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Turbo is not engaging
1991 Volvo 740

Turbo is not engaging

(1991 Volvo 740)
Turbo is not engaging, have checked all hoses, they seem fine ( no colasping) Not sure where to go from.
1 answer & 6 comments
Popular Answer
on June 27, 2010
How is the vehicle running otherwise? Is the check engine light on?
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No, but the service light comes on for about a minute or two then goes out. Overall it runs fine, with the exception of the turbo not engaging. When we take off the top vaccum test port it seems to quiet the engine and we notice less engine noise, and the rpms seem to hold steady around 1000 (when the port is replaced, rmps drop just under 1000. On the turbo "scale" it is registering only about a quarter of the scale it will fluctuate a little when rmps are raised (3000rpms) but then it will fall back down to the quarter mark. We thought it might have been vaccum hose leaks, so replaced several hoses and now it seems to have made the problem worse.
on June 29, 2010
The service reminder light needs to be reset to turn that off, just use the reset button on the instrument panel, behind the black rubber plug.
Without seeing this it's hard to know what's happening, but are you sure the turbo is the issue? How is the fuel pressure? Do you have any codes in the engine or ignition computers? Do you have a restricted exhaust system?
on July 04, 2010
We don't have a code reader. We don't have the money to invest in one right now but would like one at some point unless you know of a very good one at a low price please include where to purchase . We are interested in knowing how to test the fuel pressue. However, the car seems to idle just fine, no we are not sure that the turbo is not the issue, but we do know that the turbo is not engaging. Is there a test that can be performed on the vaccum system to make sure there is enough vaccum to perform turbo function? Is there a way to use normal household part to create these gauges for testing? We have a very limited income, however we enjoy our 740 turbo that we picked up for a grand. What I notice the most is the turbo scale is narrowed to a 1/4" to where it use to travel up to a inch and feel and hear the turbo engaging the car seems to run fine just no happy juice when getting on highway or passing or getting off the line with a bit of effort to be honest this is the wifes car and she like\loves it a lot i want it to preform for her, i'm not familar with turbo engines - however i'm aware of the reliabilty of the b230ft and i want to get a better understanding of what is going on with it so i know how to get it running corretly so that i maintain its general health im not sure on how to test for restiction of exhaust system either, let face it this is something that we may not have the tools to preform these test unless i can make them up myself willing to put effort into it just low on income I wanted to thank you for your time sorry Im so long winded i reset the button \ thanks ps the more i replaced the hoses and closed up the leaks on the vacuum system the more scale decreased - i'm lost
on July 04, 2010
Without the appropriate tools this becomes more difficult, but there is some good news, you don't need a code reader. Look at this site to learn how to read the codes. http://volvospeed.com/CheckEngine.php
Check A-2 and A-6 ports, read the codes and post them here, I'll see if I can help.
Here are the codes: http://volvospeed.com/vs_forum/index.php/topic/47502-dtc-information/
Make sure the big turbo hoses are OK, not split, loose or leaking.
Remove the air cleaner housing, if there is a foam pad on the underside of the housing and it is deteriorating, then this may be the issue. The foam will contaminate the MAF sensor, so clean out all the foam and clean the MAF sensor with compressed air or a spray MAF cleaner.
Good luck
on July 10, 2010
We did notice the foam pad had started to break down, so we cleaned it out down to the plastic and tried to remove as much of the adheasive as we could. Also sprayed out the MAF with carb cleaner. Noticed a black buildup (carbon???) on the in take screen of the MAF, in the bottom of the air box there was a 1 3/4 plug on the engine side, I felt maybe that it would be better to have more air flow coming into the box so we removed the plug. The other port on the fender side was open and free of debre. Did I make a mistake, and should I close off the port on the engine side by putting back that plug? We will do the codes and do our best to provide that information. Just wanted your opinion on the air box and the plug. Thank you very much for your time, sorry it is taking us so long to respond, this is kind of weekend project. What do you think about the throttle positioning sensor, would that inhibit the turbo from engaging? We just checked the codes and A6 came up 111 as well as A2 the rest of them had no response. We only have one port that we could find and it is located up by the drivers side strut tower. We looked at the turbo waste gate linkage and there was a cotter pin missing out of the linkage, but we did replace it and no change has been noticed. Is there a way to test the vaccum line going to the turbo? If so, what should the psi be? Is there a way to check the function of the valve that the vaccum line leads to?
on July 12, 2010
Not sure about the hole in the air box, I think that's the port for the thermostatic air cleaner system, but you don't have that so it should be plugged.
The black build up on the MAF screen is normal, but cleaning the MAF with carb clean may have been a mistake. That stuff is very caustic and can cause damage.
Hard to believe there isn't any codes, but that's good I guess.
Have you checked the fuel pressure? If you can't, while the engine is running get under the car and listen to the main fuel pump (under the drivers seat area) and it should be humming smoothly. If it sounds like it's not running or is erratic, try smacking it with a hammer and see what happens.
