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It’s every RV owner’s worst nightmare—you pack up your RV, remove the chalks, buck up your belts but when you turn the key your RV cranks but won’t start. Pumping the pedal and cranking it until the battery dies isn’t the answer.
So why does an RV crank but not start? and how do you fix it? If an RV is cranking but won’t start, the most likely suspects are the fuel delivery system or ignition system. If it’s cranking that means the battery and starter are likely fine. To fix it, start by troubleshooting the spark plugs and fuel pump, filter, and lines.
Getting an RV into a mechanic’s shop can be a major hassle. The size of the vehicle limits the available shops and many RV mechanics have extended waiting lists. Let’s go over some of the common fixes to save money and time while getting you on the road quicker.
Table of Contents
First Things First—Don’t Flood the Engine
One of the worst things you can do when you first encounter a fuel-powered vehicle that won’t start is to hit the gas over and over again. It’s very unlikely this will to get the engine started. All this does is introduce a bunch of fuel-rich air into the system that won’t ignite.
When an RV owner does this, they introduce an incorrect fuel air mixture into the combustion chamber that the spark is able to ignite. This means that the fuel-rich mixture of air must be purged from the system before the RV can be started.
Continuing to do this will end up gumming up your spark plugs preventing any spark that was occurring to stop. For this reason, flooding the engine should be avoided.
If the RV doesn’t start, don’t panic add more problems like a dead battery to the mix. Instead, you need to move on to troubleshooting the ignition and fuel systems.
Why The Starter Is Not Likely The Problem
If an RV engine will crank but won’t start, it is not likely a problem with the starter or the starter solenoid.
If the starter was dying, the car would likely not crank at all. If the RV engine will neither crank nor start, then the likely issues to start checking are a starter or starter solenoid.
But since the RV will crank in this case, the starter is a not prime suspect. The problem is more likely to be in the battery, spark or fuel systems.
Checking The Battery Connections And Cranking Amps
If your RV engine is cranking the problem is not likely the battery either. A caveat to that is if the engine is cranking slower than normal. If the starter sounds like it is struggling to turn over the battery could be suspect.
The first thing to check is that the terminals on the battery are not corroded and that the terminals are securely tightened. If there is a bad connection from the battery there is a possibility that not enough current is getting to the starter.
If the terminals are tight and clean the next thing is a battery load test. Most automotive supply stores will offer to perform a load check for free. You will likely have to disconnect the batteries and possibly even remove them for the test.
If you’re out on the road when your RV refuses to start most roadside assistance trucks will have a boost pack to start your RV. This should allow you to drive to get your batteries replaced. This is because once your RV engine is started it will run off the alternator instead of the battery.
Checking Your Ignition System
A common reason for an RV engine to crank but not start is a spark plug or wire failure. The spark plugs are the component of the engine that ignites the fuel-air mixture delivered by the fuel system. Without that spark there is no combustion and you’re not going anywhere.
Spark Plugs
Spark plugs tend to die slowly and often show signs of weakness before reaching the point where your engine won’t start. Some of the symptoms that can occur leading up to spark plug failure include the following:
- Misfires
- Engine codes
- Rough running
- Rough idle
- Lack of power/acceleration
- Excessive exhaust
You are much more likely to notice any of these more mild symptoms during the course of using your RV prior to a complete breakdown, but in some cases, especially if the spark plugs become suddenly fouled with oil or have some other issue, they can quit with no warning.
To test a spark plug, you can either pull it and test it on a multimeter if you have one, or you can pull it out and ground it on the engine block, If the spark plug is working, you’ll hear a crackle or see a small arc of sparks from the plug to the metal.
Spark Plug Wires
The spark plug wires are the path that brings the current from your distributor to the spark plugs. If your wires become loose or get damaged you can experience the same issues listed above.
Luckily it is simple to check your spark plug wires with a multimeter. Simply use a multi-meter on the Ohm (Omega) setting and touch the meter leads to each end. If the reading is less than 1 ohm the wires are good.
If you don’t have a multimeter in your RV tool kit you should add one. It is an essential tool for any electrical problem you may come across on the road. They can be purchased at any hardware store or online like this one from Amazon.com
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Be sure to check the wires one at a time so you can replace them easily without mixing them up. They are connected in a specific order so that your plugs fire at the appropriate time when your piston is at the top of its stroke.
