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1991 Dodge Dakota excessive fuel consumption

Hi, first post here so I hope I do things right!

I have a 1991 Dodge Dakota pickup truck that has quite a few problems. The biggest problem is that it uses way too much fuel. When I say too much fuel, I mean about one mile to one gallon of gas! Other problems that might be related to the problem are: engine idles a little low and idles rough, and engine stalls out often when you are coming to a stop. I have a feeling that the three problems are related to each other…any ideas on what might be the problem would be appreciated! Thanks

When was the last time you performed routine maintenance on your truck – spark plugs, air filter, etc? I have a suspicion your truck is merely suffering from general neglect. Or at least, that’s where you must start.

well, in my ownership, I have replaced the roter cap and the air filter. I haven’t done the plugs and wires yet. One thing that I did remember was that the previous owner told me that it would run rough at start up but if you drove it for a little while, it would “act normal” if that sheds any more light…

At one mile per gallon for a light duty pickup truck, the only two possibilities are a significant fuel leak, which you would smell around the vehicle (it may even leave puddles), or somebody’s stealing fuel from your tank. An engine that size, whether it be the four, six, or eight cylinder, cannot receive that much fuel and be able to use it.

You might want to check for a leaking diaphram in the fuel pressure regulator. If the diaphram has a leak gas will be pulled into the engine via the vacuum hose which can cause low/rough idling and can cause the engine to stall. Plus, the fuel mileage will suck.

Start the engine and let it idle for thirty seconds and shut the engine off. Locate the fuel pressure regulator on the fuel rail and remove the vacuum hose from the regulator. If gas leaks out of the vacuum connection the diaphram in the regulator is leaking and requires replacement.

Tester

@mark9207

I am sure that it is not leaking because you can’t smell anything. I am also sure that nobody is stealing gas because the fuel level would go down over the period of several days.

@Tester

I will give that a try. where would the the fuel rail be?

The fuel rail sits on top of the injectors. On one of the fuel rails you’ll see this component. http://www.autopartswarehouse.com/details/QQDodgeQQDakotaQQStandardQQFuel_Pressure_RegulatorQQ19881991QQSIPR188.html

Remove the vacuum hose from the regulator and if gas leaks out replace the regulator.

Tester

@Tester

I tried what you said and it all checks out right, no gas coming from the vacuum line. Thanks for your thoughts though!

A 1991 Dakota? Must have some miles on it ? Timing chain!

Remove the distributor cap. Observe the rotor position. Have someone turn the engine over by hand from under the vehicle via the crankshaft bolt to cause the distributor rotor to rotate in one direction and then stop. Now rotate the engine in the opposite direction by hand, and observe how the far the engine can be rotated before the distributor rotor begins to turn. If the crank can be rotated at least 5 degrees before the distributor rotor begins to rotate in the opposite direction, it indicates a stretched timing chain.

A stretched timing chain can cause the ignition and valve timing to be off. And that will eat gas.

Tester