February 6

2005 Nissan Sentra, Fuel Injector Replacement



Mark: Hi, it’s Mark from Top Local, we’re here with Bernie Pawlik of Pawlik Automotive in Vancouver, serving Vancouver area motorists for 38 years fixing all makes and models of cars and trucks and 18 time winners of Best Auto Repair in Vancouver. How’re you doing Bernie?

Bernie: Doing very well.

Mark: So we’re going to talk about a 2005 Nissan Sentra that had a fuel injector replacement. What was going on with this car?

Bernie: This vehicle was towed to our shop with a no start condition. It would, the engine would crank over but it wouldn’t start and what we found in doing our diagnosis, we removed the ignition coils and spark plugs and often a no start will be an ignition issue of some sort. But what we found was actually several cylinders fuel of fuel and when you crank the engine over with the spark plugs out there would be fuel spraying out. So there was an extreme amount of fuel being leaked inside the engine.

Mark: So how can an injector leak fuel in to a cylinder like that?

Bernie: Well the injector is meant to only inject fuel, well there’s two things; there’s pressure which comes from the fuel pump so it’s under pressure and it’s only meant to inject fuel when it receives an electronic signal from the fuel injection computer. What was happening in the case of at least two of the injectors in this vehicle, they were worn out to the point where they were actually dripping a bit of fuel even with the lack of injector signal. Once you turn the key off that residual pressure is being leaked down in through the fuel injector into the cylinder.

Mark: So I’ll ask the obvious question, why wouldn’t the car start even with the fuel filling the cylinder like that?

Bernie: Yeah, it kind of makes sense. You’ve got your fuel. You need  air, you need fuel, and spark and so that was all happening. But when you’ve got too much fuel, the engine won’t start because it’ll actually drown out the spark. Once the piston comes up there’s so much liquid, it won’t allow a spark to occur. Air and fuel needs to be mixed at a certain ratio, usually about 14 to 1, air to fuel but when you have like a half a cylinder full, the ratio is a little out. And interestingly enough liquid gasoline actually doesn’t burn, it’s only the vapour so theoretically you could actually throw a match onto liquid gasoline and it won’t burn but it always vaporizes so that’s what catches fire. But gasoline is very volatile, it vaporizes extremely easily but not when you have too much.

Mark: How many injectors were bad?

Bernie: Well there were at least two but we could see drips on most of them so at this point I’ll share some photos. Here’s the top of our Sentra engine. So these are the cylinder holes with the ignition coils and spark plugs removed and here we actually have the injector rail out, you can actually see the fuel injectors and you can see a little, kind of hard to look, but you can see a little bit of moistness around the tips of these injectors. And really there should be none there, they should be dry unless you’ve actually, you know fired the engine. But there was leakage in at least two of these injectors. Lets go to our other photo here. Here’s another view of the top of the engine again looking down. I was kind of hoping to capture, because you can actually, if you point a flashlight down in the cylinder, you can actually see some of the liquid fuel. But the, anyways this is sort of a view of the top of the engine. This is the valve cover, spark plugs sit in the middle of the cylinder and then the fuel injector rail sits right over here. So that’s where the injectors are and the fire fuel into the intake manifold on this particular engine. It’s a port fuel injection system.

Mark: Were there any other components damaged from the leaking injectors? 

Bernie: Well the spark plugs were. Yeah, now what happens when you have that much fuel, it ends up damaging the spark plugs. We replaced the spark plugs. That seemed to be the only issue that was visible and once we replaced the injectors and the spark plugs, the engine ran great and ran fine. But there are, you know leaving, having that much fuel running into an engine is actually, does actually create a problem. It washes down the cylinder walls of the oil that’s there that lubricates the cylinder walls because gasoline is not a great lubricant, so it can wash down and it can cause damage to the pistons, the piston rings and the cylinder wall.

Mark: So how would someone know if there was cylinder or piston ring damage?

Bernie: Well you would know, because like first of all the engine compression could be bad and you’d know because the engine would misfire and run rough. In the case of this engine, it wasn’t rough so I think the problem was caught pretty early. The other area of damage you could note, it’s more subtle and could take awhile is the engine would start burning oil and again that’d be another thing that you would notice over time. So if all of a sudden the engine is starting to burn oil, it may be that from this issue that the life span of this engine may be shortened, it’s hard to know. That’s something given over time. If it drives and it runs well, it doesn’t really use any oil, nothing really to worry about you just kind of let it go and see what happens.

Mark: So how often do you replace fuel injectors in gasoline engines?

Bernie: You know we don’t do them all that often. I’m thinking about like diesels, we tend to do them a lot more often but in a diesel the injector is so critical to the whole process of the combustion you  know, that any subtle thing could cause a problem. But gasoline injectors tend to last quite a long time and surprisingly it seems like Nissan has over the years replaced more fuel injectors in Nissan than any other brand. I’m not sure why that is. A lot of times with fuel injectors, they usually have one of two problems, well either one of a few problems, either they won’t work, they’l leak internally like these, or they’ll leak externally. So like an external leak, you’ll notice if you smell raw gasoline around the engine, you know sometimes you can see the actual body of the injector leaking. It seems like over the last 25 years a common issue with Nissan but we don’t do a lot of injectors. They’re fairly reliable.

Mark: And how are Nissan Sentra’s for reliability?

Bernie: Yeah, overall they’re pretty good cars. They’re sort of a lower end car but they’re reliable. If you’re looking for a good A to B kind of car that’s reliable and doesn’t have to many problems, I’d definitely recommend a Sentra. It’s a good vehicle.

Mark: So there you go. If you’re looking for a service for your Nissan Sentra or any Nissan product in Vancouver, the guys to see are Pawlik Automotive. You can reach them at 604-327-7112, they are busy so you have to book ahead, or call them, or check out their website at pawlikautomotive.com or on Youtube Pawlik Automotive, search for that. Hundreds of videos on there, all makes and models. Thanks Bernie

Bernie: Thanks Mark

About the author 

Bernie Pawlik

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