Best techniques for finding vacuum leaks...?

[RichLo]

Make sure your spark plug wires are good before you try this one. There's a reason I made note that WD-40 is flammable. I saw a guy try to locate a vacuum leak with WD-40, but instead the misfire was caused by spark jump. The WD-40 made a nice little fire. Propane could get a lot more fun.

I agree 100% with the spark plug wires causing a fire but I also want to note that propane dissipates quickly below its flammability concentration. WD40 or other flammable materials in liquid form coat whatever you are spraying and will cause a fire to burn longer and create more damage than propane if you are reasonable with how you use it. Of course propane is more explosive so go around one suspect area then let it dissipate before trying another suspect area.

 

[studigggs]

Thought about building my own smoke generator from some DIY videos on YouTube, but by the time you buy all the parts, it was like $30 more just to buy a complete one off of eBay. I bought this guy and it does a good job. https://ebay.us/fblVEK

 

[kennythewelder]

Thought about building my own smoke generator from some DIY videos on YouTube, but by the time you buy all the parts, it was like $30 more just to buy a complete one off of eBay. I bought this guy and it does a good job. https://ebay.us/fblVEK

Nice. Cant go wrong for less than $70.

 

[mars2878]

what about soapy water in a spray bottle? Like they do for a leak in a tire.

 

[kennythewelder]

what about soapy water in a spray bottle? Like they do for a leak in a tire.

Not really, it wont bubble up because it is not pressure escaping, It is suction pressure pulling in word.

 

[mars2878]

Not really, it wont bubble up because it is not pressure escaping, It is suction pressure pulling in word.

Gotcha, I just remember as a kid, my dad squirting water on vacuum lines. I myself have never had to diagnose any issue like that.

 

[bowtie-72]

Gotcha, I just remember as a kid, my dad squirting water on vacuum lines. I myself have never had to diagnose any issue like that.

Spray bottle of water is an old school trick. Although it will not bubble up because it is not under pressure, the idle will drop/change slightly from water being sucked into the engine. Water is also not flammable. And it is cheap, and will not harm anything. In fact, it may even clean your combustion chambers. I have done this in the past and it works!

 

[Ehall8702]

We use brake cleaner here at the shop, or starting fluid since it evaporates so quickly, but I bet if a plug wire was shorting it would flame up, use spray bottle when we are checking for bad pkug wires. Ultimately smoke machine is best, we usually only use that when it's hard to find evap leaks cause the nitrogen is expensive.

 

[Mark Gilbert]

I have not had good luck with WD-40 since it is not flammable, it is combustible. When I was a kid you could take a lighter and spray WD-40 over it and have your little flame thrower. This did not work the last time I tried it, nor did it work to start a lawn mower engine when I was diagnosing it, The carb spray worked though.

I have always used carb spray and had really good luck with it, I've tried propane and for me it seems to dissipate too fast, so you have to get really close to the lines. Most of the leaks I have found always seem to be in hard to reach places where you can spray from a distance, but hard to get a can close to.

 

[Erik the Awful]

One quick note: with TBI trucks a rythmic misfire is almost certainly an ignition problem. An arythmic misfire is likely (but not guaranteed) a fuel or vacuum problem. With Vortecs, you have individual injectors or poppets that can cause a rythmic misfire.