Volvo Penta V6-240 Fuel High Pressure Dropping to Zero

[Biz603]

I'm at a lost for what it could be and have been reading intently hoping to find the issue. Hoped @muc or others can advise, but looks like the well is running dry

Thanks for the deep look and trying. I appreciated it.

 

[Biz603]

The only thing I come up with is a different hpfp... 12733993 for the 4.3. Looks like it overlaps the pn for the one you are using. Do I think thats the issue based on the data? No... but I'm at a loss for what else it could be.

Thanks for your input. Open to trying it.

 

[Pmt133]

One other question. When installing the fuel pump, how's the lobe look?

And I don't know if I missed it but what year 4.3 is this?

It's odd to be having the same issue but something is being missed.

 

[Biz603]

One other question. When installing the fuel pump, how's the lobe look?

And I don't know if I missed it but what year 4.3 is this?

It's odd to be having the same issue but something is being missed.

2017.
Not sure what the lobe is. But, after removing the HPFP each time I looked down the hole at the cam it rides on. Admittedly without a flashlight, but under sun light I didn’t notice any excessive wear or scarring. The push pin on the HPFP looked good. Can send pix of that if needed.

 

[Pmt133]

2017.
Not sure what the lobe is. But, after removing the HPFP each time I looked down the hole at the cam it rides on. Admittedly without a flashlight, but under sun light I didn’t notice any excessive wear or scarring. The push pin on the HPFP looked good. Can send pix of that if needed.

The lobe, eccentric, cam lobe etc. Just checking. I've seen worn lobes from fuel pump failures cause issues too but usually it's noticeable either in the fuel or visually scarred or worn down. I don't think it was the problem either but worth asking just to rule out anything else.

 

[Lpgc]

Sorry I didn't visit this forum for a while but I checked this thread as soon as I visited... Just don't have anything to suggest.

Any new developments?

 

[Biz603]

Sorry I didn't visit this forum for a while but I checked this thread as soon as I visited... Just don't have anything to suggest.

Any new developments?

The latest . . .
I uploaded a zip file with several test runs in the lake, under load (a few posts back). Some test runs failed as expected, some others work just fine, like nothing was wrong, and achieved 5800 rpm, max for this engine. It was 50/50.
Here’s the really strange thing, brought the boat back home, fired it up one last time before winterizing it, and it worked just fine!! Like nothing was wrong. I couldn’t get it to fail again with several tries. Crazy I know. I couldn’t believe it. 20 minutes of a matrix of throttle ramps and position, ZERO failures!?!
I have no idea why.
I winterized it and it’s put away now.
When I take it out again in May I’ll post back here again.
Until then a big THANK YOU to all who contributed!! Much appreciate!!
Until May . . .

 

[Biz603]

So, last day of May 26' and I'm reporting back as promised. Broke the boat out. 'Springerized' it. Fired it up on the trailer, zero issues. Full 5800 RPM on demand. Looking good. I'll drop it in the water and give is a good test under load in a week or so. I'll report back then.

 

[muc]

Please don't exceed 2000 RPMs when not underload.

 

[Biz603]

Please don't exceed 2000 RPMs when not underload.

Can do. So I understand, what’s the reason?

 

[Scott Danforth]

Following along out of curiosity

 

[muc]

Can do. So I understand, what’s the reason?

Good question, made me think about why I always give this advise.
I don't have a good answer other then all the really great mechanics I've had the good fortune to work with and all the instructors at the various factory schools would say this.
After thinking about it, here are my feelings.
1. Free revving an engine provides no useful information and can only cause problems. I have had V8 automotive based engines with tuliped valves in 4 cylinders and they would still spin up over 4K RPMs.
2. I would be worried about spinning a cold engine faster then 2K RPMs. A engine won't get up to full operating temp without a load on it. It takes 10-20 minutes working under a moderate load to reach full temp. I have tried to let engines idle at the dock for 30 mins to try and shorten this time and it really doesn't help much at all.
3. Engines weren't designed to spin that fast without a load. I'm guessing combustion chamber temps and pressures are pretty low when this is done so it could affect the bearings, rings and valve train.

I know that this doesn't apply to your engine, but never free rev a 2 stroke outboard engine. These engines use roller bearings for the crankshaft and rods. Rapid acceleration of these engines will allow the rollers to "skate" on the crank. We were taught what this looked like in the O/B classes so we could instruct the customer when we came across this.

 

[Biz603]

Dropped it in the lake. For the first half hour the ECM was limiting the rpm to 5200 at each throttle up. But at 5200 I could drop the throttle back to 4000 rpm then right back up to full throttle and the engine would get to the max of 5800. After this first half hour this limiting issue went away and I had zero issues for the rest of the day. No idea why, but my boat is back. I’ll circle back if I have any more issues.

 

[muc]

Possible fuel issue?

 

[theo_morabito]

So, last day of May 26' and I'm reporting back as promised. Broke the boat out. 'Springerized' it. Fired it up on the trailer, zero issues. Full 5800 RPM on demand. Looking good. I'll drop it in the water and give is a good test under load in a week or so. I'll report back then.

