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Volvo Penta 50Gi running rich and soot buildup

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fish_bones

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"I have a Year 2000 (may b

"I have a Year 2000 (may be a 1999 build) Volvo Penta 5.0Gi (TBI) which seems to be running very rich. There is a lot of black soot buildup on the stern and the plugs are sooty as well. There is always a thin film of soot in the backwash behind the boat while at trolling speeds. There is also faint smell of unburnt fuel. She starts fine for and seems to run o.k. at cruising speeds anything below 1000rpm, there are occasional bumps/hiccups espcially at idle speed. And while it's not perfectly smooth, it doesn't run really rough either. I have done a few complete tune-ups, (plugs, cap, rotor, timing, etc), replaced temp sender, MAP, Knock sensor (corroded connector), added Freshwater cooling etc... Problem appeared to get worse when the Coil was replaced a few years back. The coil failed while underway and caused some backfiring and loss of power before if failed completely. While checking the injectors (idle speed) there seems to be some droplets of fuel forming and dripping onto the Throttle plates (too much fuel). Probably the causes of the bumps. Seems to me that it's spraying too much fuel at Idle. I have had it at the shop where the shop owner (appears to be well trained and deals with fountain boats) spent at least a full day onthe muffs going over everthing with a rinda comp and other than the MAP being slightly skewed (but not oos) along with the temp sender and both replaced, everthing seemed to be O.K. to him even though they acknowledge a problem. Even the ECM and Fuel Pump was swapped out with another and the problem was still there. I'm suspecting the IAC or the TPS but don't want to just keep throwing parts at this. Although it may be cheaper than having the local shop spend a day on it and not be able to resolve.... Any Ideas. Would the IAC or TPS cause this problem. If I replace either, how are they calibrated???

Thanx in advance!"
 
"Hello there,

I have ran in

"Hello there,

I have ran into this problem before. The over fueling was caused by a bad fuel pressure regulator. You can run a fuel pressure test and see if you are with in specs for your efi system. If it is really high I would suspect the regulator or there may be a blockage in the return line.

The TPS should set an error code in the ECM.

I am sure someone else will have more info on this for you."
 
"No Return line and no Codes..

"No Return line and no Codes...Last time the presure was checked at the shop they coould not test either the high side or low...I can't remember now. Somthing about only one port to check... They thought it was O.K. and when they replaced the fuel pump module (hiigh and low) with a known good one, nothing changed except the one they had was noisy."
 
"Thanx David,
The last commen

"Thanx David,
The last comment left by me may have been a bit confusing. Let me clarify that one side (high or low) pressure at the fuel pump was fine. The other supposedly could not be checked. I think the fitting is right at one of the fuel cells on the assembly.

If it's the pressure regulator, it appears that it is built into the TBI assembly. I'm not sure it can be pressure tested. I'm looking at the drawing for the Volvo Penta 5.0 GI PEFS TBI assembly and Item #1 on the schematic appears to be the regulator. I'm not sure if it's serviceable or needs the entire Throttle body replaced. Is there a way to check the regulator out for certain?? Is there a rebuild kit for it available for resale? Any Volvo Technicians or others familiar with this????

TIA
Peter"
 
"Hi again Peter,

I am not f

"Hi again Peter,

I am not familiar with your exact EFI system but here is a couple of links that may help you.
Year listings
http://volvopentaparts.stemtostern.com/VolvoDiagrams/volvo_penta_parts.asp

1999 Throttle body service list and if you scroll down there is a diagram:
http://volvopentaparts.stemtostern.com/VolvoDiagrams/ShowAssembly.asp?ID=71966

2000 Throttle body service list and diagram:
http://volvopentaparts.stemtostern.com/VolvoDiagrams/ShowAssembly.asp?ID=71061

Item 1 is the regulator. Normally I would T into item 23 the fuel inlet and run the pressure test. Appears Item 13 is the fuel outlet I would make sure the line that attached here does not have a blockage. You are dealing with gas here so I would suggest that a shop run this test.

