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FCP Euro Service Kits

FCP Euro Kits

Sometimes, vacuum leaks are obvious. Just by wiggling a vacuum line or intake tube, it is possible to find the offending leak. A quick spray of carb cleaner in suspected areas can also be a quick method of diagnoses. For the most part though, tracing vacuum leaks can be challenging, even more so if you don’t know if you should be chasing a vacuum leak in the first place.

seafoam5Potential symptoms of a vacuum leak include, but are not limited to:

  • Poor idle
  • Hesitation on acceleration
  • Power delivery issues
  • Long crank times
  • General drivability issues

Up until a few years ago, my family had always driven old cars. We previously owned a 91’ Toyota Previa, an 86’ Volvo 240 GL Wagon, a ’91 Mercury Topaz and a handful of other cars. Various issues of all these cars masked my ability to realize there were any problems, not to mention the majority of my driving experience was accumulated in front of a glass tube and a plastic controller in hand. Clunking front ends, bouncy suspension and loose steering, were all part of the character of our cars. In hindsight, having been around these old cars has most certainly tuned my senses to accept certain problems, which may or may not be a good thing.

My 91’ Volvo 940 GLE has been solid. Engine-wise, the only time it ever failed to start was when the radio suppression relay kicked the bucket. Apart from that, there was a slight hesitation on acceleration, occasional long crank times and odd idle on startup. If I stepped on the go pedal, a slight dip in RPM’s would follow. Okay, maybe it wasn’t that solid, but hear me out. My various diagnoses, fixes, and previous maintenance related to the issue included:

  • Cleaned throttle body and MAF
  • Replaced OEM air filter with K&N filter
  • Cleaned Idle Air Control Valve
  • Adjustment/tightening of the throttle cable and throttle switch
  • Replacing the paper gasket between the throttle body and the intake manifold.
  • Ensured tight clamps on air intake tube
  • Replaced fuel pressure regulator
  • Replaced in-tank and main fuel pump
  • Pulled and cleaned fuel injectors

Screen Shot 2014-07-24 at 9.08.13 PMIn general, I started with the easiest fixes, followed by part replacement. Its important to follow a system through all its paths to determine any possible problems. The one fix which made any noticeable difference was the replacement of the aforementioned paper gasket, which brought my crank times down to a consistent norm and improved the hesitation issue. This past polar vortex winter weather brought out the gremlins in my car, which worked to extend the crank time once again. Out of options, I decided to sit down and stare at the engine bay for a bit, letting the gears in my head work their magic.

A few weeks prior, I decided on a whim to check my flame trap to make sure it wasn’t clogged. I remembered reaching under to pull out the flame trap, and very easily pulling the vacuum lines off. At the time, I just thought that made it conveniently easy to get the job done. But now, it all started to make a lot of sense.

Vacuum Hoses Vacuum diagrams can be frightening

The oil separator box has a tube directly leading into the crankcase for blow-by gases to pass through. These gases are then routed through the flame trap and then finally back into the intake tube, just between the MAF and the throttle plate. If any of these rubber lines have leaks, unmetered air can sneak into the engine, causing various drivability and starting issues. In addition to being hidden away from plain sight, it gets very hot underneath, hardening the rubber lines. The problem worsened in the winter because the lines would be less pliable, loosening with engine vibrations, and letting air through.

Conventional wisdom would ask you to replace the lines, which I intend on doing down the road. On the other hand, placing hose clamps on offending tubes made my brick’s starting issues disappear along with the hesitation on acceleration. Whether this was the root cause of all my drivability issues, I’m not so sure, but I do believe that my previous work on the car made a cumulative difference. I guess if one fix doesn’t take care of it, just keep going until you figure it out, especially with vacuum leaks.

 


Thumbnail Tim WongAbout the Author: Tim Wong
Tim is a Canadian from Windsor, which means he has plans to use his Volvo as an emergency space heater. He is a mechanical engineer by day and backyard mechanic by night. His mantra in life is to never break another bolt. 

 


author image
Written by :
Tim Wong

Tim is a Canadian from Windsor, with a knack for taking things apart, and sometimes putting them back together. He is a mechanical engineer by day and backyard mechanic by night. His mantra in life is to never break another bolt.


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