Volvo Penta 5.8 FSi Stumble Cruise Issue

Michael Clemensen

Michael Clemensen

Member
Member
Joined
Jan 1, 2000
RO Number
2006
Messages
359
Did quite a bit of power plant maintenance this Spring, Plugs, Distributer Cap, rotor and New Plug wires. Started great after the winter layup adjusted initial timing then waited for the weather to warm and Lake Michigan to smooth out. Launched boat it started great, motored out of North Point Marina headed South towards Waukegan cruising at 3,500 RPM's. About 4 miles South, the power plant just stumbled like I turned off the Key, but it didn't completely die. Felt like it took a slug of water or?? It occurred twice more, but not as severe as the first time. Turned around and motored back to North Point Marina without incident.

Brought the Boat home, removed the fuel filter and poured the contents into a clear container. Installed a new fuel filter. After letting the fuel settle for a few hours there didn't appear to be any water or ethanol jelly globs in the container.

Made up a TEST rig to check for codes in the '96 FORD EEC-IV computer. It only had the 11 code which is No Codes Normal.

Purchased a 0-100 PSI Fuel gauge. Checked high pressure fuel pump output, 39 lbs. which is the correct output. Was unable to get a reading on the low pressure pump output with this gauge, didn't depress the Schrader valve enough. Removed the valve core and installed a vacuum gauge that also can read 0-10 psi fuel pressure. Low pressure output was now reading 3.3 psi. and I could see the pressure dip down as the LP pump filled the fuel/vapor separator that the HP pump is located on top.
Shop manual stated LP pump pressure should be 5.9-8.4 PSI cranking or at idle.
Replacement LP fuel pump on order. I didn't check the anti syphon valve on the fuel tank but will if the replacement LP pump doesn't fix the low pressure issue. B.O.A.T. Break Out Another Thousand. [:-bonc01]
 
I would replace the anti-siphon valve before trying anything else. You could replace it with a normal fitting to see if it corrects the problem. If it does get an new valve. I had intermittent problems one year where it would just bog down and ended up being the anti-siphon valve. As long as it's easy to get to it's something cheap to try before spending more time and money.
 
At what rpm did you check the fuel pressure and was that at the dock? I don't know your engine but that 39 PSI seems kind of low if that is an MPI.( FWIW-Crusader specs about 57-62psi at WOT for 5.7 & 6.0L return system MPI 66-69 psi for returnless 6.0L , & 7-9psi for LP pump at WOT.)
The pressure test should be done under load when the problem is manifesting or expected to, if possible.

If the A/S valve is suspect you can bypass it and the tank temporarily by plumbing in a clean portable O/B tank with new fresh gas and take it for a ride.

I would also suggest trying the Serious Wiggle Test of the harness wires on the engine , particularly near all connections and the fuel pump relay to see if combustion kicks up or down.

Do you see any corrosion on the LP or HP pump power connections? Is that LP pump getting hot? Some VP fuel pumps get clogged with internal paint sloughing off.
 
Have an Anti-siphon valve if the LP pump doesn't fix the issue, Getting to it is the issue.
Sandy, RPM was at 700-1500, water connected with ears along side the garage. Volvo Penta shop manual states 39 PSI at idle, 31 PSI WOT. Did the open clean on the connectors followed by a wiggle test at 1,500 RPM, LP PSI didn't change. The LP pump was warm after the incident while I was removing the fuel filter/separator. I've heard of the paint issue but thought it was on Mercrusiers. Pump is enroute, should be here Wednesday and then we'll wait for decent weather to R/R.

Thanks for the comments.
 
FWIW, The LP pump on my MPIs has a filter in the inlet.
VP had plenty of fuel pump paint problems ( I think they invented it), but the paint was clogging the cooling RW flow to overheat the pumps , not clog fuel flow.

The fuel pressure on my engines rises at higher RPM so that's a little surprising to read your manual's specs which indicate the opposite. I think my HP pump idle pressure might be close to the same as yours though.