So... it just fixed itself? I'm with an 5.3 genV volvo penta engine and its showing the exact same problem as yours was showing. Im not an english native speaker so maybe some words are not all right but i will try. I have read all your posts and its literally the same error. I have changed the pump 2 times already, new injectors, new fuel line pressure sensor, new hydraulic tappet that goes to the fuel pump, and still when i reach 4000rpm the fuel pressure drops to 50psi just like yours did, like something was shutting it down. Have no idea why. If you have any new things to add that you maybe discovered throuout time let me know, it can maybe help me very much, im trying to figure out this motor for at least 4 to 5 months by now

 

[Biz603]

I feel your pain brother. After my entire ordeal, this is my conclusion:
Make sure your engine is not in safe or rev limiting mode. Then . . .
I'm 95% convinced that GM is building crappy high pressure fuel pumps. Specifically, the relief valve (or over-pressure valve) that is built into the pump (and not adjustable at all) is defective from the factory. It ends up relieving the fuel pressure below the factory setting, somewhere around 2500-3000 PSI.
I've talked to a few GM automotive techs working on Silverado 1500, which is where my engine is used. They have the same story. They will change the High Pressure Fuel Pump (HPFP), run the truck for an hour or so, if it's still relieving pressure prematurely, they will just swap out the HPFP, again and again until they get a good one.
Here's what I'd do:
1. Put a UV gas additive in your gas tank.
2. Drop it in a lake and run it under load for at least 30 minutes. Rev to failure again and again. Rev slowly to failure, then fast to failure, repeat.
3. Stop the engine and check for UV on your oil dipstick using a UV flashlight.
4. If you see the UV additive in your oil, then it's most likely your HPFP relief valve. (Thanks GM.) If there is no UV, then you may have other issues. See all the notes of things to check in this thread.
5. Run the boat about another 10-20 minutes. The relief valve may just start working like mine.
6. After all this time it still doesn't work, you may have to swap it, I'm sorry to say.

Running it more than the times above shouldn't hurt your engine and might improve your chances of it working, as crazy as that sounds.

 

[muc]

I feel your pain brother. After my entire ordeal, this is my conclusion:
Make sure your engine is not in safe or rev limiting mode. Then . . .
I'm 95% convinced that GM is building crappy high pressure fuel pumps. Specifically, the relief valve (or over-pressure valve) that is built into the pump (and not adjustable at all) is defective from the factory. It ends up relieving the fuel pressure below the factory setting, somewhere around 2500-3000 PSI.
I've talked to a few GM automotive techs working on Silverado 1500, which is where my engine is used. They have the same story. They will change the High Pressure Fuel Pump (HPFP), run the truck for an hour or so, if it's still relieving pressure prematurely, they will just swap out the HPFP, again and again until they get a good one.
Here's what I'd do:
1. Put a UV gas additive in your gas tank.
2. Drop it in a lake and run it under load for at least 30 minutes. Rev to failure again and again. Rev slowly to failure, then fast to failure, repeat.
3. Stop the engine and check for UV on your oil dipstick using a UV flashlight.
4. If you see the UV additive in your oil, then it's most likely your HPFP relief valve. (Thanks GM.) If there is no UV, then you may have other issues. See all the notes of things to check in this thread.
5. Run the boat about another 10-20 minutes. The relief valve may just start working like mine.
6. After all this time it still doesn't work, you may have to swap it, I'm sorry to say.

Running it more than the times above shouldn't hurt your engine and might improve your chances of it working, as crazy as that sounds.

First --- thank you @Biz603 for responding!
Did you put the boat away with some sort of stabilizer of conditioner in the fuel? And maybe sitting and soaking all winter freed up the HPFP?
This one drove me CRAZY and I have always wanted to be sure what fixed it.

 

[theo_morabito]

I feel your pain brother. After my entire ordeal, this is my conclusion:
Make sure your engine is not in safe or rev limiting mode. Then . . .
I'm 95% convinced that GM is building crappy high pressure fuel pumps. Specifically, the relief valve (or over-pressure valve) that is built into the pump (and not adjustable at all) is defective from the factory. It ends up relieving the fuel pressure below the factory setting, somewhere around 2500-3000 PSI.
I've talked to a few GM automotive techs working on Silverado 1500, which is where my engine is used. They have the same story. They will change the High Pressure Fuel Pump (HPFP), run the truck for an hour or so, if it's still relieving pressure prematurely, they will just swap out the HPFP, again and again until they get a good one.
Here's what I'd do:
1. Put a UV gas additive in your gas tank.
2. Drop it in a lake and run it under load for at least 30 minutes. Rev to failure again and again. Rev slowly to failure, then fast to failure, repeat.
3. Stop the engine and check for UV on your oil dipstick using a UV flashlight.
4. If you see the UV additive in your oil, then it's most likely your HPFP relief valve. (Thanks GM.) If there is no UV, then you may have other issues. See all the notes of things to check in this thread.
5. Run the boat about another 10-20 minutes. The relief valve may just start working like mine.
6. After all this time it still doesn't work, you may have to swap it, I'm sorry to say.

Running it more than the times above shouldn't hurt your engine and might improve your chances of it working, as crazy as that sounds.

Perfect!! Thanks for the reply!
I will do all your steps than return to you with updates, hopefully good ones. Im from brazil so the gm parts all come or from europe or from the usa, so it takes about 15 to 30 days for them to ship it here. If i have to order another hpfp it will continue to take time and there is nothing i could do about it. But anyways thank you for all your help. I will continue to update in here