Wish I could be of more help but you are in the right place. This is a great forum and I am sure some else here has some more insight into your system.

Best of luck

Dave"
 
is there fuel in the clear lin

is there fuel in the clear line on top of the motor?

you need to run fuel pressure tests
 
"Just-in-time,

I don't

"Just-in-time,

I don't see any clear lines. I think your both right in that I need to have someone well versed in running presure tests verify them. Problem right now is that the boat is winterized for at the least another month or two at best. I have a great discount right now on some OEM volvo parts and was thinking of swapping out a few components. I might pull the presure regulator and replace it outright. That kit is under 80 bucks right now. It's actually cheaper than the $95/hr they are charging to troubleshoot not to mention the markup in parts they wack me with... If they could fix the problem the first time it would be another story....But they are milking me to death and I can do as good a job replacing everthing as they can if not better ;-0. I just need to be pointed in the right direction from those which have much more experience with fuel problems or have seen this before. When I start getting looks from service techs like I have 3 heads, or they start with it's your fuel or answers telling me "that's normal" (well, maybe for a diesel), I get fustrated at $95/hr."
 
"sounds like a poorly trained

"sounds like a poorly trained shop to me
if it was at my shop, diagnosis would have been different"
 
"I just got off the phone with

"I just got off the phone with a volvo technician.
He mentioned a refuel vent from the pump to the manifold. I think this may be same line your (clear) talking about. Asked if there is fuel in there...I don't have an answer because it's winterized. If so he thinks it may be the fuel vapor separator. Also, want me to check compression but I suspect it's fine. Lastly, the injectors. Thought the regulator was a rare failure and I found that it needs to be replaced as a kit with the injectors or the upper throttle body as a whole. THe repair kit for just the regulator is no longer available."
 
yes the clear line
if fuel in

yes the clear line
if fuel in there it is regulator or vst
clean the injectors also
i would run seafoam in the gas
 
"Sorry for the long delay...Be

"Sorry for the long delay...Been busy with other things recently, but now getting ready to pull the cover off. So.....Now I've Got more Questions.... I have run a compresion test on the engine. Everthing is fine. Low 155psi-High 170psi. Picked up a new Fuel pump as both a spare and to replace if its found to be the cause of the problem. Volvo has had lot's of trouble in the past with these pumps. The First pump on this boat was replaced by volvo under warranty by the original owner. Volvo changed Fuel Pump Part#'s again and now include a fuel filter/water separator as std which is nice but now redundant, since I installed a water separator several years back... The new pump looks Identical and still made by carter. I am expecting a new fuel pressure gauge and fitting for the High pressure side. I need to install the fitting at the TBI and test out the high pressure side before doing anything else just to baseline where I am.
Now for questions....
1) VST = vapor canister???
2) I believe the fuel pressure is supossed to be 29psi +/-2 on the high pressure side. Not sure about this new pump from volvo though. Both the 5.0 and the 5.7 use the same pump and spec the same pressures for Low and High. When this is checked, should the engine be running at Idle or at WOT or does it really matter.
3) if the pressure is too high then Obstruction? Regulator?
4) How do I check or test the regulator?
5) How do I confirm the VST is operational.
6) Is the regulator servicable? Spring? Diaphram?
7) Is the VST servicable
8) The return to the intake manifold from the fuel pump is black rubber, so I can't really see if there is fuel in there without replacing this tube with a clear one. Should I do this for testing purposes??? & I suppose I should not have ANY fuel in there at either idle or WOT...

