Hello everyone. this is my first post!

i bought my truck (87 F150 AT 2WD) about a year and a half ago. it's always had an issue with starting. it started as a random thing, now it's all the time. it never runs the battery down but it will just turn over and over and over til it finally starts - regardles of weather. fuel pressure when turning over is immediately at 40PSI then drops down to about 32 once started, which i'm told is good.

my mechanic has replaced everything he can possibly think of and some other things he threw on just as a guess. i'm just running the rear tank cause the front tank is rusted inside. but we replaced the low pressure pump in the rear, the high pressure rail pump, the idle air control, fuel pressure regulator, some other stuff i can't remember. until finally we decided we'd replace the computer (ECM). no luck still. although the new computer seems to have fixed my racing idle that i was experiencing the last few months.

does it have anything to do with not having the front tank operational. i only ask this cause i read a post once when i was replacing the back tank, pump and sending unit that said you are supposed to change both low pressure in-tank pumps at the same time.

i'm desperate here. my mechanic is a great friend who isn't charging me for anything yet cause he can't fix it - but i still feel bad cause he's putting a LOT of his own money in this truck which is now more than i even bought it for. i think it's a mission for him now to figure it out. plus it's an inconvenience to have my truck in the shop every week while they try to fix the problem.

any answers will be greatly appreciated!!
shawn

 

Hi and Welcome to FTE.
Your fuel pressures are fine unless you have the I6 (4.9L) engine whcich sees about 55psi.

A few questions for you or your mechanic.
Bring up the Fuel pressure to 40 but don't start it. How long does it take to bleed down 5psi (to 35) on its own?
Do you have spark during this won't start phase?
Are the injectors firing? (You should be able to hear them tick with a mechanics stethoscope when the engine is cranking)
How is the timing? (should be 10 degrees w/SPOUT removed for v8's)
Would your friend the mechanic have a known good working distributor to try, or be able to replace the PIP sensor? (Only replace if you don't have the injectors firing. No PIP = No Injector firing)

 

thanks tim,
i will pass along the info. i don't know everything he's tried, so i'll get a list from him tomorrow. it is a 5.0. it is 40 PSI as soon as you turn the key on, i believe. a couple weeks ago, he let me bring home the fuel pressure guage/tester and a test light hooked up to the pump and to the battery so i could check it in the morning, etc. and make sure that i was both, getting the right pressure and that power was to the pump. but back to your 40 PSI question, i didn't think to keep it 'on' to see how long it takes to bleed down. what does that determine?

it occured to me that he also put on a TPS and CTS as well - in part to try and fix the high and irractic idle.

thanks again.
i'll post more when i get some more info from him. but keep the suggestions coming!!!!!

shawn

 

Ok,your mechanic tried almost everything.... and your say your engine is 5.0.
maybe it would be good idea to check your truck's vin number and find motor code to see if it match to your motor because it is possible somebody been replace engine which may be original 4.9 or 5.8 ? if so, then computer ecm may have been confused as thinking it is 4.9 or 5.8 but really motor is now 5.0. who know? check vin motor code just in case. i am also mechanic... just thought not hurt to check. excuse with my bad english!!!!! let us know what u find..good luck.

 

The reasoning for turnin the key on and timing how long it takes to drop to 35 PSI from 40 is so that we can tell if you have an injector stuck open. If there is a stuck injector which it sounds like it probably is, when you turn the key on and the fuel pump "primes" the system, it is just dumpin all that fuel into the engine and then "flooding" it. Next time you go to start it, turn the key on, hold it fully to the floor for Wide Open Throttle (WOT) and see if it starts easier. Remember to take your foot off the gas once it starts lol.

 

thanks again.
i tried the 'WOT when starting' last night and this morning - no improvement (no faster start).

i went by the shop this AM to return my core ECM. I mention some of the things you guys mentioned. he said to bring the truck in and he will set up a diagnostic test on the fuel injectors to see if they're firing, etc. He'll check the PIP too.

i bought the truck from the original owner. they bought it new, drove it five years, then let it sit for the last 10+ years more or less. would this have anything to do with my troubles?

thanks for your continued help!!!

shawn

 

and another thing, when i took out the ECM computer, i noticed it was a remanufactured box. Since they bought the truck new, they must have replaced the computer for some reason at some time.... hmmm.

shawn

 

fuel filter been already replaced? since you one of tank is rusted.

 

yes, the filter has been replaced on many occasions - until i got the new gas tank in the rear because it would clog up pretty fast. i've had the new tank about a year now. i last replaced the filter a couple months ago to see if that had anything to do with the problem. which it was running fine with no indication that the filter was getting clogged, but i changed it anyway when i put on the new high pressure pump.

if only it was as simple as a $6 filter.... but that's the story of my life and vehicles.

thanks,
shawn

 

maybe better to leave fuel system alone for now and start checking ign system....Do you have spark during this won't start phase?

 

i have not personally checked that. do you mean from the coil? i can change oil and fuel pumps and stuff like that but never have checked a vehicle for spark. what kind of tools do i need, etc....

shawn

 

ok... pull one from any spark plug wire off and and use screwdriver to insert in end of spark wire and looking for ground... have screwdriver near (closer) to ground.. <TOUCH ground to>while watch it and see if any spark while someone else to start the truck... i am sorry if my english 's terrible,hope you understand what i say here... hope someone can jump in and explian it better than i do lol

 

or, just pull a plug, and touch it to the block, or manifold, and have someone try to start it.

 

well, the spark's good. then we hooked up a test light that plugs into the top of the fuel injectors and cranked it over.... the light didn't come on for a couple seconds and it was dim. He said for some reason the computer is not telling the injectors to fire.

as i said before the computer is brand new (okay, remanufactured). i'm going to drop it off to him the first of next week to tinker more with it. any ideas from you guys what might be up? when the light did come on, i could feel the injectors firing (i was holding the plug on the injectors to make sure it was a solid connection).

shawn