Is Starting Fluid Bad for Gas Engines?

In small doses and used properly, starting fluid can help coax a hard-starting engine to life. But, is starting fluid bad for diesel or two-stroke engines? Also, what is starting fluid? We’ll tackle those questions in this post.

What is starting fluid?

It’s a volatile chemical, typically ether, that’s normally packaged in a pressurized spray can. It’s designed to be sprayed in small amounts into the engine’s air intake to help it start. People often use it in extremely cold weather to help start a stubborn engine. But some people also use it to try to start an engine that turns over but won’t fire.

Warnings against its use

Ask five gearheads or mechanics their opinion on the topic and you might get five different answers.

One mechanic I talked to blamed it for ruining the bearings in a two-stroke outboard motor. Its owner, the story goes, liberally sprayed starting fluid into the intake when the engine wouldn’t start. And sprayed. And sprayed.

Ether is an effective solvent and, in this case, it washed the inside of the engine clean of oil, allowing metal components to contact and eventually seize.

Is starting fluid bad for diesel engines?

Is starting fluid bad for diesel engines?

Diesel engines, too, can suffer the effects of starting fluid. Their high compression can cause it to ignite too early, effectively causing pre-ignition, which invites all kinds of problems, like catastrophic piston or rod damage. Plus, it has no lubricating properties, so it can hasten piston wear.

With minimal work, you can find all sorts of cautionary tales on the Internet of people blowing up engines after using too much starting fluid.

Use starting fluid properly and sparingly.

Starting fluid does work (sometimes)

Given the disdain many harbor toward starting fluid, why would anyone use it?

Because it can be effective in gasoline engines – especially carbureted engines – when used as directed.

For gasoline to combust, it must first be vaporized. The fuel injectors in your car or truck do a great job of completing this task.

In carbureted engines, fuel is vaporized as it’s forced through the tiny openings or nozzles in the carburetor. But carburetors don’t vaporize fuel as effectively as fuel injectors. Plus, gasoline doesn’t vaporize as readily when it’s cold. Anyone who’s started a carbureted car or snowblower on a frigid morning knows this all too well. Plus, an engine requires more gas in the fuel/air mixture at startup, making a cold engine doubly difficult to start and keep running.

Starting fluid, on the other hand, does readily ignite in the cold, helping to start the engine and generate heat to more easily vaporize the fuel.

But a little goes a long way. Operator error is to blame for many of the problems noted here, not the fluid itself.

In short, if you have to use starting fluid, use it sparingly. If a couple short bursts into the intake don’t elicit a cough or two from the engine, emptying the can isn’t going to work, either.

Small Gas Engine Repair
No amount of starting fluid is going to revive an engine with a dirty carburetor. Identify the real problem and get it fixed.

Figure out why you need it in the first place

Instead, find out why the engine won’t start in the first place. There’s likely a bigger problem that needs fixing. (If your lawnmower won’t start, check out this post.)

I was presented with this scenario when my snowblower refused to start. So I reached for a can of starting fluid and gave the intake a shot. She sputtered a few times and quit. I repeated the process a few times with the same result.

Eventually, I took apart and cleaned the carb. She roared to life on the first pull after that.

In my case, emptying the entire can into the engine wouldn’t have done a thing, aside from washing the oil from the cylinder and causing wear. At the very least, it helped me diagnose what the problem was not: lack of spark or bad compression.

The bottom line

Starting fluid can help start a stubborn engine, but follow the directions and use it sparingly. If a little bit doesn’t work, a lot likely won’t, either. If your engine is consistently hard to start, find out why and get the real problem fixed.

Updated. Originally published: May 22, 2017.

Comments

  1. As a decades long certified GM Technician, I found, while installing injection pumps in the long-gone 5.7, 6.2 and the little V-6 diesels used in various GM vehicles, I would use a silicone spray. Obviously, it rates similarly to MP. The best part of those of us smart enough to not use starting fluid, we have never had an oil pan blow off!!!

    1. I have a 1998 Chevy van. It kept not starting. We replaced the fuel filter and other things, then today starting fluid started it three times. The fourth time the intake caught on fire and burned the hood when I closed it trying to smother the flames. The fire dept. put it out with water, but I had used a fire extinguisher. 1) Did this water damage the electrical system? 2) Is it possible a fuel-delivery problem was the cause?

  2. I also have used MP as a safe and effective aid in starting small engines for years; however, the new MP in the black can doesn’t work for that. I don’t know if the propellant was the flammable part or if the formula for MP changed, but it will not aid in starting anymore. Still great for everything else!!

  3. Diesels are not so much a worry with starter fluid. Remember the fuel is oil which lubes the cylinder walls when sprayed in.

  4. I have a generator that runs great but is hard to start if idle for several months. I always use fresh stabilized gas. One quick squirt of starter fluid gives me a start with one or two pulls. Then it starts ok there after until another long storage period. I think the rubber push pump to prime the carb does not work properly.

  5. I stay away from starting fluid, however if I have an engine that is temperamental in the cold or first start of the season I will give it a shot of Power Foam. Wakes it right up and doesn’t peal the lube off the cylinder walls like starting fluid.

  6. Used to feed cans to the old 80s cat rock truck at -30 here in northern Ontario never had a problem but I’m not the mechanic. Smoke like hell and sound like it too but always leveled out after 5 mins or so…miss abusing that beast..

  7. Hard starting John deer d140 riding mower will not Start in cold weather any ideas as to how I can start this piece of crap

    1. Hi Denny,

      I’ve run into this issue with my snowblower. Gas doesn’t vaporize and combust as readily in cold temperatures, so it often helps to warm the carburetor with a space heater. That’s what I did with my snowblower. Just be careful to place the heater close enough to heat the carb, but not so close that you start a fire. And don’t leave the heater unattended. It shouldn’t take more than a few minutes.

      Good luck, and thanks for reading.

  8. I discovered MP for a starting fluid long ago, and recommended it many times because it is a lubricant VS ether that does wash away residual oil film on cylinder walls

  9. Good article, I haven’t used starting fluid in a long time . The reason is because of something I discovered while working on a old dirt bike motor. It was a 2 stroke and I was having trouble getting it to start . Since I didn’t want to use starting fluid because it is so hard on the cylinder I decided to try a spray lube. Turns out Amsoil MP makes a great starting fluid. I have used it hundreds of times on both 2 and 4 stroke motors and it works every time and also is easier on the cylinder because it is a lubricant. Just shoot some in the carb , air box or cylinder and it will fire right up.Feel free to send me some as I am running low, LOL.

    1. Hi Eric,

      I’ve used MP for a lot of jobs, but starting an engine hasn’t yet been one of them. Thanks for the story. I’m sure some of the people around here would cringe at the thought of using MP as a starting fluid, so don’t look for us to update the recommended uses any time soon!

      Thanks for reading,

      John

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