I have had to replace 1 failing LP pump which was causing HP pump starvation at 3000 rpm under load only (not in N) and quick rail pressure drop to near 0. Up to 3000 rpm under load it ran normally. No change after plumbing-in the temporary clean portable tank of fresh gas to bypass everything else up to the LP pump inlet. Ran fine at any rpm after installing the new LP pump. The old one had corroded hidden electrical connections on the bottom of the pump where a previous RW pump leak had sprayed SW. That caused excess internal resistance and overheat.

Hope your luck is the same as mine since your shiny new LP pump is on its way.

Is your engine TBI or MPI?
 
Power plant is MPI, one of the last FORD 5.8 High Outputs marinized by VP and OMC in their joint Venture. Pump arrived yesterday, if weather permits should get it installed today.
 
Had an open weather window. Tested the defective LP pump twice more, started a 4 PSI then dropped to 2+ PSI. R/R the LP Pump, the most difficult part was cracking off the NPT/straight thread adapter between the fuel filter/separator and the LP Pump. You have to install the straight threaded portion with vitron O-ring on the inlet side of the LP Pump then tighten the adapter so the electrical connector is in the correct position.

Started it up and the PSI was/is HIGHER than desired at approx. 10-11 PSI. Manual states 5.9-8.4 PSI. That must be for a NON made in CHINA LP Pump!!! No Leaks on fittings or the fuel/vapor separator++++!!! Ran on hose ears sounds good.

Sea Trial awaits, Hopefully it will have some Fishing included.

Thanks for the comments and recommendations.

.
 
You may have just gained 50 hp. !:D .

May The Fish Be With You.
 
Sea Trial conducted this afternoon 5/29. Didn't go as SMOOTH as I had anticipated!! Same procedure as before, headed South, power plant running great at 3,500 RPM went quite a ways then the dreaded COUGH. Not as bas as the other three times, but still a stumble. Continued and we had a smaller stumble, turned around and headed in. I was SO CONFIDENT that the issue was resolved that I didn't bring any fuel pressure testing devices with. Went alongside the pier, grabbed the truck ran home to pick up the fuel pressure gauge. Back at the boat, installed the fuel pressure gauge on the HP Schrader valve. Started power plant, 31 PSI. Motored out and headed South made 3,500 RPM run followed by MULTIPLE WOT Runs with no stumbles. Noticed that the HP fuel pressure read 39 PSI at WOT, Manual stated 31 PSI at WOT. Don't know if that is critical or just a result of the regulator on the HP line. The power plant also didn't make the WOT range of 4,600-5,000 RPM, only 4,100 ish.

Filled the tank with fresh 93 octane and will take it out fishing at the next available opportunity. Still Looking.
 
Took it back out this morning, still having "drivability" issues. Going to regroup and double/triple check what I've done and make sure that I didn't make any errors!! Coughed a couple of times on the way in after fishing for 6 hours, power plant trolled great 700-880 RPM. On the way back to port it also seemed that it was consuming more fuel per the FloScan and there didn't appear to be any "snap" when the throttle was advanced.

Going to look it over without any rose colored glasses on. Have fuel line and new anti-syphon valve at the ready.

Sit-rep to follow.
 
Replaced Anti-siphon barb, new 2/8" fuel line, opened every connector, sprayed with electrical cleaner, blew out with compressed air then sprayed with T-9. Checked grounds on power plant to battery (3). Ohm'd out key sensor inputs to the 60 pin EEC connector. Ran EEC-IV KOEO test followed by KOER test and verified that the EEC was telling the distributer to advance. Nothing found.

Took boat on Sea Trial Ran at multiple throttle setting, Idle to WOT tests. It performed well with NO stumbles of coughs. Still couldn't get to WOT but that maybe a combination of re-worked props and a LOT of excess baggage in the boat.

Over all happy with the outcome, fishing trip scheduled for tomorrow weather permitting.

Just don't like not finding the "smoking gun."

Thanks to ALL!! :)
 
Remember the old adage - Death by a thousand cuts ? Sometimes its a multitude of little things that add up to a much larger problem. Glad you boat is healed. We were about to have Ernest Angley lay hands on it !
 
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