Keep me posted!
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on June 27, 2010
How is the vehicle running otherwise? Is the check engine light on?
Sign in to reply
No, but the service light comes on for about a minute or two then goes out. Overall it runs fine, with the exception of the turbo not engaging. When we take off the top vaccum test port it seems to quiet the engine and we notice less engine noise, and the rpms seem to hold steady around 1000 (when the port is replaced, rmps drop just under 1000. On the turbo "scale" it is registering only about a quarter of the scale it will fluctuate a little when rmps are raised (3000rpms) but then it will fall back down to the quarter mark. We thought it might have been vaccum hose leaks, so replaced several hoses and now it seems to have made the problem worse.
on June 29, 2010
The service reminder light needs to be reset to turn that off, just use the reset button on the instrument panel, behind the black rubber plug.
Without seeing this it's hard to know what's happening, but are you sure the turbo is the issue? How is the fuel pressure? Do you have any codes in the engine or ignition computers? Do you have a restricted exhaust system?
on July 04, 2010
We don't have a code reader. We don't have the money to invest in one right now but would like one at some point unless you know of a very good one at a low price please include where to purchase . We are interested in knowing how to test the fuel pressue. However, the car seems to idle just fine, no we are not sure that the turbo is not the issue, but we do know that the turbo is not engaging. Is there a test that can be performed on the vaccum system to make sure there is enough vaccum to perform turbo function? Is there a way to use normal household part to create these gauges for testing? We have a very limited income, however we enjoy our 740 turbo that we picked up for a grand. What I notice the most is the turbo scale is narrowed to a 1/4" to where it use to travel up to a inch and feel and hear the turbo engaging the car seems to run fine just no happy juice when getting on highway or passing or getting off the line with a bit of effort to be honest this is the wifes car and she like\loves it a lot i want it to preform for her, i'm not familar with turbo engines - however i'm aware of the reliabilty of the b230ft and i want to get a better understanding of what is going on with it so i know how to get it running corretly so that i maintain its general health im not sure on how to test for restiction of exhaust system either, let face it this is something that we may not have the tools to preform these test unless i can make them up myself willing to put effort into it just low on income I wanted to thank you for your time sorry Im so long winded i reset the button \ thanks ps the more i replaced the hoses and closed up the leaks on the vacuum system the more scale decreased - i'm lost
on July 04, 2010
Without the appropriate tools this becomes more difficult, but there is some good news, you don't need a code reader. Look at this site to learn how to read the codes. http://volvospeed.com/CheckEngine.php
Check A-2 and A-6 ports, read the codes and post them here, I'll see if I can help.
Here are the codes: http://volvospeed.com/vs_forum/index.php/topic/47502-dtc-information/
Make sure the big turbo hoses are OK, not split, loose or leaking.
Remove the air cleaner housing, if there is a foam pad on the underside of the housing and it is deteriorating, then this may be the issue. The foam will contaminate the MAF sensor, so clean out all the foam and clean the MAF sensor with compressed air or a spray MAF cleaner.
Good luck
on July 10, 2010
We did notice the foam pad had started to break down, so we cleaned it out down to the plastic and tried to remove as much of the adheasive as we could. Also sprayed out the MAF with carb cleaner. Noticed a black buildup (carbon???) on the in take screen of the MAF, in the bottom of the air box there was a 1 3/4 plug on the engine side, I felt maybe that it would be better to have more air flow coming into the box so we removed the plug. The other port on the fender side was open and free of debre. Did I make a mistake, and should I close off the port on the engine side by putting back that plug? We will do the codes and do our best to provide that information. Just wanted your opinion on the air box and the plug. Thank you very much for your time, sorry it is taking us so long to respond, this is kind of weekend project. What do you think about the throttle positioning sensor, would that inhibit the turbo from engaging? We just checked the codes and A6 came up 111 as well as A2 the rest of them had no response. We only have one port that we could find and it is located up by the drivers side strut tower. We looked at the turbo waste gate linkage and there was a cotter pin missing out of the linkage, but we did replace it and no change has been noticed. Is there a way to test the vaccum line going to the turbo? If so, what should the psi be? Is there a way to check the function of the valve that the vaccum line leads to?
on July 12, 2010
Not sure about the hole in the air box, I think that's the port for the thermostatic air cleaner system, but you don't have that so it should be plugged.
The black build up on the MAF screen is normal, but cleaning the MAF with carb clean may have been a mistake. That stuff is very caustic and can cause damage.
Hard to believe there isn't any codes, but that's good I guess.
Have you checked the fuel pressure? If you can't, while the engine is running get under the car and listen to the main fuel pump (under the drivers seat area) and it should be humming smoothly. If it sounds like it's not running or is erratic, try smacking it with a hammer and see what happens.
Keep me posted!

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