1995 850 Turbo Surges on acceleration

jdakins · Post by **jdakins** » 27 Jun 2015, 08:10

I have two issues to ask about, maybe they are related - and thanks in advance for any help.

1. Restarting after driving far enough to reach normal operating temperatures often fails if I'm trying to restart within say, 15-20 minutes. What happens is the engine will always turn over, then usually fire up on what feels like less then all 5 cylinders. Any attempt to drive it makes it quit. Codes after this always read random misfire in cylinder 1/2/3/4/5. However, if I wait a few hours or longer it starts and runs. Also, if I disconnect the battery and pull the electronic computer connection apart for a minute or so, then reconnect, it will usually run on all 5 again. This happens most often when it's hot outside. From what I've read here, the fuel pressure regulator might be at fault? If so can I get away with just getting one at O'rileys maybe?

2. The real killer: Any throttle pressure that sends the turbo pressure just into the white (I'm not savvy enough to know what pressure that is) causes it to surge. go / quit / go quit. So I have to be very careful not to try to pass anyone, or get in a spot where I have to accelerate quickly. Codes involved here always seem to be knock sensor related. So far I've replaced the mass air sensor / the turbo control valve and one mechanic was sure he had the answer and replaced the catalytic converter. Still no love. Could the FPC be causing both these issues?

Specifications:
Year = 95
Model = 850 Turbo
Engine = B5234T
Mileage = 207,000
Frustration level = 8 of 10

previous Volvo's = 240, 740, C70

John Dakins
St. Louis, MO

Post by **tryingbe** » 27 Jun 2015, 16:49

#1. Check and make sure ALL the hose clamps are tight and hoses are not torn.

#2. Get a fuel pressure gauge and test the fuel pressure.

My guess is fuel pump is on its way out.

jdakins · Post by **jdakins** » 29 Jun 2015, 17:12

Thanks.

Hoses: I found one slightly loose hose clamp and one suspicious looking 90 degree-er coming off the vacuum tree. BTW, my tree has two ports capped (I will try to attach a pic) but I think that is normal for my engine because I didn't cap them and I've owned it for 15 years at least.

: Vac_tree

Fuel Pressure: I borrowed a guage from O'Rileys. ZERO pressure. With key in ll position, also when running at idle and revved up to around 2500. Is that even possible, for the car to start and run with zero fuel pressure? I put 4000 miles on my sailboat, from Lake MI to the Bahamas and I know for a fact that my Westerbeke 30C Three would not run without fuel pressure. Course that's a diesel, but still I can't get past thinking I didn't hooked up the gauge correctly. I found and followed a guy on YouTube checking his 850 wagon and did what he did so I'm lost.

My steps: Removed the valve stem from the Schrader (sp?) valve after releasing gas/pressure. Attached EverTough pressure gauge with adapter and turned key to position II. Waited (I could hear what I though was the fuel pump) a minute or two. ZERO pressure. Started it, ran and revved. ZERO pressure. But my car ran as well as it has been lately, stumbles if I accelerate too much but I was able to drive it to O'Rileys to return the pressure gauge. I'm stumped. Sorry for being so wordy. I just can't help thinking I did something wrong in checking for fuel, but I don't know what. I did get fuel squirting out of the Schrader valve and the gauge, so I know fuel was getting to the gauge at least.

Post by **abscate** » 30 Jun 2015, 05:42

Try it with a 99 cent pencil tire gauge, which you chuck when done.

Either the gauge is bad or your connections.

Ha! A fellow sailor, too! We stay coastal from Cape May to Maine...but MV is our summer hangout

jdakins · Post by **jdakins** » 30 Jun 2015, 10:38

Aha! Leave it to a sailor to come up with a great, cheap solution. But, even the tire gauge didn't budge. I'm taking it down to a shop tomorrow and having them check it. What a puzzle. Sort of like tides, only worse.

previous Volvo's = 240, 740, C70
1974 Hallberg Rassy 31 Monsun Hull #12

John Dakins
St. Louis, MO

jdakins · Post by **jdakins** » 01 Jul 2015, 08:05

20 pounds of pressure. Now to decide between trying to do it myself or taking it to a shop. Just noting this in case someone else runs into the same thing.

John Dakins
St. Louis, MO

Post by **tryingbe** » 01 Jul 2015, 17:19

I'd change the fuel pump, sock on the fuel pump, and the fuel filter. You may or may not need the fuel pump gasket (Volvo only).

Here are the part numbers you need in there.
https://www.fcpeuro.com/products/volvo- ... 9480152kit

Post by **abscate** » 02 Jul 2015, 07:16

Try changing the fuel filter in the off chance it's plugged. They really do last 100k miles but if it hasn't been done or you got a slug of dirty gas it's possible and easy.

I don't know the FPR function that well but if that's fubar could it be killing your fuel pressure? Check that and replace before doing the fuel pump fiasco, if there is gas in it.

First first first .....

I can't remember if you checked fuel pump relay and wiring to fuel pump up thread but a reminder to do that too.

jdakins · Post by **jdakins** » 04 Jul 2015, 13:26

Big thanks to abscate and tryingbe! Turns out my original fuel pump (206,000) was clean and fine but the connecting hose clamp inside the module had loosened at the top nipple. That let the spring inside pull the hose almost all the way off the nipple, so I had 20# of pressure instead of #40, and when I would jump on it, it got starved for fuel. I'm really happy because I can send the new aftermarket pump back, woo hoo! I never even took it out of the box.
Now it runs and accelerates like a 850 turbo instead of a very tired 240.

Here is a picture of my original fuel pump AFTER I had compressed the spring by pressing up on the screen (not shown) and tightened the hose clamp again.

: volvo_pump.jpg (87.09 KiB) Viewed 825 times

My love / hate relationship with my 850 is pegged on love again - Volvo parts sure are expensive but really made well. The inside of the pump module and the hose look brand new and the car is running great so far. BTW, NAPA loaded me a fuel pump removal kit so taking the ring nut off was simple.