I have a 87 f150 4.9l inline 6 I recently moved to Florida and as I got here my truck starting making a knock noise and then as I was driving on the highway it had just cut off and hasn't started back up since it just turns over but no crank I'm completely stumped I'm thinking i f uped a valve and now it's not getting compression I still gotta check to see if I'm getting spark I'm pretty sure I am but I'm still gonna check and I'm gonna do compression test on it too but if anyone has any idea or that could help me out please let me know

 

Like you say, do a compression test. That's a solid first step. Figure that out and go from there.

 

Might want to pop the distributor cap off and see if the rotor turns when you spin the truck over, its possible the fiber timing gear sheared.

Especially if the engine spins over more quickly than it used to.

 

Big help guys i ordered a compression tester should be hear Saturday and I'll deffinetly test that with the distributor and if it sheared off is there any special thing I have to do besides get a new distributor

 

just did that and yeah the rotor didn't move at all soo what now?

 

Well, there are a couple possibilities.

One is that the roll pin holding the gear to the bottom of the distributor sheared, you would have to pull the distributor and see if you can move the gear independently of the rotor shaft. Pin may look ok from both ends but still be sheared.

I don't think this is your problem because you say it sounds like the engine has lost compression.

The next thing I would do is pull the plugs and verify you do not have compression, depending on where the valve train stopped you might have compression in some cylinders, but not all of them.

Edit: don't need an actual reading, just verify if there is or isn't compression.




You can replace the timing gears with the engine still in the truck, there are several articles about how to do it on this forum and the internet in general.

Some info here:
https://www.ford-trucks.com/forums/984226-cam-gear-newbie-needs-help.html

The place they mention for the replacement thrust plate is helpful. I ordered an new one for mine from them.

Honestly, before I would pull the gears in the truck and the pan to get the gear pieces out of the oil pump pickup I would just pull the engine.

It's a pretty easy engine to pull, maybe 2 or 3 hours but you may discover other things that need to be done while you are there, oil pump, water pump, engine mounts, etc.... So its likely to run into more money than just the gears and gaskets.

Or you have the quick and dirty option, just change the gears with the engine in the truck, watch the oil pressure and hope for the best.

Or you could drop in a used engine.

Or a rebuilt one.

I don't know how many miles are on your truck (I'd guess quite a few if the cam gear sheared), or how well it ran prior, what shape its in, or what your future plans are regarding it, or how well set up you are so I can't really say what I think your best option is.

 

Ok thanks man again like I said I ordered a compression tester it will be here Saturday and yeah it has 160k on it and yeah it ran really good prior to this happening so I think I might just go with the dirty option to just check out the gears and do them if that's what's wrong and since I'm gonna be in the front of the motor I'm gonna put a comp cam with comp timing gears in it from summitracing

 

You don't really need a gauge at this point, all you need to know is if you have any compression at all - a finger would work.

You run into another issue if you are planning on changing the cam without pulling the engine. The cam is as long as the engine itself.

The quick and dirty option is more suitable for somebody who needs their truck on the road asap and doesn't have the money to do it right.

I don't recall pulling straight 6 cam in one of these trucks, but I can tell you from the ones I do remember doing that they are a major pain to get out. I recall having to pull the radiator, condenser, jacking up the engine and fighting around the bumper.

Plus you will have to pull the upper intake, valve cover, rocker arm cover, pushrods, lifters, distributor, balancer, etc.... Those lifers may not want to come out very easily either.

If you do the cam you really need to put new lifters in as well. I guess you don't absolutely need to, but you really should, and you will need the break in oil also.

This is a lot of work to go through to leave gear pieces in your oil pan I would think.

Also, I wouldn't expect much of a gain from changing the cam. Ford did a pretty good job of matching the cam to the engine in the 4.9 and its just not a performance engine. You will get something for your effort and expense, but it won't be a night and day difference at all.

Just some things for you to consider.

 

Yeah I know they can be a pain i mean me and my (mostly me) rebuild his 4 cylinder jeep motor and yes I I know there's a difference haha but I might just leave it but would it hurt to do the com cam timing gears? Because they are both steel gears instead of one being fiber

 

Yeah I know they can be a pain i mean me and my dad (mostly me) rebuild his 4 cylinder jeep motor and yes I I know there's a difference haha but I might just leave it but would it hurt to do the com cam timing gears? Because they are both steel gears instead of one being fiber and if I did do the cam I know that I would have to do the lifters and all that but what kinda problems you talking bout that I would run into??

 

If you are just doing the gears, the biggest hassle will be getting the cam gear off. They like to break. The post I linked has some options about how to possibly get it off without breaking it or breaking the thrust plate behind the gear.

Or if you do break the thrust plate, the link in one of the posts has the place to get a replacement, it was pretty reasonable - like $15 or so if I remember correctly. There may or may not be a spacer ring as well, from what I can tell some cams have them, some don't, or rather some are cast into the cam itself. But, if you don't break the thrust plate you don't have to worry about that.

I put steel/aluminum gears in my engine. Some people complain about them being noisy, but mine don't seem to be. Sometimes when I'm shifting up through gears I get a little whine if I get close to 3k rpm, but not annoying, or not for me anyway.

If you do decide to change the cam also, the biggest problem would be getting enough room to physically remove the cam, its pretty long.

That, and if you get lifters that don't want to come out, fighting with them down inside the engine bay would not be fun.

 

Ok cool thanks man really big help and yeah Idc about them gears being noisy haha so ima deffinetly do that if this is all the problem and yeah I'll just pull the grill off and maybe the bumper if I have too

 

So I did the compression test but I'm not getting any readings on any cylinders? And was wondering if the fiber timing gear is sheared it wouldn't allow the Cam to spin making the lifters do there job and plus it does spin faster then it used to and the rotor does not move at all

 

Correct, most likely sheared cam gear.



With your finger you might have felt a little compression depending on where the cam stopped, but with a gauge you won't get enough of a reading to register.

 

If the cam gear/timing chain if it has one ( not familiar with the inline 6 ) broke that would mean at least some of the valves would be closed and allow for compression in some of the cylinders, does the crank pulley spin when you are turning it over?