stopped to rev up and down, but now the idle is High 1000 rpm. Do I have to wait for the engine to warm up in order for idle to go to 600 rpm which is the normal?

thanks a lot"

"Peter C......I have exact sam

"Peter C......I have exact same problem on my 1999 Chaparral Sunesta 232 5.0 GI (190 hrs on motor). I have done everything you have and more (cleaned injectors professionally, Volvo checked with their computer, changed out various sensors, etc, etc....one thing that a Tech performed helped to some extent was they rebuilt my fuel vapor separator tank.....stopped my plugs from fouling (being wet with fuel) but I still have black soot on them as well as my transom. My engine runs fine always (idle to WOT) - more of an inconvienience now and somewhat embarrasing to have black crap on my nice boat.....(use wax to clean it off). Have you made any significant strides with your issue lately? I'm pissed like your self that even Volvo can't figure this out. I was lucky as the one mechanic who solved part of the problem had my boat for 3 months and only charged me $1k for the fuel sep/vapor rebuild and a new water pump - he lost money but didn't want to gouge me for not knowing what the problem was - they should only get paid when they complete the task!! Regards, Chris"

"Chris,
I have not dipped the

"Chris,
I have not dipped the boat yet in the water this year. Hopefully next month if the weather holds up. I had the injectors professionally cleaned as well, I also backed off on the Fuel pressure spring. I don;t know what I have it at just yet but once it's started (winterized) i'll check. I'm shooting for 29psi. This may help the problem. I did not have any excess fuel going back from the canister into the manifold. I did not think the vapor canister was rebuildable. I thought the fuelpump and canistor had to be replaced as a whole. I have a new Fuelpump as a spare but I don't think this is the problem (vapor canistor). I think the injectors may be flowing a bit too much, hense the reason for backing off on the pressure ( did you have them flow tested? and what was your #'s). Reducing the pressure should help as long as it does not lean out too much....Which neither one of us has a problem with right now. WitchHunter did not test mine at the proper presure."

WitchHunter did mine as well -

WitchHunter did mine as well - I don't have the numbers handy but they were dubbed good and within a decent percentage of flow from each other. I had actually ran around to a number of Autozones/Napa/Pep Boys and purchased a set of Injectors but never used them....just re-installed the cleaned/flow tested oem units. I have felt for a long time that I am just chasing my tail.......wish it were an easy fix (maybe is).
I can connect you with the mechanic who rebuilt my vapor unit if you wish.....Not sure if I can give my contact info out?

"Chris, Do you have the part n

"Chris, Do you have the part numbers for the injectors you purchased? I'm haveing great difficulty matching mine up due to the part ID on them. Yes, the Contact info may come in handy. You can e-mail me if you'd like..... Click on my name. E-mail address is there....

My injectors were within 3 percent to start and came within .8% after cleaning... He checked them at 20PSI not at 43.5psi. When I contacted WitchHunter questioning the presure and flow, he told me that the pressure on the test sheet was not correct for this type of injector and that he runs them 20psi. Glad I called... CC/min are ~914 @20Psi. There's a guy that has a pretty good grasp of these injectors which I had some long but educational conversations with. I think he was in Illinois. It was a hobby of sorts due to his passion of a TBI feed car of his. I may hook up with him again this spring. He sells refurbed injectors. His name was Sean. If your interested I can give you some more detailed info and his Number. He can custom match to a specific flow.

I don't think this is an easy fix. Volvo Penta should have had a solution by now. I do think the problem is related to GM. GM had lots of trouble getting these TBI's working right on cars. Every set of injectors flowed differently and matched sets were never really matched. Volvo did wonders getting these to work better than GM ever did....It may be a combination of injector flow rate, presure and the Map table on the ECM."

I changed The IAC valve and th

I changed The IAC valve and the idle is at 900 Rpm instead of 600 rpm. Injectors are ok but sometimes there is a noise high pitch from the engine which stops after a few seconds. All the above with the boat off the water. The temp of the engine is normal. Any suggestions?

"Is it the injectors? All of t

"Is it the injectors? All of the input is appreciated and will help save many hrs & $$ if the problem is finally fixed.
I have the same type problems trying to troubleshoot my '00 5.0GI and have been searching forums for help, so if anyone finds the true fix please post.
Mine starts right up & seems to cruise & pull fine up until 7/8 to WOT then will bog like it's not getting enough fuel or maybe too much. It will fall on it's face for 2 seconds then start to gain rpm again, still able to reach 4600rpm or so with slight stumbling. Although, at the same time I have some black smoke/soot on transom at start up.
Just tired of throwing parts at it with no results."