Resolution of 850 turbo hesitation
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Resolution of 850 turbo hesitation
After three nights of messing around, I finally figured it out. About three weeks ago, I installed a new fuel pump. The OEM Volvo ones are very pricy so I decided to use an aftermarket "universal fuel pump" that requires a number of modifications to the existing fuel pump holder including lengthening the wires, putting the motor in a rubber sleve so as to increase it's outside diameter so it will fit in the Volvo holder. All in all, I thought it was kind of half _ _ s but I saved over $150.
The main problem was the fact the intake nozzle on the "universal pump" protruded much farther down from the holder than the OEM one so it was impossible to use the pick up sock. Also because the distance between the top lip of the pump to the bottom pickup is very precise it was really hard to get the cap that holds the unit to screw on tight (as it must because the fuel tank is pressurized. Finally, after an hour of adjsuting I got it too fit.
For about a week, all was well, until one day the car was hard to start and ran like it had a severe vacume leak or bad fuel pressure regulator. I actaully did find two vacume leaks, one on the blow off valve and another where a line from the turbo transitions from rubber to metal near the distributor. The car ran a little better for a couple of days but the same symptons came back; extreme hesitation under accleration and hard starting.
I observed that car had good fuel pressure when running but lost almost all pressure immediately after shut down. My assumption was the fuel pressure regulator so I replaced it. Even with a new fuel pressure regulator it was the same. I did not think it could be the fuel pump because it was only two weeks old and I could hear it running when I turned the key on.
I had no check engine lights so I figured it had to be a fuel problem. There was no smell of gas under the hood and the plugs were all dry even a little lean looking so I thought it could not be a leaking injector. The oil was not diluted either.
Finally, I decided to take one more look at the fuel pump. When I took it out I saw my problem instantly. The rubber hose that runs up from the motor to the outlet nozzle had come loose and hadnt fallen off but wasnt snug enough on the outlet pipe so the fuel could not get properly pressurized. I was really mindfull to tighten the clamp when I put it together but the hose that came with the after market kit was just a little too short so it didnt go far enough up the outlet pipe plus the hose was just a little bit bigger size than OEM hose. The whole thing was excaserabted by the fact that the because the after market universal motor was mounted in a rubber adapter it was able to move up and down eventually loosening itself from the outlet tube. Once it came loose it casued symptoms very much like a failed fuel pressure regulator.
The solution was to buy a used OEM fuel pump from a salvage yard for sixty bucks and all the problems went away. Except for the fact that one of quick connecters started to leak, most likely wore out from being popped on and off so much. Fortunately, the salvage yard included both fuel lines to the filter area so I had a replacement available.
Now I have about $120 invested in this $65 for the fuel pump and $55 for the regulator. The lesson I learned is that Volvos dont take kindly to after market universal fuel pumps. Your are really better off to get a new one or one from a salvage yard that is a direct fit. One benefit is that as a result of searching for vacume leaks my check engine lights went off for the first time in two years. They were throwing 02 sensors codes even after replacing the sensors. It must have been from the leak I found on the line near the distributor.
The main problem was the fact the intake nozzle on the "universal pump" protruded much farther down from the holder than the OEM one so it was impossible to use the pick up sock. Also because the distance between the top lip of the pump to the bottom pickup is very precise it was really hard to get the cap that holds the unit to screw on tight (as it must because the fuel tank is pressurized. Finally, after an hour of adjsuting I got it too fit.
For about a week, all was well, until one day the car was hard to start and ran like it had a severe vacume leak or bad fuel pressure regulator. I actaully did find two vacume leaks, one on the blow off valve and another where a line from the turbo transitions from rubber to metal near the distributor. The car ran a little better for a couple of days but the same symptons came back; extreme hesitation under accleration and hard starting.
I observed that car had good fuel pressure when running but lost almost all pressure immediately after shut down. My assumption was the fuel pressure regulator so I replaced it. Even with a new fuel pressure regulator it was the same. I did not think it could be the fuel pump because it was only two weeks old and I could hear it running when I turned the key on.
I had no check engine lights so I figured it had to be a fuel problem. There was no smell of gas under the hood and the plugs were all dry even a little lean looking so I thought it could not be a leaking injector. The oil was not diluted either.
Finally, I decided to take one more look at the fuel pump. When I took it out I saw my problem instantly. The rubber hose that runs up from the motor to the outlet nozzle had come loose and hadnt fallen off but wasnt snug enough on the outlet pipe so the fuel could not get properly pressurized. I was really mindfull to tighten the clamp when I put it together but the hose that came with the after market kit was just a little too short so it didnt go far enough up the outlet pipe plus the hose was just a little bit bigger size than OEM hose. The whole thing was excaserabted by the fact that the because the after market universal motor was mounted in a rubber adapter it was able to move up and down eventually loosening itself from the outlet tube. Once it came loose it casued symptoms very much like a failed fuel pressure regulator.
The solution was to buy a used OEM fuel pump from a salvage yard for sixty bucks and all the problems went away. Except for the fact that one of quick connecters started to leak, most likely wore out from being popped on and off so much. Fortunately, the salvage yard included both fuel lines to the filter area so I had a replacement available.
Now I have about $120 invested in this $65 for the fuel pump and $55 for the regulator. The lesson I learned is that Volvos dont take kindly to after market universal fuel pumps. Your are really better off to get a new one or one from a salvage yard that is a direct fit. One benefit is that as a result of searching for vacume leaks my check engine lights went off for the first time in two years. They were throwing 02 sensors codes even after replacing the sensors. It must have been from the leak I found on the line near the distributor.
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Joined: Mar 2010
Posts: 4,517
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From: Cape Coral, FL
Why didn't you just post this under your thread instead of creating a new one just for the answer?
https://volvoforums.com/forum/volvo-...eration-57765/
https://volvoforums.com/forum/volvo-...eration-57765/
Senior Member
Joined: Apr 2011
Posts: 174
Likes: 1
From: Florida
Oh I had some work but figured out how to install an aftermarket pump! I installed a Wahlbro 255lph pump. Had to modify how it all connected but got it no issues so far! Plenty of fuel pressure available for modifications as per manufacturer good up to 600Hp!
Wish I had taken some pictures to post but, didn't think about it just wanted it out of my shop and off my lift!
Wish I had taken some pictures to post but, didn't think about it just wanted it out of my shop and off my lift!
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