Spark plugs and wires are fairly inexpensive and not difficult to replace. For an RV owner who spends a lot of time on the road, learning how to change them yourself is a good idea.
Troubleshooting The Fuel Delivery System
If your spark plugs and wires check out the next suspect on the list to rule out is the fuel delivery system. This system can break down in the following ways:
- The fuel pump may have failed.
- Cracks in the fuel line cause the fuel to leak out before reaching the combustion chamber.
- The fuel filter may be clogged.
- There’s bad gas in the system.
Clogged Fuel Filter
Of these four suspects, the fuel filter is the first one you should look at. RV fuel filters tend to get very quickly clogged with dust and other debris. Many RV owners recommend keeping a spare fuel filter around in case it starts to act up in the middle of a long-distance trip.
The main function of a fuel filter is to catch any contaminants in the fuel delivery system and prevent them from making their way into the engine.
Once this filter becomes dirty enough, it prevents the fuel from getting through the system to the combustion chamber.
Because clogged fuel filters can be an easy fix, it is recommended to go ahead and check your fuel filter first. Many people neglect changing their fuel filters but it’s an important step because RVs tend to sit around causing the filters to get clogged easier.
Bad Gas
If you are trying to start up your RV after a period of storage or sitting time and it will crank but not start it. Gas can sit in your gas tank for 3-4 months and typically still be used without causing any real performance issues.
However, if gas has been sitting in an RV tank for a year or more, it can go completely bad, and using it can cause a variety of serious running problems, including clogged fuel injectors or an engine knock.
When an RV has been sitting and is suspected to have bad gas, the first order of business is to drain the bad gas and dispose of it. Once the tank is empty, fill it with fresh gas and try starting the engine again. If the RV starts at this point, the gas was the culprit.
To avoid this problem, do not store your RV for long periods with less than a full tank of gas. Having empty space in your tank allows for the accumulation of water in the system that makes the gas go bad.
If you plan to leave it sitting for more than a few months, add some fuel stabilizer to the tank and fill it up completely. Stabilizer can be purchased for less than $20 at most automotive stores or can be ordered from Amazon.com.
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Cracked Fuel Lines
An issue that can be harder to troubleshoot than a filter or spark plug are your fuel lines. On an RV with a mechanical fuel pump, these cracks can cause air to be mixed into the system, rather than fuel mixture.
depending on the position of a cracked or damaged fuel line the problem can be difficult to locate and repair. When cracked fuel lines are identified depending on the RV owner’s level of mechanical expertise, it is recommended to see a mechanic.
Gasoline is highly flammable, toxic to inhale and can be absorbed by direct contact with skin. Fuel is dangerous to work with and repairing a line is no easy task, so unless you have a lot of mechanical experience, it is probably better to let a professional technician handle a problem like this one.
The fuel system in the RV is a safety hazard. If you do not reassemble the system properly you can cause a fuel leak that could potentially start a fire. So this is not a repair procedure to be done off a YouTube video or online tutorial. If you suspect fuel lines, call a professional.
Bad Fuel Pump
If your RV engine will crank but not start, a bad fuel pump is the next thing to start looking at. Fuel pumps can stop working without warning, and their mechanical failure is a common problem in all motorized vehicles, not just RVs.
One way to test your fuel pump is to get a fuel pressure gauge and check your fuel pressure. If you are not getting adequate pressure in the fuel delivery system, that means that the fuel pump has likely failed.
Tapping on your fuel pump with a wrench can sometimes get a it working again temporarily. This may allow you to get to a shop without having to pay for a tow.
In fact, many people who have a failing fuel pump get towed only to find out their car starts just fine at the repair garage. The jarring action of the tow can temporarily fix the fuel pump and camouflage the symptoms.
Other Potential Issues with the RV Engine
There a few other problems that can occur in an RV system that can cause the symptom of cranking but not starting. These issues are the distributor cap, the ballast resistor, or the crank position sensor.
- Distributor cap: If your RV only has a problem starting after the RV has been warmed up (for example, after a short stop at a gas station) then your problem could be a cracked distributor cap. When heated up, a crack in the distributor cap will cause the component to work incorrectly and prevent the engine from starting.
