96 volvo 850 Walbro fuel—the wrong one?

Post by **JimBee** » 21 Sep 2017, 12:09

Installed the Walbro AOU203 fuel pump and my 850 2.3 won't start. Checked the wiring and pump for continuity, all seems good. No other problems in the system because the oem Bosch which is on its last legs still starts and runs the engine. I reinstalled the Bosch to get around and it starts the engine immediately.

I've read that the Walbro 255 is sometimes used. The Walbro sales rep says the 255 is only used on cars with modified engines.

Suggestions appreciated.

Post by **erikv11** » 21 Sep 2017, 13:33

I don't know the details of these different Walbro models, to really help with your actual question.

When you had the Walbro installed, was it providing pressure at the fuel rail (if so, you'd want to measure it)? Did the pump fire up when you turned the key (Walbro pumps are pretty noisy, so that should be pretty easy to tell)? I see you inspected the wiring etc. but I am curious if there was a power fault or not.

The higher pressure Walbro (255) can be used just fine, the FPR takes care of things for you.

Post by **rspi** » 21 Sep 2017, 17:34

Did you test the pump?

Post by **JimBee** » 22 Sep 2017, 10:13

rspi: I haven't bench tested the pump dry, if that's what you're asking. The failing Bosch pump starts the car instantly, though that is in a different housing. Then the question arises about the housing containing the new Walbro, but like I said, I've tested the wiring for continuity in that housing, so I'm assuming voltage is getting to the pump.

I just talked with the rep. He told me there were serial numbers that were known to be faulty, so I need to pull it from the housing and check that.

Erik. Pressing the Schraeder valve, key off, produced just a dribble for both the Bosch and the Walbro. Key on, not much different. But, like I said, the failing Bosch starts the engine instantly, like it always has. Yet, not even a pop from the Walbro.

Post by **j-dawg** » 22 Sep 2017, 12:21

I have the 255. Not a problem. 99 and 96 fueling systems work differently, but as Erik pointed out the fuel pressure regulator will keep you in the zone.

Post by **JimBee** » 22 Sep 2017, 16:50

Got the update from the Walbro tech. Some serial numbers were known to be faulty (why this is not known up front, IDK!). He checked and found that mine is one of them. They're sending me a new one. I asked him to check with the manufacturer to make sure the SN checks out okay.

BTW: The seller's (fuelpumps.net) price for the 255 is $62.00 with no installation kit, the standard one that I ordered is $54.00 + $15.00 for installation kit. Rather than redo the transaction, I agreed to get a replacement for the standard one that I originally ordered. Because today is Friday, I won't have it until late next week. Hopefully, that solves it. I'll update the post when I confirm.

Post by **erikv11** » 22 Sep 2017, 19:49

JimBee wrote: ↑22 Sep 2017, 10:13 rspi: I haven't bench tested the pump dry, if that's what you're asking. The failing Bosch pump starts the car instantly, though that is in a different housing. Then the question arises about the housing containing the new Walbro, but like I said, I've tested the wiring for continuity in that housing, so I'm assuming voltage is getting to the pump.

I just talked with the rep. He told me there were serial numbers that were known to be faulty, so I need to pull it from the housing and check that.

Erik. Pressing the Schraeder valve, key off, produced just a dribble for both the Bosch and the Walbro. Key on, not much different. But, like I said, the failing Bosch starts the engine instantly, like it always has. Yet, not even a pop from the Walbro.

Robert and I are asking the same thing: does the pump get power, and when it gets power does it go buzz and pump gas? I guess if the new one works, you have an answer to that by inference. Hope it takes care of it!

Post by **tryingbe** » 24 Sep 2017, 11:15

Fuel pump is a simple device, you put 12v and ground and it turns...

Post by **JimBee** » 24 Sep 2017, 14:34

I've never tested an electric pump dry, but when I install the new one when I get it next week and confirm that it works I will put 12v. to the "new" one that won't start my engine. On the bench. Dry. Just to see what it will do. If it runs, I might stick it in a bucket of water to see if it pumps at all.

BTW: The pump in my 93 850 that ran the engine fine in June or July last year before I parked it until winter wouldn't start the engine in November—though it did buzz. That mystified me; it had been working normally and was working well enough to make an audible sound but not well enough to get even a pop out of the engine. After tuning the engine (okay, it was due for plugs) and checking all the wiring, I swapped in a used (previously confirmed working) pump and it fired right up. If the Walbro turns out well I'll get another new one for the 93. I don't relish the thought of dealing with a pump failure in February.

Post by **JimBee** » 26 May 2018, 10:12

UPDATE 9 months later with no problems—finally—with the new fuel pump. So what had caused the new one not to work? I and techs at Walbro (and the vendor) were totally puzzled. They sent me a second one that didn't work as shipped either.

Finally, I left the sock filter off and voila! it worked. WTH? Put the sock filter back on. Nothing. This became the next conversation with the vendors. After much head scratching, and assurance that the correct filter had been shipped with the unit, they determined that in fact the filter was the wrong one. The one that was shipped was for an ethanol E-85 fuel that for some reason I don't understand doesn't pass gasoline through the mesh.

Another tech looked up the filters that might work and sent me one that did. So, it's been fine after swapping that one in.