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I think I have a leak in the fuel system: how do I find it?

I hadn’t driven since last February and had run the tank dry then. I knew I’d have to drive this week when a friend visited, so I prepared it last week by buying a can’s worth of gas, driving to the station, filling up. The first start took about a minute, which didn’t surprise me: I had expected the fuel line to take time to fill.

I was surprised when, 11 days later, it took a minute of cranking to start. The battery kept the starter motor cranking (with the help of a booster) but it wouldn’t go, as if it weren’t getting any fuel. My friend concurred and suggested a leak in the fuel line. There’s no sign of spilt fuel, not on the ground or in the engine compartment, or the smell of gas. He suggested that it draws in air, which dilutes the suction the pump (an external which works off a cam). It started normally on subsequent starts that day.

I rebuilt the carb in February and replaced all the rubber hoses. They all look good. They look like they’re installed properly.

What do you-all suggest?

'87 Toyota pickup, 5-speed manual, 4-cylinder engine, xtracab, longbed, red with green power crystals added.

On my carb’d truck , if it sits too long without being driven the fuel in the fuel bowl will all evaporate. When that happens it can take 15-20 seconds of cranking, usually over several attempts, to get it to start. If it takes longer than that, then no matter how much cranking I do it won’t start. The problem then is usually the fuel inlet valve in the carb is stuck shut. I just remove the top from the carb for access and use the tip of a pencil to unstick it.

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If my 1979 Toyota truck sat for weeks or more, it did the same thing. I found that dropping a teaspoon or two of gas down the carburetor did the trick. I kept a pint of gas in a can for this purpose.


15-20 seconds after a week is my usual experience. This is different.

Mine started after about a minute.

I don’t have a safe place for a can of gas. I’d use carburetor cleaner as starter fluid.

I’ve had this truck for 21 years. For the last 13 it’s sat most of the time. I haven’t had this problem before. I’m worried I’ve left something undone when putting the carburetor back together. It drove well after the rebuild; I passed the emissions test easily. I’d like to test the system safely. I did get a new muffler after the rebuild - the inspector insisted on it. I replaced the fuel pump 8 years (2K miles) ago.

If you can’t see or smell a gas leak, you don’t have one. Look in the carb and work the accelerator linkage.If you don’t see gas spray in the carb, you either have a ruptured accelerator pump diaphragm or gas isn’t getting to the carb. I don’t know where the fuel filter is on this truck but it could be clogged solid with rust given how little it is driven.
You could have a bad fuel pump, you can check that out by rigging a line from the intake side of the pump into a jar of gas, disconnecting the line at the carb and cranking the engine to see if gas comes put. if it does, the fuel pump is ok, and you have either a clogged filter if it is between the tank and pump or a pinhole in the fuel line high up where it won’t leak from gravity and the fuel pump can’t draw fuel if it can’t create a vacuum.

You didn’t leave the power crystal can open did you? They absorb moisture, and everyone knows you can’t use “soggy” crystals. :slightly_smiling_face:

After sitting empty for almost a year, I wouldn’t be surprised if the inside of the fuel tank is rusty and the fuel filter is clogged.

That’d disappoint: I installed a new one in February. Other than leaking, the old one worked.

It’s over a rear wheel well. It looks okay. It’s only 7K miles (13 years) old.

Considering that I installed this one 2K miles ago and the last worked for 149K, that’d disappoint.

I replaced all the rubber hoses. I’d like to test for leaks. What’s the best way to do that?

It has sat around mostly empty for 13 years. I add drier. I haven’t had this problem before.

I keep a fresh can sealed up and refresh them regularly.

Here’s the first thing I’d do: After it sits for a week, and before cranking the engine, take the top off the carb see if the fuel bowl is full or not. That will eliminate a lot of possibilities for why it takes a lot of cranking to start. This assumes your carb is configured so that’s possible while it remains installed on the engine of course.

Can’t I count on it to be empty after 9 months? To inspect the fuel bowl I have to remove the air cleaner, which is a drag. On top of that I have a hard time viewing it: I have to look at a high angle and it’s dark; if I use a flashlight more light reflects from around it. I need a mirror - unless somebody has a better suggestion.

Before I rebuilt the carb it started okay: took about 30 seconds if I hadn’t started it for a few weeks, a few seconds if only a few days. And it seemed like it was getting gas but balking. Now it doesn’t balk but acts as if it’s not getting enough gas.

Pull the dipstick and if it indicates the engine is overfilled with oil smell it. The fuel pump may be dumping gas into the engine. If so you’re lucky it didn’t start.

Does it have a fuel pump on the engine, operated via the camshaft, or an electric fuel pump?

If electric, where is it mounted? And does it run constantly when the key is at On or only for a few seconds when the key is turned to On?

After 9 months? Yes, of course it would all evaporate. And long cranking times before starting would be expected then obviously. But not after just a week.

Oil’s okay. I check everything before I start after a month or so. I keep a part out to prevent theft so I have to open the hood anyway.

As I mentioned in the original message, it has a mechanical fuel pump.

Sorry I missed that in your first post.

My 1979 Toyota truck apparently had a mechanical cam-operated FP when it was new. By the time I got it, an electric FP had been mounted near the right side of the gas tank. It was wired to run constantly when the key was set to On/Run. Not the safest in case of an accident and an unconscious driver. I am not sure what problem that electric FP was intended to address, and I did sometimes have to pour some gas down the throat if the truck had sat for some weeks or months. Once it started, there were no more fuel delivery problems.

I might not have thought of the gas down the throat idea except for an experience years prior. I was with a friend whose Corolla ran out of gas, not very far out of town. The man at the Standard station brought a gallon of gas and poured most of it into the tank, but the engine didn’t fire up. He then poured some down the throat and said, “Gotta prime the pump” and it started right up.

I hope it was illegal. Must have had a cover where the mechanical pump used to have been. I paid $40 for a new pump in 2009: expense couldn’t have been the problem.

I’m not asking about why I need to get fuel into the carburetor when the system has drained, but why it drained in only 11 days. It behaved differently in November than it has in the last 20 years under the same circumstances.

So, this problem began right after your rebuild. Sounds like an internal leak in the carb.

Good idea. A leaking power valve can cause this. I had that problem on my Ford truck’s carb not too long ago. That problem however will usually also cause the engine to be hard to start if you try to start it soon after it has recently been running at operating temperature, then turned off and sat for 30 minutes. The leaking fuel causes the mixture to be too rich for a warm start and it won’t start right away b/c it is flooded.

The rebuild kit included a power valve, which I installed because I installed everything the kit included. The old one looked just as good - still have it. How did you know it was leaking? I don’t have a problem with warm starts.

Just put in a primer bulb (made for outboard engines) upstream of the mechanical fuel pump:


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