Volvo 850 turbo wagon diversion

[2000StreetRod]

Just when I was getting ready to depend on my Volvo for transportation and start replacing the knock sensor on my Explorer Sport I'm having problems. After driving the vehicle for about 15 minutes in warm weather it suddenly loses almost all power. I haven't checked for diagnostic trouble codes yet because the symptoms seem fuel pressure related. Today I checked the fuel pressure with a cold engine and just the first turn on of the ignition. The pressure jumped to 32 psi and stayed there for about a minute before very slowly dropping. I started the engine and let it idle for a few minutes. The fuel pressure stayed steady at 35 psi.

The Schrader valve on the fuel rail points toward the throttle linkage which must be disconnected to connect my fuel pressure gauge hose. So I can't drive the vehicle with the gauge connected. Also, I can't quickly connect the gauge if I'm driving and suddenly lose power.

I suspect that the pump is weak and starts to fail after running for 10 to 15 minutes. Or it could be that there is crud in the fuel tank that collects on the intank "sock" filter as the pump runs and evenutally starves the pump. After shut off the crud settles back to the bottom of the tank allowing the next start. Tomorrow I'll check for DTCs. Then, since I don't want to waste fuel or get stranded away from home I'll jumper the fuel pump relay to run continuously with the battery charger connected and the ignition module disconnected. If I don't see the fuel pressure drop within an hour I'll start looking for something else.

[2000StreetRod]

Today I checked for DTCs and the only one present was the persistent one for the VSS. I removed the fuel pump relay and jumpered the main connection. Then I disconnected the ignition module, connected my battery charger and turned on the ignition key. I let the fuel pump run continuously for 15 minutes. The pressure was steady as specified at 43 psi (no vacuum present) the entire time. Then I disconnected the charger, turned off the ignition key, connected the ignition module and started the engine. The fuel pressure stayed steady at 34 psi while the engine warmed up. I switched back and forth between engine running and not while continuing to keep the fuel pump running for an hour. The sound of the fuel pump was steady as well as the sound of the fuel being returned by the fuel pressure regulator. The engine ran well for several minutes at 2,500 rpm with a few "blips" to 5,000 rpm.

The road to my subdivision is hilly with sharp curves. There's a possibility that the fuel sloshing around in the tank causes an intermittent connection with the submerged electrical blade type connectors. I tried rocking the vehicle from side to side in the garage but the suspension allows little sway so it wasn't a good test. My next effort will be to remove the fuel pump assembly and replace the blade connectors with soldered connections covered with shrinkable tubing. I would have done that before when the pump was out but I was concerned about igniting fuel remaining in the pump.

[osteologation]

My explorer did the same thing. I'd drive for about 20 minutes and lose power, sometimes stall. Kept my fuel pressure gauge with me. With no load my fuel pump would keep pressure fine. So it took awhile to diagnose. When I dropped the tank the sick had fallen off and it had probably sucked up enough crud to prematurely wear out the pump. Could be similar in your case.

[mudpie]

Originally Posted by 2000StreetRod

After driving the vehicle for about 15 minutes in warm weather it suddenly loses almost all power.

I suspect that the pump is weak and starts to fail after running for 10 to 15 minutes.

Howdy. I stumbled across this thread while doing a google search for other Volvo related info, and thought I'd offer up a possible solution.

For what it's worth....

Volvo fuel pumps are pretty bulletproof. They work, or they don't, and I've only had one that didn't in 20 years of playing with Volvos. In that case, I had loaned my 740 to a friend who was having other car troubles, and she (seems every car killing story involves a "she") liked to put $5 worth of gas in the car at a time, and then run it empty. Not good for electric fuel pumps.

I once had a problem very similar to yours in a '95 850 turbo. The car would run great for about 15 minutes and suddenly die. If I let it sit for an hour or so, it would start up, and run great for another 15 minutes.

Long story short, it was the rear cam seal, on the exhaust cam, leaking into the housing for the cam position sensor. When I started the car, the seal would leak into the housing, and the rotating parts would fling oil all over until there was no more signal. When the car sat for a while, all the oil would drain off, and the car would start, at which point the whole process repeated.

Took me forever to figure that one out. Good luck.

[2000StreetRod]

Originally Posted by mudpie

. . . Volvo fuel pumps are pretty bulletproof. They work, or they don't, and I've only had one that didn't in 20 years of playing with Volvos. In that case, I had loaned my 740 to a friend who was having other car troubles, and she (seems every car killing story involves a "she") liked to put $5 worth of gas in the car at a time, and then run it empty. Not good for electric fuel pumps.

The pump in the vehicle looks like it has been replaced - probably with a "cheapo" that could be unreliable.

Originally Posted by mudpie

I once had a problem very similar to yours in a '95 850 turbo. The car would run great for about 15 minutes and suddenly die. If I let it sit for an hour or so, it would start up, and run great for another 15 minutes.

Long story short, it was the rear cam seal, on the exhaust cam, leaking into the housing for the cam position sensor. When I started the car, the seal would leak into the housing, and the rotating parts would fling oil all over until there was no more signal. When the car sat for a while, all the oil would drain off, and the car would start, at which point the whole process repeated. . .

I checked for leaks when I retimed the camshafts and didn't see any. However, the engine had not run for more than a year when I did that so I'll check for leaks again. Thanks for the tip!

