Help!...8.1Gi fuel pump failures

[262Shamu]

Looking for any ideas here as Cobalt and my service guys seem to have run out. We have replaced the hi/lo fuel pressure assembly 5 times in 9 mos. First and fourth failure happened thirty seconds from the dock at idle. The others on the hose at home or the dealer. They have completely pulled everything apart that they can around injectors, fuel lines, plugs, wiring, fuse box to inspect. They’ve run it with a voltage meter to check for voltage spikes with no issues.
From what I’ve read, two issues possible. Too much pressure and hi pressure runs hot and burns out. pump heats fuel and essentially creates a vapor lock during idle because it is recirculating the fuel.
Or faulty corroded fuse block causing spikes. We aren’t seeing any voltage spikes tho.
No idea what to do next. The mechanic has had back and forth with Cobalt and they are at a loss. I’m throwing out crazy suggestions like swapping a mercruiser cool fuel unit on it. Any ideas?

[AsLan7]

.Hey 262S. Welcome to the Cobaltchat forum. So glad you found us!

Sorry to hear about your engine woes.

What year make and model Cobalt?
262?

What did the ECU scan show?

Let’s get you fixed.

...and welcome aboard mate
.

[262Shamu]

It’s a 2004 262 with the 375hp 8.1Gi. I don’t have the ECU codes as the mechanic read that. But they said it didn’t show anything outside of the ordinary. I should mention that it was blowing the associated fuse as well. I couldn’t work out which was popping first, but I assume the pump was locking up and then the fuse was blowing. Not the other way around.

[Big Block Power]

1 thing we do is add separate fuses in diff circuits to try and narrow it down. Too much voltage drop across some wires. Check all cables and grds.

[AsLan7]

Agreed. How does your grounding block look?

It should look similar to this...

.

[BOZ282]

Had a problem on my 282 with twin 6.2 ,ended up being the RELAY for the fuel pump sending low voltage to LP and HP fuel pump.
relay is on top of fuel rail.

[262Shamu]

Thanks everybody for your suggestions! I’ve passed them on. I actually rang up another Volvo specialist in our area. He actually suggested my crazy solution of putting a cool fuel mercruiser pump on it. Apparently he’s done it a few times with good results. I didn’t even suggest it so I was surprised that was his first idea! We aren’t seeing voltage drop, even when running on the hose with a special voltage recorder for hours. This mercruiser idea may be a $1500 waste of time. But hell, I’ll try anything at this point.

[Auburnbuilder]

May want to give this guy a call, all he does is Volvo Penta fuel pumps.

https://mancavemechanic.com/

[262Shamu]

Thanks to all who commented. We swapped to a Mercruiser Cool Fuel pump. Had 2 and a half days of it working great. That’s fixed the pump burning out issue. But I seem to have found what caused the overall problem. After getting rescued by the coast guard in heavy seas, the filter in the new setup was caked in salt. Somebody installed the fuel vent without a loop or fixing the hose. It spun around at some point and was sucking sea water into the upside down fuel vent. Now I’m trying to get the salt residue out of the tank after pumping out the seawater/gas mess! Installed a Racor and replacing a bunch of stuff. What a mess. Last time I’m using this mechanic as they should have discovered this from the beginning.

[Big Block Power]

Yecks odd. Pictures.

[AsLan7]

Thanks to all who commented. We swapped to a Mercruiser Cool Fuel pump. Had 2 and a half days of it working great. That’s fixed the pump burning out issue. But I seem to have found what caused the overall problem. After getting rescued by the coast guard in heavy seas, the filter in the new setup was caked in salt. Somebody installed the fuel vent without a loop or fixing the hose. It spun around at some point and was sucking sea water into the upside down fuel vent. Now I’m trying to get the salt residue out of the tank after pumping out the seawater/gas mess! Installed a Racor and replacing a bunch of stuff. What a mess. Last time I’m using this mechanic as they should have discovered this from the beginning.

.
Wow. I’ve never heard of that 262S. Thanks for the follow up. So this fuel vent with the two screens was actually upside down? How did the water get that far up near the gunnel?

.