5.7 Volvo Penta lean popping

[alldodge]

The injectors should be the same, the amount of fuel is controlled by the ECU. Pull the connectors off the ECU and check for bad connections (+/-). Your ECU might be the issue but guess it could also be a bad connection,

Just found some more notes I made on these motors. Which GXI do your have?
Would post a pic but there is still an issue with IE 11 :facepalm:

Reason for asking for 5.0

GXI-A fuel pressure high side is 29 +/- 2 psi
Timing 8 BTDC

GXI-B,C,D,E fuel pressure high side is 50 to 60 +/- 2 psi
Timing 10 BTDC

 

[LakeSinclairGreg]

Mine is a GSI PEFS not a GXI. Not sure if that changes the info you gave me. I tried another ECU off a friends engine. Same model. Problem didn't go away. I looked at the connections as good as I could without taking the connector apart and didn't see any signs of bad connections. My buddy has agreed to let me swap engine harness' to try. Which may be the way to go, but that's a lot to ask of someone in my opinion. I don't want him to have a problem later this year and look at me as possibly being the cause of it

 

[LakeSinclairGreg]

I really appreciate your help on this issue! I don't have any Volvo people around me to help me out. I could take it to a dealer in Atlanta I guess, but they would charge me an arm and a leg and probably replace all the stuff I've already replaced.

 

[alldodge]

Mine is a GSI PEFS not a GXI

Always good to know what were working on. Don't have any info on yours
My pic shows these all with higher pressure
5.7 Gi-B thru E
5.7 GXi-B thru E
5.7 OSi-B theu D
5.7 OSiX A thru E

I don't have anything for the GSi. Compared the GXI to the GSI in the VP catalog and the pumps are the same but there is not enough info about parts on the TB. Figured if I could find the same or different part number then this would at least verify it.

Pretty sure I'm just chasing smoke because even Merc TBI's in the 1997 thru 2001 used 30 psi TB

 

[LakeSinclairGreg]

I always thought the gxi was a multi port injected motor, but I could be wrong. I think I'm going to try the harness and keep my fingers crossed. I've pretty much been turned into a parts swapper now anyway

 

[alldodge]

always thought the gxi was a multi port injected motor, but I could be wrong

Your correct it is

 

[LakeSinclairGreg]

Well tried a different wiring harness and injectors. Problem still exists. Think the Volvo has beaten me.

 

[Lou C]

What do the plugs look like, are they white/lean? Does it run smoothly except for the lean pop or back fire?
Is it possible that there could be an intake leak at the intake manifold? Either at the intake to cyl head gasket or the one under the throttle body?

 

[QBhoy]

Guys

just reading this and thinking along simple lines.
Here is my thinking. Forgive me if already eliminated...

popping and miss firing is caused by a couple of things mostly.

Retard in timing
ignition system set up
Fuel starvation

So given that your trouble shooting seems to have addressed most of these at first glance, there perhaps is one thing that hasn’t been mentioned and please forgive if it’s so simple and been looked at already.

My instant thought was water in the fuel causing the symptoms. It’s amongst the most common cause. Then I read you had ran it from a separate tank......but...did you change the filter ? This is where loads of water will be if pulled from the main tank initially. Haven’t read you did.

 

[LakeSinclairGreg]

Thanks for the input guys. Sorry I haven't had much time to respond on here. LouC Yes it runs great other than when this occurs. I originally did pull the intake manifold and replaced the gaskets and so forth. I was thinking the same thing. The plugs all look consistent and the electrode coloring seems good to me.
QBhow I replaced the entire fuel module on this thing at some point in all this. I was hoping I had some fuel pressure issue or supply problem.

Guys I have just about given up. I don't like to admit it, but this one beat me. I am looking at purchasing a used engine of the same year and just replace the complete engine, fuel system and ignition system. A lot of trouble but I really like this boat. If this all works out and I do replace it I just can't figure out what to do with the problem child. I was thinking of a sledge hammer, but I don't think that would do it justice. Maybe drain all the fluids and make it an anchor for something.

Thanks for the help guys!!

 

[Lou C]

Well I'd feel bad to see you go through all that, and not really know the cause. IF possible, I'd almost rather convert it to a Holley 4bbl carb as long as the ignition system is not controlled by the EFI computer. Certainly would be cheaper than changing everything. Go back and look at the Volvo parts catalog, for the same engine same year but the carb'd version and see what parts are different. This is why I am a fan of simple carbed engines. You have a problem, bolt on a new Holley for 550 or so and then go boating! No mystery box/wiring/fuel pump BS!

First, are you 100% sure, that an intake valve is not sticking open, when the engine warms up? Have you done a comp test RIGHT AFTER you have this problem? Certainly it is possible and if so the problem could be resolved with a good valve job and new gaskets.

Since the engine you have was available with a carb, you should see if there was a difference between the carb and EFI models in how the ignition system was controlled. If so you might have to convert that too.
4bbl cast iron intake
4bbl Holley
Low pressure fuel pump for carb...in fact....if there is a block off plate for the old style mechanical fuel pump, you can just use any marine pump for a small block Chevy V8 and save a bunch 'o cash! If no provision for the mechanical pump, then you have to use the electric, but there are cheaper options than the Volvo pump. Check with Michigan Motorz for ideas.....