[2000StreetRod]

Before removing and inspecting the fuel pump I jumpered the fuel pump relay with my multimeter and measured the pump current to be 4.5 amps which slowly decreased to 4.4 amps after a minute or two. The battery charger was connected so the voltage was stable. I don't have access to the specified current draw but what I measured seems reasonable.

I removed and inspected the fuel pump assembly. The intank filter "sock" is not full of crud but there is a concentration of rust particles just below the inlet to the pump. The sock can move vertically and gets sucked up to the inlet port. One plastic prong that holds the pump in the assembly is broken off and allows the pump to move 1/8th inch downward on one side. If the pump inlet is located very close to the bottom of the tank the downward movement could restrict flow and starve the pump. I ran the pump for a few seconds to eject the fuel from it and heard a recurring irregular sound. I have decided to purchase an inexpensive (Walbro) pump replacement kit (pump, hose, clamps, sock, connectors, sound insulation). A replacement assembly fuel pump assembly is expensive so I'll try to find another way to mount the pump securely.

Note: as mudpie mentioned in his post the fuel pump should not be allowed to run dry. It requires fuel for cooling and lubrication. Never test a new fuel pump without a fuel supply.

[2000StreetRod]

While trying to figure out a way to repair my fuel pump assembly with a broken plastic tab a used assembly bargain showed up on eBay. I bought it and it arrived today. I was pleased to find it in very good condition with a clean "sock" filter. I installed the pump and measured the current flow with it running. It was 5.2 amps compared to 4.4 amps for my other one. The fuel pressure with no vacuum was 43 psi and it held pressure for more than 10 minutes after shut off so the check valve is good. The fuel flow thru the fuel pressure regulator sounds more continuous so I think the flow is greater than before. The fuel pressure was a steady 34 psi with the engine running at idle. I put everything back together and will do a short test drive staying close to home tomorrow afternoon if it isn't raining. If the test goes well maybe I can start the knock sensor replacement on my Sport.

[Joe Dirt]

Nice. It did sound like the fuel pump was giving up the Swedish ghost...

[2000StreetRod]

Yesterday I drove the turbo wagon to the nearest (2.5 miles) gas station to get gas for my lawn mower. The engine pulled the vehicle up the hills and thru the turns with no problems both ways. This morning I drove to the nearest (2.5 miles) grocery store to pick up some postal stamps. On the way home I accelerated enough to register a slight boost on the gauge and still no problems. It's been cool the last few days so the real test comes when the weather turns warm again.

[2000StreetRod]

Originally Posted by toypaseo

You could look for a 155-80-15 tire. BFG has a Radial T/A in that size, and recommended wheel width is 4½"-5½".

Tires around that size are popular with the old school VW cars and buses...

Thank you for your suggestion! I've been watching eBay for several months for the best price on the 155/80R15. I finally got a new one for $89 with free shipping. I got the tire installed on the spare 4 inch wide rim today for $12. The tire shop installer said replacing a donut spare with the small 155/80R15 was definitely thniking outside of the box. They would use the idea in the future with their customers. I'm embarrassed to say that I failed to give you credit.

The tire fit fine on the smaller width rim. It only has an S speed rating, a 1073 lb load rating and a 24.8 inch diameter compared to my Bridgestone Potenza RE-960 W speed rating, 1356 lb load rating and a 24.9 inch diameter. But the ratings are vastly superior to the original donut spare 45 mph and 50 mile ratings.

By the way, a 4th decent remaining tread 205/55R16 Potenza finally showed up on eBay so I bought it a few days ago. My Potenza RE-960 size has recently been discontinued by Bridgestone except for the run flat tires so that was a lucky break.

I've been driving my 850 instead of my Sport the last week since I'm making two 25 mile round trips per day to the nursing home where my mother is. The 850 got 18.3 mpg with the A/C running a lot.

[sport97]

Glad to see its been running good!

[toypaseo]

That is one dinky BFG

Is that load rating enough...?

[2000StreetRod]

The specified curb weight is only 3,400 lbs/4 = 850 lbs per wheel assuming a 50/50 weight distribution. I no longer have the shredded original spare but I think the rating was only about 900 lbs.

[2000StreetRod]

Unfortunately, I've learned not to trust someone selling a used vehicle. I assumed that the wheel in the spare compartment was for my Volvo but when I attempted to use the spare to replace my fourth dry rotted tire I found out otherwise. The first clue was the lack of the locator pin hole. The next clue was the obvious difference in the bolt circle diameter of the spare rim vs the hub. To resolve the problem I purchased a used Volvo donut spare, paid to have the donut tire removed from the Volvo rim, and the new BFG tire removed from the unknown rim and installed on the Volvo rim as shown below.

Below is a comparison of the stock Volvo donut spare tire to a turbo wheel with Bridgestone 205/55R16 Potenza RE-960.

It has been an expensive process to end up with a decent spare.

[toypaseo]

Damn, what a nightmare. Good that you figured it out now, and not on the side of the road somewhere.

[Joe Dirt]

No doubt... Is the Volvo still running top yet?

[2000StreetRod]

Originally Posted by Joe Dirt

No doubt... Is the Volvo still running top yet?

I haven't driven the 850 for more than two weeks. I loaned it to my cousin who came out from Oregon to be a caregiver for my mother who is on hospice at home. I was appalled at the treatment she was receiving at the nursing home. The Volvo did well for the three weeks I drove it twice a day to the nursing home - 25 miles round trip. My cousin says it's doing fine for her.