Soon I will be deciding on keeping my truck or not. The engine is the only thing I am consered about at this point. The od reads 216000 but the engine was replaced at some point so I don.t know the true miles. It is a 351 and seems kind of low on the power end. But this is the first 351 I've had so maybe its normal. Should I et a compression test and would it tell me anything about the engine. I'm pretty good as a parts replacer but troubleshooting is a weak point. The engine does not burn oil and has no leaks/ funny noises to speak of. Just terrible gas mileage(expected) and not much power(not expected). The truck is a 95 F150 4x4 Supercab.

Thanks

Chris

 

There is an old saying, "if its not broke don't fix it", just kidding.


Your definiton of poor mpg and power may differ from others so thats a tough one.

I might focus on the poor mpg aspect and see what happens. I might suggest, Being the truck is a 95 I will assume it still has efi, you might wanna go to autozone and have them pull your codes, there may be a chance your having a problem of some sort with a sensor or two, and its not showing up, I wouldn't expect anything but it never hurts to check.

Thats a lot of miles, given the engine was replaced but what about the O2 sensor(s)? If your pretty sure the O2 sensor(s) are original to the vehicle it would be a good time to replace them, that might help your mpg and power some. IMO, the stock 351w never were a power house, with that said, mine does what I want it too, my expectations probably differ from yours.

I don't think you need to do a compression test but again, it will hurt nothing to do it, and the gauge usually runs $20 and its simple to do, take the coil wire off your coil, remove plug wires from spark plugs, mark them if needed for replacement, take your spark plugs out, start with one cyinder, screw the gauge in, turn the engine over 6-7 times using the igniton switch, take note of how the psi builds up and how much it builds too, write this down per cylinder and which cylinder. Check for consistancy, your gauge should come with instructions and suggestions, if not post your results on here, you should get a reply in short order. facing the front of the engine/truck, the left side, nearest to you to furthest away is cylinders 1-4 (passenger side), right side, 5-8 (drivers side).

Good luck

 

Thanks for the reply. I have replaced everything I can think of including O2 sensor, fuel filter, plugs, wires,rotor,and cap. i get 10- 12 which is not horrible but with the 31" mud tires I know that is all I can expect. The reason I was looking at a compression test is I am soon to invest some money into headers and exhaust and some other upgrades, but I want to make sure the engine is worth the investment. i don't know the history of it and the person I bought the truck from did not seem to take very good care of it. ANYHOO. I'll so the test and post the results. Thanks again.

Chris

 

What ratio gears do you have in that thing?


The comression test will give you a general idea of the condition of the engine, hopefully your experience will be a good one, good luck

 

I dont know why no one does this anymore. It is the most basic diagnostic test of an engine I can think of. Modern computerized fuel injected engines still have rings and valves and internal combustion cannot take place without good compression.

The wear limit on Ford engines is that the lowest is at least 75 percent of the highest. Do the test on a warm engine.

Jim

 

3.55 LS.

Chris