I have this 1988 f150 with a 4.9 in it and it wouldnt run properly it would run but it would blow flames out the exhaust, then it wouldnt start at all after awhile.
I let it sit for a year and decided to trouble shoot it again this is what i have done so far. put in a new fuell pump in the front tank and cleaned the tank. new fuel filter,checked the fuel pressure it has 50 psi, it has spark . Pulled codes but no codes. cleaned the injectors. Dont know where to start now it is not getting fuel to the cylinders but has good fuel pressure. Does any one know what controls the injectors? i put a screwdriver to my ear on the injectors and can hear them pulsing . I am stumped.

 

Have you checked out your fuel pressure regulator?

 

yes it was leaking and have replaced it .
Just not getting fuel out of the injectors.
have good pressure and flow.
i am stumped .
I have put the code reader on and it gave me codes once then the next couple times it says unable to communicate.
then it will say system ok the next time.
hate to buy a computer if that is not the problem .
could it be one of the relays on the fender drivers side?

 

Did you verify that you are actually getting fuel to the injectors? You could check both fuel pump relays as it won't hurt - just swap them around to see if you have any different luck. I had an 89 that would eat fuel pump relays for some reason. However, it sounds that your ECM might be toast. Either that or you might have some bad grounds. I would start with the grounds and relays first and see if that helps.

 

If you search a bit there are several posts on how to check out your problem. Some of the posts are extremely well detailed and include step by step instruction with photos, at least one of them is for your exact engine/year.

I don't recall their names right off hand but searching for 4.9 no start would probably bring them up.

Have you tried spraying a little starting fluid in the intake to see if the engine would run then?

 

both fuel pumps are working and i have good fuel at the rail. Where are the two relays located ? i could try to swap them just to see what happens.

 

Agreed (although I typically refer to it by the more modern "PCM" acronym). Remove your computer - it's easier with the '87 - '91 trucks since you can remove it from the cab side once the harness connector is removed - and then open up the case (probably need a T-15 socket).

Inside you'll see three blue capacitors on the circuit board. I will just about guaranty that you'll find one or more of them have leaked out - the one in the most central location tends to go first I've found.

You can search for some of my other posts on this topic, but so far 4 out of 4 of the PCMs I've checked show evidence of capacitor leakage. What's not clear to me is when does the PCM actually fail to work since apparently there can be some leakage and the PCM still works. Regardless, best bet is to replace the capacitors or get a rebuilt one that is actually rebuilt. There was a guy on here a couple months ago that rebuilds these and understands the issue.

 

ECM, PCM...I think when his truck was produced they were still called ECMs.

My wife's 2001 Grand Caravan has 5 computers in it, if I recall correctly. Crazy stuff and it can make it a pain to work on if you don't have the right scan tools.

 

You've already found them in your previous post. However, I don't think it will do any good and Brad agrees with me. Unless you have corroded terminals on your relays, they probably aren't the problem if you are consistently getting fuel when the prime, crank, and run signals are given by the computer. You could have bad grounds, but you probably would have other problems too. Your PCM is probably the culprit.

bdelmar2 brought up an excellent idea for you to check out the other threads dealing with the same problem you are experiencing. Search for "4.9 no start" just like he recommended and you'll come up with some good results.

Let us know what you come up with.

 

I pulled the computer and took the cover off. no evidence of any leakage or any kind of corrotion. Why would the code reader read system ok then?
could it still be faulty? and the relays if they didnt work wouldnt the fuel pumps not run? just trying to understand this better. thanks.

 

Did you explicitly look at the three blue capacitors and their solder connections to the board? The other thing you can do is very lightly push the side of the capacitors. On the two I've got open in front of me as I type this, the center-most capacitor moves with almost no resistance. This indicates that the connection inside the can is broken.

If you'd like us to look, please feel free to post a pic or three. Frankly, I've yet to see a single F150 PCM of this era where at least one of the capacitors wasn't leaking.

 

I'd like to see a pic as well.

 

I replaced the ECM or PCM main computer what ever you want to call it.
Still has the same trouble. I went as far as putting gas in the cylinders with the plugs out and it still wont fire. It puffed out the intake once and that was it. I can check for spark on the plugs and they have spark. I have had the distributor out about fifty times to check the timing and still no luck. Could it be a cam sensor. no matter what I do nothing changes. Fuel pressure on the guage is 50 to 55 with just turning the key on. Thinking more ignition trouble at this time. If i hook up a timing lite should I be able to see the marks just turning it over? that way I can see if it is sparking at the correct time . Or does it need to be running. Which timing marks on the harmonic balancer do I use Ive been using the tick mark not the notch and the timing marks on the timing chain cover on the passenger side not the drivers side. is this correct

 

Correct, see this thread...

https://www.ford-trucks.com/forums/1...-91-4-9-a.html

If you've got spark, fuel, and compression, it's a pretty good bet that timing is your problem.

BTW, there is no cam sensor, so get that idea out of your head.

 

That post is exactly how i have set for TDC .
I have also tried 180 deg and still no difference.
I will double check for the 100th time again. Not like I havent done this before. doesnt take a rocket scientist to set a distributor.