- Ballast resistor: If your RV tries to start, but then dies as soon as you let the key return to the RUN position, then you could possibly have an issue with the ballast resistor. This component goes bad often in RVs and can be easily replaced, so it can be useful to keep a spare.
- Crank position sensor: The crank position sensor is the mechanism in the RV engine that determines the position and RPMs of the engine crank. Because RVs are becoming increasingly digitized systems, a crank position sensor failure can cause the engine to not want to start.
Scan for Fault Codes
Before you start troubleshooting and pulling your hair out over a no-start issue in an RV, one quick way to get a good idea of what is going wrong with the RV is to scan the car’s computer systems for fault codes using a diagnostics (OBD) scanner.
These scanners are available at most automotive supply shops or you can purchase one online like this one from Amazon.com. Any repair shop will be able to scan your RV’s computer for fault codes as well but often charge an hour’s labor to do so. This makes the purchase of a scanner a cheap alternative and a possible quick fix.
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If you do not have one and don’t want to spend the money to buy one, some automotive supply shops, such as AutoZone and O’Reillys will scan your system with an OBD scanner and give you the fault codes for free.
Scanning your RV’s system with an OBD scanner can often give you a strong clue as to where your engine’s problems ultimately lie. An OBD scanner can also tell you at a glance whether the problem is simple, or whether you need to schedule repairs with a repair shop.
Don’t Throw Parts at A Problem
It can be worth it to replace some small, less expensive parts on a vehicle in an attempt to get it running. If you’re stuck in a place where mechanics are not easy to come by there may be no alternative choice. However, it is not recommended to start buying and throwing parts at a vehicle in an attempt to repair it.
For one thing, this is the most expensive way to go about a repair and you’ll often end up replacing parts that were functional. This is a waste of time, effort, and money. On average, a vehicle has around 30,000 parts on it, so you could indulge in this fruitless process forever.
Changing your fuel filter or spark plugs can be a simple solution, and in many scenarios, you can get your RV running. But if you replace some small parts and there is no change in performance contact a professional for assistance.
When in Doubt, Call a Mechanic
If you have tried the troubleshooting techniques recommended above and still can’t get your RV to start, it may be time to call in the experts. There is no shame in calling a professional mechanic if you have tried some simple fixes and none of them have worked.
Unless you are an experienced mechanic in your own right, replacing fuel lines and dropping fuel tanks in an RV or other vehicle is no easy task. Few people have the tools or environment necessary to perform quality repairs on a vehicle as large as an RV.
Many electronic programming modules and wiring harnesses have been inadvertently fried by DIY mechanics who didn’t really know what they were doing. You could accidentally turn a repair of a few hundred dollars into a few thousand dollars in less than ten minutes.
When in doubt, call a mechanic. It might be painful to pay the bill for a professional diagnostic process and the subsequent repairs but the job should get done right. It’s also a lot less painful than having to pay for even more repairs knowing that you accidentally caused damage to the system trying to fix it.
Prevent Start Problems in the Future
To prevent start-up problems, there are some steps you can take that will help avoid common issues. Here are some tips for preventing issues with your RV starting correctly.
- Replace spark plugs and other components at the recommended mileage, rather than when they cause the vehicle to break down.
- Make sure you use a fuel stabilizer in any gas that will be sitting in an RV gas tank longer than two months.
- Don’t let your fuel tank get below a fourth of a tank of gas, as this can cause the fuel pump to run hot and introduces debris into the fuel system.
- Have a mechanic check fuel lines for dry rot during regularly scheduled maintenance to have them replaced before they break down completely.
- Check your fuel filter often and replace it regularly. Ditto for your oil and oil filter. Oil is the lifeblood of any motorized vehicle so letting it get dirty or low can lead to an array of expensive, annoying mechanical problems.
- Keep a fuel pressure gauge and OBD scanner available in your RV’s kit so that you can inspect it for problems should they arise (and potentially solve them) before having to resort to a mechanic.
If you get your RV serviced on schedule, keep some spare parts such as a fuel filter, spark plugs, and a code reader handy for troubleshooting you should be able to avoid most of the problems that lead to an RV cranking but not starting.
