Hello, this is my first post so please let me thank you ahead of time for any information you can provide for me. I own a 1988 F150, 302, supercab. The fuel pressure flutters very rapidly from about 20 to 30 pounds while it runs. The pressure falls within the normal range that it should it is just that if is constantly fluctuating(vacume connected). It also ticks like a grandfather clock while running and the ticking speeds up as you rev the engine. If you place your hand on the regulator or fuel rail you can feel the ticking noise. I replaced the regulator and that did not fix the problem. The fuel filter is relatively new as well. I am leaning towards a bad injector but there are no codes on the computer at all so I am confused. It drives normal, but seems to be a little underpowered and pings a lot no matter what brand of gas or octane. The truck has 125,000 thousand miles on it. Thanks for any help.! Sorry for the length, Aaron.

 

You might have a vacuum leak. As you know the pressure should be roughly as smooth as the throttle inputs. And yes, the ticking is probably an injector, also may cause the irreguler fluttering. Do you have a misfire?

Ping might be caused by the plug wires being to close together. My 302 pinged like a bastage until I seperated the back two wires on the drivers side. At no point in their paths should they run parrallel with eachother. Use some zip ties to seperate them and give it a shot.

Welcome to the machine!

 

No it does not have any kind of miss. It just seems to be lacking power. I have a set of 19# injectors laying around from my mustang that I was going to swap in, but if I am not getting a code for a bad injector(s) then I really don't want to go to all that extra work for nothing. The tick is really loud and sounds like it is comming from the regulator. It is pulling constant vaccum not jumping around like the fuel pressure so I don't think it is a vaccum leak. Could the pump be bad? I will check the wires but my guess is carbon build up. I have not always owned the truck and it seems the prior owner may have missed some regular maintenance items.

 

Whats the fuel pressure with key on engine off?

 

Key on engine off = 39 PSI.

 

The KOEO pressure is in spec so you know your pump is good, you need to check it on each tank if you have duals. Your regulator is probably OK too. Pull the vacuum line off the top of the regulator and check if there is fuel present in the vacuum line. If it is dry the regulator is good, if there is fuel present you have a bad regulator.

Next question, what is the KOEO fuel pressure 30 seconds after shutoff? If the pressure holds then your injectors are good. If it bleeds off more than a couple of PSI then you have a leaking injector.

 

It will hold 39 psi for several hours before it begins to bleed off. While it was running I tried pulling the conector of each of the fuel injectors that are accessable without removing the upper manifold an did not notice any change to the ticking and fluctuation pressure.

 

Is it possible to have an injector that will hold pressure for several hours after priming it only be bad when the truck is running? Keep in mind that the truck runs well it is just down on power and is a little ruff. I keep coming back to the injectors because everything else checks out. The ticking really is quite loud and can be felt in the rail, regulator, injectors, and lines. It doesn't seem to be worse in any one place. I guess I will have to pull the manifold and swap injectors.

 

Maybe...
Sounds like an injector is leaking while running, or just not spraying well, drooling. Your pressure is good when KOEO, whats the pressure while running?

Can you do a compression test? Or maybe if you disable the ignition, crank over about ten times, and look for a wet piston through the plug holes. Once in awhile we get drooly injectors on Saturns and they leave a lot of white crap on the plug and the piston is always wet.

Use a long screw driver as a stethascope to see if you can pin point the noise or loud injector. All will click while running, one might click louder than the others.

 

Are the 19 lb'ers from a Mustang truly the same as the 19s in our 302s? (1990 model here)

I too have a set of 19s from my Mustang (~92k mi) that I am tempted to swap into my 149k mi F150......

Wade

 

I think they are all universal, correct me if I'm wrong

 

They are the same. When you clean off the crud you'll probably find they are the exact same color (tan/orange). I've done the exact same thing, no problems.

 

Have you tried pulling the engine codes? You say its pinging as well? Have you checked your base timing? You have dual tanks right? MY 95 has dual pumps, my 88' had a single inline pump. Point is if you have dual intank pumps just switching between tanks should isolate your problem. If not, Autozone sells the inline for like $80 and its a VERY easy swap but you will smell like gas when you're done You could still have a bad fuel pump but you may also have your timing set wrong and or a bad plug wire causing it to ground out (ticking sound) or an exhaust leak could also = a ticking sound.. Check the codes, check the basics (timing at 10 degrees initial) make SURE you have good plug wires and plugs and cap/rotor and maybe TFI module..

Lots of ramblings sorry but you have two problems, they may related, but I would review the basic setup as well as the fluctuating fuel pressure. You know it is supposed to fluctuate (increase) about 8psi when you rev it right? That is normal and per design.

 

Thanks Sprocket and Jerry!

Alollich - Jerry just mentioned something that jogged my memory - about the plug wires; I had a plug wire to burn pretty badly once. It melted to a header tube, and produced a loud ticking. Check those wires as they mentioned above. If you have a burned one, or one in otherwise bad shape, that's a possible source of ticking....

Wade

 

Thanks again for all the replies. I quess the plug wires could be part of the problem since they are Autozone wires. I don't see the connection to the fluctuating fuel pressure though. I have the maifold off and the injectors swapped, but don't have it back together yet. I did notice that the upper manifold gasket was cracked and brittle in several places so a vaccum leak may have something to do with it. As usual Ford did not have several of the things I needed in stock so I am waiting for them to come in. There are no codes present and the timing is right at 10 degrees. Yes it is a dual tank truck. I should have it back together soon and I will let you know if it is any better.