Soot buildup is occuring only at idle and low RPM's

Thanx in advance for your help!
Peter"
 
"1- not servaiable
2-low is 8

"1- not servaiable
2-low is 8 psi, high is 48-62psi
3- might be a vaccum line clogg also
4-regulator test, switch a volter meter to a/c and put on battery anything over .8v is bad
5-pinching the f-press regulator
6-i have no idea, i say no
7-NO
8-yes you want a clear hose on it
but when u pull it, fuel in there is bad"
 
Run for around 40 hrs and the

Run for around 40 hrs and the problem remains....
added a clear line from the vapor canistor to the tbi and no fuel is present at WOT or at idle. I did see just a small amount of fuel (bubble) make it to the top of the vapor canistor fitting. But that did not go any further and then disappeared. TPS and IAC appear to be working fine (TPS Measured electrically). I also removed and cleaned out the IAC (lots of carbon build up) but this did not really help. It moves back and forth maintaining the RPM @ 600 just fine like it is supossed to... Any more ideas???? Only thing left is to pull the Injectors and have them cleaned or replaced and maybe just putting an adjustable regulator and dropping the pressure a bit. It's running ~31psi at Idle. I have not changed the fuel pump yet but it appears that the vapor cannister is fine and I'm getting plenty of fuel.
 
"Peter:
I have the exact sam

"Peter:
I have the exact same problem on my '98 5.7 Gsi. So far, all I have is a $1700 bill. I hope you find a fix, I'll be watching.
Cheers, RL"
 
"One 'item I do not see me

"One 'item I do not see mentioned is the temp sensor for the ECM, not gauge. Corrosion, defective sensor etc sending wrong info to the ECM will often create these problems at idling."
 
I am not an expert on marine i

I am not an expert on marine injection systems but 31psi at idle for a TBI injection system seems extreamly high and would cause the rich condition you are getting. I would replace the presure regulator and then go from there.

Dave
 
"31 psi is a legit pressure on

"31 psi is a legit pressure on the high-side of the TB.

Does the engine appear to run OK when it is first started and cold?

A malfuntioning IAC solenoid will cause the engine to run rich. Pull yours and inspect it. Sometimes they can be cleaned and reused. You should see the small piston retract (or extend, depending config.) once the engine warms to operating temp."
 
"Your fuel pressure is correct

"Your fuel pressure is correct. Have you replaced the plug wires? If not, do this first, I have seen several Volvos with very similar symptoms caused by bad plug wires (i.e. misfiring cylinder passing unburned fuel out the exhaust)."
 
"Thanx everyone...Ron, the rea

"Thanx everyone...Ron, the reason I'm here is that the Yahoo's at a several shops I've paid my dues to were scratching thier heads and just replacing parts....I could do that myself with less expensive parts and labor!:) So now I come to the experts for help!

Spec on this engines Fuel Pressure is 29 +/- 2psi. I'm at the high side while at idle. Would love to try a replacment regulator....If anyone can find one, please let me know. These are discontinued from Volvo...and possibly GM. I'm trying to figure out what will work here. There are a few Adjustable's on Ebay...But I'm not certain this is really the problem.
Engine runs well at speed. At Idle or up ~1000rpm it's rich. Starts up O.K. but with a bit of blue smoke that burns off well before the engine warms. Engine does not burn oil per se.

IAC pulled, cleaned and appears to work O.K. It moves trying to maintain 600rpm. After I cleaned it, a small hesitation when I hit the throttle disappeared. You previously could see the injectors stop injection for a split second when the throttle was pushed hard. Then again, maybe it was something else that fixed that like when I pulled the TPS (r & r) and checked it? The engine is not perfectly smooth at idle or slightly higher. But it's not rough either, it has it's bumps as if it gets a drip of extra fuel on an intake stroke. Spray pattern seems heavy from the Injectors at idle....But I'm not sure that it's bad. It's just an observation and I really don't have anything to compare it to. I'm looking for a Injector gasket kit and will send these out to have cleaned and checked in time. The Intake manifold is wet (fuel) as if there is just too much fuel.

Just-in-time, What type of computer?? There are no codes present. Was at dealer with Diacom computer and the shop manager could not see anything really oos. I was there and questioned several things and got a nod (o.k) with everthing except the Timing. They checked that manually and it was fine. They did replace the MAP and one of the Temp sensors (told me they were inspec but borderline) and this did not help. I eventually changed the other Temp sensor. There is a Intake manifold temp sensor (Open to the manifold) on this 5.0GI that is not shown on the schematics or listed under this engine. Shematics show a plug in it's place. It is however shown under the MPI engine. Not sure what the part# is for my engin or it's operating specs. I think it's used to monitor the incoming air/fuel temp mix and adds another parameter to the ECU to do it's job! Since I don't have a part# for this I can't order one. I've discussed this part several times with parts stores and they keep giving me Water temp senders."
 
"Dave,

Replaced the Wires 2

"Dave,

Replaced the Wires 2 years ago with OEM volvo penta wires. It's possible one is bad but then one plug would be black....not all of them unless the coil wire is bad.. Which brings me to having the coil replaced 2 years ago by another "Crackpot" shop... I was in a jam 100 miles from home on the water on a memorial day weekend and lost the spark while on the water. No one had the time to work on it except for this one shop. After telling the shop mechanic all the symtoms and that the coil may be bad....4hr's of labor later they told me the coil was bad! Looks like they replaced it with a GM Auto part and not a marine grade coil. I think electrically they are the same....Maybe not and this is my problem??? weak spark??"
 
"No, they did not. I'm sur

"No, they did not. I'm sure that if they had they probably would have charged double
angry.gif

and not resolved anything anyway. Don't get me wrong, I don't mind paying someone if they can fix the problem. I have not found many shops very capable and have got fed up paying them top $$ for swapping parts or shoddy workmanship.

JUSTINTIME, I'm also giving some thought to loading. One thing I did change several years ago was prop size and material. I had an Al 3 blade 15x17 volvo penta prop and moved down to a SS 14.25x17(or moved up depending on how you look at it
happy.gif
). It's hard for me to believe this would have any effect. If I get a chance this weekend, I'll swap props and see if the soot buildup along the transom goes away.

Any suggestions as to what software package would be best to use on the water? Diacom? Is there a demo version to see if it's going to help??"
 
"I stumbled accross this from

"I stumbled accross this from the Rinda site:

Two other sensors that are optionally
used in a MEFI system are a manifold
air temperature sensor (MAT) and fuel
pressure sensor (FPS). The MAT
sensor, sometimes referred to as an
intake air temperature sensor (IAT), is
used in conjunction with the coolant
temperature sensor to fine tune fuel
delivery based upon the temperature of
the air entering the engine. As with the
CTS, this is accomplished by modifying
the base injector pulse width values
obtained from the MEFI module’s main
fuel table. MAT sensors are commonly
found on multi-port engines and rarely
used on throttle body injected systems.

This MAT or IAT is what I have on my TBI intake manifold. If I knew the part# I could replace or Voltage vs temp curve I could test it out. If this Fine Tunes the fuel then maybe it's my problem. The Volvo/penta manuals I have do not show this on the 5.0Gi For model year 1999 or 2000. But's it's installed on my engine.

If the engine compartment (air intake) is warm or hot, would this cause it to enrichen or lean out the mixture??? I'm thinking cooler/leaner? Any thoughts here?"
 
"Peter, I have also been deali

"Peter, I have also been dealing with a fuel problem on my 97' 5.7L. The engine would purr like a kitten at idle, but at high rpm/speed the engine would stumble and act as though it was starving of fuel. After running a fuel pressure test on the high pressure side, I was only getting 15psi. This eventually led me to the FPR. The FPR is adjustable but it didn't seem to make much of a difference (1 or 2 psi). I removed the adjuster screw on the FPR and put a longer one in (in order to apply more pressure to the FPR spring) and was able to achieve 30psi. Now the boat starts but idles rougher with much more black smoke/soot coming out......which seems to be your condition…too much gas.

I haven't ran the engine under load yet so I am eager to see if the higher fuel pressure fixed my high rpm problem.

You could try reducing the pressure on you FPR and see if that fixes your idle problem."
 
"Matt,
Sure sounds like my pr

"Matt,
Sure sounds like my problem all right. She runs great at all RPMS except the soot build up (at Idle) and the rough idle.
I'm currently looking to pull the injectors and have them cleaned professionally some time in the near future. I had asked about using an adjustable after market regulator but no one had responded to that. Since i'm right in the middle of some fishing trips, I have refrained from pulling the TBI apart. Short season here so every day counts. Once things wind down a bit I will play.
I was a bit surprised that you were able to adjust the FPR. I did not think they were adjustable. I had read somwhere they were tack welded... at a fix setting and not serviceable. I would love to see the response when the FPR adjusted down to the bottom end of spec at 27PSI instead of being at the upper end of it.

Let us know how yours runs at the higher RPMs and the Higher fuel pressure."
 
"I was able to test the boat t

"I was able to test the boat this weekend and it seems that the higher fuel pressure didn't help. The boat still seemed to be missing at high rpm but now at full throttle it would bog out.
After doing some more internet searching, it seems that the 5.7L TBI is the same combination that the 1988 to 1995 GM trucks use but, the GM trucks specify a 9-13 psi fuel pressure...not 30 psi as the Penta manual indicates.
How can the exact same motor and throttle body have different fuel pressure ratings?

Peter, the FPR is adjustable. The set screw has thread lock on it which makes it difficult to break free after 10+ years but a little heat might help."
 
"Good Morning Guys,

Has any

"Good Morning Guys,

Has anyone tried a new Pressure regulator yet? Be interesting to hear the results........

If Mat is correct about the 88 - 95 GM trucks.... You could run a test with an Auto Pres. Reg. (Even if you had to buy a used TB from a wrecker to get one it would be allot cheaper than paying shop fees).

I also would suggest that if it solves your problem you SHOULD then replace the auto version with the more expensive marine version.

Sounds like everyone including the shops are banging their heads against the wall on this one."
 
"Peter and Matt,

I think I

"Peter and Matt,

I think I am also experiancing the same problem my 1999 5.0Gi. Sooty, lack of power at high RPM but runs perfect uder 2000RPM. My testing for fuel pressure is giving me the same results with 30 PSI.

I am finding with my boat when alone I can get it up to 4200 RPM but when making sharp turn or I am with passengers the boat will slowly start loosing power until I cannot get enough power to get over 2000 RPM. I turn off the motor and restart and I am able to repeat the process. Can you do that with your's?

Peter, I don't know if this matters but your comment "If the engine compartment (air intake) is warm or hot, would this cause it to enrichen or lean out the mixture?}?? I'm thinking cooler/leaner? Any thoughts here?" because my friend (outboard mechanic) mentioned that he felt heat increasing from the motor before the power loss. We thought little about it at the time.

My current thinking is the computer is not adjusting the air/fuel for the changing conditions.

Have you noticed anything on your ignition cap. After 2 1/2 hours on new cap it was already showing signs of arcing."
 
"the fuel injectors are the pr

"the fuel injectors are the problem. It sounds crazy but if you can find a replacement pair, just replace them. I work at a shop in New Mexico and I've had problems with 3 5.0 gi's. After swaping complete t.b.i. units (after getting my ass kicked in troubleshooting)the problem went away. I then started swapping all sensors and everything related. It still ran crappy. I then swaped the injectors and problem was solved. The next two boats with the same symptoms were also injectors. I have another boat in here now with the same problems but I can't find injectors. Talked the the volvo rep and he supposedly spoke with g.m. (being as it's a g.m. part) and he said I'm outta luck. My next bet is to purchase a throttle body or switch to carb."
 
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